Development and Experimental Evaluation of an Automated Charge Testing Methodology for Domestic Refrigerators

Optimizing the refrigerant charge in a vapor compression cycle can lead to improvements in system performance and energy savings. Manufacturers often perform extensive experimental charge testing under different operating conditions to determine the optimal system charge of a certain product. However, the current de-facto industry standard procedure for performing such evaluation involves repeated charging and evacuating of equipment which is a time-consuming effort. In this work, an automated charge testing device and method were developed to perform a charge optimization for domestic refrigerators with the unit operating. This device consists of a combination of three solenoids to isolate a small calibrated volume of liquid refrigerant. This calibrated volume is typically around 2cc and allows a very small amount of refrigerant, usually less than 5 grams based on the density of liquid, to be charged into a unit with consistent accuracy and repeatability. This work also includes the development of a methodology for utilizing the device including software that automatically operates the device to charge the unit with additional refrigerant, collects and compares performance data, and detects when the optimal charge is reached to end the experiment. With the developed methodology, the entire procedure can be performed without human interaction saving a great amount of time and effort compared to conventional charge testing methods