US3362179A

US3362179A - Heat exchangers

Info

Publication number: US3362179A
Application number: US520679A
Authority: US
Inventors: Henry O Kirkpatrick
Original assignee: Cummins Engine Co Inc
Current assignee: Cummins Inc
Priority date: 1966-01-14
Filing date: 1966-01-14
Publication date: 1968-01-09
Anticipated expiration: 1985-01-09

Description

6 Sheets-Sheet l Jan. 9, 1968 H. o. KIRKPATRICK HEAT EXCHANGERS Filed Jan.l 14, 1966 mfj y ATTORNEYS Jan. 9, 1968 H.O.K1RKPATR|CK 3,362,179

HEAT EXCHANGERS 6 Sheets-Sheet 2 Filed Jan. 14, 1966 INVENTOR 104 Henry O. Kirkpatrick W W y@ ATTORNEYS Jan. 95 1968 H'. Ao. KIRKPATRlcK HEAT EXCHANGERS Filed Jan. 14, 1966 6 Sheets-Sheet v5 INVENTOR Henry O. Kirkpatrick Jan. 9, 1968 H. o. KIRKPATRICK 3,362,179

HEAT EXCHANGERS 6 Sheets-Sheet 4 Filed Jan. 14, 1966 WQL INVENTOR Henry O. Kirkpatrick H. o. KIRKPATRICK 3,362,179

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MGM, NQN www nur w www WNW \ msm United States Patent O M 3,362,179 HEAT EXCHANGERS Henry 0. Kirkpatrick, Dalias, Tex., assignor to Cummins Engine Company, Inc., Columbus, Ind., a corporation of Indiana Filed Jan. 14, 1966, Ser. No. 520,679

' 21 Claims. (Cl. 62-97) The present invention relates to heat exchangers and more particularly to a heat exchanger unit of a refrigeration system and to a refrigeration system utilizing such heat exchanger unit.

An object of the invention is to provide a new and limproved heat exchanger Which may be used as an evaporator unit of a refrigeration system to maintain a low temperature in a chamber.

A further object is to provide an evaporator unit for a refrigeration system which comprises a plurality of modular units.

Another and further object is to provide an improved evaporator unit which may be mounted along the ceiling of a chamber.

Still another object is to provide an improved modular heat exchanger which may be mounted along the ceiling of a chamber to form an elongated unit spanning the chamber from one end to the other.

Another and further object is to provide an improved heat exchanger which is economical to manufacture.

A still further object is to provide an improved heat exchanger of modular construction which can be made up in any desired length.

Yet another object is to provide an improved heat exchanger which adequately circulates air in an elongated chamber.

Still another object is to provide an improved heat exchanger which can provide air circulation throughout the entire length of an elongated chamber.

Another and further object is to provide an improved heat exchanger which permits precise control of the temperature within an elongated chamber.

A still further object is to provide an improved heat exchanger which takes up no usable storage space in a chamber.

Another object is to provide an improved heat exchanger which takes up less room in a chamber than air distribution ducts of conventional refrigeration systems.

Still another object is to provide an improved heat exchanger for 4a chamber which eliminates the need for air distribution ducts.

Still another object is to provide an improved heat exchanger which provides cross-ow of air below products stored on the floor of a cooling chamber.

A further object is to provide an improved heat exchanger for a refrigerated truck body which eliminates the necessity of cutting and framing an opening in the front wall of the truck body.

A still further object is to provide an improved heat exchanger for an elongated chamber which provides crossflow of air throughout the length of the chamber.

An important object is to provide an improved heat exchanger which provides a curtain of owing `air along the interior surfaces of a chamber and thus ensures substantially uniform temperature conditions throughout the chamber.

Another object of the present invention is to provide an improved heat exchanger which provides air circulation around stored objects in a chamber.

Another object is to provide an improved refrigerated body for a transport vehicle.

Another and further object is to provide an improved body for a transport vehicle with a modular heat exchanger structure therein.

3,362,179 Patented Jan. 9, 1968 ICC Another object is to provide an improved -body for a transport vehicle having an elongated heat exchanger spanning a horizontal dimension of said body.

'Yet another object of the present invention is to prov1de an improved body for a transport vehicle having a heat exchanger disposed therein extending substantially the entire length of the body.

n Still another object is to provide a heat exchanger providlng an air circulation pattern in a vehicle chamber which minimizes loss of cold air and entrance of warm outside air into the chamber when the doors of the vehicle are opened.

A still further object of the present invention is to provide an improved method and apparatus for forming a screen of flowing air along the walls of an elongated chamber.

Yet another object of the present invention is to provide an improved method and apparatus for refrigerating and circulating air through the body of a transport vehicle.

A further object of the present invention is to provide an improved method and apparatus for refrigerating and circulating air about the cargo in a transport vehicle.

A further object is to provide a heat exchanger comprising a plurality of modules, mounted along the ceiling of a chamber to form an elongated unit spanning the chamber from one end to the other, wherein when each of the modules is provided with its own individual air moving means and individually controlled air cooling means to maintain the temperature of the air being moved thereby at predetermined value.

A still further object is to provide an elongate heat exchanger comprising a plurality of modules each having vertical spaced cooling sections through which air is movable transversely of the modules in opposite directions by thc air moving means of the module wherein, the heat exchanger including a main inlet duct and a main exhaust duct, the cooling coils of the modules being connected in parallel through expansion valves across the inlet and exhaust conduits.

A still further object is to provide a heat exchanger of the type described wherein each module has its own individual expansion valves through which the liquid refrigerant gas from the main inlet conduit is allowed to evaporate and expand into the coils of its cooling sections and flow therethrough to the exhaust conduit.

Another object is to provide a refrigeration system wherein the heat exchanger is provided with a main bypass conduit, the cooling coils of the modules being connected in parallel across the main exhaust conduit and the bypass conduit and the refrigeration system has means for supplying liquid refrigerant uid to the inlet conduit and withdrawing expanded evaporated refrigerant iiuid from the exhaust conduit and for alternatively supplying hot compressed refrigerant fluid to the main exhaust conduit for passage through and liquication in the cooling coils and withdrawing liquefied refrigerant fluid from the bypass conduit.

Still another object is to provide a heat exchanger wherein the main inlet and exhaust conduits extend through the heat exchanger in good heat exchange relationship to one another to constitute a heat exchanger.

Additional objects and advantages of the present invention will be readily apparent from the reading of the following description of a device, constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

FIGURE l is a schematic top view, with some parts broken away, of a body of a transport vehicle embodying t-he invention;

FIGURE 2 is a schematic vertical sectional View, with 3 some parts broken away, of the body illustrated in FIG- URE 1;

FIGURE 3 is a sectional View, taken on line 3 3, of FIGURE 2;

FIGURE 4 is a sectional view taken on line 4-4 of FIGURE 5;

FIGURE 5 is a top view, with some of the parts broken away, of a plural module heat exchanger embodying the present invention;

FIGURE 6 is a side view of the heat exchanger illustrated in FIGURE 5;

FIGURE 7 is a top view, with some parts broken away, of a module of a modified form of a heat exchanger embodying the invention;

FIGURE 8 is a side View of the module illustrated in FIGURE 7;

FIGURE S-A is a sectional View taken on line 8A S-A of FIGURE 7;

FIGURE S-B is a sectional view taken on line S-B- 8-B of FIGURE 7;

FIGURE 9 is a rear end view, with some parts broken away, of the module illustrated in FIGURE 7;

FIGURE 10 is a top View, with some portions broken away, of another heat exchanger module embodying the invention;

FIGURE ll is a side View of the module illustrated in FIGURE 10;

FIGURE l2 is a schematic vertical sectional view of a body of a vehicle having a refrigeration system including an evaporator unit formed of the modules illustrated in FIGURES 7 through ll;

FIGURE 13 is a fragmentary schematic vieuI of the refrigerator system; and

FIGURE 14 is a schematic sectional view of the valve of the refrigeration system illustrated in FIGURE 13.

