کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1550312 | 998090 | 2013 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
A figure of merit for selective absorbers in flat plate solar water heaters
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی انرژی
انرژی های تجدید پذیر، توسعه پایدار و محیط زیست
پیش نمایش صفحه اول مقاله
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چکیده انگلیسی
We derive from first principles an analytical expression for a figure of merit (FM) for a selective solar absorber in a single glazed flat plate water heater. We first show that the efficiency of a collector with an absorber with absorptance α and emittance ε, relative to the maximum efficiency for an ideal absorber, can be expressed as ηR = α â Aε â B. The effectiveness of the absorber can then be written as a figure of merit, FM = α â Aε. The larger the value of FM, the better the solar absorber performs in the collector. This is shown to give quite different results from the coating selectivity, α/ε. A is a function of many heater parameters as well as the orientation and geographical location of the heater but, to a good degree of approximation, can be simplified sufficiently to be expressed as a linear function of the inlet water temperature only: Aav = 0.0073Tin. For typical average water temperatures between 30 °C and 60 °C, Aav ranges from 0.22 to 0.44 so the emittance is relatively less important than the absorbtance. In the latter case, for example, the figure of merit is a very simple expression which can be used by developers of solar absorbers without any knowledge of the parameters or location of the HWH: FM=α-0.44ε
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Solar Energy - Volume 98, Part C, December 2013, Pages 503-510
Journal: Solar Energy - Volume 98, Part C, December 2013, Pages 503-510
نویسندگان
D.E. Roberts,