Experimental Investigation of Refrigeration and Defrost Energy Consumption in Commercial and Walk-In Freezers
The energy consumption of commercial and walk-in freezers has been experimentally investigated in this project. Three different sizes of walk-in freezers were tested to observe the difference of the energy consumption among them. The freezers tested are of 5.98 kW, 1.49 kW & 0.57 kW cooling capacity and 37.84 m3, 3.67 m3 & 0.49 m3 in storage volume respectively. In addition, the temperature distribution inside the freezers cabinet were measured to investigate the temperature variation at different places inside the cold spaces. We conducted the tests under different loading conditions and observed the performance of those freezers. While we ran the tests, we determined the defrost to refrigeration energy consumption ratio and the percentage increase in the temperature from the storage set-point. This ratio represents the amount of energy consumed during the defrost process and the energy required to cool the freezer to the set-point after the defrost process ended. It was found that the average defrost to refrigeration ratio was 37.4% for freezer A in closed door test, 5.6 % in closed door test for freezer B, 2.8% in 10 minutes time interval of open door test for freezer B, 4.9% in 20 minutes time interval of open door test for freezer B and 3.7% in 30 minutes time interval of open door test for freezer B. In closed door test for freezer C, the defrost to refrigeration ratio was 33.6% in 4 hours timer and 18.15% in 7 hours timer. The defrost to refrigeration ratio was 37.9% and 31.3% in 4 hours timer and 6 hours timer respectively in 10 minutes time interval of open door test for freezer C.