Referring now to FIGURES l-6 of the drawings, the transport vehicle or trailer 10, whose body 11 provides a chamber 12 in which goods and merchandise whose temperature must be maintained below a predetermined value is stowable, is adapted to be towed by a towing vehicle or tractor. The trailer body is supported at its rear end by two pairs of wheels 13 rotatably mounted on sluitable axles 14. The axles 14 are secured by means of any suitable support assembly 15 to the bottom or bed 16 of the body. The front end of the tractor is supportable by a usual front prop assembly 17 secured to the bottom 16. A suitable forwardly projecting tow bar 18 is connectable by any suitable, well known coupling means to the towing vehicle.

The trailer body includes vertical front and

side walls

21, 22 and 23 which extend upwardly from the front and sides of the bottom 16 and a top or roof 24 which extends between and is secured to the side walis and .the front wall. The rear opening of the body is closable by a pair of rear doors 25 and 26 which are hingedly secured at their outer side edges to the rear edges or ends of the

side walls

22 and 23, and when closed, constitute a rear wall of the body. The walls, roof, doors and bed of the body are of such construction as to minimize conduction of heat therethrough. For example, the roof 24 may be formed of an exterior sheet or lamination 28 of metal, an inner layer or lamination 29 of insulating material, such as rockwool or the like, and an inner sheet 3) also of metal. The outer and inner laminations 29 and 3) of the top wall are preferably formed of a light metal, such as aluminum, in order to minimize the weight of the trailer body. The walls and the doors of the body may be of this same construction.

The inner sheets of the front and

side walls

21, 22 and 23 are provided with vertical spaced inwardly extending

ribs

32, 33 and 34, respectively, which provide vertical

internal passages

35, 36 and 37, respectively, along the internal surfaces of these walls to permit cool air to flow downwardly therethrough in the event that t-he cargo in the chamber 12 is so loaded that it contacts the ribs. The

doors 25 and 26 preferably also have vertical spaced ribs 38 and 39 respectively, which provide the vertical passages 40 and 41 which serve the same purposes as the passages formed by the ribs of the front and side walls of the trailer body.

The bottom of the body has longitudinally extending transversely spaced upwardly projecting runners 44. The runners are substantially T-shaped in cross section and their vertical or leg portions are provided with longitudinally spaced transverse apertures 46 through which transverse flow of air may take place below any cargo resting upon the top or horizontal head portions 46a of the runners. The runners also provide longitudinal upwardly opening passages 47 which extend the length of the bed. The outermost runners 44a and 44b are spaced inwardly from the

side walls

22 and 23 respectively, and their

ribs

33 and 34 whereby the lower ends of the vertical passages 36 and 37 open to the outermost passage channels 47a and 47b so that any air flowing downwardly through such passages 36 and 37 may ow into the outermost passage 47a and 47b and then flow either longitudinally through such passages or from these outermost passage 47a and 47b through the apertures 46 of the runners and transversely and longitudinally through the inner passages 47 across the bottom of the body and below any cargo which may be supported by the runners. The air in the passages 47 may also ow upwardly therefrom to circulate through openings in the cargo.

The usual compressor and condenser assembly 50 of a conventional refrigeration system mounted on the front wall 21 of the trailer which includes a compressor 51 and the condenser 52 provides cooled and liquefied refrigerant fluid to the evaporator unit 53 of the system mounted in the trailer body. The refrigeration system may utilize a suitable refrigerant uid such as Freon. The refrigeration system operates in the usual well known manner, the compressor compressing the refrigerant fluid which it draws from the evaporator unit and delivering the hot compressed refrigerant fluid in gaseous state to the condenser 52 wherein the hot compressed refrigerant fluid is cooled and liquied and is then transmitted through a suitable expansion valve 55 to the evaporator unit. The expansion valve controls the rate of flow of the refrigerant fluid into the evaporator unit and in turn is controlled by suitable well known means responsive to such factors as the pressure of the refrigerant fluid immediately upstream of the expansion valve and the temperature of the refrigerant uid immediately downstream of the evaporator unit. The refrigerant fluid owing through the evaporator unit evaporates and expands and absorbs heat from the chamber 12.

The evaporator unit 53 is of modular construction and includes a front module 56, a pair of

intermediate modules

57 and 58 and a rear module 59. The front module includes a pair of longitudinally extending laterally spaced cooling sections 61 and 62 mounted between a bottom or drain pan 63 and a top wall or cover 64. The cooling section 61 includes a plurality of vertically spaced longitudinal tubes 66, vertically disposed and longitudinally spaced cooling fins 65 provided with suitable apertures through which the tubes extend, and support angle members 67 and 68. The tubes extend forwardly of the transverse flange 69 of the front support member 67 and have flared outer end portions 70 in which are telescoped the ends of the outlet conduits 71 of the expansion valve 5S. The telescoped end portions of the outlet conduits are secured to the tubes 66 in seal tight relationship by any suitable means, such as solder or the like. Rear end portions of the tubes extend rearwardly through apertures in the transverse flange 72 of the rear support member 68.

The cooling section 62 similarly includes a plurality of vertically spaced longitudinal tubes 73 which extend through suitable apertures in the cooling ns 74 and the transverse anges 75 and 76 of the front and -rear support angle members 77 and 78 respectively of the cooling section. End portions of the inlet conduits 79 of an exhaust manifold 80 are telescoped in the iiared or enlarged forward end portions 81 of the tubes 73 which extend forwardly of the front support member.

Cooled and liquilied refrigerant fluid from the condenser is transmitted to the inlet conduit 82 of the expansion valve through a suitable conduit 83 whose upper end is connected by a suitable coupling to the threaded coupling section 84 on the outer end of the inlet conduit. The lower end of the conduit is connected to one end of an elbow joint 85 to whose other end is connected a conduit (not shown) which extends through a suitable aperture in the front wall to the outlet of the condenser 52. The warmed refrigerant iiuid which is now in its gaseous state ows from the exhaust manifold to the inlet of the compressor through its outlet conduit 86, a conduit 87 whose upper end is secured by a coupling to the threaded coupling section 88. The lower end of the conduit 87 is connected to one end of an elbow 89 to whose other end is connected a conduit which extends to the compressor through a suitable aperture in the front wall.

The

conduits

83 and 87 are protected against damage by the cargo in the trailer body by a guard assembly 90 which includes substantially U-shaped vertical brackets 91 which are secured tothe inner surface of the front wall, as by screws, and vertical bars 94 rigidly secured to the brackets in any suitable manner, as by welding.

The front transverse flanges 69` and 75 of the forward support members of the cooling sections 61 and 62 are connected by a vertical plate 96 which is secured thereto by screws 97. Similarly the

transverse flanges

72 and 76 of the rear members 68 and 78 of the cooling sections are connected by a vertical plate 98 which is secured thereto by screws 99. The two plates extend between the drain pan 63 and the cover 64.

The drain pan 63 has longitudinally extending

sections

101 and 102 which converge downwardly,

vertical side flanges

103 and 104 and a front vertical flange 105. The lower portions of the cooling sections telescope into the drain pan 63 which is secured thereto by means of screws or bolts 107 which extend through the side flanges thereof into the outer vertical anges 111, 112, 113 and 114 of the front and rear support members of the two cooling sections.

Longitudinal strips

116 and 117 of resilient material, such as rubber or the like, are disposed between the lower ends of the fins of the cooling sections and the

drain pan sections

101 and 102 to prevent flow of air therepast so that substantially all air flowing into or out of the central chamber 118 between the cooling sections and the vertical plates 96 and 98 must pass through the cooling sections.

