Unglazed transpired solar collectors
Unglazed transpired solar collectors offer a potentially low-cost, high-efficiency option for once-through applications such as preheating air for ventilation, crop drying, and desiccant regeneration. Such collectors consist of a permeable absorber exposed to the sun, through which air is drawn. This chapter examines the major heat-loss mechanisms associated with this concept. Convective heat losses are obtained by integrating the product of the temperature and velocity profiles in the boundary layer at the downwind edge of the collector. This convective heat loss is then expressed in terms of the thermal equivalent length of irradiated absorber. Analysis shows that this loss can be very low for large collectors, even under windy conditions. These results are incorporated into a simple computer model that predicts collector efficiency as a function of suction velocity, wind speed, ambient temperature, and radiation. A linear model for convective and radiative heat losses is also presented, which allows a simple means for performance prediction. A small test collector has been built, and outdoor experimental results have been compared with the model. Full-scale test walls are also described. Remaining research issues are discussed. 24 refs., 7 figs.
- OSTI ID:
- 460362
- Journal Information:
- Advances in Solar Energy, Journal Name: Advances in Solar Energy Vol. 7; ISSN 0731-8618; ISSN ASOED9
- Country of Publication:
- United States
- Language:
- English
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Unglazed transpired solar collectors
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