Unit cooler with integrated refrigeration and dehumidification

Abstract

An integrated refrigeration and dehumidification unit cooler for a refrigerated space, such as a cold room, includes directly serially connected refrigeration and heating coils operationally interfaced to effect passive control of room temperature and humidity conditions preventing overhead condensation.

1 . A unit cooler dehumidification system for maintaining a design temperature of below about 41° F. in a refrigerated space with supply air at a humidity and at a dew point temperature preventing condensation during operation, said system comprising: a compressor located exterior of the space, said compressor having a suction side to which a working fluid is supplied as a vapor at a saturated suction temperature and a discharge side from which the working fluid is discharged as a vapor at a high pressure and elevated temperature; a condenser heat exchanger located exterior of the space, said condenser heat exchanger supplied with said superheated vapor from said compressor for exhausting heat from said vapor and discharging the working fluid as a saturated liquid at high pressure; a unit cooler located entirely in the space, said unit cooler having a fan for providing an air flow passage between an inlet receiving return air from said room and an outlet delivering the supply air to said room, a cooling coil in said air flow passage registering with said inlet for cooling and dehumidifying said return air to a temperature below said design temperature to said dew point temperature and a heating coil in said air flow passage downstream of said coiling coil and registering with said outlet for heating the cooled return air from said cooling coil to a temperature at about said design temperature, said heating coil directly supplied with said liquid at high pressure from said condenser heat exchanger and discharging said liquid at a reduced temperature; an expansion device directly supplied with said liquid at a reduced temperature from said heating coil and supplying said liquid at reduced pressure to an inlet of said cooling coil, said cooling coil discharging said liquid at reduced pressure from an outlet directly and continuously to said inlet of said compressor. 
   
   
       2 . The system as recited in  claim 1  wherein said saturated suction temperature of said compressor is sufficient to attain said dew point temperature at said cooling coil and a relative humidity of 70% to 85%. 
   
   
       3 . The system as recited in  claim 2  wherein said saturated suction temperature is below 25° F. 
   
   
       4 . The system as recited in  claim 3  wherein said heating coil has about 15% to 35% of the heat transfer surface of the cooling coil. 
   
   
       5 . The system as recited in  claim 4  wherein said heating coil has about 20% to 30% of the heat transfer surface of the cooling coil. 
   
   
       6 . The system as recited in  claim 2  wherein said dew point temperature is below about 25° F. 
   
   
       7 . The system as recited in  claim 2  wherein said supply air temperature is about 31° F. 
   
   
       8 . A method of operating a unit cooler contained in a refrigerated room at a room design temperature below 41° F. under conditions avoiding condensation on overhead surfaces of the room, comprising the steps of: selecting a dew point for supply air that avoids the condensation and a supply air temperature for maintaining said room design temperature; providing a unit cooler having a refrigeration coil and a heating coil serially disposed in a fan assisted air passage to routing return air to an inlet and the supply air from an outlet; providing a first working fluid flow path between an outlet of the refrigeration coil and the heating coil having a compressor and a heat exchanger; providing a second working fluid flow path directly serially connecting an outlet of said heating coil and an inlet of said cooling coil; providing an expansion device in said second working fluid flow path; operating said heating coil at a temperature to achieve said dew point; and operating said heating coil to achieve said supply temperature while enabling said heating coil to achieve said dew point temperature. 
   
   
       9 . The method as recited in  claim 8  including the step of providing said heating coil with about 15% to 35% as much heat transfer area as said cooling coil. 
   
   
       10 . The method as recited in  claim 9  including the step of providing said heating coil with about 20% to 30% as much heat transfer area as said cooling coil. 
   
   
       11 . The method as recited in  claim 10  including operating said compressor as a suction temperature sufficient for the cooling coil to attain said dew point temperature and said heating coil to attain said supply air temperature. 
   
   
       12 . A unit cooler for mounting at the ceiling area of a refrigerated space comprising: a housing having an inlet and an outlet; means for mounting said housing at the ceiling area of the refrigerated space; a fan in said housing for establishing an air flow between said inlet and said outlet; a coiling coil in said housing adjacent said inlet having a cooling heat transfer surface; a heating coil disposed in said housing between said cooling coil and said outlet whereby said air flow is directed serially from said cooling coil to said heating coil; first conduit means for directly fluidly connecting an inlet of said heating coil with a source of high pressure fluid at an elevated temperature whereby said heating coil is effective for heating the air flow from said cooling coil and lowering the temperature of said high pressure fluid; second conduit means in said housing for directly and continuously operatively fluidly connecting an outlet of said heating coil with an inlet of said cooling coil; an expansion device in said second conduit means for converting said high pressure fluid from said outlet of said heating coil to a low pressure cooled vapor at a cooled temperature for supply to an outlet of said heating coil; and third conduit means for directly fluidly connecting an outlet of said cooling coil to the inlet of a compressor, wherein said heating heat transfer surface has an effective area of about 15% to 35% of said cooling heat transfer surface. 
   
   
       13 . The unit cooler as recited in  claim 12  wherein said heating heat transfer surface has an effective area of about 20% to 30% of said cooling heat transfer surface