An improved technique for computing the heat loss factor of a tubular absorber
- Indian Institute of Technology, Delhi (India)
A different approach to evaluate the heat loss factor of a tubular absorber with a concentric glass cover, often employed as the target of a linear solar concentrator, is proposed. The equation for the heat loss factor in analytical form is employed instead of the semiempirical form hitherto employed for solar collectors. The glass cover temperature is, however, estimated by an empirical relation, replacing the empirical relation for the factor f of earlier work. This simple method predicts the overall heat loss factor, U{sub L}, within {plus minus}1% of the value obtained by iterative solution of the simultaneous equations in the range of variables-absorber temperature 60 to 240{degree}C, absorber coating emittance 0.1 to 0.95, wind velocity 1.5 to 10 m/s, and absorber diameter 12.5 to 75 mm. The method can also predict this factor for absorber temperatures up to 350{degree}C with maximum computational error {plus minus}2% compared to iterative solution. There is an improvement in computational accuracy by a factor greater than five over the current practice using a semiempirical equation. The effect of variation of air properties with temperature has been taken into account.
- OSTI ID:
- 5061336
- Journal Information:
- Solar Energy; (USA), Vol. 42:1; ISSN 0038-092X
- Country of Publication:
- United States
- Language:
- English
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