Author: Zhang, Yiyi
Title: Study on energy saving potential of indirect evaporative pre-cooling system in hot and mid-humid region
Advisors: Yang, Hongxing (BSE)
Degree: M.Sc.
Year: 2018
Subject: Hong Kong Polytechnic University -- Dissertations
Evaporative cooling
Energy conservation
Department: Faculty of Construction and Environment
Pages: ix, 75 pages : color illustrations
Language: English
Abstract: Due to the acceleration of urban development, the environmental pollution and energy shortage caused by the energy consumption of buildings, which has risen more attention by the public. To deal with this serious situation, on the one hand, the renewable energy are explored, on the other hand, how to improve the efficiency of the energy use is the key of the study as well. In this study, traditional evaporative cooling theory is used to take the role of energy recovery. Based on the data from the experiment of indirect evaporative pre-cooling system used in Kowloon park swimming pool from October to November. The tested data was analyzed to evaluate the practical performance of the indirect evaporative pre­cooling system. And then the collected data was used to fit equation which can show the relationship between outdoor dry temperature, relative humidity and the amount of total energy recovery by software Origin9.0. The total energy recovery consists of two parts: latent heat transfer caused by the condensation due to the high outdoor relative humidity and the temperature of wet channel surface which reaches to dew point. The fitted equation was planned to evaluate the total energy recovery of Hong Kong in summer. However, it is found that the fitted equation is not suitable for the weather condition of summer in Hong Kong. Because the relative humidity in summer of Hong Kong is too high and the latent energy caused by high relative humidity was supposed to have more influence on the total energy recovery. In fact, in the fitted equation, the relative humidity part only accounts for small amounts of total energy recovery and the large amount of energy recovery is sensible heat. Therefore, this fitted equation is more appropriate to evaluate the energy recovery of region with hot and mid-humid weather in summer. To better explore the technical and economic feasibility of this technology, three cities with hot and mid-humid summer were selected, Zhangjiakou, Xian, Ganzhou. After calculation, Zhangjiakou is not suitable apply this technology because the saving of cooling load is not enough to make up the consumption of fan and pump power. The reason is the average dry bulb temperature is 25 °C, which is not high enough to recover enough total energy and ensure good performance of system. The economic feasibility is checked by the payback cycle. Assuming the fresh air volume flow was 1m3/s, if the system was 14 hours a day from June to August, the payback cycle of Xian and Ganzhou were both less than 4 years, which means that deducting the initial investment and operation maintenance cost, the system can recover all the investment, after four years, the saving will become net income. In conclusion, after the check of technical and economic feasibility, the indirect evaporative cooling system is worthy being applied in regions with hot and mid-humid summer. Specifically, the outdoor average dry bulb temperature is higher than 27 ° from June to August and the outdoor relative humidity is lower than 70%. Under this precondition, the more fresh air volume flow is required, the more amount of total energy can be recovered.
Rights: All rights reserved
Access: restricted access

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