Performance analysis of air handling processes with decoupled cooling and dehumidification

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Performance analysis of air handling processes with decoupled cooling and dehumidification


Author: Chow, King Sang
Title: Performance analysis of air handling processes with decoupled cooling and dehumidification
Degree: M.Eng.
Year: 2015
Subject: Air conditioning -- Control.
Humidity -- Control.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: ix, 95 pages : color illustrations
Language: English
Abstract: Air conditioning systems play an important role in maintaining the indoor built environment. Continuing to improve the energy efficiency and reducing the energy consumption of air-conditioning systems in order to provide a suitable and comfortable environment are foundations to the development of new strategies for the indoor built environment. Taking these requirements into account, the temperature and humidity independent control (THIC) air-conditioning system is generally considered to be a possible and effective solution. However, existing THIC systems usually involve two independent temperature and humidity control subsystems which require two air handling units and thus significantly increase the initial cost and occupy more space. Therefore, how to control humidity and temperature independently within the same cooling coils in air conditioning system worth more studying.In this study, a new HVAC system using THIC device to achieve temperature and humidity controlled separately in the same cooling coil was proposed. The THIC device consists of two three-way valves which can adjust the chilled water flow rate and supply chilled water temperature independently through by-pass and mixing respectively. In order to conduct performance analysis of air handling processes for the proposed HVAC system, a dynamic model was applied for performing extensive simulations through the software Compact Visual FORTRAN 6.5.The purpose of the study is to investigate the performance of cooling coil in the proposed THIC system by means of examining the variation of SHR of cooling coil with the chilled water temperature and flow rate. Different cooling coils under a variety of weather conditions were evaluated. The results show that the proposed HVAC system using THIC device can achieve independent control in temperature and humidity and the performance are well. Besides, this system especially do excellent jobs in high latent load conditions for cooling coil with larger number of rows. In addition, it is advised to use temperature as the dominate control and mass flow rate as the minor control to regulate the SHR of cooling coil.

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