Patent Application
20240328694
The present disclosure relates to controlled environment rooms, and more particularly to temperature control systems for controlled environment rooms.
Controlled environment rooms that are used in the life sciences and technology industry are typically tempered using a standard refrigeration cycle and a hot gas bypass injection system to the evaporator (cooling coil) to precisely control the air temperature for the environment. This typical system design meets the intended purpose but is not particularly energy efficient since the compressor and supporting components must run twenty-four hours a day, consuming significant amounts of energy to achieve the desired temperature control settings. This approach has been commonly used in the controlled environmental room industry for many years with much success, but energy consumption has never been a driving factor in the design of such systems.
In one aspect, a temperature control system for refrigeration of a controlled environment room is provided. The temperature control system comprises a room evaporator having a room evaporator refrigerant inlet and a room evaporator refrigerant outlet and at least one room impeller adapted to cycle return air from the controlled environment room through the room evaporator and back into the controlled environment room. The temperature control system further comprises a control unit and a variable speed compressor having a compressor refrigerant inlet and a compressor refrigerant outlet. The temperature control system further comprises a room temperature sensor adapted to be positioned inside of the room to detect an internal temperature of the room, wherein the room temperature sensor is in communication with the control unit. The temperature control system further comprises a condenser having a condenser refrigerant inlet and a condenser refrigerant outlet, and a fluid return loop wherein the room evaporator refrigerant outlet is in valve-controlled one-way fluid communication with the compressor refrigerant inlet, the compressor refrigerant outlet is in one-way fluid communication with the condenser refrigerant inlet, the condenser refrigerant outlet is in valve-controlled one-way fluid communication with the room evaporator refrigerant inlet and a metering valve is interposed in the fluid return loop between the condenser refrigerant outlet and the room evaporator refrigerant inlet. The control unit is adapted to use input from the room temperature sensor to adjust a speed of the compressor and control the metering valve to meter a mass flow through the metering valve to the room evaporator refrigerant inlet to cause the metering valve and the compressor to cooperate to maintain the mass flow at a level required to maintain a temperature setpoint of the room while limiting compressor frequency.
In an embodiment, the temperature control system further comprises a valve-controlled hot gas bypass link interposed between the compressor refrigerant outlet and the condenser refrigerant inlet. The hot gas bypass link has a bypass control valve interposed therein, and is adapted to, under control of the bypass control valve, selectively flow uncooled refrigerant from the compressor refrigerant outlet, upstream of the condenser, to the room evaporator refrigerant inlet, downstream of the metering valve.
In one particular embodiment, a muffler is interposed in the hot gas bypass link.
In one particular embodiment, the temperature control system further comprises a fresh air evaporator having a fresh air evaporator refrigerant inlet and a fresh air evaporator refrigerant outlet. Fresh air moves through the fresh air evaporator and toward the room evaporator whereby the fresh air moves through the room evaporator and into the controlled environment room. The condenser refrigerant outlet is in valve-controlled one-way fluid communication with the fresh air evaporator refrigerant inlet, upstream of the metering valve. The fresh air evaporator refrigerant outlet is in valve-controlled one-way fluid communication with the compressor refrigerant inlet. In one specific implementation of this particular embodiment, a temperature-controlled modulating valve is interposed between the condenser refrigerant outlet and the fresh air evaporator refrigerant inlet. The temperature-controlled modulating valve is controlled by an outlet temperature sensor disposed downstream of the fresh air evaporator refrigerant outlet and adapted to detect a temperature of refrigerant exiting the fresh air evaporator refrigerant outlet.
