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Research Papers

Preliminary Study on a Solar Water Heater Using Supercritical Carbon Dioxide as Working Fluid

[+] Author and Article Information
H. Yamaguchi

Department of Mechanical Engineering, Doshisha University, Kyoto 630-0321, Japan

N. Sawada, H. Suzuki, H. Ueda

 Showa Tansan Co., Ltd., 7-1 Ogimachi, Kawasaki-Ku, Kawasaki City, Kanagawa 210-0867, Japan

X. R. Zhang

Department of Energy and Resources Engineering, College of Engineering, Peking University, Beijing 100871, China; Department of Mechanical Engineering, Doshisha University, Kyoto 630-0321, Japan

J. Sol. Energy Eng 132(1), 011010 (Jan 04, 2010) (6 pages) doi:10.1115/1.4000350 History: Received September 10, 2008; Revised June 28, 2009; Published January 04, 2010

In this paper, a solar water heater using supercritical carbon dioxide as working fluid is proposed and experimentally studied. For supercritical carbon dioxide, a small change in temperature or pressure can result in large change in density, especially in the state close to the critical point. Thus, natural convective flow of the supercritical carbon dioxide can be easily induced by solar heating or water cooling. Such convective flow absorbs and transports heat to water in solar collector tubes. Motivated by the above idea, an experimental setup was designed, and a solar water heater was tested. The obtained results show that natural convective flow is well induced, and a flow of 1900 Reynolds number can be achieved even in winter, when the lowest level of solar radiation condition occurs. Furthermore, the measured collector and heat recovery efficiencies are 66.0% and 65.0%, respectively. More details of its mechanism are to be studied, and a complete performance analysis is needed.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of the experimental system of the solar water heater using supercritical CO2 as working fluid in the evacuated solar collector. (a) Flow diagram of the experimental system and (b) evacuated solar collector utilized in the present experimental setup system.

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Figure 3

Variations of the measured data with the test time, which include CO2 temperature and CO2 pressure

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Figure 4

CO2 fluid states in the solar collector during the test period, presented in CO2 p-h diagram. The dash line represents the CO2 fluid state at the collector inlet and the solid one shows the CO2 fluid at the collector outlet, respectively.

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Figure 5

Variations of the measured water flow rate and water temperatures with the test time

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Figure 6

Variations of the performance parameters with the test time, which include collected heat quantity and recovered heat quantity

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Figure 7

Variations of the performance parameters with the test time, which include collector efficiency and heat recovery efficiency

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Figure 2

Variations of the measured data with the test time, which include solar radiation and CO2 flow rate

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