US20140096562A1

US20140096562A1 - Cooling system including a controlled atmospheric heat rejection cycle with water re-capture

Info

Publication number: US20140096562A1
Application number: US14/050,324
Authority: US
Inventors: Gerald McDonnell; Earl Keisling
Original assignee: Inertech IP LLC
Current assignee: Inertech IP LLC
Priority date: 2012-10-09
Filing date: 2013-10-09
Publication date: 2014-04-10

Abstract

The present disclosure relates to a cooling system including a controlled atmospheric heat rejection cycle with water re-capture. The cooling system for cooling a heat load includes a first evaporative section configured to circulate a first fluid to enable heat transfer from the heat load to the first fluid, a second evaporative section in fluid communication with the first evaporative section and configured to circulate the first fluid, and a liquid refrigerant distribution unit in thermal communication with the second evaporative section. The liquid refrigerant distribution unit is configured to circulate a second fluid to enable heat transfer from the first fluid to the second fluid.

Description

BACKGROUND

Evaporative cooling systems are commonly employed to remove waste heat in many applications and are usually referred to as cooling towers, evaporative coolers, or fluid coolers because they are often configured in a tower structure that facilitates the evaporative cooling process. Unlike a dry cooler process, which strictly relies on dry bulb ambient conditions as a means to reject heat and is therefore limited in how low a returning coolant fluid temperature can be achieved, the evaporative process utilizes water, in either a spray mist, drizzle, or water fall type process to enable contact time with the wet bulb atmosphere to effectively reject heat and produce lower coolant fluid temperatures. Such systems are two or three component fluid cooling systems in which air and water or, in some instances, glycol are the only fluids involved in the evaporative cooling process.
The process of evaporative heat rejection is far more energy efficient than alternative dry cooling heat rejection processes. However, the down side of the process of evaporative heat rejection is that a significant amount of water is consumed and evaporated into the atmosphere. Since water is a precious resource, and has limited availability in certain regions, the process of evaporative heat rejection has an impact on the earth's water resources.
The process of rejecting heat into the atmosphere currently relies on cooling towers, fluid coolers, and evaporative coolers that are simple cycles, of pumping, evaporating, and discharging heat and vapor. This equipment is not easily controlled to effectively limit water use or capture the latent vapor that is expelled into the atmosphere.
Existing water cooled heat rejection equipment has significant inherent limitations in its ability to produce coolant fluids beyond a minimum leaving water temperature. This is commonly referred to as the wet bulb approach temperature.
Also, existing water cooled heat rejection equipment has significant inherent limitations in its ability to change and optimize coolant production operation over a full spectrum of environmental weather and load conditions. The performance capabilities of this equipment are limited to, and reliant on, the present environmental enthalpy value during operation.
Further, existing water cooled heat rejection equipment require significant chemical treatment systems in order to control internal and external biological hazards, in addition to corrosion issues in the pipe system.
Still further, existing heat rejection equipment is limited by its air flow patterns. This heat rejection equipment provides either a 100% draw through or 100% blow through air exchange of air from the environment to the environment. This equipment uses full air pass through cycles. The coolant production process can be varied by varying the production water flow rates (basin pumps on or off), the coolant flow rates (condenser water pumping variable frequency drives (VFDs) or speed controls), or the air flow rates (fan VFDs or speed controls).
However, the existing heat rejection equipment (e.g., towers, fluid coolers, or evaporative coolers) are not capable of effectively containing, capturing, or processing the discharge vapor that is expelled to the atmosphere in the process.
In addition, existing heat rejection equipment (e.g., towers, fluid coolers, or evaporative coolers) is not capable of producing potable (distilled) water as a by product of the cycle.
Also, existing cooling towers cannot be easily operated as free coolers when operated in sub-freezing conditions.

SUMMARY

The present disclosure relates to a controlled atmospheric heat rejection cycle with a water reclamation process that can be used in place of traditional evaporative coolers or dry coolers. The benefits are numerous. The cycle has the ability to be operated as a water conservation unit, or is capable of processing clean water from the atmosphere as well as reclaiming the water that is created from the vapor produced in a heat rejection cycle. The unit is designed to operate and optimize energy use through a wide spectrum of open atmospheric conditions similar to a standard evaporative process. It also has the ability to systematically control the introduction of outside atmospheric air by regulating its introduction in order to provide a proportionally balanced atmosphere within the apparatus.
This proportional regulation and control between the atmosphere, the in series refrigerant and air cycles, and the manner with which the vapor is captured enables the apparatus to operate most efficiently across a broad operational spectrum. The unit can efficiently produce clean water at greatly reduced energy cost. It can optimize the consumption of water that is typically consumed in a traditional evaporative process. It can also significantly reduce the electrical impact of chillers and other heat producing equipment by effectively delivering lower temperature and better quality transport cooling process water at all times.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram illustrating a liquid refrigerant-assisted evaporative cooling system according to an embodiment of the present disclosure; and

FIG. 2 is a schematic flow diagram illustrating the liquid refrigerant assist system for the evaporative cooling system in which evaporation coils illustrated in FIG. 1 are positioned at an angle with respect to the horizontal axis.

