The non-uniformity of frost distribution on evaporator of indirect cooling refrigerator will increase the defrosting time and decrease the defrosting efficiency. Therefore

based on the optimization of defrosting this paper proposes an optimization method for return air duct of indirect cooling refrigerator. Firstly

the surface temperature distribution of the defrosting heater is measured through experiments

and the heat distribution of defrosting heater is calculated accordingly

thus the frost distribution on the evaporator that matches the defrosting heat distribution is obtained. Then the optimal air flow rate distribution of return duct is determined by the frost distribution on the evaporator. Finally

the optimal air flow rate distribution is achieved by designing the return air duct of refrigerator compartment to improve the defrosting performance. An optimization case shows that the optimized return air duct can make the air flow rate distribution in accordance with the defrosting heat distribution

which decreases the defrosting time by 38.9%

and increases the cooling capacity of the refrigerator by 3.43%.