In one embodiment, the temperature control system further comprises a desuperheating temperature controller and a desuperheating fluid loop, wherein the condenser refrigerant outlet is in one-way valve-governed fluid communication with the compressor refrigerant inlet. A compressor inlet temperature sensor is disposed on the desuperheating fluid loop upstream of the compressor refrigerant inlet, wherein the compressor inlet temperature sensor is in communication with the desuperheating temperature controller. A desuperheating control valve is interposed in the desuperheating fluid loop between the condenser refrigerant outlet and the compressor refrigerant inlet. The desuperheating temperature controller is adapted to control the desuperheating control valve in response to the compressor inlet temperature sensor to mix cooled refrigerant from the condenser refrigerant outlet with uncooled uncompressed refrigerant from the room evaporator refrigerant outlet upstream of the compressor refrigerant inlet to inhibit superheating of the compressor. A capillary may be interposed in the desuperheating fluid loop downstream of the desuperheating control valve.
In an embodiment, the temperature control system further comprises a suction accumulator interposed in the fluid return loop between the room evaporator refrigerant outlet and the compressor refrigerant inlet.
In an embodiment, the temperature control system further comprises a receiver interposed in the fluid return loop between the condenser refrigerant outlet and the metering valve, wherein the receiver is adapted to provide a reservoir of pressurized liquid refrigerant. In a particular embodiment, a dryer is interposed in the fluid return loop between the receiver and the metering valve.
In an embodiment, boil-off condensate piping is interposed in the fluid return loop between the compressor refrigerant outlet and the condenser refrigerant inlet, downstream of the hot gas bypass.
In a preferred embodiment, the temperature control system is mounted atop the controlled environment room in a penthouse arrangement.
In a preferred embodiment, the room impeller(s) have variable speed and the control unit is adapted to use the input from the room temperature sensor to control the speed of the room impeller(s) according to cooling demand.
In another aspect, a temperature control system for refrigeration of a controlled environment room is provided. The temperature control system comprises a room evaporator having a room evaporator refrigerant inlet and a room evaporator refrigerant outlet, and at least one room impeller adapted to cycle return air from the room through the room evaporator and back into the room. The temperature control system further comprises a fresh air evaporator having a fresh air evaporator refrigerant inlet and a fresh air evaporator refrigerant outlet, wherein fresh air moves through the fresh air evaporator and toward the room evaporator whereby the fresh air moves through the room evaporator and into the controlled environment room. The temperature control system further comprises a control unit, a variable speed compressor having a compressor refrigerant inlet and a compressor refrigerant outlet, and a room temperature sensor adapted to be positioned inside of the room to detect an internal temperature of the room, wherein the room temperature sensor is in communication with the control unit. The temperature control system further comprises a condenser having a condenser refrigerant inlet and a condenser refrigerant outlet, and a fluid return loop. In the fluid return loop, the room evaporator refrigerant outlet is in valve-controlled one-way fluid communication with the compressor refrigerant inlet through a suction accumulator interposed between the room evaporator refrigerant outlet and the compressor refrigerant inlet, the compressor refrigerant outlet is in one-way fluid communication with the condenser refrigerant inlet and the condenser refrigerant outlet is in valve-controlled one-way fluid communication with the room evaporator refrigerant inlet. The condenser refrigerant outlet is in valve-controlled one-way fluid communication with the room evaporator refrigerant inlet through a metering valve interposed between the condenser refrigerant outlet and the room evaporator refrigerant inlet, a receiver interposed between the condenser refrigerant outlet and the metering valve, wherein the receiver is adapted to provide a reservoir of pressurized liquid refrigerant, and a dryer interposed between the receiver and the metering valve. The condenser refrigerant outlet is in valve-controlled one-way fluid communication with the fresh air evaporator refrigerant inlet, upstream of the metering valve and downstream of the dryer, and the fresh air evaporator refrigerant outlet is in valve-controlled one-way fluid communication with the compressor refrigerant inlet through the suction accumulator. The temperature control system further comprises a valve-controlled hot gas bypass link interposed between the compressor refrigerant outlet and the condenser refrigerant inlet. The hot gas