Refrigeration apparatus and method

Abstract

Methods and apparatus for an energy efficient freezer or cooler defrost, which are particularly suited for an automated system, include procedures utilized for this purpose. The procedures are included in the firmware of an embedded controller and operate the cooler or freezer defrost cycle when required for increased energy efficiency.

What is claimed is: 
     
         1 . A refrigeration apparatus comprising:
 a fan that provides an airflow;   an evaporator assembly that comprises an evaporator coil disposed in said airflow;   a refrigerant assembly disposed in fluid communication with said evaporator coil to supply refrigerant to said evaporator coil;   a first sensor that senses a temperature of said airflow at an airflow input side of said evaporator coil;   a second sensor that senses a temperature of said airflow at an airflow output side of said evaporator coil;   a third sensor that senses a temperature on a suction line near the outlet side of said evaporator coil;   a fourth sensor that senses a temperature in a location that is representative of an evaporator coil temperature;   a fifth sensor that senses pressure of said refrigerant leaving said evaporator coil, wherein said pressure of said refrigerant corresponds to an output saturated suction refrigerant temperature; and   a controller that is connected to said first, second, third, fourth and fifth sensors, that controls said evaporator assembly and said refrigerant assembly in a cooling mode and in a defrost mode, and that controls an initiation of said defrost mode based on comparison of a reference dynamic efficiency with a dynamic efficiency that is a function of current values of said temperature of said airflow at said airflow input side of said evaporator coil, said temperature of said airflow at said airflow output side of said evaporator coil and said output saturated suction refrigerant temperature of said refrigerant leaving said evaporator coil.   
     
     
         2 . The refrigeration apparatus of  claim 1 , wherein said evaporator assembly is disposed in an enclosed space that requires refrigeration and/or air conditioning. 
     
     
         3 . The refrigeration application of  claim 2 , wherein said refrigerant assembly and said controller are located outside said enclosed space. 
     
     
         4 . The refrigeration apparatus of  claim 1 , wherein said dynamic efficiency is determined by a difference between the current temperature values sensed by said first and second sensors divided by a difference between the temperature value sensed by said first sensor and said output saturated suction refrigerant temperature value sensed by said fifth sensor. 
     
     
         5 . The refrigeration apparatus of  claim 1 , wherein said first sensor is an input air temperature sensor. 
     
     
         6 . The refrigeration apparatus of  claim 1 , wherein said second sensor is an output air temperature sensor. 
     
     
         7 . The refrigeration apparatus of  claim 1 , wherein said third sensor is an evaporator output refrigerant temperature sensor. 
     
     
         8 . The refrigeration apparatus of  claim 1 , wherein said fourth sensor is a defrost termination sensor. 
     
     
         9 . The refrigeration apparatus of  claim 1 , wherein said fifth sensor is a refrigerant suction pressure transducer. 
     
     
         10 . The refrigeration apparatus of  claim 1 , further comprising a heater safety termination switch. 
     
     
         11 . The refrigeration apparatus of  claim 1 , wherein said heater safety termination switch is a safety switch which opens or closes based on said evaporator coil temperatures sensed by said heater safety termination switch and is located on said evaporator coil. 
     
     
         12 . A method for efficient defrosting of an evaporator assembly, said method comprising:
 a. Initiating start up of a refrigeration assembly, fan motor and fan if Tair, in is greater than a temperature set point;   b. Cooling Tair, in to within a predetermined temperature setting relevant to a thermostat set point;   c. Initiating a defrost program if Tair, in is within a predetermined range of said thermostat set point;   d. Calculating reference dynamic efficiency (RE) and dynamic efficiency (DE) values;   e. Determining if RE minus DE divided by RE is equal to a predetermined threshold (DET) and if yes, then initiating an electric defrost by deactivating said refrigeration assembly, deactivating said fans and activating at least one defrost heater or initiating an air defrost by deactivating said refrigeration assembly and maintaining continued operation of said evaporator fans;   f. Determining if (a) a temperature sensed by a defrost termination sensor is equal to or greater than preset defrost termination temperature, (b) a defrost time is equal to or greater than a preset defrost termination time, or (c) a evaporator coil temperature is equal to or greater than a heater safety termination temperature; and   g. If any one of (a)-(c) in step (f) occur, deactivating said defrost heater, activating said refrigeration assembly and activating said fans.