3249 -- Estimation of the Seasonal Cyclic Losses of an Air Conditioner PDF

This paper illustrates the effects of degradation in the coefficient of performance (COP) of an air conditioner caused by cyclic operations. This is demonstrated by considering a 1076 ft 2 (100 m2) residence in Dhahran equipped with a 5 ton (17.6 kW) central unit. A cornputer model estimates cooling loads and transient (start-up) losses. Simulations show cyclic losses can be as high as 24% during the months of low cooling when system on-time is minimal; little degradation was experienced during the hot months when the system on-tirne is high with fewer startstop cycles. This study found that annual steady-state energy consumption was 17,900 kWh; transient losses required an additional 2100 kWh. The total predicted value of 20,000 kWh is within 5% of the metered consumption. Cyclic losses can be reduced by design changes that prevent refrigerant migration during the off-cycle period, since this phenomenon is responsible for most start-up losses. Degradation may also be lowered by installing an inverterdriven, variable-speed air-conditioning system. Such a system has the ability to precisely match capacity with cooling load, resulting in few on-off cycles.