The top 64 is of inverted channel shape having a horizontal planar web 119 and downwardly extending side flanges 120 and 121. The upper portions of the cooling sections telescope between the side anges of the cover and the cover is secured to the outer vertical flanges of the support members of the cooling sections by screws 122. Sealing strips or gaskets 123 are disposed between the web 119 and the top of the cooling sections to prevent air from flowing between the cover and the cooling sections.

A channel shaped bra-ce member 12311 extends horizontally between outer sides of the fins 64 of the cooling section 61 and the outer anges 111 and 112 of its front and rear support members and may be rigidly secured thereto in any suitable manner as by welding. A vertical brace member 124 also channel shaped is positioned between the outer sides of the fins 65 and the side anges 103 and 121 of the drain pan and the cover. The vertical brace member is provided with suitable slots in its flanges through which the horizontal brace member extends. 'Ihe transverse lianges 69 and 72 have apertures 125 aligned with the channel member so that an electric cable (not 6 shown) may extend through these apertures and the horizontal brace member through the full length of the module.

A similar horizontal brace 127 is disposed between the outer sides of the iins 74 of the cooling section 62 and the outer anges 113 and 114 of its front and rear support members and in alignment with the apertures 128 in the

transverse flanges

75 and 76 thereof. A vertical brace member, not shown, similar to the brace member 124 extends between the outer sides of the ns 74 and the side flanges 104 and 121 of the drain pan and the cover.

The chamber 118 is divided into front and rear outer pa-ssages and 136 and a central passage 137 by a pair of orifice plates 138. The orice plates are identical and each has a top flange whose top surface abuts the bottom surface of the web 119 of the cover, vertical longitudinally extending side anges 141 and 142 which abut the inner sides of the iins of the cooling sections 61 and 62, respectively, and bottom flanges 143 and 144 which abut the top surfaces of the

sections

101 and 102 of the drain pan. The oriiice plates may be secured to the web 119 and to the drain pan by any suitable means, such as screws or bolts. Each orifice plate is provided with a downwardly opening slot 148 of relatively small dimension to permit ilow of condensate through the full length of the drain pan. An insulated electric heater 149 may also extend longitudinally through these slots of the orifice plates.

A condensate outlet duct 150 which is connected to the front flange 105 of the drain pan permits flow of condensate forwardly from the drain pan. The condensate outlet duct may be connected to the upper end of the condensate drain conduit 152 which is secured to the front wall and whose lower end extends to a suitable aperture in the bottom wall. If desired, an enlargement or reservoir 153 may be secured to the bottom end of the drain conduit 152, whose outlet may be provided with a suitable valve 155. The two orifice plates 138 of the Afront module are provided with orifices in which are disposed Afans 161 mounted on opposite ends of the drive shaft 162 of a motor 163 rigidly mounted in the middle passage 137. The pitches of the fans are such that when the motor is energized, air is drawn inwardly by the fans through the outer end portions of the cooling sections 61 and 62 into the

outer passages

135 and 136 and then inwardly through the orifices 160 into the middle passage 137, and then moved outwardly in opposite directions through the middle or intermediate portions of the two cooling sections. The particular mounting of the motor and the detailed structure of such orice plates is fully -described in the copending application of William E. Lind and Burt J. Mitchell, Ser. No. 405,380, filed Oct. 2l, 1964, and will not, therefore, be described in detail. Electric current is supplied to the motor 163 by a pair of electric conductors (not shown) of a cable which may extend through one of the horizontal braces and the apertures 125 or 128 of the support members which conductors extend to the motor through a suitable aperture in one of the vertical plates 96 or 98.

The

modules

57, 58 and 59 are similar in structure to the front module 56 and, accordingly, their elements have been provided with the same reference numerals, to which the suffixes a, b and c, respectively, have been added, as the corresponding elements of the front module 56.

The drain pans 63 and 63a are connected by a substantially U-shaped connector member which overlaps the adjacent ends of the drain `pans and is secured thereto by the screws 107 which connect the drain pan 63 to the rear support members of the cooling sections of the front module and the s-crews 107a which connect the drain pan 63a to the front support members of the cooling section 61a and 62a of the intermediate section 57. A suitable sealing means is used to seal between the connector member 170 and the drain pan. Similar connector members 171 7 and 172 connect the opposite ends of the drain pans 63 and 63b of the intermediate Imodules 57 and 58 and the drain pans 63b and 63C.

The pan 63e has a rear extension 173 whose forward portion overlaps the rear end portion of the drain pan 63C and is provided with a vertical flange 174 provided with a condensate discharge duct 175. The outer end of the outlet condensate discharge duct may be disposed over a funnel 174a at the upper end of a drain duct 17411 secured to the rear door 25 whose lower end, when the door is closed, is adjacent the upper end of a discharge pipe 174C which may have a reservoir 174d connected to its lower end from which the condensate may be drained when its valve 174e is opened.

The rear end portions of the

tubes

63 and 73 of the cooling section of the front module are telescoped in the flared front end portions 70a and 81a of the tubes 66a and 73a of the cooling section 61a and 62a of the intermediate module 57. The adjacent ends of the tubes of the cooling sections of the

modules

57, 58 and 59 are similarly connected. The rear end portions of the tubes 66e and 73C of the rear module are connected by means of the elbow joints 176 and 177 and connector pipes or conduits 178.

It will be apparent that the refrigerant ows from the expansion valve to each of the tubes 66 of the front module and then flows through the tubes 66a, 66h and 66C, the elbows 176, the pipes 178, the elbows 177, the tubes 73C, 73b, 73a and 73 and the conduit 79 to the exhaust manifold 80.

The motors 163e, 163]; and 163C of the modules 57, SS, and 59 function in the same manner as the motor 163 of the front module to rotate the fans mounted on their shafts to cause them to draw air inwardly through the outer end portions of their cooling sections into their outer passages, thence into their middle passages and then outwardly in opposite directions through the middle portions of their cooling sections.

As many intermediate modules are connected between the front and rear modules as is required for the evaporator unit to be of such length that it will extend through substantially the full length of the chamber 12 of the trailer or truck body in which it is to be mounted.

An electric heater 149 may be mounted in the exchanger for use during a defrost cycle of operation of the refrigeration system to melt ice in the drain pan.

The evaporator unit is secured to the roof 24 of the trailer body by any suitable means, as by

longitudinal angle members

180 and 181 whose

vertical flanges

182 and 183 are secured to the outer flanges of the support members of the cooling sections of the modules by the same screws 122 which secure the side flanges of their covers thereto. The top surfaces of the

horizontal flanges

184 and 185 of the mounting angle members are then disposed in the same plane as the top surface of the cover. The brackets are then secured to the roof in any suitable manner, as by means of the screws 186 which extend into the roof through suitable longitudinally spaced apertures in the flanges.

The refrigeration system is provided with usual well known control means which may include a thermostat in the chamber 12 for causing the refrigeration system to operate in such manner as to prevent the temperature in the chamber from rising above a predetermined value. Such control means include suitable electric controls which cause the motors of the evaporator unit to be placed in operation whenever the compressor is in operation.