DETAILED DESCRIPTION

The present disclosure relates to a system that is capable of operating as an evaporative cooler, dry cooler, water recovery unit, and chiller optimization circuit. The system includes a housed enclosure including modulating intake and discharge dampers. Modulation of the dampers enables full proportional control of the air intake from and air discharge to the external environment, as well as regulation of the amount and quality of air that is taken and rejected (enthalpy control). The spray water cycle and collection basin allows the apparatus to act as an evaporative cooler.
The in-series evaporator coils are capable of reducing the high latent air sufficiently below the dew point in order to extract water from the high latent vapor. The coils can also be utilized to lower the effective wet bulb condition ahead of the heat rejection coil, thereby creating a “false atmosphere” that is more beneficial for producing cooler leaving water off the heat rejection coil or coils. By placing the coils in series, the cycle is enabled to cool the latent air in steps. The air is cooled as it enters the primary heat exchanger evaporator coil.
The heat absorption is accomplished by rejecting the heat through the process of latent heat of vaporization. The heat is absorbed into the pumped liquid refrigerant that is present at the evaporator heat exchanger. The refrigerant cycle utilizes a pump to deliver liquid refrigerant to the evaporator coil. It is an “over-feed” or over-pumped system. The amount of heat that is absorbed at the primary coil is dependent on the rate of boil off of the refrigerant.
The boil-off temperature set point (condensing line) is set at the primary condenser. The primary circuit is capable of cooling the high latent air down (discharge air) to within approximately eight degrees of the wet bulb temperature. The leaving air temperature can be further reduced by enabling the compressor circuit to lower the entering condenser water temperature to the main condenser, or the primary compressor may stay off, and the balance of the air cooling can be accomplished with the secondary evaporator cycle.
The secondary evaporator circuit has similar operational characteristics at the primary circuit. However, the effective load on the secondary compressor is significantly reduced because much of the heat has already been rejected at the primary evaporator coil. A pumped water cooled condenser cycle is in series with the basin collection pan, the air stream (spray nozzles), and the water-cooled condenser that rejects the heat from the evaporator coils that are in the air stream. The air at the intake and at the discharge can be varied from 100% fresh air to 0% fresh air depending on the load, the environmental conditions, and the desired operational mode such as: water recovery, free cooling, liquid refrigerant assist, or a combination of these modes.
More particularly, referring to FIGS. 1 and 2, there is illustrated liquid refrigerant-assisted evaporative cooling system 100 according to an exemplary embodiment of the present disclosure. A cooling tower 102, shown generally by the dashed lines and as described in more detail below, may include an air intake hood 104 having air intake dampers 104′ on one side of the cooling tower 102 that provides an air intake pathway. The cooling tower 102 may also include an exhaust or relief hood 106 having exhaust dampers 106′ on another side of the cooling tower 102 that provides an exhaust air pathway. The flow of air through the air intake dampers 104′ is indicated by arrow 10. The flow of air from the exhaust dampers 106′ is indicated by arrow 20.
A liquid refrigerant assist cycle 200, which is described in more detail below with respect to FIG. 2, is included within the cooling tower 102 within a lower section 102 a of the cooling tower 102 that functions as a Cooling Distribution Unit (CDU) mechanical section or liquid refrigerant distribution unit. Those skilled in the art will recognize that the CDU mechanical section within the lower section 102 a may also be configured as a stand-alone CDU mechanical section.
The evaporative cooling system 100 is in thermal communication with a generalized heat load 50 via a cooling water return (or refrigerant or any other process cooling fluid) header 120 a from the heat load 50 and a cooling water (or refrigerant) supply header 120 b. For the purposes of illustration herein, the return header 120 a and the supply header 120 b are described herein as cooling water return header 120 a and cooling water supply header 120 b although a refrigerant or any other process cooling fluid may flow through the headers 120 a and 120 b to transfer heat from the heat load 50.
More particularly, via cooling water return header pump 210, the heated cooling water return from the heat load 50, representing the transfer of heat Q₀to the cooling water return header 120 a on the suction side of the cooling water return header pump 210, is in fluidic communication with the cooling water return header pump 210. As described in more detail below with respect to FIG. 1, the cooling water return discharges from the cooling water return header pump 210 to a heat exchange member or heat rejection member, e.g., heat rejection coils 302 that are included in an evaporative recirculation cooling cycle 300 that is generally disposed in a middle or first evaporative section 102 b of the cooling tower 102. The first evaporative section 102 b of the cooling tower 102 is disposed adjacent to, and vertically above, the lower section 102 a.
