Patent ID: 7765831
Filing Date: 2010-08-03
Classification: F25B,F25D

Abstract:
1. A method of operating an air cargo container temperature control system Utilizing multiple refrigeration circuits, each circuit having a compressor, a condenser and an evaporator in fluid communication with each other, comprising the steps of: initiating a start-up routine to determine if the temperature control system is operating correctly; sensing temperature to record a temperature T and transmit temperature data to a system controller; comparing the temperature T recorded by a sensor to a set point temperature Tsp and if the temperature T is greater than the set point temperature Tsp, the controller is programmed to calculate the difference between T and Tsp and determine whether to continue in null mode or to operate the temperature control system in a cooling mode, and if the cooling mode is chosen, the controller is programmed to choose between a high speed cooling mode in which at least one of the compressors operates at a high speed and a low speed cooling mode in which at least one of the compressors operates at a low speed; and if the temperature T is less than or equal to the set point temperature Tsp then the controller is programmed to calculate the difference between T and Tsp and determine whether to operate in null mode or to activate heater elements to heat load space air; wherein the controller is programmed to determine whether the temperature T is greater than or equal to the sum of the set point temperature Tsp and a temperature constant T 3 and if the temperature T is greater than the sum of the set point temperature Tsp and the temperature constant T 3 the controller moves to operate all compressors and refrigeration circuits at high speed and operate a fan to direct load space air across the evaporator coils of all of the refrigeration circuits to cool load space air; wherein if the temperature T is less than the sum of the set point temperature Tsp and the temperature constant T 3 the controller is programmed to determine whether the temperature T is greater than or equal to the sum of the set point temperature Tsp and a temperature constant T 4 and if the temperature T is greater than or equal to the sum of the set point temperature Tsp and the temperature constant T 4 the controller moves to operate the compressors of all refrigeration circuits at low speed and operate the fan to direct load space air across the evaporator coils of all of the refrigeration circuits to cool the load space air.