US3798920A

US3798920A - Air conditioning system with provision for reheating

Info

Publication number: US3798920A
Application number: US00303179A
Authority: US
Inventors: R Morgan
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 1972-11-02
Filing date: 1972-11-02
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26

Abstract

An air conditioning system including a refrigeration unit comprising a compressor, a condenser, thermal expansion means and an evaporator are connected together to form a closed circuit. A reheat coil is provided downstream of the evaporator and upstream of the space being conditioned by the system. When reheat is required, a mixture of vaporous and liquid refrigerant is supplied to the reheat coil to pass in heat transfer relation with the conditioned air being supplied to the space so as to reheat the air subsequent to its having been cooled and dehumidified by passing in heat transfer relation with refrigerant flowing through the evaporator. Dehumidified air is provided at a temperature level that will not cause the space to be overcooled.

Description

United States Patent [191 Morgan AIR CONDITIONING SYSTEM WITH PROVISION FOR REHEATING Primary Exqminer-William J. Wye Attorney, Agent, or Firm-Barry E. Deutsch Mar. 26, 1 974 5 7 ABSTRACT An air conditioning system including a refrigeration unit comprising a compressor, a condenser, thermal expansion means and an evaporator are connected toget'her to form a closed circuit. A reheat coil is provided downstream of the evaporator and upstream of.

the space being conditioned by the system. When reheat is required, a mixture of vaporous and liquid refrigerant is supplied to the reheat coil to pass in heat transfer relation with the conditioned air being sup-.

plied to the space so as to reheat the air subsequent to its having been cooled and dehumidified by passing in heat transfer relation with refrigerant flowing through the evaporator. Dehumidified air is provided at a temperature level that will not cause the space to be over cooled.

2 Claims, 2 Drawing Figures 22-\ 27\ 2 44\ 42 pix Q \30 4o PATENTEU MR 2 6 I974 AIR CONDITIONING SYSTEM WITH PROVISION FOR REHEATING BACKGROUND OF THE INVENTION This invention relates to air conditioning systems operable to provide relatively cool and dehumidified air to a space being conditioned. In particular, this invention relates to such a system having a reheat coil provided therein and being solely operable to provide deation unit operable to supply solely dehumidified air humidified air to the space when the temperature level in such space does not require cooling, but the humidity level therein requires dehumidified air.

It has now been recognized that maintaining comfortable conditions within a space or room adapted for human occupancy requires not only that the temperature of the air be controlled, but, in addition thereto, the moisture content or humidity of the air be similarly controlled. Many internal environments or spaces typically have air conditioning systems which provide conditioned air to regulate the temperature of the space. When relatively cool air is provided to the space, not only is the temperature level therein reduced but, in addition, the humidity level is also lowered since the removal of heat from air will dehumidify the same by lowering the airs dew point.

However, there are many times when the temperature level in the room or space does not require cooling, albeit human discomfort may still be experienced due to a relatively high humidity level within such space. Such temperature generally falls within the range of 70 to 75F. If cool'air were to be provided to dehumidify the space, uncomfortably cool temperatures would be obtained, thereby causing discomfort to the occupants.

In the past, it has been proposed to'cool the air in a conventional manner and then reheat the same prior to its being supplied to the space. The cooling of the air will remove the moisture or dehumidify the same and the reheating of the air will raise the temperature thereof so the space will not be overcooled. Examples of prior art illustrating air conditioning systems having reheat capabilities are disclosed in US. Pat. Nos. 2,515,842; 2,679,142; and 2,940,281. Each of the arrangements disclosed in the cited patents suffer from a common failure.

When reheating is required, vaporous refrigerant is provided to a heat exchange coil functioning as a reheat coil. The ambient air which has been cooled and dehumidified by passing in heat transfer relation with refrigerant flowing through the evaporator of the refrigeration unit is thence passed in heat transfer relation with the vaporous refrigerant flowing through the reheat coil. The air is thus warmed prior to its delivery to the space. However, as noted hereinbefore, the temperature conditions at which solely dehumidified air is required generally falls within the range of 70 to 75F. Therefore, by passing the cooled and dehumidified air in heat transfer relation with vaporous refrigerant, the air has generally been reheated to an excessively high level, thus elevating the temperature in the space to an uncomfortable level. In addition, the vaporous refrigerant supplied to the reheat coil has generally been unregulated. As is obvious, the prior art defects caused such reheat systems to be generally unsatisfactory.