bypass link has a bypass control valve interposed therein. The hot gas bypass link is adapted to, under control of the bypass control valve, selectively flow uncooled refrigerant from the compressor refrigerant outlet, upstream of the compressor, to the room evaporator refrigerant inlet, downstream of the metering valve. The temperature control system further comprises a desuperheating temperature controller and a desuperheating fluid loop wherein the condenser refrigerant outlet is in one-way valve-governed fluid communication, through the receiver and the dryer, with the compressor refrigerant inlet through the suction accumulator. A desuperheating control valve is interposed in the desuperheating fluid loop between the dryer and the compressor refrigerant inlet and a compressor inlet temperature sensor is disposed upstream of the compressor refrigerant inlet and downstream of the suction accumulator, wherein the compressor inlet temperature sensor is in communication with the desuperheating temperature controller. The desuperheating temperature controller is adapted to control the desuperheating control valve in response to the compressor inlet temperature sensor to mix cooled refrigerant from the condenser refrigerant outlet with the uncooled refrigerant from the room evaporator refrigerant outlet, upstream of the suction accumulator, to inhibit superheating of the compressor. The control unit is adapted to use input from the room temperature sensor to adjust a speed of the compressor and to control the metering valve to meter a mass flow through the metering valve to the room evaporator refrigerant inlet to cause the metering valve and the compressor to cooperate to maintain the mass flow at a level required to maintain a temperature setpoint of the room while limiting compressor frequency. The control unit is also adapted to control the bypass control valve to flow the uncooled refrigerant from the compressor refrigerant outlet to the room evaporator refrigerant inlet downstream of the metering valve.
In an embodiment, a muffler is interposed in the hot gas bypass link.
In a preferred embodiment, the room impeller(s) have variable speed, and the control unit is adapted to use the input from the room temperature sensor to control the speed of the room impeller(s) according to cooling demand.
In an embodiment, a temperature-controlled modulating valve is interposed between the condenser refrigerant outlet and the fresh air evaporator refrigerant inlet. The temperature-controlled modulating valve is controlled by an outlet temperature sensor disposed downstream of the fresh air evaporator refrigerant outlet and adapted to detect a temperature of refrigerant exiting the fresh air evaporator refrigerant outlet.
In an embodiment, a capillary is interposed in the desuperheating fluid loop downstream of the desuperheating control valve and upstream of the suction accumulator.
In an embodiment, boil-off condensate piping is interposed in the fluid return loop between the compressor refrigerant outlet and the condenser refrigerant inlet, downstream of the hot gas bypass.
In a preferred embodiment, the temperature control system is mounted atop the controlled environment room in a penthouse arrangement.
These and other features will become more apparent from the following description in which reference is made to the appended drawings wherein:
Energy efficiency can be improved through a refrigeration system that only evaporates enough refrigerant to precisely match the cooling load for a controlled environment room while maintaining the desired temperature control conditions with appropriate precision. To this end, in addition to matching the size of the compressor for the refrigeration system to the size of the controlled environment room, a variable refrigerant flow is provided. This variable refrigerant flow is achieved by a variable speed compressor and one or more metering valves that precisely regulate the refrigerant flow to the evaporator. The variable speed compressor responds to the varying refrigerant flow and consumes less energy than traditional hot gas bypass systems. The impellers that move air across the evaporator may also be variable speed fans and be electrically commutated, increasing heat transfer in the refrigeration system while reducing energy consumption.
Reference is now made to
The temperature control system 100 comprises a room evaporator 102 (evaporator coil) having a room evaporator refrigerant inlet 102A and a room evaporator refrigerant outlet 102B, along with at least one room impeller 104 (e.g. evaporator fan) that is adapted to cycle return air from the controlled environment room through the room evaporator 102 and back into the controlled environment room. In one preferred embodiment, two variable speed fans are provided as room impellers 104; these are preferably provided with high-efficiency motors having electrically commutated motor windings for energy efficiency. The room impeller(s) 104 are positioned on the air outlet side of the room evaporator 102 to draw air across the surface area of the cooling coil thereof.