When the refrigeration system is in operation, liqueed and cooled refrigerant liquid llows to the expansion valve 55 and then flows through the tubes of the cooling sections in the manner described and absorbs heat from the air being circulated through the cooling sections by the fans driven by the motors 163 of the evaporator unit. The air is drawn inwardly through the outer end portions of each module and is discharged horizontally transversely outwardly in opposite directions through the middle portions of the cooling sections between the orifice plates. Such air, which has been cooled in passing through the cooling sections, moves substantially in the manner indicated by the arrows in FIGURE l perpendicularly outwardly from the middle portions of the cooling sections and transversely relative to the chamber to the side walls. This sheet or curtain of cooled air moving from each side of the evaporator unit spreads or fans out as it moves away from the evaporator unit and approaches the side walls and then flows downwardly along the inner surfaces of the side walls and at least the outer end portions of the front wall and of the doors. lf the cargo is so placed in the chamber that some of the cargo engages the ribs of the walls and the door, the cooled air may ow outwardly of the outer surfaces of such cargo through the vertical passages provided by the ribs. The cooled air sinks or flows downwardly through such passages and enters the outermost passages 47a and 47h. The cool air ows beneath any cargo resting on the runners and through the apertures 46 of runners and may of course flow longitudinally through the passages 47 beneath the cargo. During such flow of the cooled air it absorbs heat from the cargo and also any heat being conducted into the chamber through the trailer body. As the air which is thus warmed approaches the transversely middle portion of the trailer, it flows upwardly through the transversely middle portion of the chamber 12 and spreads longitudinally into two streams as it approaches the upper portion of the chamber and is drawn through the outer end portions of the cooling sections of each module to its outer passages.

The cooled air, of course, ows downwardly through any passages or interstices of the cargo in the transversely outer portions of the chamber and the slightly warmed air flows upwardly through any such passages of the cargo in the transversely middle portions of the chamber. This circulation of air produced by each module provides a substantially tubular circulation or cell of flow of air, as seen in FIGURE 3. The several modules thus establish a plurality of longitudinally aligned cells of air ow in the chamber throughout its full length and a very uniform circulation of substantially cool air of very small temperature gradient between any two locations within the chamber is achieved thus enabling all portions of the cargo to be maintained at a substantially uniform and constant temperature.

It will be apparent that in contradistinction to the conventional evaporators for trailer bodies of this type which are mounted on the front wall adjacent the top of the chamber and blow the cooled air in a longitudinal direction rearwardly through the chamber, and in some instances through longitudinal ducts mounted in the trailer body, and draw the air from the bottom upwardly to the evaporator at the front end thus providing a substantially longitudinal horizontal circulation of air throughout the body, the evaporator unit embodying the invention pro vides a substantially transverse horizontal flow of air through the chamber.

It will further be seen that this transverse horizontal ow of air does not tend to pull air in through the rear end of the truck when the rear doors 25 and 26 are opened, since there is relatively little longitudinal circulation of the air through the chamber.

It will be noted that the outer passages of the modules are substantially one quarter of the length of the middle passage thereof so that the rate of flow of air through all portions of the cooling sections of each module is substantially uniform.

It will also be apparent that while each module has been shown as having a single motor which drives the two fans of its orifice plates, individual motors can be provided for each fan.

It will further be seen that, if desired, the rear end plate 98 of the front module, the front end plate 96C of the rear module and the rear and front plates of the intermediate modules could be removed. In this case, suitable plates would be connected to the outer support -members of adjacent support members of adjacent modules to close the gaps therebetween so that the evaporator unit would have one continuous passage therethrough with the orifice plates and fans of the modules still causing substantially the described cellular or tubular circulation of the air to result.

It will now be seen that the evaporator unit secured to the roof of the body extends substantially the length of the chamber occupies a relatively small volume ofspace, being, for example, approximately six inches high and eight inches wide, so that a relatively large proportion of the full capacity or volume of the chamber may be utilized for the storage of cargo therein.

It will further be seen that since the tubes of cooling sections of the evaporator unit are of relatively great length, a single vertical 4row of tubes at each side of the unit is sufficient to provide the required heat transfer from the air which is circulated through a relatively great area of the cooling sections thus providing for optimum eiliciency of operation of the fan motors and the compressor as compared to conventional evaporator units whose cooling sections have a plurality of rows of tubes past which the `air is moved progressively and which provide a relatively small area for ow of air therethrough.

It will further be seen that the modular structure of the evaporator unit provides for economy of manufacture since any number of the identical intermediate modules may be connected between the front and rear modules as required to provide a unit of desired length for a particular installation.

It will further be seen that while the evaporator unit has been illustrated and described for use in cooling the chamber of a mobile trailer body, it may be used to cool any chambers, such as food storage warehouse chambers or rooms, wherein a constant temperature of relative low gradient between any two locations must be maintained.

It will further be seen that, if desired, the direction of circulation of air through each module could be reversed, i.e., the fans could be rotated in such manner as to cause air to be drawn inwardly through the middle portions of the cooling sections into the middle passage and then outwardly through the outer end portions of the cooling sections.

It will now be seen that a new and improved evaporator unit has been illustrated and described which includes a plurality of air circulating means which, when the unit is mounted adjacent the top of an elongated chamber and extends longitudinally therethrough, provide a plurality of longitudinally aligned cells or paths of air flow each of which includes a top horizontal transversely outward portion, an outer downward vertical portion, a bottom horizontal transversely inward portion and an inner upward vertical portion.

It will further be seen that a new and improved method of circulating air in an elongate chamber has been illustrated and described which provides for a low temperature gradient -between any two locations within the chamber.

Referring now to FIGURES 7 through 14 of the drawings, the refrigeration system 200 embodying the invention includes an evaporator unit 201 which functions to maintain the

separate compartments

202 and 203 of a trailer body 11a at the same or different predetermined temperatures. The trailer body has a partition 204 which divides its interior into the two compartments. The trailer body is in all other respects similar to the trailer body 11 and, accordingly, its various components have been provided with the same reference numerals, to which the suiiix a has been added, as the corresponding elements of the trailer body 11.

The evaporator unit 201 includes a front module 206 located in the front compartment 202 and modules 207 and 207e located in the compartment 203.

The

evaporator unit modules

206, 207 and 20711 are of a preferred construction providing greater eiciency and flexibility of operation of the refrigeration system than the modules illustrated in FIGURES l through 6.

The module 207 includes a pair of longitudinally extending parallel laterally spaced cooling

sections

210 and 211 which extend downwardly into a bottom drain pan 212. The cooling section 210 includes a plurality of vertically spaced longitudinal tubes 214 which extend through suitable apertures in vertical spaced cooling ns 215, the rear and front end plates 216 and 216:1, a central divider plate 216b and orifice plates 219 and 219a. The ns are rigidly secured in a good heat conducting relationship to the tubes as by expanding the tubes after they have been inserted through the fins and the plates. The rear end of the lowermost bottom tube 214 is connected by a conduit 221 to a distributor 222 in turn connected to the discharge outlet of an expansion valve 224 The front end of the top tube is connected to one inlet of a T-connector or fitting 225 by a conduit 226. The rear ends of adjacent tubes, except the bottom tube, are connected by substantially U-shaped tube connectors 227 while the forward ends of adjacent tubes, except the top tube, are connected by similar U-shaped tube connectors 228. The tubes and tube connectors, which may be soldered at their connections, thus form a serpentine coil with the refrigerant flowing from the distributor to the bottom tube 214 and then through such coil to the T- connect-or 225.

The other cooling section 211 similarly has a plurality of vertically spaced longitudinal tubes 229 which extend through apertures in vertical spaced cooling fins 230 and the plates 216, 216:1, 216b, 219 and 21911. The rear end of the bottom tube is connected to the distributor 222 by a connector conduit 231 while the front end of the top tube is connected to the other inlet of the T-connector 225 by a conduit 232. The rear ends of adjacent tubes, except the bottom tube, are connected by U-shaped tube connectors 234 and the front ends of adjacent tubes, except the top tube, are connected by similar tube connectors 235.

