https://orcid.org/0000-0002-4152-8798
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ABSTRACT
In this study, the prototype of solar parabolic trough collector (PTC) is investigated to study experimental, optical and thermal efficiencies. The motive of this study is to develop low-cost PTC capable of producing warm water for low-temperature applications. Three different reflectors and three different receiver pipes with and without black graphite paint coating are tested. This paper deals with some of the feasible solutions to find out theoretical efficiency, optical efficiency and intercept factor. Design of experiment technique is used to design and analyze experiments. A regression model is prepared based on the analysis. As a solution, a combination of intercept factor = 0.231 and receiver value = 0.98 is found to be the best-fitted pair. Maximum efficiency of ηtheo = 15.3%, ηopt = 15.9% and ηexp = 12.4% are obtained.
Nomenclature
| ηexp | = | Experimental thermal efficiency |
| ηtheo | = | Theoretical efficiency |
| ηopt | = | Optical theoretical efficiency |
| Q uexp. | = | Experimental useful heat energy (W) |
| Ib | = | Beam (direct) radiation (W/m2) |
| Io | = | Total solar radiation (W/m2) |
| A a | = | Aperture area (m2) |
| A r | = | Area of receiver (m2) |
| M | = | Mass flow rate of water (kg/hour) |
| Cp | = | Specific heat of water (J/kg. 0C) |
| To | = | Outlet temperature of water (0C) |
| Ti | = | Inlet temperature of water (0C) |
| Tr | = | Surface temperature of receiver (0C) |
| Ta | = | Ambient temperature (0C) |
| α | = | Absorption coefficient of receiver |
| ρm | = | Reflection coefficient of reflector |
| γ | = | Intercept factor |
| K | = | Incident angle modifier factor |
| h w | = | Convective heat transfer coefficient (W/m2. 0C) |
| N ua | = | Nuselt number of air |
| k a | = | Conductivity of air (W/m 2 0C) |
| Dr.ext | = | Receiver external diameter (m) |
| