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Title: Heat transfer enhancement in integrated phase change drywall system
Author: Tetlow, David
ISNI:       0000 0001 3516 3932
Awarding Body: Nottingham Trent University
Current Institution: Nottingham Trent University
Date of Award: 2008
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The building sector continues to be the highest energy consuming sector in most developed nations. For instance in the UK the building sector accounts for about 50% of total energy usage and emissions; 60% in the United States of America; 45% in Germany; 40% in Japan; 35% in Sweden and 45% in France. Any technological development towards reducing energy usage and emissions in the building sector would therefore go a long way in achieving a sustainable energy-environment. Integration of phase change materials (PCMs) into the fabric of buildings has been proposed and developed as a potential technological concept for minimising energy consumption and emission levels. PCMs are energy storage materials that can absorb, store and release heat when they change state, such as from a solid to a liquid or vice versa. There are however a number of problems which are associated with PCMs. For instance there is a heat transfer problem due to low apparent thermal conductivities. There are life cycles limitations associated with repeated melting and freezing of PCMs which result in voids formation and degradation of thermal energy storage/release capability of PCM wallboards. There is also a multi-dimensional heat transfer phenomenon associated with the integration of PCM particles in building fabrics, which makes energy recovery ineffective. Extensive literature reviews have been canied out into various scientific and technical studies which, enabled a composite laminated PCM system to be proposed for the drywall system. A numerical model and computer simulation program were developed to evaluate the system. In order to validate the results, samples of composite laminated PCMs based on two selected materials (pure hexadecane and aluminium/hexadecane) were manufactured, tested and results compared with the numerical output. Analysis of the experimental and numerical results showed a comparable level of heat transfer enhancement with the aluminium/hexadecane sample performing thermally better than the pure hexadecane PCM. However the estimated energy storage density for aluminium/hexadecane PCM was less than the pure hexadecane version and was attributed to the higher conductivity. This correlated with the numerical results as lower energy storage density was obtained when the thermal conductivity was increased. For instance when the thermal conductivity was increased from 0.17 to 0.25 W /m.K the magnitude of heat discharged was reduced by about 30%. The problem associated with bleeding and life cycles limitations due to repeated melting and freezing of a PCM was overcome by encapsulating the composite PCM. This point was proved after a number of tests were conducted on the samples. There were no signs of voids formation and degradation of thermal energy storage/release capability. The study has shown that some of the scientific and technical bam ers associated with integrated PCM drywall systems can be overcome by using the composite laminated PCM technique. In general the research has achieved all the objectives of the study. There is however the need for ftirther investigation into integration of other heat conducting materials and the effects of their configurations on PCM drywall systems. The effects of adhesives properties on the laminated PCM systems are also recommended for further investigation towards commercial development and exploitation of the laminated PCM drywall system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available