The end plate 216 has a top rearwardly extending flange 237 which is adapted to abut the roof of the trailer body and rearwardly extending downwardly convengent side anges 238 and 239 whose lower end portions extend inwardly of the

top side portions

240 and 241 of the drain pan 212 and are rigidly secured thereto in any suitable manner as by the bolts 243. Substantially triangular hanger brackets 245 are secured to the end plate 216 by means of bolts 247 and have top horizontal flanges 249 which are adapted to abut the roof -of the trailer body and be rigidly secured thereto by bolts 250 extending upwardly through suitable apertures in the hanger brackets. The rear end plate has a rearwardly extending bottom flange 252 which is spaced above the central bottom portion 253 of the drain pan.

Filler plates

254 and 255, whose top flanges 257 and 25S, respectively, abut the bottom flange 252 of the rear end plate and are secured thereto by means of suitable clips or clamps 260, extend between the lower end of the rear end 4plate and the drain pan. A large diameter exhaust conduit 262 and a small diameter inlet conduit 263 extend longitudinally through the pan and between the two filler plates. The exhaust and inlet conduits are soldered or brazed to one another throughout substantially their full lengths to facilitate the transfer of heat lfrom the refrigerant flowing through the inlet conduit to the inlet 264 of the expansion valve 224, t-o which the inlet is connected by the branch duct 265, to the refrigerant flowing from the coils of the cooling sections through the exhaust conduit 262, the outlet of the T-connector 225 being connected to the exhaust conduit by the branch -duct 266. The exhaust and inlet conduits are held against movement relative to the rear end plate by a clamp 267 whose ends are rigidly secured to the bottom flange 252 of the end plate by bolts 268.

l The expansion valve 224 is rigidly secured to the rear 1 1 end plate by a clamp 270 whose opposite ends are rigidly secured to the rear end plate by means of bolts 271 which extend through suitable apertures in the end plate. The hanger brackets and the rear end plate are provided with suitable aligned apertures through which the electric conduit 248 extends.

The tfront end plate 21611 and the central divider plate 21617 are similar in structure to the rear end plate 116, and, accordingly, the elements of the rear end plate and of the divider plate have been provided with the same reference numerals, to which the suffixes a and b, respectively, have been added, as the corresponding elements of the rear end plate. The flanges of the front end plate 21611 extend forwardly, instead of rearwardly as in the case of the flanges of the rear end plate 216, and certain apertures present in the rear end plate, as for ex ample those which are required for the passage of the bolts 271 which secure the clamp 270 to the rear end plate, are not present in the front end plate and the divider plate. Filler plates 25411 and 25511, are secured to the bottom iiange of the front end plate and filler plates 254b and 25511 are secured to the bottom fiange of the divider plate.

A front orifice plate 219 positioned between the divider plate and the front end plate is also similar to the front end plate differing therefrom in having a central aperture 280 in which is positioned a fan or blower 281 mounted on the drive shaft 282 of an electric motor 283. The motor is rigidly secured to the orifice plate by means of a suitable mount 284 whose spaced support rods 285 extend through suitable apertures of the -orifice plate and are rigidly secured thereto by means of nuts 286 threaded on the support rod on opposite sides of the orifice plate. Washers 287 are interposed between the nuts and the orifice plate.

Electric conductors

288 and 289 extend from the junction box 290, connected in the electric conduit 248, downwardly between the cooling section 211 and the side of the drain pan and then upwardly to the electric motor.

The orifice plate 119 has a top tiange 291, side tianges 292 and 293, and a bottom ange 294. Filler plates 254C and 255C are connected to the bottom flange.

The orifice plate 21911 is similar to the orifice plate 219 and accordingly its elements have been provided with the same reference numerals, to which the suffix a has been added, as the corresponding elements of the orifice plate 119. A fan 28M positioned in the orifice of the plate is rigidly secured to the drive shaft 28211 of the motor 28311 secured by means of a mount 28411 to the lorifice plate in the same manner as the motor 283. Electric conductors 28811 and 28911 extend to the motor from the junction box 29011 connected in the electric conduit 248. The pairs of

conductors

288 and 289, and 28811 and 28911 are connected to the

main conductors

295 and 296 which extend through the electric conduit 248, the junction boxes 290 and 29011 and the

end boxes

297 and 298 connected to the opposite ends of the electric conduit.

It will be apparent that the plates of the module 207 divide the space between the roof of the trailer body and the drain pan 212 and between the two cooling

sections

219 and 211 into front and

rear passages

301 and 302 and

middle passages

303 and 304. The pitch and direction of rotation of the iront fan 281 is such that the air is drawn inwardly through the portions of the cooling

sections

210 and 211 between the Kfront end plate 21611 and the orifice plate 219 into the end passage 301, then moved through the orifice 280 into the middle passage 303 and then outwardly through the 4portions of the cooling sections between the orifice plate 219 and the divider plate 216b. Similarly, the pitch and direction of rotation of the rear fan 28111 is such that air is drawn inwardly into the end passage 302 through the portions of the cooling sections between the rear end plate 216 and the orifice plate 21911, through the orice of the orifice plate 21911 into the middle passage 304, and then outwardly through the portions of the cooling sections between the divider plate 216b and the orifice plate 219.

The exhaust and inlet conduits extend below the end, divider and orifice plates of the mandrel and are of greater length than the drain pans so that opposite end portions of the exhaust and inlet conduits extend longitudinally outwardly of opposite ends of the drain pan. The branch duct 266 extends rearwardly from the T-connector 225 through suitable aligned apertures in the plates and its rear downwardly extending portion 306 is connected to a tubular coupling 351 connected to the rear end of the exhaust conduit 262.

A bypass conduit 308 extends through suitable apertures in the end, orifice and divider plates and is connected adjacent its rear end to the manifold 222 by means of a branch duct 309 and a T-connector 310.

The filler plates, the end, orifice and divider plates, and the drain pan have various small spaces therebetween so that adjacent passages 301-304 are not completely separated from each other. The lower portions of the cooling sections also are spaced somewhat from the sides of the pan. Such spaces between these elements of the module do not appreciably or deleteriously alter the paths and rates of ow of air through the cooling sections and the passages of the module in the paths described above. If desired, of course, suitable gaskets or other closure means may be provided to close such spaces which are not provided in the module 207 in order to facilitate assembly of the module and decrease its cost.

The module 20711 is identical in structure to the module 207 and accordingly its elements have been provided with the same reference numerals, to which the suffix a has been added, as the corresponding elements of the module 207.

The two adacent ends of the end pans 212 of the modules 207 and 20711 are connected by a connector member 312 rigidly secured to the drain pans by means of rivets 311. The drain pan 212 of the rear module 20711 has a rear extension 313 also secured to the drain pan 212 whose rear vertical side is provided with a condensate discharge duct 315 which opens to the drain pan. The outer end of the outlet condensate duct may be disposed over a tunnel 317 at the upper end of a drain duct 318 secured to the rear door 25a of the trailer body 11a. The lower end of the drain duct, when the door is closed, is adjacent the upper end of a discharge pipe 319 which may have a reservoir 320 connected to its lower end from which the condensate may be drained when its valve 321 is open.

The module 206 is similar in structure to the module 207 and, accordingly, its elements have been provided with the same reference numerals, to which the sufiix b has been added, as the corresponding elements of the module 207. The module 206 is employed wherever a short module is needed, for example, if the length of a trailer body or other compartment in which the evaporator unit 201 is disposed is of such length that the use of only the modules 207 would leave too great a space at one end or the other of the unit and an end wall of the trailer body or if, as in the illustrated installation in FIGURE 14, one of the compartments 202 which is to be maintained at a lower temperature than the compartment 203 is of shorter length than the module 207.

The pitch and direction of rotation of the fan 281b is such that air is drawn into the passage 330 through the portions of the cooling sections 210!) and 211b between the front end plates 2161115 and the central orifice plate 219b, moved through the orifice of the orifice plate into the passage 331 between the orifice plate and the rear end plate 216b and then outwardly through the portions of the cooling sections between the orifice plate and the rear end plate.

