Experimental Study on the Thermal Behavior of a Domestic Refrigeration Compressor during Transient Operation in a Small Capacity Cooling System

Generally, domestic refrigerators and freezers are running in non-continuous operation mode most of the time, which is a necessity to match cooling capacity to thermal loads. In currently available domestic appliances it can be observed, that this matching is mainly realized in two different ways: On the one hand, a simple on/off control of the hermetic compressor is installed in lower priced appliances with limited energy efficiency for the mass market. On the other hand, modern top efficiency class appliances have a variable frequency controlled compressor installed. Both control strategies have a repetitive and transient change of thermodynamic states of the refrigerant in common.
For better understanding of these cyclic patterns in terms of internal temperature distribution, a state of the art domestic refrigeration compressor with a displacement of approximately 6 cubic centimeters is integrated in a commercial freezer. The compressor which has an on/off control is equipped with extensive measurement instrumentation. Several temperature probes are inserted and temperatures on surfaces inside and outside the compressor as well as refrigerant temperatures are logged for both cyclic and steady-state behavior.
Finally, a comparison between transient experimental data and steady-state data from a standardized calorimeter test bench is done.