The system 100 further comprises a fresh air evaporator 106 having a fresh air evaporator refrigerant inlet 106A and a fresh air evaporator refrigerant outlet 106B. Fresh air may be supplied to the system 100 from a conventional HVAC or air ventilation system under positive pressure, with the fresh air evaporator 106 being positioned to pre-cool the supplied fresh air before it is deposited on the return air side of the room evaporator 102 to be moved across the room evaporator 102 by the room impeller(s) 104. This arrangement is described in more detail in respect of
Additionally, the temperature control system 100 comprises a control unit 110. The control unit 110 may be, for example, a programmable logic controller (PLC) or a programmed computer. Other suitable devices may also be used as a control unit.
As noted above, the temperature control system 100 comprises a variable speed compressor 112, which has a compressor refrigerant inlet 112A and a compressor refrigerant outlet 112B. In a preferred embodiment, the variable speed compressor 112 is a scroll compressor. The control unit 110 is communicatively coupled to the variable speed compressor 112, for example by wired or wireless communication, and can control the speed of the variable speed compressor 112. Where the room impeller(s) 104 are variable speed impeller(s), the control unit 110 is also communicatively coupled thereto to control the speed thereof, for example by wired or wireless communication.
A room temperature sensor 114 (see
The system 100 also includes a condenser 116 having a condenser refrigerant inlet 116A and a condenser refrigerant outlet 116B. The condenser 116 may be a water-cooled condenser or optionally an air-cooled condenser. Where the condenser 116 is a water-cooled condenser as shown, a condenser water input 116C and condenser drain 116D are provided.
The various components are connected in fluid communication by a fluid return loop through which refrigerant can flow. The fluid return loop comprises a main portion 118 which connects the room evaporator 102, the variable speed compressor 112 and the condenser 116, as well as other components, as described in more detail below.
The main portion 118 of the fluid return loop connects the room evaporator refrigerant outlet 102B in valve-controlled one-way fluid communication with the compressor refrigerant inlet 112A through a suction accumulator 120, which has a suction accumulator inlet 120A and a suction accumulator outlet 120B. The suction accumulator 120 is interposed in the main portion 118 of the fluid return loop between the room evaporator refrigerant outlet 102B and the compressor refrigerant inlet 112A. The suction accumulator 120 traps any liquid entrained in the gaseous low pressure refrigerant received from the room evaporator refrigerant outlet 102B. Fluid communication between the room evaporator refrigerant outlet 102B and the suction accumulator inlet 120A is governed by a crankcase pressure regulator valve (CPRV) 122 interposed in the main portion 118 of the fluid return loop between the room evaporator refrigerant outlet 102B and the suction accumulator inlet 120A. The CPRV 122 regulates the flow of gaseous refrigerant to prevent overpressure. In a preferred embodiment, refrigerant emerges from the suction accumulator outlet 120B, and enters the compressor refrigerant inlet 112A, at a pressure of approximately 50 to 60 pounds per square gauge (PSIG).
The main portion 118 of the fluid return loop connects the compressor refrigerant outlet 112B in one-way fluid communication with the condenser refrigerant inlet 116A. In the illustrated embodiment, boil-off condensate piping 124 is interposed in the main portion 118 of the fluid return loop between the compressor refrigerant outlet 112B and the condenser refrigerant inlet 116A. The boil-off condensate piping 124 is circuited within an elongate narrow plastic condensate capture pan 292 (see
The condenser refrigerant outlet 116B is in valve-controlled one-way fluid communication with the room evaporator refrigerant inlet 102A through a series of components. Beginning with the component closest to the room evaporator refrigerant inlet 102A and moving progressively toward the condenser refrigerant outlet 116B, with the description proceeding opposite the direction of refrigerant flow in the main portion 118 of the fluid return loop, these components comprise a metering valve 126, a main portion solenoid valve 128, sight glass 130, a dryer 132 and a receiver 134.
The metering valve 126 is interposed between the condenser refrigerant outlet 116B and the room evaporator refrigerant inlet 102A, and is in communication with the control unit 110, for example by wired or wireless communication, so that the control unit 110 can control the mass flow of refrigerant through the metering valve 126. The metering valve 126 may be, for example, an electronic expansion valve, for example an electronic thermostatic expansion valve or other suitable valve. The metering valve 126 regulates the precise superheat of the refrigerant gas through the room evaporator 102 back to the variable speed compressor 112.