If the module 206 is the front module of the evaporator unit, as in the evaporator unit 201, its drain pan 212b is provided with a front extension 232 whose rear portion overlaps the front end portion of the drain pan 212b and is secured thereto by rivets 311. The front pan extension 13 has a vertical flange 334 through which the upper end of the condensate discharge duct 335 opens to the pan. The discharge duct extends downwardly along the front wall 21a of the trailer body and has a reservoir 336 at its lower end from which the condensate may drain when its valve 337 is open.

The front ends of the exhaust, inlet and

bypass conduits

262b, 263b, and 308b of the front module 206 are connected to

conduits

341, 342, and 343, respectively, which extend forwardly through suitable apertures of the vertical flange 334 and then through suitable apertures of the trailer front wall to the compressor and condenser assembly 50a of the refrigeration system 200 which is mounted on the trailer body front wall.

The rear end of the drain pan 212b of the front module is connected by a pan connector 346 to the front end of the drain pan 212 of the module 207. The drain pan connector 346 extends through a suitable aperture in the partition 205. The openings between the rear end plate 216b of the front module and the rear end plate 216 of the module 207 above the sides of the pan connector 346 may be closed by suitable panels 347 secured by bolts or the like to the adjacent side flanges of these end plates. The aperture in the partition 205 preferably conforms to the configuration of the drain pan connector 346 and the panels 347 to prevent flow of air between the

compartments

202 and 203. If desired, a suitable gasket may be provided to seal between the evaporator unit and the partition. The evaporator unit 201 of the refrigeration system 200 may include as many long modules 207, and if necessary a short module 206, as are necessary to make the unit of such length as to extend substantially the full length of the trailer body.

If the evaporator unit has a front short module 206, a middle module 207 and a rear module 2li-7a, the rear end of the exhaust conduit 262b of the module 206 is connected to the front end of the conduit 262 of the middle module 207 by a T-connector 351b which also connects the conduit 266b to the exhaust conduit 262b. The rear end of the exhaust conduit 262 of the middle module 207 is connected to the front end of the exhaust conduit 262a of the rear module 207a by the T-connector 351 which also connects the conduit 266 to the exhaust conduit 262. The rear end of the exhaust conduit 262a is closed by a suitable plug or closure. The rear end of the inlet conduit 263b of the front module 206 is connected to the front end of theinlet conduit 263 of the middle module 207 by a connector 353-b which is connected to a T-connector 3541) which connects the conduit 265b to the inlet conduit 26317. The rear end of the middle module inlet conductor 263 is similarly connected to the front end of the rear module inlet conduit 26311 by a similar connector 353 which extends between the T-connector 354 and the front end of the inlet conduit 263a. The rear end of the inlet conduit 26301 is closed by suitable closure or plug.

The bypass conduits 308 and 30811 of the front and mid-dle modules are similarly connected by a connector 355b which connects the T-connector 310b to the front end of the bypass conduit 308 of the module 207. The rear end of the bypass conduit 308 is connected by a similar connector 354 to the front end of the conduit 308a of the rear module 207a. The rear end of the T-connector (not shown) of the bypass conduit 30811 is of course closed by suitable plug or closure.

It will now be apparent that the inlet conduits, the exhaust conduits, and the bypass conduits of the modules of the evaporator unit are connected in series to constitute main inlet, exhaust and bypass conduits A, B and C, respectively, that the cooling coils of the modules are connected in parallel across the main inlet and exhaust conduits A and B by means of their individual expansion valves and their

conduits

265 and 266 and that the cooling coils are also connected in parallel across the main 14 exhaust and bypass conduits B and C by means of their

individual conduits

309 and 266.

The expansion valves 224 of the modules of the evaporator unit 201 are preferably of a well known type whose operation is regulated in accordance with the temperature and pressure of the exhaust refrigerant uid flowing from the cooling

sections

210 and 211 of their modules. The temperature of the refrigerant fluid flowing from the coils of the cooling sections of each module is sensed by a fluid filled temperature bulb 360 connected to a diaphragm chamber of the expansion Valve by a conduit 361, the pressure of such fluid being exerted on one side of a diaphragm, not shown, of the expansion valve tending to open the expansion valve. The pressure of the refrigerant liuid in the conduit 266 downstream of the temperature bulb communicated to the other side of the expansion valve diaphragm through a conduit 362 tends to close the Valve. The expansion valves being of Well known structure and mode of operation will not be described in greater detail.

The conduits 265 which connect the main inlet conduit A to the inlets of the expansion valves 224, 224a and 22412 of the modules have solenoid valves 363 connected thereto which are operable by thermostat switches 364. The thermostat switch of each valve may be preset to cause the solenoid valve to close when the temperature sensed thereby drops below a predetermined value. For example, the thermostat switch 364b in the compartment 202 may be set to cause closure of the expansion valve 224b when the temperature in the compartment 202 drops to a low temperature, for example 0 Fahrenheit and lthe thermostat switches 364 and 364a may be set to close when the temperature at their thermostat switches drops to 35 Fahrenheit.

The refrigeration system 200 of which the evaporator unit 201 is a component, may be of any suitable desired type, as for example the reversible type illustrated in FIGURE 13 having means for delivering liquelied and cooled refrigerant fluid to the main inlet conduit A and exhausting evaporated and heated refrigerant iiuid from the main exhaust conduit B or for delivering hot compressed refrigerant fluid to the main exhaust conduit B and withdrawing liquefied and cooled refrigerant gas from the main bypass conduit C. The refrigerant system includes a compressor 365 driven by a suitable prime mover, not shown, a condenser 366 through which ambient air may be circulated by a suitable blower or fan means, not shown, an expansion valve 365 for controlling the llow of cooled and liquefied refrigerant fluid into the condenser during the defrost cycle of operation of the system, and a four-way valve 368. The four-way valve has a housing 369 in which a shuttle or bobbin 370 is movable between a first position illustrated in FIGURE 13 in which the Valve permits flow of hot compressed refrigerant fluid from the discharge outlet 371 of the compressor to the condenser and of the heated and evaporated liuid from the conduit 341 to the suction inlet 372 of the compressor and a second position in which the valve permits flow of the hot compressed refrigerant fluid from the discharge outlet 371 to the conduit 341 and the flow of evaporated refrigerant fluid from the condenser to the suction inlet 372. The shuttle of the valve may be moved between its first and second positions by a suitable solenoid 375 controlled by a thermostatic switch 376 responsive to the temperature adjacent one of the cooling sections and which closes when a predetermined amount of frost or ice covers such cooling section.

The valve housing has a pair of

ports

377 and 378, which are in communication when the shuttle is in the position illustrated in FIGURE 13, to permit ow of the hot compressed gas from the discharge outlet 371 of compressor through the conduits 380, which connects the discharge outlet to the port 378 to the conduit 381 which connects the port 377 to one end of the condenser coil 382. The opposite end of the condenser coil is connected through a T-connector 384, a conduit 385, a check valve 386, and a conduit 387 to the inlet 388 of a receiver 389. The outlet tube 390 of the receiver, which opens to the interior of the receiver adjacent the bottom end thereof, is connected by a connector 391, a conduit 392, a dehydrator 393, a conduit 394 and a moisture sight glass 395 to the conduit 342.

The valve housing also has a pair of

ports

397 and 398 which are in communication when the valve is in the position illustrated in FIGURE 13 to permit flow of the evaporated refrigerant fluid from the conduit 341 to the suction inlet of the compressor, the conduit 341 being connected to the valve housing to communicate with the port 397 and the port 398 being in communication with the suction inlet of the compressor through a conduit 399.

