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An experiment has been carried out for examining the performance of an air conditioning unit under constant outdoor wet-bulb temperature and varied dry-bulb temperature. During the experiment, the wet-bulb temperature of the compartment for outdoor unit was maintained at 22℃ and the dry-bulb temperature was varied from 24℃ to 36℃. The increase of outdoor air temperature results in the increase of supply air temperature, discharge temperature, suction temperature, and liquid line temperature. These cause the degradation of the air conditioner performance. An increase of power consumption by 1.4% and decrease of cooling capacity by 0.8% were observed for each 1℃ increase of outdoor air temperature. As a result, the energy efficiency ratio drops by 2% for each 1℃ increase of outdoor air temperature.

Studies related to the effects of ambient temperature on the performance of an air conditioning unit have been carried out for decades. However, specific study concerning the effect of varied ambient temperature under constant relative humidity has not been reported yet. This paper discusses the operating conditions and performance of an air conditioner with R32 and nominal capacity of 2.6 kW. The test was carried out in a controlled psychrometric chamber under constant relative humidity of 50% and varied outdoor air temperature from 24 to 38°C. The increase of outdoor air temperature affects the operating conditions of the air conditioner. Generally, if the outdoor air temperature increases by 1°C the evaporating temperature increases by 0.27°C. Meanwhile, refrigerant suction temperature, discharge temperature, and condensing temperature increase by 0.08°C, 1.08°C, and 1.04°C, respectively. Under the same tests, the cooling capacity decreases by 1% and power consumption increases by 1.6%. In addition, the energy efficiency ratio of the air conditioner decreases by 2.1% per 1°C increase of outdoor air temperature.

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