Author: Wang, Caixia
Title: Applying phase change materials (PCMs) to disaster-relief prefabricated temporary houses (PTHs) for improving their indoor thermal environments in summer time
Advisors: Deng, Shiming (BSE)
Niu, Jianlei (BSE)
Degree: Ph.D.
Year: 2021
Subject: Emergency housing
Disaster relief
Materials -- Thermal properties
Prefabricated houses
Hong Kong Polytechnic University -- Dissertations
Department: Department of Building Services Engineering
Pages: xxii, 181 pages : color illustrations
Language: English
Abstract: Natural disasters endanger the lives and properties of people and their frequent occurrences have left hundreds of thousands of disaster victims homeless. Therefore, providing disaster victims with suitable temporary shelters has been one of the key issues in post-disaster management. It is noted that disaster-relief prefabricated temporary houses (PTHs) have been massively used during disaster relief reconstructions period due to the advantages of convenient transportation, easy installation and short construction period to provide the much-needed shelters. However, previous related field studies have demonstrated that as no energy-consuming environmental control systems such as an air conditioner were normally installed inside PTHs, in summer time, the thermal environment inside PTHs can become intolerably hot, and thus harmful to disaster victims' health both physically and mentally. It has been therefore urgently needed to apply simple and low cost measures to disaster-relief PTHs for improving their indoor thermal environments in summer. On the other hand, phase change materials (PCMs) have been extensively used in various permanent buildings for helping improve indoor thermal environmental control successfully, with however little application to disaster-relief PTHs for enhancing their indoor thermal environmental controls. Consequently, a programmed research work on applying PCMs to disaster-relief PTHs for improving their indoor thermal environment in summer time has been carried out and is reported in this Thesis. This Thesis begins with, firstly, describing a purposely established experimental setup having two different Designs of applying PCMs to PTHs to facilitate the experimental work required in this programmed research work. For Design 1, two different scaled model houses (MHs) were used and for Design 2, a full-scale experimental PTH was used. Appropriate measuring instrumentations were provided to the setup. Secondly, an experimental study on applying PCMs to disaster-relief PTHs for improving their internal thermal environment in summer is presented. The experimental setup was used and the two designs examined in the experimental study. In Design 1, PCMs were fixed to the internal surfaces of one of the two MHs and the related experimental results demonstrated that both indoor air temperature and internal surface temperatures of the PCM based MH can be reduced at daytime. However, in Design 2, a movable PCM based energy storage system (PESS) was used and the related experimental results suggested the use of the movable PESS with a total charge of 148.8 kg PCM helped reduce the average indoor air temperature by 3.2 to 3.6 °C. The experimental results for both Designs suggested that, due to the nature of disaster relief and since outdoor air at a lower temperature may be the only cooling energy source for charging the PCM, a movable PESS was preferred, so that it can be moved to outdoor at night time for being charged with more cooling energy using lower temperature outdoor air or via sky radiation but not adversely increasing the air temperature inside PTHs.
Thirdly, the Thesis presents a numerical study on optimizing the designs of applying PCMs to a disaster-relief PTH to improve its summer daytime indoor thermal environment. The numerical study followed up the experimental study to numerically examine different designs of applying PCMs to a disaster-relief PTH in order to identify the best design for guiding future practical applications. A numerical model for the full-scale PTH was established using EnergyPlus platform and experimentally validated. The numerical study included two parts. In the first part, a total of 16 different designs were defined and the simulated results demonstrated that the 10th design, or D10, was identified as the most effective design, and could result in the highest number of acceptable hours at 90 hours. In the second part, increasing PCM's thickness to beyond 20 mm would lead to negligible effects on further improving the thermal environment inside the full-scale PTH. Hence, 20 mm thickness for PCM was recommended as a reference design value for future practical applications. Finally, a further numerical study on applying the movable PESS to disaster-relief PTHs used in 12 selected cities located in different climate regions to improve the thermal environments inside PTHs in July is reported. The previously developed and experimentally validated EnergyPlus based simulation model for a PTH incorporating the movable PESS was deployed. In this further numerical study, in order to quantitatively describe the degree of improvement in the thermal environment inside PTHs after applying PCMs, a number of evaluating indexes including Unacceptable Degree Hours inside a PTH without incorporating the movable PESS (UDH) and after incorporating the movable PESS (UDH') and the absolute difference between UDH and UDH' ( Δ ), were proposed. Using the meteorological data in the typical weather year of 1989, the further numerical study showed that, in all the 12 selected cities in July, after introducing the movable PESS to the PTHs, both the monthly maximum and the averaged air temperature inside the PTHs, the daily peak and daily average indoor air temperature on the hottest day were lowered. In all the 12 selected cities, although applying the movable PESS to disaster-relief PTHs in July was functional, it was more effective for the following seven cities including Singapore, Miami, Bangkok, Chengdu, Damascus, Hanoi and Urumqi, with six of the seven cities located in both tropical and temperate climate regions, based on the proposed evaluating indexes.
Rights: All rights reserved
Access: open access

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