A numerical study of micro flow and its applications on thermal energy conversion and water desalination.

(1) A new model for the mass transfer in Direct Contact Membrane Distillation (DCMD) process is developed. The model is based on Direct Simulation Monte Carlo (DSMC) method. It avoids the over simplification of the resistance mechanisms and hence, give more accurate prediction. The model is validate...

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Bibliographic Details
Other Authors: Zhang, Peng
Format: Others
Language:English
Chinese
Published: 2010
Subjects:
Online Access:http://library.cuhk.edu.hk/record=b6074886
http://repository.lib.cuhk.edu.hk/en/item/cuhk-344519
id ndltd-cuhk.edu.hk-oai-cuhk-dr-cuhk_344519
record_format oai_dc
collection NDLTD
language English
Chinese
format Others
sources NDLTD
topic Energy conversion
Energy harvesting
Fluid mechanics
Micromechanics
Saline water conversion
spellingShingle Energy conversion
Energy harvesting
Fluid mechanics
Micromechanics
Saline water conversion
A numerical study of micro flow and its applications on thermal energy conversion and water desalination.
description (1) A new model for the mass transfer in Direct Contact Membrane Distillation (DCMD) process is developed. The model is based on Direct Simulation Monte Carlo (DSMC) method. It avoids the over simplification of the resistance mechanisms and hence, give more accurate prediction. The model is validated by means of experiments. The influences of the main parameters in DCMD are also studied, including temperature difference between the feed side and the permeate side, the membrane's thickness and the pore size. Moreover, it is proposed to use aerogel as the membrane material. It is shown that the aerogel's hydrophobic property, low thermal conductivity and high porosity offer a much improved performance over the commonly used membrane material PTFE. The fresh water productivity can reach 10.0 kg/m2 per day. === (2) A new energy harvesting method for converting thermal energy to kinetic energy is proposed. This method is based on the rarefied gas phenomenon called Knudsen effect. By Knudsen effect, a gas flow can be generated from temperature difference. In order to generate Knudsen effect, a special material, aerogel, is used. It is a porous material full of holes of dozens of nanometers. Using Direct Simulation Monte Carlo (DSMC) simulation, it is shown that Knudsen effect still works under atmosphere pressure with aerogel material. Accordingly, a device is designed. Based on the numerical simulation, the device can generate about 70 W kinetic energy when driven by a solar panel with intensity of 1 kW/m2. === (3) A solar desalination system is designed. This system is based on a combination of Knudsen compressor and simple solar still. The Knudsen effect is generated from the aerogel driven by solar radiation. As a result, the system operates at lower pressure resulting in enhanced water evaporation process. Based on the simulation, the evaporation rate is significantly increased. It is found that in a typical summer day in tropic region like Hong Kong, such a system can generate about 5 kg fresh water per 1 m2 solar still per day. This number is about 30% higher than the simple direct solar still. Moreover, the proposed technology can be readily combined with other technologies such as condensation heat recovery to further improve the fresh water productivity. The optimal working condition is also studied. === Energy and water are two of the most important issues in the world today. The social and economic health of the world depends on sustainable supply of both energy and water. Especially, these two critical resources are always inextricably linked. To solve the emerging crisis of energy and water, renewable energy technologies is the key. On the other hand, recent advances in Micro-Electro-Mechanical Systems (MEMS) technology have opened new ways for us to use micro/nano scale physical and chemical effects. It is no doubted that the combination of the renewable energy technologies and micro/nano technologies will have great potential and there are plenty of room to explore. === The research presented in this thesis focuses on extending the micro scale effect to the macroscopic applications. Based on this idea, a new energy harvesting method and two new water desalination technologies are proposed, with computer simulations and experiment validations. These include: === Zhang, Peng. === Adviser: Ruxu Du. === Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . === Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. === Includes bibliographical references (leaves 123-135). === Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. === Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. === Abstract also in Chinese.
author2 Zhang, Peng
author_facet Zhang, Peng
title A numerical study of micro flow and its applications on thermal energy conversion and water desalination.
title_short A numerical study of micro flow and its applications on thermal energy conversion and water desalination.
title_full A numerical study of micro flow and its applications on thermal energy conversion and water desalination.