SUMMARY OF THE INVENTION It is therefore an object of this invention to reheat conditioned'air to acceptable levels without overheating the same.

It is a further object of this invention to discharge conditioned air into a space that requires solely dehumidified air without overheating such space.

It is a further object of this invention to provide an air conditioning system having a conventional refrigerwhen the space being conditioned requires dehumidification, without lowering or raising the temperature in such space to an unacceptable level.

These and other objects of the present invention are obtained by providing an air conditioning system including a refrigeration unit having a heat exchange coil provided in the path of flow of the conditioned air downstream from the evaporator and upstream from the space being conditioned When the humidity in the space is at an uncomfortable level and the temperature in such space does not require cooling, a mixture of vaporous and liquid refrigerant is passed through the heat exchange coil. I

Ambient air, which has been cooled and dehumidified by passing in heat transfer relation with refrigerant flowing through the evaporator is thence passed in heat transfer relation with the mixture of vaporous and liquicl refrigerant flowing through the coil. The relatively cold air absorbs heat from the vaporous refrigerant and thereby condenses the same. Regulating means is provided to regulate the quantity of vaporous refrigerant supplied to form the mixture of vaporous and liquid refrigerant. Thus, dehumidified air may be supplied to a space when such space solely requires dehumidified air, without overheating the space.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of an air conditioning system embodying the present invention; and

FIG. 2 illustrates a control arrangement which may be employed with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT An outdoor heat exchange coil or condenser 16 is I connected by means of line 14 to the discharge side of a suitable refrigeration compression mechanism, for example a reciprocating type'compressor 12. The gaseous refrigerant produced in compressor 12 flows to condenser 16 and is condensed by ambient air routed over the surface of the condenser by an outdoor fan 20 which is suitably connected to a motor or other prime mover 18. Liquid refrigerant formed in condenser 16 flows via line 22, thermal expansion valve 32 and line 28 to indoor heat exchange coil or evaporator 42. It is sion valve 32.

Liquid refrigerant in evaporator 42 is converted to vaporous refrigerant as it extracts heat from the medium, for example, air passed over its surface by fan 40 which is suitably connected to a prime mover such as electric motor 38. The cooled air is discharged into the area being conditioned through a suitable outlet (not shown). Vaporous refrigerant from evaporator 42 flows via line 46 to compressor 12 to complete the refrigerant flow cycle. The foregoing describes a refrigeration unit of the conventional type employed in air conditioning systems as is well known to those skilled in the art.

A conduit 24 having first solenoid valve 26 and throttle valve 27 disposed therein connects line 14 to line 22. Asecond solenoid valve 30 is disposed in line 28. The manner in which

valves

26 and 30 are controlled shall be described in detail hereinafter.

A second heat transfer coil 44 is provided in the path of flow of the conditioned air being discharged into-the space or room in the enclosure. Preferably coil 44 is disposed in the path of conditioned air flow downstream of evaporator 42. Branch line 23 connects line 22 with the inlet to heat exchange coil 44. A line 36 connects the outlet from heat exchange coil 44 to line 28. Line 36 has a check valve 3.4 disposed therein. The check valve only permits the refrigerant to flow from coil 44 through line 36 and thence into line 28.

Referring now to FIG. 2, a preferred form of control, suitable for use with the air conditioning system hereinabove described, is schematically shown. A suitable source of electric power, represented by lines L1 and L2, is connected to primary winding 52 of transformer 48. It is understood, a polyphase source of electric power may be employed if the circuit is suitably modified.

A secondary winding 50 of transformer 48 is connected to first control relay S8 and second control relay 60. The first and second relays are connected in parallei with each other. Connected in series with

relays

58 and 60 is a temperature responsive switch 54.-Switch 54 is movable between

terminals

55 and 59 for a reason to be more fully explained hereinafter. Connected in series with second relay 60 is a humidity responsive switch 56. Switch 56 in a closed position contacts terminal 57.

Terminals

55 and 57 are in parallel with each other. When either

terminal

55 or 57. has switch S4 or 56 respectively in contact therewith, control relay 60 is energized. Control relay S8 is energized when switch 54 is moved into con-tact with terminal 59.

