An Experimental Investigation on multi-V and protrusion element on absorber plate of solar air heater

ABSTRACT

In this paper, an experimental based performance analysis of solar air heater having absorber plate roughened with combination of multi-V and protrusion shape geometry has been reported. The effect of multi-V with protrusion type and multi-V with protrusion arc type on convective heat transfer and friction parameters has been discussed with varying Reynolds number from 10,000 to 16,000. The thermohydraulic performance of solar air heater is also determined and compared with already investigated roughened absorber plates. The multi-V with protrusion type geometry found maximum value of Nusselt number and thermohydraulic performance at higher value of Reynolds number.

KEYWORDS:

• Solar air heater
• multi–V with protrusion
• roughness
• thermohydraulic performance

Nomenclature

A_c = cross-sectional area of duct, m²

c_p= specific heat of the air, JKg⁻¹ K⁻¹

D= hydlaulic diameter of duct,(dirnensionless)

e= rib height m

e/D= relativeroughness height(dirnensionless)

f =friction factor, (dimensionless)

H =height of the duct, m

h= convectiveheattmsfercoefftcient, Wm⁻¹K⁻¹

k =thermal conductivity of air,Wm⁻¹ K⁻¹

L =length of duct test section, m

m= mass flowrate,kg s⁻¹

Nu =Nusselt number (dimensionless)

p= pitch,of roughness element m

p/e =relative roughness pitch(dimensionless)

∆P =pressure drop inducts, Nm⁻¹

Re= Reynolds number (dimensionless)

T_i =inlet air tempemture of duct test section, K

T_o =outlet air temperature of duct test section, K

T_am = mean temperature of air, K

T_pm=mean temperature of absorberplate, K

V =velocity of air,m s⁻¹

W =widthof theduct, m

Greek symbols

p =fluid density,kg m⁻³

µ =dynamic viscosity of air, kg s⁻¹m⁻¹