Xu, "Numerical investigation of heat transfer and fluid flow in a solar air heater duct with multi V-shaped ribs on the absorber plate
," Energy, vol.
The previous SAH designs with the cross-corrugated absorber plate
 and the SAH design with jet impingement on a flat absorber plate
 are illustrated in Figures 10(a) and 10(b), respectively.
The obstacles ensure a good air flow over the absorber plate
, create the turbulence and reduce the dead zones in the collector.
where [Q.sub.abs] is the product of the mass flow rate ([??]), the specific heat of the circulating water ([C.sub.P]), and the temperature rise between the inlet and outlet of the absorber plate
The highest average temperatures of drying chamber and bottom absorber plate
of the solar dryer, 69.0[degrees]C and 77.5[degrees]C, respectively, were attained at 12:00 GMT.
where [eta] = thermal efficiency (%), [M.sub.w] = mass of water (Kg), [M.sub.cu] = mass of the copper pipe (Kg), [C.sub.w] = specific heat capacity of water (4200 J [Kg.sup.-1] [degrees][K.sup.-1]), [C.sub.cu] = specific heat capacity of copper pipe (400 J [Kg.sup.-1] [degrees][K.sup.-1]), I = total solar radiation (W [m.sup.-2]), A = area of absorber plate
([m.sup.2]), [DELTA]T = difference in temperature ([degrees]C), and At = difference in time (seconds).
From the literature review cited above, it is revealed that both experimental and numerical analysis works ar e done using the roughness geometries fitted on the flow side of absorber plate
. Promvonge et al.
Subscripts and Abbreviations a: Ambient b: Lower plate bp: Bottom surface of absorber plate
c: Solar cell f: Fluid inl: Inlet g: Glass cover in: Insulator p: Upper plate pv: Electric out: Outlet s: Sky ted: Tedlar Exp: Experimental t: Total th: Thermal tp: Top surface of absorber plate
Theo: Theory mav: Mean value.
The PCM is prepared in modules, with the modules equispaced across the absorber plate
. The system was tested under daytime no-load conditions at Nsukka, Nigeria.
The T-type thermocouple wires were used to measure the surface temperature of the absorber plate
(in three rows at six points), the surface temperature of the glass at two points, and the temperature of the ventilation air trapped between the glass surface and the absorber plate
(using nine thermocouple wires in three rows suspended on a string at the mid height of the glazing gap).
Conventional solar air heaters have poor thermal efficiency primarily due to the low-convective heat transfer coefficient between the absorber plate
and flowing air stream [1, 2].
Nomenclature Nu Nusselt number (hd/k) Ra Rayleigh number, Gr.Pr Re Reynolds Number d diameter of the tube, m g Acceleration due to gravity, m/[s.sup.2] Gr Grashof number, g[beta]'[d.sup.3] ([DELTA]T)/ [[upsilon].sup.2] Pr Prandtl number h convective heat transfer coefficient, [Wm.sup.-2] [K.sup.-1] L spacing between the absorber plate
and glass cover [DELTA]T Temperature difference, [degrees]C [T.sub.pm] Absorber Plate
mean Temperature, [degrees]C Z Non Dimensional Distance Greek symbols [sigma] Stefan-Boltzman constant, [Wm.sup.-2] [K.sup.-4] [beta]' Film Temperature, [K.sup.-1] [upsilon] kinematic viscosity [delta] Inclination angle of the pipe [alpha] Tilt angle of the collector tube with the horizontal [theta] Temperature Ratio Appendix