The cooling water flowing through the heat rejection coils 302, which has been cooled, as illustrated by the transfer of heat Q_RCfrom the heat rejection coils 302, is returned to cool the generalized heat load 50 via the cooling water (or refrigerant or process fluid) supply header 120 b. Thus, the heat load Q₀at 50 is in thermal communication with the evaporative recirculation cooling cycle 300 via cooling water (or refrigerant or process fluid) supply header 120 b.
The evaporative recirculation cooling cycle 300 includes one or more recirculation fans 310 and also a water spray sub-system that includes first and second spray nozzle headers 3201 and 3202 that are in thermal and fluidic communication with the heat rejection coils 302.
As explained in more detail below, due to the pressure of the water in the spray nozzle headers 3201 and 3202, a spray of water is established from the spray nozzles 320′ in the spray nozzle headers 3201 and 3202 into the first fluid, e.g., air or an air and water mixture. Within the first evaporative section 102 b of the cooling tower 102, the first fluid is circulated across the fluid coils 302 via the recirculation fans 310 as shown by arrows A, resulting in the transfer of heat Q_RCfrom the heat rejection coils 302 to the first fluid in the direction of arrow A, such that the first evaporative section 102 b is configured to circulate the first fluid to enable heat transfer Q0 from the heat load 50 to the first fluid.
The percentage of entering air is regulated by the air intake dampers 104′ and exhaust relief dampers 106′ based upon an enthalpy control outside air wet bulb temperature sensor (TS) 14 disposed on the fresh air intake hood 104 in the vicinity of the intake air inlet pathway represented by the arrow 10. Thus, the first fluid may include air and the air intake pathway 10 is in fluid communication with the first evaporative section 102 b to enable the flow of air external to the evaporative cooling system 100 into the first evaporative section 102 b. The wet bulb temperature sensor 14 senses the wet bulb temperature of the air that is external to the evaporative cooling system 100.
The cooling tower 102 may include an upper section or second evaporation section 102 c disposed adjacent to, and vertically above, the first evaporation section 102 b to enable fluid communication between the first evaporation section 102 b and the second evaporation section 102 c. Within the upper section or second evaporation section 102 c, the first fluid is circulated across the fluid coils 302 via the recirculation fans 310, as shown by arrows A, is discharged from the recirculation fans 310 into the upper section 102 c which may include evaporation coils 331 and 332 (e.g., “micro0channel coils”).
The first fluid is circulated across the evaporation coils 331 and 332 in the direction shown by arrows B. The first fluid, traveling in the direction shown by arrows B, is then circulated from the upper or second evaporation section 102 c to the spray nozzles 320′ and fluid coils 302 to again travel in the opposite direction shown by arrows A. The movement of the first fluid (e.g., air or a mixture of air and water spray) is forced into the direction shown by arrows B above a potable water basin or vessel 340 positioned above the evaporation coils 331 and 332. It can be appreciated that the one or more fans 310 are thus configured to recirculate the first fluid through the first and second evaporative sections 102 b and 102 c.
In the exemplary embodiment of FIG.1, the liquid refrigerant assist cycle 200 is implemented by providing a first liquid refrigerant assist circuit 2001 of a first liquid refrigerant distribution unit 211 and a second liquid refrigerant assist circuit 2002 of a second liquid refrigerant distribution unit 212 that are functionally mirror images or duplicates of each other. That is to say, although generally the capacity and sizing of the second evaporation coil 332 and second liquid refrigerant distribution unit 212 are the same as the capacity and sizing of the first evaporation coil 331 and first liquid refrigerant distribution unit 211, the capacity and sizing may differ one from the other, depending on the particular design requirements or choices. The first liquid refrigerant assist circuit 2001 is dedicated to, and in fluid communication with, the first evaporation coil 331 while the second liquid refrigerant assist circuit 2002 is dedicated to, and in fluid communication with, the second evaporation coil 332.
Accordingly, the first and second evaporation coils 331 and 332 are in fluid communication with the first and second liquid refrigerant assist circuits 2001 and 2002 via first liquid refrigerant assist cycle supply headers 201, 202 and first liquid refrigerant assist cycle return headers 251, 252, respectively.