The main portion solenoid valve 128 functions as an on/off switch to selectively prevent refrigerant from the condenser refrigerant outlet 116B from reaching the room evaporator refrigerant inlet 102A, and is interposed in the main portion 118 of the fluid return loop between the metering valve 126 and the condenser refrigerant outlet 116B. Thus, fluid communication between the condenser refrigerant outlet 116B and the room evaporator refrigerant inlet 102A is controlled by both the metering valve 126 and the main portion solenoid valve 128.
The sight glass 130 allows an observer to visually inspect the liquid refrigerant flow to determine whether bubbles are present in the refrigerant, in which case remedial action is required. In the illustrated embodiment, the main portion solenoid valve 128 is interposed in the main portion 118 of the fluid return loop between the metering valve 126 and the sight glass 130.
The dryer 132 removes residual moisture from the refrigerant received from the receiver 134, which is adapted to provide a reservoir of pressurized liquid refrigerant. The receiver 134 is interposed between the condenser refrigerant outlet 116B and the metering valve 126; more particularly, the receiver 134 is interposed between the condenser refrigerant outlet 116B and the dryer refrigerant inlet 132A. The dryer 132 is interposed between the receiver 134 and the metering valve 126; more particularly, the dryer 132 is interposed between the receiver 134 and the sight glass 130.
Accordingly, the main portion 118 of the fluid return loop enables compressed refrigerant to flow from the compressor refrigerant outlet 112B through the boil-off condensate piping 124 to the condenser refrigerant inlet 116A. The refrigerant emerges from the condenser refrigerant outlet 116B as a liquid under high pressure, and enters the receiver refrigerant inlet 134A. In the illustrated embodiment, the refrigerant leaving the receiver refrigerant outlet 134B is a liquid at a pressure between 250 PSIG and 290 PSIG. In the illustrated embodiment, the pressure of 250 PSIG is a low-end pressure, a pressure of 275 PSIG is a mid-range pressure, and pressure of 290 PSIG is considered a high pressure and would be used only if the condensate capture pan 292 (see
The control unit 110 is adapted to use input from the room temperature sensor 114 (see
The control unit 110 can vary any one or more of: the speed (frequency) of the variable speed compressor 112, the speed of the room impeller(s) 104, and/or the setting of the metering valve 126, upon detecting a difference between the desired temperature setpoint (which may be set by a user) and the temperature reported by the room temperature sensor 114. The control unit 110 may use, for example, one or more of proportional, integral and derivative intelligent control. Variable speed drive (VSD) may be used for the variable speed compressor 112 and/or the speed of the room impeller(s) 104.
By providing the room impeller(s) 104 as variable speed evaporator fans that can, under control of the control unit 110, respond to deviations from the room temperature setpoint in parallel with changes in the compressor frequency, the system 100 can effectively respond to changes in cooling load within the controlled environment room. The ability of the control unit 110 to change the speed of the impeller(s) 104 and the frequency of the variable speed compressor 112 enable the refrigeration cycle to counteract sudden increases in cooling loads, notably when a door of the controlled environment room is opened. When a cooling load is imposed, such as a door opening, the control unit 110 can receive a signal, for example from a door sensor and/or from the room temperature sensor 114. The control unit 110 can then cause the room impeller(s) 104 to speed up in conjunction with the variable speed compressor 112 to provide more net refrigeration effect and additional dehumidification when it is needed most to control the moisture level within the controlled environment room.
Increasing the speed of the room impeller(s) 104 can provide an immediate increase in face velocity at the room evaporator 102 and thereby increased heat transfer providing more net refrigeration effect at the room evaporator 102 to cool the room. In addition, the ability of the control unit 110 to vary the air volume moved by the room impeller(s) 104 and to vary the pumping rate of the variable speed compressor 112 depending on the cooling load of the room can reduce energy usage and also reduce wear and tear on the variable speed compressor 112 and the motor(s) of the room impeller(s) 104.
