Field Efficiency of Split-Type Air Conditioners with Evaporative-Cooled Condensers
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Abstract
In Thailand, split–type air conditioners are commonly used in residential buildings. These mainly rely on air-cooled compressors for the heat rejection process. However, the constant hot-humid conditions of Thailand reduce the efficiency of air conditioning systems significantly. As a result, an indirect evaporative condenser was proposed as a solution to improve the performance of a split–type system. Though the laboratory tests are promising, this system still requires field testing as dynamic ‘real’ conditions could be significantly different to a laboratory controlled scenario.
This research aims to study the field performance of split–type air conditioners with air cooled and evaporative condensers during day time, night time and throughout a 24-hour cycle. The results from this research were the comparison of the Coefficient of Performance (COP), electricity consumption and energy expense. Based on these results, the most effective user pattern for when an evaporative condenser is applied can be determined. This can provide efficient gudelines to save energy when using evaporative condensers in residential buildings.
The research results indicate that the field performance efficiency of an evaporative condenser is lower than that of the laboratory test. The impact from the cooling load is the main cause. By operating with a sufficient cooling load, the performance of an evaporative system could be enhanced. This could happen through heat transfer in summer or heat accumulation during the early hours of turning on the air conditioner. Moreover, low outdoor relative humidity is an additional factor to boost the performance of this system. Based on these findings, an air conditioner with evaporative condensers reduces energy consumption by 14.98 percent during daytime, 9.49 percent during nighttime and 4.26 percent through a 24-hour cycle. Given these results, the evaporative condenser should be used in rooms with daytime usage, which are the best candidate for an evaporative system. The second best option would be rooms with nighttime usage such as the bedroom because of the significant accumulation of heat from the day. 24-hour usage is the least suitable application for this system because energy savings could not be expected during the night.
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