Optimum condensing temperature at part-load operation of air-cooled chillers for energy efficiency

Four existing chilled water plants have been investigated and evaluated in this study in order to identify their operating characteristics and energy performance. This field investigation reveals that chillers are often improperly staged, and the chiller efficiency drops considerably when the chiller load or outdoor temperature decreases. An experiment has been carried out on an air-cooled reciprocating chiller in a test chamber to verify the workability of condensing temperature control with electronic expansion valves and to identify the extent of decrease in the condensing temperature.; Using the chiller model developed and using TRNSYS to model the building and air-conditioning system, simulations are carried out to establish the load-frequency and weather-load profiles of representative office and hotel buildings. The matching between building cooling load and chiller part-load ratio in multiple-chiller systems is studied. The strategy for optimizing the efficiency of chilled water plants by proper design and operation of the systems is developed. Accordingly, the implication of this improvement in chiller performance on the growth of electricity demand by the commercial building sector is analysed.; The main contribution to knowledge of this work is the development of a workable method of floating condensing temperature control applicable to make air-cooled chillers more efficient and sustainable. Building services engineers will benefit from the information disseminated on how to stage multiple chillers and pumps in the most efficient manner in the design and operation of chilled water plants. This information should help engineers evaluate different chiller plant design options for energy efficiency, and support chiller plant operators in setting up proper operating schemes for their chilled water plants to cut down electricity bills. On the legislative aspect, a scheme is proposed for setting requirements on the chiller efficiency in relation to the part-load ratio, outdoor temperature and limit of condensing temperature. The results of this study will also help chiller manufacturers apply condensing temperature control in their search for the most efficient chiller products. (Abstract shortened by UMI.)...