When relay 60 is energized, switches 62, 64, and 65 operatively connected thereto are closed. The closure of switch 62 energizes motor 38 which thereby causes fan 40 to route air over coil 42. The closure of switch 64 energizes motor 18, thereby causing fan to route outdoor air over condenser 16. The closure of switch 65 energizes motor 11 which is operatively connected to compressor 12.

Operatively connected to first relay 58 is a switch 66. The deener-gization of relay 58 causes switch 66 to contact terminal 68. Terminal 68 is in series with solenoid valve 30. When switch 66 contacts terminal'68,

engage terminal 70. When switch 66 contacts terminal 70, solenoid valve 26 is energized to an open position. When switch 66 disengages from terminal 68,- valve 30 is placed in a normally'closed position.

The manner in which the present invention functions to provide dehumidified air without overcooling or overheating the area or space being conditioned shall now be explained.

Assume the space being conditioned requires cooled and dehumidified air. Temperature responsive switch 54 senses the requirement for cooled air and moves so it engages terminal 55 in the manner illustrated in FIG. 2. Control relay 60 is thus energized. Control relay 58 remains deenergized since switch 54 is disengaged from terminal 59.

When control relay 60 is energized, switches 62, 64,

and close, thereby energizing

motors

38, 18, and 11 respectively.

With control relay 58 in its deenergized state, switch 66 remains in contact with terminal 68. Solenoid valve 30 is thus energizedinto its open position. Since switch 66 is disengaged from terminal 70, solenoid valve 26 remains deenergized and in a closed condition. Refrigerant flow through line 24 is thus prevented. Thus, all of the refrigerant discharged from compressor 12 passes through condensercoil l6.

As-solenoid valve 30 is energized, the liquid refrigerant flowingthrough line 22 is directed through line 28 to evaporator coil 42. Check, valve 34 prevents any. of

the refrigerant from flowing into heat exchange coil 44. The refrigerant passing through coil 44 passes in heat transfer relation with ambient air, absorbing heat from such air and becoming vaporous. The cooled air is then delivered to the area or space requiring the same.

Assume now cooled air is no longer required in the area, but dehumidified air is still needed to obtain comfortable environmental conditions for the human occupants thereof. As noted before, if the supply of cooled air were to be continued, uncomfortable conditions would be created by the resultant overcooling of such space.

Temperature responsive switch 54 will disengage from terminal 55 and move into contact with terminal 59 when'cooling is no longer required in the space. However, since the humidity level in such space is still above a desired value, switch 56 remains in contact with terminal 57; thus control relay 60 remains energized. Control relay S8 is also energized since switch 54 now contacts terminal 59.

The energization of control relay 58 causes switch 66 to become disengaged from terminal 68 and engaged with terminal 70. Solenoid valve 30, in series with terminal 68, thereby becomes deenergized and the valve moves to a normally closed position. Simultaneously, solenoid valve 26, which is in series with closed terminal 70, becomes energized and thereby moves into an open condition, thus permitting vaporous refrigerant to flow from line 14 to iine 22 about condenser coil 16. Throttle valve 27 provides a restriction in line 24 to regulate the amount of vaporous refrigerant flowing through line 24 and simultaneously the amount of rethe solenoid is energized so that valve 30 is placed in frigerant passing through the condenser. Valve 27 may be manually or automatically operated; if automatically operated, the valve will regulate flow in accordance .with temperature conditions in the space. As an alternative, since the operating conditions at which solely dehumidified air is required is generally from 7075F,

a suitably sized orifice may be provided as an integral part of solenoid valve 26. A mixture of vaporous and its ability to hold moisture is also reduced. Thus, cooled and dehumidified air is provided.

The cooled and dehumidified air is passed in heat transfer relation with coil 44 having the mixture of vaporous and liquid refrigerant passing therethrough. The air passing thereover absorbs heat from the mixture of vaporous and liquid refrigerant, thereby'condensing the vaporous component of such refrigerant mixture and being warmed thereby. The air is subsequently supplied to the area or space being conditioned.

By passing the air in heat transfer relation with the mixture of liquid and vaporous refrigerant, the dehumiditied air is reheated to a satisfactory temperature level.

