System and Method For Controlling Working Fluid Charge In A Vapor Compression Air Conditioning System

Abstract

Vapor compression air conditioning systems are provided with a flow restrictor for transferring working fluid to and from at least one of the compressor low pressure inlet conduit and compressor high pressure outlet conduit to provide for accurate charge adjustment to achieve predetermined fluid sub-cooling. Pressure and temperature measurements are taken at a condenser fluid outlet conduit and provided to a microcontroller for determining fluid sub-cooling and comparing sub-cooling with a predetermined target sub-cooling. A charge addition or recovery apparatus may include a solenoid valve controlled by the microcontroller to more accurately control the addition or recovery of refrigerant fluid charge.

1 . A method for adjusting the charge of working fluid in a vapor compression air conditioning system including a compressor, a low pressure conduit, a high pressure conduit, a condenser unit operably connected to said high pressure conduit and to a condenser discharge conduit, a pressure sensor and a temperature sensor operably associated with said condenser discharge conduit for measuring a pressure and a temperature of the working fluid, the temperature and the pressure being related to a working fluid sub-cooling, a working fluid flow restrictor device operably associated with at least one of said conduits for at least one of transferring fluid to and from said system, said method comprising:
 measuring the temperature and the pressure of the working fluid within the condenser discharge conduit, the temperature and the pressure corresponding to sub-cooling of the working fluid flowing through said system;   comparing said sub-cooling with a target sub-cooling operating condition of said working fluid to determine if a charge of working fluid should be added to said system or recovered from said system; and   carrying out at least one of adding working fluid to said system and recovering working fluid from said system by restricting the flow of working fluid with said flow restrictor device.   
     
     
         2 . The method set forth in  claim 1  including the step of:
 determining system running time prior to measuring said one or more working fluid parameters.   
     
     
         3 . The method set forth in  claim 1  including the step of:
 determining the variance of sub-cooling of said working fluid over a predetermined interval of time.   
     
     
         4 . The method set forth in  claim 1  including the step of:
 providing a signal to an operator of said system of a need to one of recover working fluid from said system and add working fluid to said system.   
     
     
         5 . The method set forth in  claim 4  including the step of one of:
 recovering working fluid and adding working fluid continuously until a predetermined amount of sub-cooling is measured indicating a desired charge of working fluid.   
     
     
         6 . The method set forth in  claim 3  including the step of:
 providing a fluid charge adding apparatus including a reservoir, a conduit connected to said reservoir and a valve interposed in said conduit; and   providing a signal indicating a condition requiring providing working fluid to said system from said apparatus.   
     
     
         7 . The method set forth in  claim 6  wherein:
 said valve is motor operated and said signal is provided to said valve to provide operation thereof to control flow of working fluid to said system.   
     
     
         8 . A method of charging a vapor compression air conditioning system, comprising:
 measuring a temperature of a working fluid exiting a condenser of the system;   measuring a pressure of the working fluid exiting the condenser;   determining a working fluid sub-cooling value based on the measured temperature and the measured pressure; and   comparing said determined working fluid sub-cooling with a target sub-cooling to determine if a charge of working fluid should be added to said system or recovered from said system.   
     
     
         9 . The method of  claim 8 , further comprising:
 adding working fluid to the system in response to a result of the comparing the determined working fluid sub-cooling with the target sub-cooling.   
     
     
         10 . The method of  claim 9 , wherein the working fluid is added into the system through a flow restriction device. 
     
     
         11 . The method of  claim 8 , further comprising:
 evacuating working fluid from the system in response to a result of the comparing the determined working fluid sub-cooling with the target sub-cooling.   
     
     
         12 . The method of  claim 11 , wherein the working fluid is evacuated from the system through a flow restriction device. 
     
     
         13 . A method of correcting a working fluid charge of an air conditioning system, comprising:
 measuring each of a pressure and a temperature of a working fluid as the working fluid exits a condenser of the system;   calculating one of an actual sub-cooling of the working fluid or a pressure representation thereof;   calculating a charge error by comparing either the actual sub-cooling of the working fluid or the pressure representation thereof to a target sub-cooling; and   adjusting an amount of working fluid within the system in response to the calculated charge error.   
     
     
         14 . The method of  claim 13 , further comprising:
 removing a portion of the working fluid from the system if the charge error indicates excessive sub-cooling.   
     
     
         15 . The method of  claim 13 , further comprising:
 adding working fluid to the system if the charge error indicates insufficient sub-cooling.   
     
     
         16 . The method of  claim 13 , wherein working fluid is passed through a flow restriction device during the adjusting the amount of working fluid within the system.