As liquid refrigerant is supplied to first and second evaporation coils 331 and 332 via the first liquid refrigerant assist cycle supply headers 201, 202, the liquid refrigerant is at least partially vaporized by transfer of heat Q1, Q2, from the first and second evaporation coils 331 and 332 such that at least partially vaporized refrigerant in the form of a gas or a gas and liquid refrigerant mixture is returned via liquid refrigerant assist circuit return headers 251, 252 to evaporators 261, 262, included within first and second liquid refrigerant assist circuits 2001 and 2002, respectively.
Within the evaporators 261, 262, heat Q3, Q4 is transferred from the gas or gas and liquid refrigerant mixture such that condensation of the liquid refrigerant occurs within the evaporators 261, 262 and liquid refrigerant is discharged via evaporator to liquid receiver supply lines 253 and 254 to liquid receivers 255 and 256, respectively. The liquid refrigerant receivers 255 and 256 are operated to maintain a supply of liquid refrigerant on the suction sides of liquid refrigerant pumps 257 and 258, which discharge liquid refrigerant into the liquid refrigerant assist cycle supply headers 201 and 202 to supply liquid refrigerant again to the evaporation coils 331 and 332, respectively.
Thus, the liquid refrigerant distribution unit is in thermal communication with the second evaporative section 102 c and is configured to circulate a second fluid, i.e., the first liquid refrigerant flowing in the first liquid refrigerant assist cycle supply headers 201, 202 and first liquid refrigerant assist circuit return headers 251, 252, respectively, thereby enabling heat transfer Q1 and Q2 from the first fluid that includes an air or a mixture of air and water spray to the second fluid, i.e., the first liquid refrigerant.
Flow of the gas or gas and liquid refrigerant mixture may be bypassed around the secondary evaporator coils 331 and 332 utilizing secondary evaporator coil bypass valves 259 and 260, respectively. The bypass valves 259 and 260 provide direct fluid communication between the liquid receivers 255 and 256 and the liquid refrigerant assist cycle supply headers 201 and 202, respectively, and thus assures a minimum level of liquid refrigerant in the respective receivers 255 and 256 under all load conditions.
Thus, a portion of the liquid refrigerant in the liquid refrigerant assist cycle supply headers 201 and 202 is bypassed around the evaporator coils 331 and 332, respectively. Bypassing of a portion of the liquid refrigerant in the liquid refrigerant assist cycle supply headers 201 and 202 in this manner with modulation of the bypass valves 259 and 260 to increase the percent-open position, increases liquid refrigerant flow to the respective receivers 255 and 256 as the heat load Q0 at 50 diminishes. This provides more precise control over the cooling process.
The circulation or flow of a second fluid, e.g., a first liquid refrigerant, from the evaporators 261 and 262 to the evaporator coils 331 and 332 via the liquid refrigerant pumps 257 and 258 and the liquid receivers 255 and 256, and back to the evaporators 261 and 262 as a gas or a gas and liquid refrigerant mixture, define first liquid refrigerant circuits.
The heat flow Q3 and Q4 is transferred within the evaporators 261 and 262 from the condensation side represented by the flow of gas or gas and liquid refrigerant mixture in the liquid refrigerant assist circuit return headers 251, 252 to the liquid refrigerant assist cycle supply headers 201, 202 to the trim evaporation side of the evaporators 261 and 262. The trim evaporation side is represented by the flow to the evaporators 261 and 262 of a second liquid refrigerant flowing in second liquid refrigerant circuits or trim compressor circuits 2003 and 2004 of the first and second liquid refrigerant distribution units, respectively.
The trim evaporation side is also represented by the second liquid refrigerant trim circuits 2003 and 2004, in which a second liquid refrigerant is circulated from the evaporators 261 and 262 to the condensers 269 and 270 such that the second refrigerant is received in liquid form from the condensers 269 and 270 via the second refrigerant condenser to the evaporator supply lines 273 and 274. The second refrigerant in liquid form is then evaporated in the evaporators 261 and 262 via the transfer of heat Q3 and Q4.
The at least partially evaporated second refrigerant, evaporated via a trimming method, flows or circulates from the evaporators 261 and 262 to the suction side of trim compressor 265 and 266 via evaporator to compressor suction connection lines 263 and 264, respectively. The trim compressors 265 and 266 compress the at least partially evaporated second refrigerant to a high pressure gas having a pressure range of approximately 135-140 psia (pounds per square inch absolute) if spray nozzle headers 3201 and/or 3202 are not operating. If spray nozzle headers 3201 and/or 3202 are operating, the pressure range is approximately 100-115 psia. The high pressure second refrigerant gas circulates from the discharge side of compressors 265 and 266 to the condenser side of condensers 269 and 270 via compressor discharge to condenser connection lines 267 and 268. Heat Q5 and Q6 is transferred from the condenser side of condensers 269 and 270 to the water sides of the condensers 269 and 270.
