Page 157 - IJES Special Issues for AIEC2016

International Journal of Environment and Sustainability, 2016, 5(1): 54-60 57

passing inside the absorber tubes is heated Table 1
because of the contact underneath the PV Characteristics of PVT collector
module. The water flows along the absorber
through a manifold and pipes before being finally Ambient temperature Ta 297 K
fed to a water tank. The absorbers are equipped Inlet fluid temperature Ti 300 K
with an inlet and outlet at opposite ends of the Collector width b 0.555 m
hollow tubes, which ensure that the trapped Tube spacing W 0.02 m
water in the absorber can be released. The Collector parameter P 3.3 m
system is considered a closed-loop system, Collector area Ac 0.875 m²
wherein the fresh and cool water that enters the Number of glass cover N 1
round tubes is heated continuously. The Emittance of glass εg 0.88
collector conceptual designs used in this study Emittance of plate εp 0.95
are shown in Figure 1, comprising three new Tilt (slope) º 14
design configurations. Fluid flow rate mdot 0.068 kg/s
Fluid thermal conductivity kfluid 0.613
Figure 1: New Ellipse Absorber Design for PV/T Back insulation conductivity Cp 4180
Collector Specific heat kb 0.045 W/mºK
Back insulation thickness Lb 0.05 m
3.4 Boundary Conditions Insulation conductivity ke 0.045 W/mºK
Appropriate boundary conditions are empha- Edge insulation thickness Le 0.025 m
sized on the CFD domain as the physics of the Absorber conductivity kabs 51 W/mºK
problem. Inlet boundary conditions are specified Absorber thickness Labs 0.002 m
as velocity inlet conditions. The outflow bound- Fin conductivity kf 84 W/mºK
ary condition is applied at the outlet. Wall Fin thickness δ 0.0005 m
boundary conditions are used to bind fluid and Heat transfer coefficient from hca 45 W/mºK
solid regions. At the wall, velocity components cell to absorber hfi 333 W/mºK
are set to zero in accordance with the no-slip and Heat transfer inside tube τ 0.88
impermeability conditions that exist in viscous Transmittance α 0.95
flow models. The interface between the water Absorptance
and absorber tube is characterized as the wall
with coupled condition to conjugate heat ex- 4. Results and Discussion
change from the absorber tube to water. A
shifting high temperature flux comparable to the In order to numerically evaluate the perfor-
solar insolation is connected at the top surface of mance of the PV/T Collector, the whole day
the PV panel. The outer surface of the absorber numerical results are shown in Figure 2 to Figure
tube is characterized as the wall with zero heat 4, which illustrate solar irradiance, ambient tem-
flux condition that affects insulated conditions. perature, PVT module temperature, and outlet
water temperature. According to Figure 2, the
maximum outlet water temperature from the
ellipse design absorber reached approximately
55.53 °C, whereas the maximum PV temperature
reached approximately 59.86 °C under the same
conditions. Heat loss between the PV/T collector
and environment was altogether higher than
that between the conventional solar collector
and environment. Hence, the thermal effec-
tiveness of the PV/T collector was marginally
lower than that of the conventional solar collec-
tor because of the expanded hear-loss coeffi-
cient.

Based on Figure 2 and the equations of PVT
energy balance, the electrical PVT power,

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