By employing a mixture ofliquid and vaporous refrigerant to reheat the air prior to its being discharged into the space being conditioned, the temperature of such conditioned air is neither below a satisfactory temperature level, nor above the same, so that desired temperature and humidity conditions may be readily obtained in the space.

It should be particularly understood that the position of the heat exchange coil relative tothe evaporator may be altered without departing from the spirit and scope of this invention. For example, the reheat coil and evaporator may be arranged so that only a portion of the total ambient air being conditioned will pass over each heat exchange element. The separate air streams will thence be mixed together prior to their delivery into the space. Other variations that might readily occur to one skilled in the art may also be employed.

While 1 have described and illustrated a preferred embodiment of my invention, my invention should not be limited thereto, but may be otherwise embodied within the scope of the following claims.

I claim:

1. in an air conditioning system for providing cooled and dehumidified air to a space to be conditioned, a refrigeration unit comprising a compressor, a condenser, thermal expansion means, and an evaporator connected together in a closed circuit and having liquid refrigerant flowing in a first portion thereof, and vaporous refrigerant flowing in a second portion thereof, the improvement comprising:

A. means to pass a relatively cold heat exchange medium in heat transfer relation with vaporous refrigerant flowing through said condenser from said compressor, said heat exchange medium absorbing heat from said vaporous refrigerant to condense the refrigerant;

B. means to pass relatively warm air to be conditioned, for subsequent discharge into said space, in heat transfer relation with liquid refrigerant flow ing through said evaporator, the refrigerant absorbing heat from said air, the air being cooled thereby;

C. heat exchange means disposed in the path of flow of said cooled air downstream of said evaporator and upstream from said space;

D. bypass means about said condenser to pass at least a portion of said vaporous refrigerant discharged from said compressor about said condenser;

E. first valve means 'operably associated with said bypass means and having first and second operating positions, said valve means in its first position passing vaporous refrigerant about said condenser to mix with liquid refrigerant flowing therefrom and in its second operating position passing all the vaporous refrigerant discharged from the compressor through said condenser;

F. second valve means disposed between said condenser and said evaporator and having first and second operating positions, said valve means when in its first operating position directing the refrigerant through said heat exchange means and thence through said evaporator and when in its second operating position directing the refrigerant about the heat exchange means and directly to the evaporator; and

G. control means operable to place said first valve means in its first operating position and said second valve means in its first operating position when dehumidified air is solely required in said space and being further operable to place said first and second valve means in their second operating positions when cooled and dehumidified air is required in said space.

2. An air conditioning system in accordance with claim 1 wherein said bypass means includes regulating means to control the amount of vaporous refrigerant in said mixture of vaporous and liquid refrigerant.

i t i l i

Claims

1. In an air conditioning system for providing cooled and dehumidified air to a space to be conditioned, a refrigeration unit comprising a compressor, a condenser, thermal expansion means, and an evaporator connected together in a closed circuit and having liquid refrigerant flowing in a first portion thereof, and vaporous refrigerant flowing in a second portion thereof, the improvement comprising: A. means to pass a relatively cold heat exchange medium in heat transfer relation with vaporous refrigerant flowing through said condenser from said compressor, said heat exchange medium absorbing heat from said vaporous refrigerant to condense the refrigerant; B. means to pass relatively warm air to be conditioned, for subsequent discharge into said space, in heat transfer relation with liquid refrigerant flowing through said evaporator, the refrigerant absorbing heat from said air, the air being cooled thereby; C. heat exchange means disposed in the path of flow of said cooled air downstream of said evaporator and upstream from said space; D. bypass means about said condenser to pass at least a portion of said vaporous refrigerant discharged from said compressor about said condenser; E. first valve means operably associated with said bypass means and having first and second operating positions, said valve means in its first position passing vaporous refrigerant about said condenser to mix with liquid refrigerant flowing therefrom and in its second operating position passing all the vaporous refrigerant discharged from the compressor through said condenser; F. second valve means disposed between said condenser and said evaporator and having first and second operating positions, said valve means when in its first operating position directing the refrigerant through said heat exchange means and thence through said evaporator and when in its second operating position directing the refrigerant about the heat exchange means and directly to the evaporator; and G. control means operable to place said first valve means in its first operating position and said second valve means in its first operating position when dehumidified air is solely required in said space and being further operable to place said first and second valve means in their second operating positions when cooled and dehumidified air is required in said space.