The system return water (or refrigerant return fluid) 120 a to the heat rejection coil 302 transports the heat Q₀from the system heat load 50. The temperature of the return water 120 a varies based on the internal load 50 that is present. The system supply water 120 b is cooled to a desired setpoint as monitored by a temperature sensor or switch (TS) 122 disposed in the supply water discharge 120 b generally close to the heat load 50.
In order to increase the efficiency of cooling the load side Q0 of the system 50, the fluid temperature at temperature sensor or switch (TS) 122 in system supply water header 120 b is maintained as low as required by utilizing a mixed air enthalpy sensor (ES) 312 disposed in atmosphere chamber 304 on the air intake side of the heat rejection coil 302 in the vicinity of the spray nozzle headers 3201 and 3202. The mixed air enthalpy sensor 312 senses the enthalpy of the air flowing across the heat rejection coil 302 and controls the intake air temperature to the heat rejection coil 302. There are various methods of cooling the intake air flowing in the evaporative recirculation section 102 b to the heat rejection coil 302, including modulating the air intake and relief dampers, 104′ and 106′, and/or pumping water through the spray nozzle headers 3201 and/or 3202.
Cooling the intake air to the heat rejection coil 302 also occurs by operating the primary evaporator cooling coil 331. Operation of the primary evaporator cooling coil 331 is initiated by energizing the liquid refrigerant pump 257 thereby causing liquid refrigerant to flow to the primary evaporator cooling coil 331 from the liquid receiver 255 in the first liquid refrigerant assist circuit 2001. The level of cooling of the mixture of air and water spray, traveling in the direction shown by arrows B, at the primary coil 331 can be further enhanced by energizing the trim evaporator circuit 2003 and its associated compressor 265. The trim compressor evaporation circuit 2003 is generally in operation to cool the first liquid refrigerant assist circuit 2001.
The secondary cooling evaporator coil 332 can further cool the air or air and water spray stream traveling in the direction of the arrows B by initiating the liquid refrigerant trim pump 258. The temperature of the air or air and water spray stream B can be further reduced by initiating the secondary trim compressor evaporation circuit 2004. The secondary trim compressor 266 is energized and cycled to maintain a set point temperature using the enthalpy sensor ES 312 in the air chamber 304.
In addition to controlling the temperature in the system water supply header 120 b to a desired value, evaporative recirculation cooling cycle 300 can be utilized to extract clean water from the air stream traveling in the direction of arrow A. The evaporator coils 331 and 332, and respective associated trim circuits 2003 and 2004, can be energized to reduce the temperature of the air flow at the location of arrows B sufficiently below the dew point, in order to extract pure water from the air stream.
Pure water may be extracted from the air stream by drawing high latent air from the environment into the evaporative cooling system 100 through the air intake dampers 104′ indicated by arrow 10 at the air intake hood 104, and/or by processing the spray water in the spray water headers 3201, 3202, which is essentially grey or untreated water 352. The grey or untreated water 352 is supplied to the water side of the condensers 269 and 269 from a grey water storage vessel, e.g., hot water basin 350, located or disposed in the middle section 102 b of the cooling tower 102 below the heat rejection coils 302 but above the lower section 102 a of the cooling tower 102 that functions as the Cooling Distribution Unit (CDU) mechanical section.
The grey or untreated water 352, which is at a temperature ranging from approximately 60° F. (degrees Fahrenheit) to approximately 76° F., is supplied to the water side of the condensers 269 and 270 via a hot water basin to condenser connection lines 3203 and 3204, respectively. Grey or untreated water 352 from outside of the evaporative cooling system 100 can also be supplied to the hot water basin 350 via a grey or untreated water supply line 354.
Thus, the spray water sub-system is coupled to the grey water storage vessel 350. The grey water storage vessel 350 forms the water supply for the water spray sub-system.
By lowering the temperature at primary evaporator coil 331 by increasing the heat transfer Q1, and further lowering the temperature of the air flowing in the direction of arrow B at secondary evaporator coil 332 below the dew point, pure water can condense on, and drip down from, evaporator coil 331 and/or evaporator coil 332, and collect in potable water basin or vessel 340 as potable water 342. The potable water 342 is discharged from the potable water basin or vessel 340 via an effluent line 344 and can be further treated by optional ultraviolet (UV) light 346 located in the effluent line 344. The potable water 342 can be directed to a potable water storage tank or reservoir 348, via effluent line 344′ downstream of the UV light 346, for other uses, or the potable water 342 in the effluent line 344′ downstream of the UV light 346 that has been treated via the UV light 346 can be returned to the potable water basin 340 via a connecting line (not shown) between the downstream effluent line 344′ and the potable water basin 340.
