Abstract
Quasi-steady state thermal performance of a solar air heater with a combined absorber is studied. The whole energy balance equations related to the system were articulated as a linear system of temperature equations. Solutions to this linear system were assessed from program based on an iterative process. The mean temperature variation with time and the thermal performance parameters were deduced from simulation outputs. Simulations were performed for typical days of the twelve months of the year. Results show maximum values of mean temperatures at solar noon ranging between: 78°C and 87°C for the cover, 102°C and 114 °C for the absorber 61°C to 67°C. Experimental and simulated results correlate well for hours before solar noon (with R²≈0.988) and show some discrepancies for hours after solar noon. These differences were related to the neglect of heat capacity effects in the model. Experimental and calculated solar heater efficiencies at solar noon approached respectively about 62 and 61%. The removal factor FR and the efficiency factor F’ calculated were respectively 0.4 and 0.33, whereas the values assessed from experiments were respectively 0.79 and 0.63. This model allowed predicting the collector performances and is more suitable for hours before solar noon.
Highlights
For low temperature solar heating applications two kind of solar air heaters are commonly used relates to the type of absorber: porous absorber collectors and non-porous absorber collectors
In order to improve the thermal performances of the solar air heater, we suggest a new type of this system with a composite absorber combining a porous absorber made of a porous metallic medium and a nonporous absorber made of a non-porous metallic plate placed above
The solutions gave the mean temperatures variation according to time and the thermal performance parameters of the system
Summary
For low temperature solar heating applications two kind of solar air heaters are commonly used relates to the type of absorber: porous absorber collectors and non-porous absorber collectors. Ekechukwu & Norton [4] carried out a review of various designs and performance evaluation technique of low temperature air-heating solar collectors for crop drying applications These authors highlighted the appropriateness of each design of solar heater and the choice of materials to operate for each component. [6] carried out a parametric study of solar air heater with and without thermal storage for solar drying applications These authors investigated the effects of design parameters of the air heater such as length, width, gap spacing between the absorber plate and glass cover, mass flow rate and type of the storage material (sand, granite and water) on the outlet and average temperatures of the flowing air. He explored the influence of the air speed inside the collector and wind speed above the collector on the collector efficiency
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