title_fullStr A numerical study of micro flow and its applications on thermal energy conversion and water desalination.
title_full_unstemmed A numerical study of micro flow and its applications on thermal energy conversion and water desalination.
title_sort numerical study of micro flow and its applications on thermal energy conversion and water desalination.
publishDate 2010
url http://library.cuhk.edu.hk/record=b6074886
http://repository.lib.cuhk.edu.hk/en/item/cuhk-344519
_version_ 1718977628460810240
spelling ndltd-cuhk.edu.hk-oai-cuhk-dr-cuhk_3445192019-02-19T03:40:03Z A numerical study of micro flow and its applications on thermal energy conversion and water desalination. CUHK electronic theses & dissertations collection Energy conversion Energy harvesting Fluid mechanics Micromechanics Saline water conversion (1) A new model for the mass transfer in Direct Contact Membrane Distillation (DCMD) process is developed. The model is based on Direct Simulation Monte Carlo (DSMC) method. It avoids the over simplification of the resistance mechanisms and hence, give more accurate prediction. The model is validated by means of experiments. The influences of the main parameters in DCMD are also studied, including temperature difference between the feed side and the permeate side, the membrane's thickness and the pore size. Moreover, it is proposed to use aerogel as the membrane material. It is shown that the aerogel's hydrophobic property, low thermal conductivity and high porosity offer a much improved performance over the commonly used membrane material PTFE. The fresh water productivity can reach 10.0 kg/m2 per day. (2) A new energy harvesting method for converting thermal energy to kinetic energy is proposed. This method is based on the rarefied gas phenomenon called Knudsen effect. By Knudsen effect, a gas flow can be generated from temperature difference. In order to generate Knudsen effect, a special material, aerogel, is used. It is a porous material full of holes of dozens of nanometers. Using Direct Simulation Monte Carlo (DSMC) simulation, it is shown that Knudsen effect still works under atmosphere pressure with aerogel material. Accordingly, a device is designed. Based on the numerical simulation, the device can generate about 70 W kinetic energy when driven by a solar panel with intensity of 1 kW/m2. (3) A solar desalination system is designed. This system is based on a combination of Knudsen compressor and simple solar still. The Knudsen effect is generated from the aerogel driven by solar radiation. As a result, the system operates at lower pressure resulting in enhanced water evaporation process. Based on the simulation, the evaporation rate is significantly increased. It is found that in a typical summer day in tropic region like Hong Kong, such a system can generate about 5 kg fresh water per 1 m2 solar still per day. This number is about 30% higher than the simple direct solar still. Moreover, the proposed technology can be readily combined with other technologies such as condensation heat recovery to further improve the fresh water productivity. The optimal working condition is also studied. Energy and water are two of the most important issues in the world today. The social and economic health of the world depends on sustainable supply of both energy and water. Especially, these two critical resources are always inextricably linked. To solve the emerging crisis of energy and water, renewable energy technologies is the key. On the other hand, recent advances in Micro-Electro-Mechanical Systems (MEMS) technology have opened new ways for us to use micro/nano scale physical and chemical effects. It is no doubted that the combination of the renewable energy technologies and micro/nano technologies will have great potential and there are plenty of room to explore. The research presented in this thesis focuses on extending the micro scale effect to the macroscopic applications. Based on this idea, a new energy harvesting method and two new water desalination technologies are proposed, with computer simulations and experiment validations. These include: Zhang, Peng. Adviser: Ruxu Du. Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. Includes bibliographical references (leaves 123-135). Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. Abstract also in Chinese. Zhang, Peng Chinese University of Hong Kong Graduate School. Division of Automation and Computer-Aided Engineering. 2010 Text theses electronic resource microform microfiche 1 online resource (xiii,135 leaves : ill.) cuhk:344519 isbn: 9781124498010 http://library.cuhk.edu.hk/record=b6074886 eng chi Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) http://repository.lib.cuhk.edu.hk/en/islandora/object/cuhk%3A344519/datastream/TN/view/A%20%20numerical%20study%20of%20micro%20flow%20and%20its%20applications%20on%20thermal%20energy%20conversion%20and%20water%20desalination.jpghttp://repository.lib.cuhk.edu.hk/en/item/cuhk-344519