When the valve is in its opposite position illustrated in FIGURE 14, the

ports

378 and 397 are in communication to permit the hot compressed gas to flow from the discharge outlet 371 of the compressor through the conduit 341, the main exhaust conduit B, the conduits 266, T-connectors 225 and the coils of the cooling

sections

210 and 211 of the three modules, the conduits 309 and the connectors 310 of the modules to the main bypass conduit C, the conduit 343, the check valve 402 and the conduit 403 to the inlet 405 of the condenser expansion valve 367. The outlet 406 of the condenser expansion valve is connected through the T-connector 384 to one end of the condenser 366. The condenser expansion valve controls the flow of the liquid refrigerant fluid to the condenser coil 382 in accordance with the temperature of the refrigerant fluid flowing from the condenser coil 382 to the conduit 381, the expansion valve having a diaphragm to which fluid pressure from the temperature bulb 407 is communicated through a conduit 408 which tends to open the valve. The valve allows a greater rate of flow of the refrigerant fiuid to the condenser coil when the temperature of the refrigerant flowing from the condenser coil rises. The vaporized refrigerant flows from the condenser through the conduit 381 to the inlet 372 of the compressor when the valve is in the position illustrated in FIGURE 14 the

ports

377 and 398 then being in communication through the central longitudinal passage 410 of the shuttle 370 of the valve.

The check valve 386 prevents flow of fluid from the receiver to the conduit 385 during the defrost cycle of operation and the check valve 402 prevents flow of refrigerant fluid from the conduit 343 to the inlet of the condenser expansion valve during the normal or cooling cycle of the operation of the system 200.

In use, during the cooling cycle of operation of the refrigeration system 200, the compressor 365, the condenser and the receiver cooperate to supply cool liquid refrigerant fluid to the main inlet conduit A and the fans of the modules preferably are in continuous operation.

As long as the temperature in the front compartment 202 is above Fahrenheit, the solenoid valve 363b is open and the expansion valve 224b allows refrigerant uid to flow to the coils of the cooling sections 210b and 211k. The rate of flow of the refrigerant fiuid through the expansion valve varies with the temperature and pressure of the refrigerant fluid flowing from these coils through the conduit 266b which in turn vary with the temperature of the air being circulated through the cooling sections, the higher the temperature of the circulated air the higher the temperature of the fluid flowing through the cooling sections and the greater the rate of flow of refrigerant fluid through the expansion valve. If the temperature in the compartment drops to below 0 Fahrenheit, the thermostat switch 364b will close the solenoid valve 363b and then will again cause it to open when the temperature rises above 0 Fahrenheit.

Each of the expansion valves of the modules 207 and 207a and their associated thermostat switches 364 and 364a and solenoid valves operate similarly but independently in the same manner to maintain substantially constant the temperature of the air being circulated through its cooling sections. For example, if the temperature of the air in the rear end of the compartment 203 which is being circulated by the fans of the rear module 207a tends to rise due to the fact that the doors have been opened for loading or unloading of cargo and cold air escapes from the compartment and some warm air enters into the compartment at its rear end, the temperature of the air being circulated in the front portion of the compartment by the fans of the middle module 207 does not tend to rise since the circulating air cells of the two modules tend to remain separate. As a result only the expansion valve of the rear module will increase the rate of flow of the refrigerant fluid therethrough to its cooling sections.

The compressor of course is provided with the usual controls responsive to the pressure at its suction inlet which permit operation of the compressor only as long as the pressure at its suction inlet is above a predetermined value.

It will thus be apparent that by the use of modules of an evaporator unit comprising a plurality of modules each having its own expansion valve, a very uniform temperature may be maintained throughout a compartment 203 of relatively great length and that if one or more of the modules of the refrigeration evaporator unit 201 are in different compartments it is possible to maintain one compartment at a different temperature than the other.

The inlet and exhaust conduits A and B being in good thermal relation with each other constitute a heat exc-hanger so that heat is absorbed by the refrigerant fluid flowing in the main exhaust conduit B to the inlet of the compressor from the liquid refrigerant flowing through the inlet conduit A to the expansion valves thus increasing the efficiency of operation of the refrigeration system and also tending to prevent any liquid refrigerant from reaching the inlet of the compressor.

The solenoid 375 is actuated to move the shuttle 37 to the position illustrated in FIGURE 14 to initiate the defrost cycle when the cooling section 211 of the module 207 becomes coated excessively with frost or ice, which condition is sensed by a suitable temperature bulb 412, located adjacent the cooling section 210, of the thermostatic switch 376. During such defrost cycle of operation, the hot compressed refrigerant fluid flows directly from the compressor outlet to the main discharge conduit B which extends through the bottom of the drain pan, and in flowing through the main discharge conduit B melts the ice or frost present in the bottom of the drain pan and then in flowing from the main discharge conduit B through the conduits 266 and the cooling coils of the cooling sections of the three modules and melts the frost or ice present thereon. The liquid refrigerant fluid iiows from the coils of the cooling sections through the bypass conduit and the conduit 309 to the condenser expansion valve 367 which permits the liquefied refrigerant fluid to evaporate and expand in the condenser coil 382 and then flow back to the compressor suction inlet 372. When the frost or ice is melted off the cooling sections, the thermostatic switch opens and causes the solenoid to move the fourway valve back to the position illustrated in FIGURE 13. The solenoid controlled four-way valve and the thermostat switch being of usual well known structure and operation are not described in greater detail.

While a particular reversible refrigeration system has been illustrated and described in connection with the use of the evaporator unit 20 embodying the invention, it will be apparent that the evaporator unit may be employed in various other refrigeration systems employing different means for reversing the fiow of refrigerant fluid through the coils of the cooling section. If desired, a refrigeration system of the non-reversible type may also be employed in which case defrosting of the modules or the heating of the air being circulated by the modules may be accomplished by suitable electric heating elements which 17 would be located in the drain pan and adjacent the cooling sections.

It will be apparent that if the temperature to be maintained in the compartment by the evaporator unit 201 is to be relatively high so that no frost or ice will form on the cooling sections so that provision for reverse flow of hot compressed refrigerant fluid, i.e., the defrost cycle, is not needed, the bypass conduit C and the conduits connecting it to the expansion valves are not needed and may be left out of the unit.

It will also be apparent that the evaporator unit or heat exchanger 201 may be employed to heat two compartments instead of merely cooling them if desired.

It will further be seen that the evaporator unit 201 illustrated in FIGURES 7 through 13 which employs a plurality of modules having the coils of its cooling sections connected in parallel across the main inlet and exhaust conduits through individually controlled expansion valves is preferred over the evaporator unit illustrated in FIGURES l through 6 which employs a plurality of modules the coils of whose cooling sections are in effect connected in series `and has only a single expansion valve for controlling the flow of refrigerant gas therethrough since the latter evaporator unit if Iused in a compartment of relatively great length may cause the temperature in one end of the compartment remote from the doors thereof to be considerably lower than the temperature in the end adjacent the doors if the doors are opened frequently.

The foregoing description of the invention is explanatory only, and changes in the details of the construction illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A method of maintaining the temperature in a chamber substantially uniform throughout the chamber, said method comprising: drawing air transversely relative to said chamber to a plurality of locations spaced longitudinally in said chamber along substantially the full length of said chamber; and simultaneously with the movement of air to said locations forcing air away transversely from a plurality of second locations spaced longitudinally in said chamber, each of said second locations being between a pair of the first mentioned locations, said locations being in the top central portion of said chamber.

2. The method of'claim 1, and simultaneously with the passage of air to `and from said locations altering the temperature of said air.

3. The method of claim 1 wherein air is caused to liow transversely outwardly in opposite directions from said second locations in the upper portion of the chamber, then downwardly in the transversely outer portions of said chamber, then transversely inwardly in the bottom portions of the chamber, and then upwardly in the transversely middle por-tions of said chamber and to said first locations; and simultaneously with the passage of air to and from said locations cooling the air being forced away from said second locations.