In addition to the main portion 118, the fluid return loop also includes a fresh air portion 136. The fresh air portion 136 of the fluid return loop carries high pressure liquid refrigerant through the fresh air evaporator 106, which provides for pre-cooling of fresh air when supplied to the room evaporator for introduction into the controlled environment room (for example, when personnel are inside the room). For example, the fresh air evaporator 106 may pre-cool the fresh air to between about 7 degrees Celsius and about 10 degrees Celsius. The fresh air portion 136 of the fluid return loop branches off from the main portion 118 between the sight glass 130 and the main portion solenoid valve 128. Thus, the fresh air portion 136 of the fluid return loop branches off from the main portion 118 upstream of the metering valve 126 and downstream of the dryer 132. The fresh air portion 136 of the fluid return loop returns to the main portion 118 between the CPRV 122 and the suction accumulator 120.
The condenser refrigerant outlet 116B is in valve-controlled one-way fluid communication with the fresh air evaporator refrigerant inlet 106A via the fresh air portion 136 of the fluid return loop. A fresh air portion solenoid valve 138 is interposed in the fresh air portion 136 of the fluid return loop, downstream of where the fresh air portion 136 of the fluid return loop branches off from the main portion 118 and upstream of the fresh air evaporator refrigerant inlet 106A. The fresh air portion solenoid valve 138 functions as an on/off switch to selectively prevent refrigerant from reaching the fresh air evaporator refrigerant inlet 106A.
The fresh air evaporator refrigerant outlet 106B is in valve-controlled one-way fluid communication with the compressor refrigerant inlet 112A through the suction accumulator 120 via the fresh air portion 136 of the fluid return loop. More particularly, refrigerant travels from the fresh air evaporator refrigerant outlet 106B through an evaporator pressure regulator valve (EPRV) 140 downstream of which the fresh air portion 136 of the fluid return loop rejoins the main portion 118 of the fluid loop, downstream of the CPRV 122 and upstream of the suction accumulator 120. The low-pressure gaseous refrigerant from the fresh air evaporator refrigerant outlet 106B thus mixes with the low-pressure gaseous refrigerant from the room evaporator refrigerant outlet 102B, and the mixture enters the suction accumulator inlet 120A.
In a preferred embodiment, a temperature-controlled modulating valve 142 is interposed between the condenser refrigerant outlet 116B and the fresh air evaporator refrigerant inlet 106A. More particularly, in the illustrated embodiment the temperature-controlled modulating valve 142 is disposed downstream of the fresh air portion solenoid valve 138 and upstream of the fresh air evaporator refrigerant inlet 106A. The temperature-controlled modulating valve 142 is controlled by an outlet temperature sensor 144 disposed downstream of the fresh air evaporator refrigerant outlet 106B and adapted to detect a temperature of the refrigerant exiting the fresh air evaporator refrigerant outlet 106B. In the illustrated embodiment, the outlet temperature sensor 144 is disposed upstream of the EPRV 140.
The fluid return loop further comprises a valve-controlled hot gas bypass link 146 interposed between the compressor refrigerant outlet 112B and the condenser refrigerant inlet 116A. The hot gas bypass link 146 has a bypass control valve 148 interposed therein. The hot gas bypass link 146 is adapted to, under control of the bypass control valve 148, selectively flow uncooled refrigerant from the compressor refrigerant outlet 112B, upstream of the condenser 116, to the room evaporator refrigerant inlet 102A, downstream of the metering valve 126. In the illustrated embodiment, the hot gas bypass link 146 branches off from the main portion 118 of the fluid return loop downstream of the compressor refrigerant outlet 112B and upstream of the condenser refrigerant inlet 116A (and upstream of the boil-off condensate piping 124).
