Entropy generation and thermodynamic analysis of solar air heaters with artificial roughness on absorber plate

Abstract

This paper presents mathematical modelling and numerical analysis to evaluate entropy generation analysis (EGA) by considering pressure drop and second law efficiency based on thermodynamics for forced convection heat transfer in rectangular duct of a solar air heater with wire as artificial roughness in the form of arc shape geometry on the absorber plate. The investigation includes evaluations of entropy generation, entropy generation number, Bejan number and irreversibilities of roughened as well as smooth absorber plate solar air heaters to compare the relative performances. Furthermore, effects of various roughness parameters and operating parameters on entropy generation have also been investigated. Entropy generation and irreversibilities (exergy destroyed) has its minimum value at relative roughness height of 0.0422 and relative angle of attack of 0.33, which leads to the maximum exergetic efficiency. Entropy generation and exergy based analyses can be adopted for the evaluation of the overall performance of solar air heaters.

Optimization of air chamber in solar air collector

“…5. The holes in the bafflers on Schemes 3... 9 were made open-ended, changing only the configuration. Openings in the bafflers on Schemes 1...2 were made by fat contour line, then the dimmed plane was bent inwards at an angle of 45°.…”

“…Solar air collectors are simple devices, however have a numerous of options of constructive execution, warming, a material and a covering of an absorber, a translucent covering, and means of ensuring creation of turbulent air streams inside. Therefore, a large number of scientific studies of various authors is devoted to the study of their properties and design features [8][9][10][11][16][17][18][19].…”

Analysis of exergetic performance for a solar air heater with metal foam fins

“…Thermal performance represents the amount of transferred energy; therefore, heat may be recovered at low temperatures. So, the maximum work produced by a system in a quantified manner can be referred to as exergy 3 . The actual processes that take place in real life are irreversible, thus the efficiency of a solar collector is also irreversible.…”

“…Saha and Sharma 8 conducted a numerical investigation of a double‐flow SAH, with a corrugated absorber plate possessing different flow channel arrangements, and observed that an increase in the air flow rate leads to a decrease in exergy, because at higher air flow rates, the outlet air temperature is low. A comprehensive study for the entropy generation and calculation of exergy efficiency for an SAH with a roughened absorber plate was presented by Prasad and Sahu, 3 who reported that exergy efficiency increased with increasing Reynolds number (Re). However, it was found that a smooth solar collector was more efficient than a roughened solar collector at high values of Re.…”

“…So, the maximum work produced by a system in a quantified manner can be referred to as exergy. 3 The actual processes that take place in real life are irreversible, thus the efficiency of a solar collector is also irreversible. The degree of irreversibility for any system can be expressed in terms of entropy generation, and it is thus a criterion for the performance of engineering systems.…”