On the water side of the condensers 269 and 270, the temperature of the grey or untreated water 352 varies based on the atmospheric condition at fresh air intake hood 104 in the vicinity of the intake air inlet represented by the arrow 10, and within the atmosphere chamber 304. The temperature of the water 352 in the hot water basin 350 may vary from approximately 60° F. to approximately 80° F. degrees based on an approximately 4° F. degree approach temperature to the available wet bulb temperature of the air in the vicinity of the intake air inlet of the fresh air intake hood 104 represented by arrow 10.
The temperature of the grey or untreated water 352 sprayed at the spray water nozzle headers 3201 and 3202 may range from approximately 64° F. to approximately 76° F. The grey water 352 in hot water basin 350 provides suction head to spray water pumps 3205 and 3206, which pump spray water, i.e., grey water 352, to and through the water side of the condensers 269 and 270 via hot water basin to condenser connection lines 3203 and 3204, respectively. The grey water 352 absorbs the heat Q5 and Q6 that is rejected from the trim circuit compressors 2003 and 2004 via heat transfer within the condensers 269 and 270, respectively.
The hot grey water 352, which may be approximately 6 to 7 degrees F. hotter at the outlet sides of condensers 269 and 270 as compared to the inlet sides, is then transported to the spray nozzles 320 in the spray nozzle headers 3201 and 3202 and sprayed via the discharge head provided by the spray water pumps 3205 and/or 3206. Water at a temperature of approximately 60° F. to approximately 76° F. is returned to the condensers 269 and 270. The heat load Q0 at 50 should be equal to the difference between the enthalpy of the exhaust air having temperature T2 at relief hood 106 compared to the enthalpy of the air having temperature T1 at fresh air intake in air intake hood 104.
Under certain environmental conditions, such as when the environment is in the general range of, or close to, a maximum annual recorded temperature, it may prove more efficient to operate the first liquid refrigerant assist circuit 2001 to reduce the air temperature in the atmosphere chamber 304 without operating the compressor 265 in the primary trim circuit 2003. The air temperature is lowered as much as potentially possible for the particular temperature conditions of the water intake to condenser 269 via the condenser connection line 3203 from the hot water basin 350.
The balance of the heat load Q0 not being removed by the first liquid refrigerant assist circuit 2001 and the trim circuit 2003 for the first liquid refrigerant assist circuit 2001 can be more efficiently removed via the secondary liquid refrigerant assist circuit 2002 and the secondary trim circuit 2004. Thus, the compressor 266 in the secondary trim circuit 2004 can be operated to cool or remove the remainder of the heat load Q0.
The total operating efficiency is significantly increased by the splitting of, or staging of, the heat load Q0 into two different portions, namely an upper portion of the heat load Q0, which is removed by operation of the first liquid refrigerant assist circuit 2001 and the trim circuit 2003 (without operation of the trim compressor 265) and a lower portion of the heat load Q0, which is removed by operation of the second liquid refrigerant assist circuit 2002 and the trim circuit 2004, including operation of the trim compressor 266 to lower the air temperature below the dew point.
In one embodiment, the liquid refrigerant-assisted evaporative cooling system 100 includes a direct bypass connection (not shown) from the grey water 352 in the hot water basin 350 to the first liquid refrigerant assist circuit 2001 to simulate the foregoing operation of the first liquid refrigerant assist circuit 2001 and the trim circuit 2003 without operating the trim compressor 265 to remove the upper portion of the heat load Q0.
Although not explicitly illustrated in the figures, those skilled in the art will recognize that a controller may be configured and applied to control the operation of the one or more fans 310 and the first and second liquid distribution units 211 and 212 based on the wet bulb temperature sensed by the wet bulb temperature sensor 14 and the enthalpy sensed by the enthalpy sensor 212.
In one embodiment, a discharge cool air hood 108 is positioned in the upper section 102 c of the cooling tower 102 in the vicinity of the downwind side of the air or air and water mixture exiting from secondary evaporator coil 332, which travels in the direction of the arrows B. A set of discharge cool air hood dampers 108′ are positioned to allow at least a portion of the air or air and water mixture flowing in the B direction to discharge tangentially through the discharge cool air hood dampers 108′ as cool air into the surrounding environment as indicated by the arrow 30. The flow of the cool discharge air 30 can be controlled by the set of dampers 108′. This cool or cold air is a by product of the evaporation process occurring at evaporator coils 331 and 332. The temperature T3 of the air or air and water mixture discharging from the discharge cool air hood dampers 108′ at arrow 30 is generally low, approximately 55° F. to approximately 60° F., when the evaporative recirculation cooling cycle 300 is energized for water reclamation and/or enthalpy control by utilizing the mixed air enthalpy sensor (ES) 312 disposed in atmosphere chamber 304 on the air intake side of the heat rejection coil 302 as described above.