4. A method of changing the temperature of air in an elongated vehicle body comprising: drawing air transversely inwardly relative to said body to a plurality of locations spaced longitudinally along substantially the full length of said body and located adjacent `the ceiling of said body and spaced between the side walls of the body; simultaneously with -the passage of air to said locations, forcing air away transversely from a plurality of second locations each disposed between a pair of the first-mentioned locations to cause air to ow transversely and horizontally beneath the ceiling of said body, down the side walls of said body transversely and horizontally across the floor of said body and lupwardly in t-he transversely middle portions of said chamber to said first locations; and simultaneously with the passage of air to and from said locations altering the temperature of said air.

5. A heat exchanger including: a plurality of heat exchanger assemblies each having a pair of parallel spaced heat exchanger means providing an elongate space therebetween; air moving means in each of said exchanger assemblies for simultaneously circulating air lbetween said space and the exteriors of said heat exchange means in opposite directions through different portions of each said heat exchanger means and transverse to the length of said heat exchanger means; and means for coupling said pairs of heat exchanger means of said assemblies together to form a substantially continuous elongate heat exchanger.

6. The heat exchanger of claim 5, wherein said assemblies are connected to one another in end to end relationship; and means dividing said space of each of said heat exchanger assemblies into a plurality of longitudinally aligned passages, said heat exchanger rneans permitting the flow of air therethrough between said passages and the exterior of said heat exchanger, each of said assemblies having air moving means associated with said dividing means for moving air between passages on opposite sides of said dividing means.

7. The heat exchanger of claim 6, wherein each of said heat exchanger means comprises a cooling coil, and wherein said heat exchanger includes conduit means for circulating a refrigerant fluid through said cooling coils of said heat exchanger means.

8. The heat exchanger of claim 7, wherein said conduit means includes a main inlet conduit and `a main exhaust conduit extending substantially the full length of said heat exchanger, said cooling coils of said heat exchanger assemblies being connected in parallel Iacross said main inlet and exhaust conduits.

9. The heat exchanger of claim 8, wherein each of said heat exchanger assemblies includes a refrigerant fluid expansion valve connected between said main inlet conduit and one end of each of the cooling coils of each of its heat exchanger means, the other ends of the cooling coils being connected -to said main exhaust conduit.

10. The heat exchanger of claim 9, and a main bypass conduit extending substantially the full length of said heat exchanger, and means for selectively connecting said one end of each of the cooling coils of e-ach of said heat exchanger means to said bypass conduit.

11. The heat exchanger of claim 10, and means for selectively supplying said main inlet conduit with cool liquid refrigerant fluid and withdrawing heated evaporated refrigerant fluid from said exhaust conduit and supplying hot compressed gaseous refrigerant fluid to said main exhaust conduit `and withdrawing cooled liquefied refrigerant Huid from said bypass conduit.

12. The heat exchanger of claim 8, wherein said main inlet and exhaust conduits are in good heat conducting relationship throughout substantially their full lengths whereby heat is `absorbed from liquid refrigerant fluid owing to said coils through said inlet conduit by `the efrigerant fluid flowing through said main exhaust conuit.

13. The heat exchanger of claim 12, wherein said heat exchanger includes drain pan means extending below said heat exchanger means and said main exhaust conduit extends adjacent the bottom of said drain pan.

14. A vehicle including: a lbody providing an elongate chamber for holding cargo, said body having top, bottom, side and end walls; -a plurality of longitudinal runners on said bottom wall to space cargo in said body above said bottom wall, said runners having transverse apertures therethrough to permit the ow of air therethrough transversely of said body, at least said side walls having internal vertical ribs providing vertical inwardly opening air passages; ya heat exchanger extending longitudinally substantially the full length of said body adjacent said top wall of said body and between and spaced from said side walls, said heat exchanger having a pair of longitudinal parallel transversely spaced heat exchanger means through which air is movable and which provide a longitudinally'extending space therebetween; and a plurality of air moving means longitudinally spaced -between said heat exchanger means for simultaneously circulating air in opposite transverse directions through different portions of each of said heat exchanger means between said space and the exteriors of said heat exchanger means.

15. The vehicle of claim 14, wherein said heat exchanger means define opposite vertical sides of a longitudinal space of said heat exchanger and wherein said heat exchanger includes divider means dividing said space into a plurality of longitudinally aligned passages, and air moving means associated with said divider means for moving air inwardly in opposite transverse directions through a plurality of longitudinally spaced first portions of said pair of heat exchanger means and outwardly in opposite transverse directions through second portions of said pair of heat exchanger means located between said first portions, said heat exchanger means cooling air being moved therethrough by said air moving means and establishing a plurality of transversely aligned pairs of cells of air flow in said chamber, the air in each of said pairs of cells of air flowing transversely outwardly in upper portions of said chamber toward the side walls in opposite transverse directions, downwardly in the transversely outer portions of the chamber, transversely inwardly in opposite directions along the lower portions of the chamber, and upwardly through transversely middle portions of the chamber.

16. The vehicle of claim 15, wherein said heat exchanger has means for individually controlling the cooling of air in at least some of said pairs of air cells.

17. A heat exchanger including: a pair of parallel spaced cooling sections each having a refrigerant flow coil, said cooling sections permitting flow of air therethrough; a drain pan extending below said cooling sections, said drain pan and said cooling sections defining an elongate chamber; a pair of end plates and at least one plate spaced between said end plates extending perpendicularly to and between said cooling sections dividing said chamber into a plurality of passages; air moving means associated with said one of said plates for moving air from one passage to an adjacent passage; a refrigerant inlet conduit and refrigerant exhaust conduit extending through said drain pan longitudinally outwardly of said end plates, and means connecting coils of said cooling sections across said inlet and exhaust conduits.

1-8. The heat exchanger of claim y17, wherein Said last mentioned means includes an expansion valve connected between said inlet conduit and the coils of said cooling sections.

19. The heat exchanger of claim 18, wherein said heat exchanger includes a by-pass conduit extending longitudinally between said cooling sections, and means for selectively connecting said by-pass conduit to one end of the coil of each of said cooling sections, the other ends of the coils of said `cooling sections being connected to said exhaust conduits.

20. The heat exchanger of claim 19 wherein when said heat exchanger is in use as an evaporator of a refrigeration system, liquid refrigerant fluid flows rearwardly through substantially the full length of said inlet conduit to said expansion valve and refrigerant fluid from the coils of said cooling sections flows forwardly through substantially the full length of said exhaust conduit, said inlet and exhaust conduit being secured in good heat transfer relationship to one another whereby heat is absorbed by the refrigerant fluid flowing in said exhaust conduit from refrigerant fluid flowing in said inlet conduit.

21. The heat exchanger of claim 20 wherein when said heat exchanger is in use as a condenser of a refrigeration system hot compressed refrigerant fluid flows rearwardly through substantially the full length of said exhaust conduit to the coils of said cooling sections and from the coils forwardly through substantially the full length of said by-pass conduit.

References Cited UNITED STATES PATENTS 2,053,395 9/1936 Dodge 62-414 2,149,382 3/1939 Anderson 62-414 2,203,814 6/1940 Clements 62-414 2,211,568 8/1'940 Henny 62-414 2,241,579 5/1941 Bergstrom 62-419 2,460,150 1/ 1949 Schupp 62-4 2,474,069 6/1949 Silvera 62-419 2,619,803 12/1952 Doering 62-414 2,678,546 5/1954 Campbell 62-414 2,871,677 2/ 1959 Bradfield 62-419 2,882,701 4/1959 Nelson 62-239 WILLIAM J. WYE, Primary Examiner.