FacePlateCollector

FacePlateCollector - Sustainable Energy Science and...

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S ustainable E nergy S cience and E ngineering C enter Flat Plate Collectors - Domestic Heating Reference: Chapters 5 & 6 of Solar engineering of thermal processes, Duffie & Beckman, 2nd edition, Wiley Interscience, 1991.
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S ustainable E nergy S cience and E ngineering C enter Simplified Collector Performance Model Prediction of the thermal output of various solar collectors: The quantity of thermal energy produced by any solar collector can be described by the energy balance equation where = rate of thermal energy output = rate of optical energy absorbed by receiver = rate of thermal energy lost from receiver. Q out = Q opt Q loss Q out Q opt Q loss Source: Solar energy Fundamentals and Design, William B. Stine & Raymond W. Harrigan, John Wiley 7Sons, 1985
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S ustainable E nergy S cience and E ngineering C enter Optical Energy Absorbed by the Receiver Q opt = A a ρ s , m τ g α r RSI a A a = specular reflectance of concentrating mirror, if any (1.0 for non- concentrating flat-plate collector) s , m = transmittance of any glass envelope covering the receiver (e.g. glass cover plate in a flat-plate collector) A a = aperture area of the collector S = receiver shading factor (fraction of collector aperture not shadowed by the receiver; 1.0 for a flat-plate collector) R = receiver intercept factor (fraction of reflected beam intercepted by receiver; 1.0 for a flat-plate collector) r = absorbance of the receiver I a = isolation (irradiance) incident on collector aperture (W/m 2 ) S, R, r , s,m and g are constants (in a more detailed model, the dependence of the angle of the incident insolation can be considered) dependent only on the materials used and the structure accuracy of the collector - they can be lumped into a single constant term η opt , the optical efficiency of the collector. For a flat-plate collector utilizing no reflectors, S, R and are set equal to 1.0.
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S ustainable E nergy S cience and E ngineering C enter Thermal Energy Lost from the Receiver Q loss = A r U l T r T a () A r = averaged receiver temperature ( o C) T r = surface area of the receiver (m 2 ) = ambient temperature ( o C) T a U l = overall heat loss coefficient (W/m 2 o C) T r = T out + T in 2 T out is the temperature in degrees C of the fluid leaving the collector while T in is the temperature of the fluid entering the collector. The heat loss coefficient U l is not a simple constant but instead may vary as heat-loss mechanisms change with temperature. For example as the temperature increases, radiant heat loss from the receiver increases.
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S ustainable E nergy S cience and E ngineering C enter Q out = A a η opt I a A r U l T r T a () col = Q out A a I a = η opt A r A a U l T r T a I a col = η opt U l C g T r T a I a Collector Efficiency Where col is the aperture efficiency of the collector and A r /A a is the geometric concentration ratio ( C g ) C g = A a A r Aperture Receiver Sun @ T s
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S ustainable E nergy S cience and E ngineering C enter Reflectance of Surfaces Specular reflection θθ Diffuse reflection General reflection
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This note was uploaded on 10/22/2011 for the course ESC 2005 taught by Professor Staff during the Spring '11 term at FSU.

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FacePlateCollector - Sustainable Energy Science and...

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