The relief hood 106 and exhaust or relief dampers 106′ are positioned within the upper section 102 c of the cooling tower 102 on a side of the cooling tower that is opposite to the side of the cooling tower on which the intake hood 104 and intake dampers 104′ are positioned in the second section 102 b.
A portion of the air and water spray mixture circulating in the direction of the arrows B in the upper section 102 c may be diverted through the relief dampers 106′ to flow in a direction opposite to the direction indicated by arrows B, as shown by arrow D.
Thus a circulatory flow of air and water spray mixture is created within the middle and upper sections 102 b and 102 c, respectively. Heat Q7 that is removed from the relief hood 106 is a function of the difference between temperature T2 of the air or air and water mixture flowing in the direction of the arrow 20, the temperature T3 at the discharge of the cold air dampers 108′ at the cold air discharge 108, the temperature T1 at the fresh air intake 10 as monitored by temperature sensor 14, and the heat load Q0 at 50. The heat Q7 is a function of the enthalpy control achieved by utilizing the mixed air enthalpy sensor (ES) 312 disposed in atmosphere chamber 304 on the air intake side of the heat rejection coil 302 as described above.
As can be appreciated from the foregoing description, the air at the intake 10 and at the exhaust air discharge 30 can be varied from 100% fresh air to 0% fresh air depending on the load and the environmental conditions, and the desired operational modes such as: water recovery (condensation), free cooling liquid refrigerant assist or a combination of modes. During water recovery, condensation occurs at the potable water storage vessel 340 while a portion of the heat load Q0 at 50 is rejected to the environment.
FIG. 2 illustrates one embodiment of the present disclosure in which the heat rejection coil 302 and the first and second spray nozzle headers 3201 and 3202 are tilted above the grey water 352 in the hot water basin 350 at an angle Θ with respect to the horizontal. The heat rejection coil 302 is pivotally supported by a support member 322 attached to the underside of the potable water basin 340. The first and second spray nozzle headers 3201 and 3202 are rotatable around pivotal joint members 3201′ and 3202′ located upstream from the spray nozzles 320′ in each of the spray nozzle headers 3201 and 3202, respectively.
This tilted configuration of the heat rejection coil 320 and the spray nozzle headers 3201 and 3202 above the grey water 352 allows for increased evaporation of the grey water 352 due to the more direct impact of the air flow A on the surface of the grey water 352. The angle Θ can vary from about 90 degrees as illustrated by the position of the heat rejection coil 302 and the spray headers 3201 and 3201 in FIG. 1 to about 0 degrees, in which case the heat rejection coil 302 and the spray headers 3201 and 3201 are essentially horizontal and parallel to the surface of the grey water 352.
Comparing the evaporative cooling system 100 to conventional evaporative cooling tower, in view of the foregoing disclosure, the power input to the spray water pumps 3205 and 3206 is generally the same as for a conventional evaporative cooling tower, e.g., about 5 Horsepower (HP) to about 7.5 HP (about 3.75 KW (kilowatts) to about 5.65 KW). The power input to the compressors 265 and 266 is generally scalable over a range of about 40 tons to about 90 tons (about 141.3 KW to about 317.7 KW) of refrigeration with generally a maximum power consumption of about 0.25 KW/ton of refrigeration. The power input to the fans 310 is generally about the same power input to the fans of a conventional evaporative cooling tower, e.g., about 25 HP to about 40 HP (about 18.75 KW to about 30 KW) and the power is proportionally regulated via variable frequency drive of the fan motors (not shown).
The reclamation of water is advantageous as compared to conventional methods which provide no water reclamation. During the water reclamation process, the compressors 265 and 266 operate in a very efficient mode in terms of kilowatts (KW)/ton of refrigeration and the operation can be varied as necessary to match the Q1 and Q2 heat removal requirements. The resulting operation may achieve a reduction in water consumption of about 93% to about 97% as compared to the water consumption of a conventional evaporative cooling tower. The remaining about 3% to about 7% of the water, respectively, is generally blown down from the cooling tower 102 to remove solids in the potable water basin 340 and the hot water basin 350. Although in principle all of this water can be recovered, the energy consumption would increase significantly.

