Exergetic analysis and comparative study of a roughened solar air heater using MATLAB

Yıl 2017, Cilt: 1 Sayı: 3, 78 - 85, 30.09.2017

Ankit Kumar

Öz

A
comparative study based on exergetic performance of two different types of
artificial roughness geometries on the absorber plate of solar air heater has
been presented. The performance evaluation in terms of thermal efficiency (ɳ_th),
effective efficiency (ɳ_eff), exergetic efficiency (ɳ_II)
and different exergy loss parameters has been carried out analytically, for
various values of temperature rise parameter (∆T/I) and relative roughness
height (e/D). The second law based exergy analysis is suitable for design of
rib roughened solar air heaters as it incorporates quality of useful energy
output and pumping power. The two roughness geometries are discrete W-shape rib
roughness and W-shape rib roughness have been selected. The correlations for
heat transfer and coefficient of friction developed by respective investigators
have been used to calculate efficiencies. It was investigated that discrete
W-shape rib roughness has better thermal efficiency (ɳ_th), effective
efficiency (ɳ_eff) and exergetic efficiency (ɳ_II) as
compared to the W-shape rib roughness. The optimum parameters are relative
roughness height (e/D) of 0.3375 at an angle of attack of 60º and isolation
value of 1000 w/m². It was investigated that discrete W-shaped rib
roughness has 33% more exergetic efficiency then W-shaped rib roughness under
similar performance parameters such as aspect ratio (8), relative roughness
height (e/D) of 0.03375, angle of attack (α) of 60º, relative roughness pitch
(P/e) of 10 and isolation value of 1000 w/m² with Reynolds number
ranges from 4000 to 14000. Curves of thermal efficiency (ɳ_th),
effective efficiency (ɳ_eff), exergetic efficiency (ɳ_II)
and different exergy loss parameters with respect to temperature rise parameter
(∆T/I) and relative roughness height (e/D) are also plotted.

Anahtar Kelimeler

MATLAB; Solar air heater; Roughness; Exergetic efficiency; W and discrete W shape.

Kaynakça

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