Experimental investigation of a solar air heater with copper wool on the absorber plate

ABSTRACT

The thermal performance of a novel solar air heater was experimentally studied in this paper. For this aim, a new solar air collector was designed using copper wool on its absorber plate to be a selective surface. Hence, the area of absorber plate was enhanced to absorb much amount of heat energy. The experimental study was conducted for both cases (presence and absence of copper wool on the absorber plate) to determine the effect of copper wool on the thermal efficiency of the collector. The mass flow rate values of the study were 0.035 and 0.044 kg/s. The results pointed out that fluid temperature at outlet of collector with copper wool was increased by about 8 to14%. Therefore, these collectors may be suitable for space heating and drying of food applications. However, copper wool caused more pressure loss through the collector by 40% compared to simple case of collector. The thermal efficiency of the collectors was obtained as 34 to 83% depending on experimental variable parameters. Similarly, effective efficiency of collectors was computed to be 24 to 70%. It is found that efficiency of the collector was improved when using copper wool on the absorber plate as well as increasing mass flow rate of air.

KEYWORDS:

• Copper wool
• solar air heater
• thermal efficiency

Nomenclature

AcCollector surface area (m2)	=
AdDuct cross-sectional area (m2)	=
cpSpecific heat capacity(kJ/kg⋅K)	=
ISolar radiation (W/m2)	=
mMass flow rate (kg/s)	=
${\dot{Q}}_{\mathrm{a}\mathrm{b}\mathrm{s}}$Absorbed rate of energy (kW)	=
${\dot{Q}}_{\mathrm{a}\mathrm{c}\mathrm{c}}$Accumulated rate of energy by absorber (kW)	=
${\dot{Q}}_{\mathrm{l}\mathrm{o}\mathrm{s}\mathrm{t}}$Lost energy rate (kW)	=
${\dot{Q}}_u$Useful energy rate of SAH (kW)	=
$\dot{W}$Power consumption of fan (kW)	=
ΔpPressure drop through collector (Pa)	=
TTemperature (°C)	=
UTotal energy loss coefficient (W/m2·K)	=
VMean velocity of fluid (m/s)	=
wUncertainty (%)	=
Greek letters	=
ρFluid density (kg/m3)	=
$\tau \alpha$Effective transmittance-absorbance	=
ηThermal efficiency	=
ηeffEffective efficiency	=
Subscripts	=
aAmbient	=
fFluid	=
iInlet	=
oOutlet	=
pPlate	=

Additional information

Funding

The experimental study was financially supported by Dicle University with the research project no. MÜHENDİSLİK.15.006..