Control of Household Refrigerators Part II: Alternate Control Approaches for Improving Temperature Performance and Reducing Energy Use

Abstract

In Part I it was shown that conventional control of household refrigerators is achieved by regulating the distribution of air in the freezer compartment to all other parts of the plant. In Part II three alternative approaches to the conventional control of a top-mount refrigerator are presented: variable temperature bandwidths, uncoupled compressor and evaporator fan, and the combination of these two. These allowed the plant to achieve near-ideal control with respect to improved temperature performance in each compartment. Automatic airflow dampers were used with the dual controllers to independently regulate refrigerator compartment temperature. Plant performance was simulated using a model that computes the refrigerant and airflow systems behavior. Together, these alternate configurations and approaches define new control algorithms that reveal the plant's optimal control model for improving performance and energy usage relative to conventional controllers. Results based on model simulations are dependent upon the model's accuracy and validity. However, the model validation studies cited here, though limited in scope, do show agreement between simulation and experimental data for the ambient temperatures and thermal load conditions considered. This suggests that these model results are reasonable, and representative of actual plant behavior under these conditions and configurations for a top-mount style refrigerator plant.