Advanced sequential dual evaporator domestic refrigerator/freezer: System energy optimization

• Built prototype of sequential dual evaporator refrigerator/freezer appliance.
• Implemented visible refrigerator evaporator in direct contact with PCM.
• Analyzed impact of refrigerant flow control components on the system.
• Increased refrigeration compartment's evaporation temperature by 7.8 K.
• Preserved natural convection heat transfer mode in refrigeration compartment.

Fundamental energy efficiency advantage of the sequential dual evaporator (SDE) refrigeration circuit in domestic refrigerator/freezer appliances arises from the ability of evaporating refrigerant at elevated temperature during cooling of refrigeration compartment (RC) and consequently achieving higher RC COP. Frequently RC evaporator is foamed-in driven by natural convection with very low heat transfer coefficient which practically limits evaporation temperature. The paper presents experimental results of the SDE prototype appliance with visible RC roll-bond evaporator in direct contact with phase change material (PCM) to increase RC evaporation temperature. Melting PCM is absorbing cabinet heat in continuous manner thus we could keep natural convection as preferred mode of heat transfer in RC. Control including pump out phase and particular components were implemented to deal with refrigerant charge migration between refrigerator and freezer evaporators. RC evaporation temperature was increased by maximum 8.4 K. Energy consumption during RC operation was reduced by 19.9% and overall energy consumption dropped by 5.6% after condenser fan was installed. At least 8.1% energy saving was predicted if condenser with 30% higher UA value was implemented instead of the condenser fan.