Developing an optimum operating strategy with floating condensing temperature for chiller plant in CityPlaza One

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Developing an optimum operating strategy with floating condensing temperature for chiller plant in CityPlaza One

 

Author: Chu, Ho-yin
Title: Developing an optimum operating strategy with floating condensing temperature for chiller plant in CityPlaza One
Degree: M.Eng.
Year: 2006
Subject: Hong Kong Polytechnic University -- Dissertations
Air conditioning -- Equipment and supplies
Air conditioning -- Efficiency
Energy conservation
Department: Dept. of Building Services Engineering
Pages: xx, 183 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1973667
URI: http://theses.lib.polyu.edu.hk/handle/200/5526
Abstract: The inefficient operation of chillers at part load conditions has engaged the attention of engineers to implement a more energy efficient control strategy such as the condensing temperature control (CTC). Traditionally, air-cooled chillers which are operated under head pressure control (HPC) with a fixed high condensing temperature set point (45 ℃) have undesirable high condensing temperature when the outdoor temperature and chiller part load ratio decrease. This control strategy results a low chiller COP of air-cooled chillers at part load operation. This project focused on the existing chiller plant for CityPlaza One office tower and investigated the performance of existing air-chillers under head pressure control with a fixed low condensing temperature set point (21.7 ℃). For an optimum control strategy, a floating condensing temperature set point is required for existing air-chillers due to the use of thermostatic expansion valves and high static condenser fans. The field investigation indicated that condenser fans were improperly staged and condensing temperatures were not optimized under the existing control strategy. A validated chiller model was developed to investigate the performance of air-cooled chillers with the improved condenser features of condensing temperature control (CTC), variable speed condenser fans (VSF) and evaporative pre-cooler (EC). The building and air conditioning system was modeled using TRNSYS 15 to simulate the operation of the chiller plant and evaluate the annual energy consumption under different control strategies. The annual electricity consumption savings of the chiller plant were estimated at 1 56,25OkWh (4%) with variable speed condenser fans and 253,227kWh (6.45%) with floating condensing temperature control and variable speed condenser fans, comparing to the existing annual electricity consumption of 3,927,45OkWh, A further energy saving of 489,383kWh (12.46%) was obtained for the air-cooled chillers with evaporative per-cooler (EC) and variable speed condenser fans (VSF) under floating condensing temperature control, A concise methodogy instruction was developed in this research for the chiller plant operator in order to implement the floating condensing temperature control. This research provides a reference for the implementation of floating condensing temperature control (CTC) for the chiller plant in CityPlaza One office tower.

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