Performance degradation of an air-conditioner caused by cyclic operations

We have illustrated the effect of degradation in the seasonal coefficient of performance (COP) of an air-conditioner caused by cyclic operations. This degradation is demonstrated for a 100 m² residence in Dhahran equipped with a 17.6 kW capacity central unit. A computer model simulates cooling loads and transient (start-up) losses. Simulations show that cyclic losses can be as high as 22% during months of low cooling. The system experienced little degradation during the peak cooling period. The annual steady-state energy consumption is 17,900 kWh; transient start-stop penalties required an additional 2100 kWh, which agrees within 5% with the annual metered consumption. Cyclic losses are significantly reduced with design changes that prevent refrigerant migration during the off-cycle period. The seasonal steady-state and cyclic COP values were found to be 2.11 and 1.88, respectively.