A Feasibility Study on Utilizing Cooling Water for Air-Conditioning in High-Tech Manufacturing

• Main Authors: Yuan Chun Lee, 李沅錞
• Other Authors: Yew-Khoy Chuah
• Online Access: http://ndltd.ncl.edu.tw/handle/ug6vep

碩士 === 國立臺北科技大學 === 能源與冷凍空調工程系碩士班 === 103 === In higher latitude region the outdoor air wet-bulb varies greatly in different seasons. The cooling tower supply temperature may approach that of the chilled water in cooler seasons. Therefore this thesis explored the feasibility of modifications of piping, adding plate heat exchangers and control systems, so that cooling towers could produce low temperature cooling water to substitute chilled water in some seasons. Finally energy saving and the investment return was analyzed. The case study was a factory of a high tech company in Shanghai in 2014. Shanghai meteorological data was used as a benchmark to obtain the wet-bulb temperature, air enthalpy, absolute humidity, dew point temperature etc. These factors were use in the research analysis of using cooling tower to produce chilled water and energy saving. From mid-autumn to late spring generally cooling load was lower in the factory, and the chilled water supply temperature could be raised from 7 ℃ to 9 ℃. During this period the outside air wet bulb temperature was also lower according to the 2014 Shanghai meteorological data. The arithmetic-mean of cooling towers enthalpy difference and number of transfer units indicate that cooling tower supply temperature could be low enough to meet the chilled water temperature required. A plate type heat exchanger was design to isolate chilled water and cooling water system but provide low temperature through the heat exchange. The system was redesigned so that the present system and equipment could be used with minimum modification of the piping. Moreover less maintenance would be needed later. The case study analysis showed that the application low-temperature cooling water for cooling purposes, for the weather of the reference site case, chiller energy saving of about 580,073 kWh could be achieved. It corresponds to a payback period of 1.36 years, or first year capital recovery of 73.47%. The annual electricity saving also corresponds to about 597,475 kilograms of CO2 reduction. The above results show that diverse energy saving strategies can be applied in different regions. Shanghai is located at the climate zones 3A in ASHRAE Standard 90.1. It has been shown that the outdoor air wet bulb temperature is suitable of producing cool water so to reduce the operating hours of chillers. The results of this study can be used as a reference case that geographical weather could be used for energy saving strategy. It also shows that diversified strategies can be used by industries in the consideration of energy saving planning.