Investigation of thermo-hydraulic performance of concentrated solar air-heater with internal multiple-fin array

Abstract

This study presents a thermo-hydraulic analysis of a solar air heater with an internal multiple-fin array. A preliminary simple test was carried out to confirm the efficiency enhancement of the proposed arrangement.A mathematical model of heat transfer processes was proposed.A thermo-hydraulic efficiency test was used to find the best fin arrangement of the receiver. For an applied set of ducts, calculations were carried out to find the thermo-hydraulic efficiency of the collector against the volumetric air flux. As a comparison, a smooth pipe arrangement was used.Calculation results of the mathematical model showed an existing optimum of thermo-hydraulic efficiency against the volume flux, fin thickness and duct width. If there is no limitation of the air speed, proposed half-pipe finned technology enables a 14% efficiency improvement in relation to the smooth pipe arrangement of the solar collector with black paint and double glass envelope, and 3.3% for the solar collector with selective layer and single glass envelope. If 5 m/s speed limit of air in piping system is assumed, proposed half-pipe finned technology enables a 13% efficiency improvement in relation to the smooth pipe arrangement of the solar collector with black paint and double glass envelope, and 11% for the solar collector with selective layer and single glass envelope.Proposed multiple fin-array technology enables to decrease the demanded air flux of 7–10 times in comparison to the smooth pipe arrangement of the absorber. Even with the flux decreased, the efficiency of internal multiple-fin array arrangement is higher than the one available for smooth pipe arrangement.The solution could be applied in solar space heating with rock bed storage systems or in solar dryers.