Thus, the hot gas bypass link 146 can enable refrigerant exiting the compressor refrigerant outlet 112B to bypass the boil-off condensate piping 124, condenser 116, receiver 134, dryer 132, sight glass 130, main portion solenoid valve 128 and metering valve 126 and proceed to the room evaporator refrigerant inlet 102A. The bypass control valve 148 is preferably a rapid cycle solenoid valve. An optional muffler 150 is interposed in the hot gas bypass link 146. In the illustrated embodiment, the muffler 150 is disposed downstream of the variable speed compressor 112 and upstream of the bypass control valve 148; a shut-off valve 152, such as an isolation ball valve, is disposed in the hot gas bypass link 146 between the muffler 150 and the bypass control valve 148.
The control unit 110 can control the bypass control valve 148 to flow the uncooled refrigerant from the compressor refrigerant outlet 112B to the room evaporator refrigerant inlet 102A downstream of the metering valve 126. The control unit 110 can also control the main portion solenoid valve 128 and the fresh air portion solenoid valve 138. The hot gas bypass link 146 may be used to maintain a precise temperature in the room evaporator 102.
The fluid return loop additionally comprises a desuperheating fluid loop 154. The desuperheating fluid loop 154 places the condenser refrigerant outlet 116B in one-way valve-governed fluid communication, through the receiver 134, the dryer 132, the sight glass 130 and the suction accumulator 120, with the compressor refrigerant inlet 112A. More particularly, the desuperheating fluid loop 154 branches off from the main portion 118 of the fluid return loop downstream of the sight glass 130 and upstream of the main portion solenoid valve 128 (and hence also upstream of the metering valve 126). The desuperheating fluid loop 154 rejoins the main portion 118 of the fluid return loop downstream of the CPRV 122 and upstream of the suction accumulator inlet 120A. A desuperheating control valve 156, preferably a solenoid valve, is interposed in the desuperheating fluid loop 154 between the sight glass 130 and the suction accumulator 120 and hence between the dryer 132 and the compressor refrigerant inlet 112A. In the illustrated embodiment, a capillary 158 is interposed in the desuperheating fluid loop 154 downstream of the desuperheating control valve 156 and upstream of the suction accumulator 120; the capillary 158 serves a metering function and provides a pressure drop.
A compressor inlet temperature sensor 160 is disposed upstream of the compressor refrigerant inlet 112A and downstream of the suction accumulator outlet 120B. The compressor inlet temperature sensor 160 functions as an independent return gas temperature sensor, and is in communication with a desuperheating temperature controller 162. The desuperheating temperature controller 162 is adapted to control the desuperheating control valve 156 in response to the compressor inlet temperature sensor 160 to mix cooled refrigerant from the condenser refrigerant outlet 116B with the uncooled refrigerant from the room evaporator refrigerant outlet 102B, upstream of the suction accumulator 120, to inhibit superheating of the variable speed compressor 112. In some embodiments, the desuperheating temperature controller may be integrated into the control unit.
Thus, the desuperheating fluid loop 154 is controlled and regulated by the temperature of the return gas flowing to the variable speed compressor 112, which will then pulse liquid into the suction accumulator 120 to quench the suction gas to the variable speed compressor 112, thereby providing internal cooling to the variable speed compressor 112 to support long lifecycle duty.
Under control of the control unit 110, by operation of the bypass control valve 148 and the main portion solenoid valve 128, the hot gas bypass link 146 can be used to provide a warming rather than a cooling function. The uncooled refrigerant, which will in fact be relatively heated as it exits the compressor refrigerant outlet 112B, can be used to temper the temperature of the coil of the room evaporator 102 to provide a warm air delivery system. Simultaneously, the desuperheating fluid loop 154, under control of the desuperheating temperature controller 162, can ensure the return gas temperature of the refrigerant entering the compressor refrigerant inlet 112A is satisfactory to cool the compressor windings of the variable speed compressor 112. Thus, necessary desuperheating can be provided to the variable speed compressor 112 during warming operation. Accordingly, the temperature control system 100 can be configured to be able to provide either cooling or heating using only the refrigeration cycle without the use of electric heating elements. In one embodiment, the temperature control system 100 can control the temperature of a controlled environment room to a temperature between +4 degrees Celsius up to +37 degrees Celsius within a surrounding ambient environment of +21 degrees Celsius.
