This study investigates how to improve the coefficient of performance (COP) of an air-cooled chiller by using variable speed condenser fans. The experimental chiller had a cooling capacity of 282 kW and a COP of 2.8 at the full load condition. Comprehensive trend logging was performed on the electric power and temperature variables at the chilled water side, the condenser air side and the refrigerant side at 5-min intervals. The condenser fans were retrofitted with dual operating modes-cycling in different numbers and regulating their rotating speed by a frequency inverter controlled by an adjustable condensing temperature. Operating conditions covered various combinations of part load ratios of 0.1-1.1 and outdoor temperatures of 20.3-36.8°C. Variable speed control of condenser fans helped reduce greatly the condenser fan power while allowing the condensing temperature to float closer above the outdoor temperature. This enabled the COP to increase by 5.4-61.9% in relation to the head pressure control with a fixed condensing temperature set point of 41°C. The increase of COP is more appealing at the low load conditions. Pearson correlation analysis ascertained that the variation of COP correlated closer with the controlled variables under improved control of condensing temperature. The COP can be optimized by regulating the rotating speed of condenser fans as a stepwise function of the chiller part load ratio.
|Publication status||Published - 2016|
|Event||8th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2016 - Taipei, Taiwan, Province of China|
Duration: 15 May 2016 → 17 May 2016
|Conference||8th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2016|
|Country/Territory||Taiwan, Province of China|
|Period||15/05/16 → 17/05/16|