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Abstract: This paper reports the evaluations of energy efficiency, plume potential as well as plume control of a huge chiller plant using water-evaporative cooling towers for heat rejection for a super high-rising commercial office building in a subtropical region of Hong Kong. The evaluations were carried out in a dynamic Transient Simulation Program (TRNSYS)-based simulation platform using alternative control strategies including set-point control logics of the supply cooling water temperature and cooling tower fan modulation control methods as well as different number control means of cooling towers. The results show that different control strategies have significant effects on the energy efficiency of the chiller plant. The quantification of the energy efficiency demonstrates significant energy-saving potential by using advanced technologies for implementing optimal control strategies in this cooling system. The results also reveal that the plume may occur frequently in spring and summer seasons and occasionally in other months due to the odd subtropical weather conditions. Control strategies also have significant effects on the frequency of the plume occurrence. The effective energy efficiency control and effective plume control using wet–dry (i.e., hybrid) cooling towers are also discussed. [Copyright &y& Elsevier]

Abstract: Heat pumps could be used to produce hot water for hybrid cooling towers for preventing the occurrence of plume in subtropical regions. The evaporative side of the heat pump system could be arranged either at the inlet side or at the outlet side of these cooling towers for cooling down the cooling water temperature. Alternatively, the evaporative side of the heat pump system could also be arranged at the evaporative side of chillers to reduce return chilled water temperature and therefore to reduce the cooling load of chillers. This study presents the evaluation of the impacts of these three arrangements of the heat pump system on the plume control performance and the energy performance in a large-scale chiller plant in Hong Kong. The performance prediction and evaluation of the chiller plant and the plume abatement system were conducted on a dynamic simulation platform. The results show that these three arrangements have almost the same plume control performance with sufficient plume control capability. The results also show that the arrangement of the evaporative side of the heat pump system for cooling down return chilled water temperature has much better performance that the other two arrangements for improving the overall energy efficiency. [Copyright &y& Elsevier]