Claims

What is claimed is:

1. An evaporative cooling system for cooling a heat load, comprising:

a first evaporative section configured to circulate a first fluid to enable heat transfer from the heat load to the first fluid;

a second evaporative section in fluid communication with the first evaporative section, the second evaporative section configured to circulate the first fluid; and

a liquid refrigerant distribution unit in thermal communication with the second evaporative section, the liquid refrigerant distribution unit configured to circulate a second fluid to enable heat transfer from the first fluid to the second fluid.

2. The evaporative cooling system of claim 1, wherein the first fluid is a mixture of air and water, and the second fluid is refrigerant.

3. The evaporative cooling system of claim 2, wherein the first evaporative section comprises a heat exchange member, wherein the heat of the heat load is transferred to the first fluid as an air and water mixture flowing across the heat exchange member.

4. The evaporative cooling system of claim 3, wherein the first evaporative section further comprises a water spray system configured to spray water into to the recirculating flow of the air and water mixture flowing across the heat exchange member.

5. The evaporative cooling system of claim 4, wherein the water spray system is coupled to a grey water storage vessel disposed below the heat exchange member, wherein the grey water storage vessel forms a water supply for the water spray system.

6. The evaporative cooling system of claim 1,

wherein the liquid refrigerant distribution unit comprises a first liquid refrigerant distribution unit and a second liquid refrigerant distribution unit, and

wherein the second evaporative section comprises a first evaporation coil in fluid communication with a first liquid refrigerant assist circuit of the first liquid refrigerant distribution unit.

7. The evaporative cooling system of claim 6,

wherein the second evaporative section further comprises a second evaporation coil in fluid communication with a second liquid refrigerant assist circuit of the second liquid refrigerant distribution unit.

8. The evaporative cooling system of claim 1, wherein the liquid refrigerant distribution unit comprises a liquid refrigerant assist circuit in fluid communication with the second evaporative section.

9. The evaporative cooling system of claim 8,

wherein the first fluid is a first refrigerant, and

wherein the liquid refrigerant distribution unit further comprises a trim compressor circuit, in which a second refrigerant flows, in thermal communication with the refrigerant flowing in the liquid refrigerant assist circuit.

10. The evaporative cooling system of claim 9, wherein the liquid refrigerant distribution unit comprises a second liquid refrigerant assist circuit in fluid communication with the second evaporative section.

11. The evaporative cooling system of claim 10, wherein the liquid refrigerant distribution unit further comprises a second trim compressor circuit, in which the second refrigerant flows, in thermal communication with the first refrigerant flowing in the second liquid refrigerant assist circuit.

12. The evaporative cooling system of claim 1, wherein the second evaporative section further comprises at least one evaporation coil in fluid communication with the liquid refrigerant distribution unit.

13. The evaporative cooling system of claim 12, wherein the at least a portion of the first fluid recirculating in the first evaporative section is condensed into a potable water receiving vessel disposed below the at least one evaporation coil.

14. The evaporative cooling system of claim 13, further comprising a conduit in fluid communication with the potable water receiving vessel to enable flow of potable water from the evaporative cooling system.

15. The evaporative cooling system of claim 1, wherein the first fluid is air, the evaporative cooling system further comprising:

an air intake pathway in fluid communication with the first evaporative section to enable the flow of air external to the evaporative cooling system into the first evaporative section; and

a wet bulb temperature sensor disposed in the air intake pathway for sensing the wet bulb temperature of the air external to the evaporative cooling system.

16. The evaporative cooling system of claim 15, further comprising:

a heat rejection member disposed in the first evaporative section to enable the cooling of the heat load;

an enthalpy sensor disposed in proximity to the heat rejection member configured to sense the enthalpy of the air flowing across the heat rejection member;

at least one fan configured to recirculate the air through the first and second evaporative sections; and

a controller configured to control the at least one fan and the liquid refrigerant distribution unit based on the wet bulb temperature sensed by the wet bulb temperature sensor and the enthalpy sensed by the enthalpy sensor.