In a preferred embodiment, the temperature control system 100 is assembled in a pre-packaged unit that can be mounted atop the controlled environment room in a penthouse arrangement. The use of a penthouse arrangement avoids the need for internally mounted cooling coils and drain lines as are required in conventional systems.
Reference is now made to
In the illustrated embodiment, the components of the temperature control system 100 other than the control unit 110 and the room temperature sensor 114 are disposed on the roof 278 of the controlled environment room 270 in a penthouse arrangement, and may be enclosed within a housing 280. The housing 280 may include external fresh air vents through which air from outside of the controlled environment room 270 may be passed through the fresh air evaporator 106. Note that in some embodiments, the control unit may be disposed other than within the control panel, for example within the housing, in which case the control panel may provide only the user interface, which communicates with the control unit located elsewhere, for example by wired or wireless communication.
Within the housing 280, the room evaporator 102 and the room impeller(s) 104 are enclosed within a non-metallic (e.g. plastic), fully insulated and sealed enclosure forming a room evaporator compartment 282 having a room return air inlet 282A and a room supply air outlet 282B, both of which are sealed in position within an opening in the ceiling 284 of the controlled environment room 270. The room impeller(s) 104 draw room return air RRA from the interior 276 of the controlled environment room 270 through the room return air inlet 282A and across the room evaporator 102 and then expel the treated air TA back into the interior 276 of the controlled environment room 270 through the room supply air outlet 282B as room supply air RSA. The room supply air outlet 282B may be covered by a supply air grille 286, which may be configured to diffuse the room supply air RSA ejected from the room supply air outlet 282B. Importantly, the room impeller(s) 104 are disposed on the air outlet side of the room evaporator 102 so as to “suck” air across the coil of the room evaporator 102; this provides a more uniform air distribution across the fin surface. An external air supply duct 287, for example from a conventional HVAC or other ventilation system, supplies fresh air FA at positive pressure (for example, from about 20 cubic feet per minute (CFM) to about 30 CFM) to a fresh air duct 288 which communicates the fresh air FA into the room evaporator compartment 282 on the room return air side of the room evaporator 102. The fresh air evaporator 106 is interposed between the external air supply duct 287 and the fresh air duct 288 so that the fresh air FA suppled from the external air supply duct 287 is pushed across the fresh air evaporator 106 to be pre-treated before reaching the room evaporator compartment 282.
The room impeller(s) 104 are configured, under control of the control unit 110, to provide adequate air changes per hour (ACH) within the controlled environment room 270 when running at lower speeds, while enhancing precision temperature control of the interior 276 of the controlled environment room 270. During normal operation the room impeller(s) 104 will circulate an adequate amount of air to maintain precise room conditions while balancing the face velocity of the air across the coil of the room evaporator 102 in conjunction with the capacity of the variable speed compressor 112. During periods of low cooling loads, the room impeller(s) 104 will operate at a base (e.g. lowermost) speed. In one embodiment, for an 8 foot by 8 foot by 8 foot room, a base speed is designed to generate approximately 75 ACH, with the room impeller(s) 104 configured, under control of the control unit 110, to double the volume of air circulated to 150 ACH once a cooling load is imposed. This allows a significant amount of air to pass across the room evaporator 102, providing additional refrigeration effect while also creating additional dehumidification to better control relative humidity in the interior 276 of the controlled environment room 270. This additional airflow and increase in the net refrigeration effect with accompanying increase in compressor capacity allows the temperature in the controlled environment room to recover quickly.
Selection of suitable components to implement a temperature control system as described herein is within the capability of one of ordinary skill in the art, now informed by the present disclosure. Moreover, temperature control systems as described herein may include other aspects and/or components as are known to those of ordinary skill in the art even though not explicitly described herein.
It will be appreciated that the present disclosure describes merely one illustrative implementation of a method for controlling refrigeration of a controlled environment room.
One or more currently preferred embodiments have been described by way of example. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the claims.
The following list of reference numerals is provided for convenience of reference, without limitation of any kind, express or implied.
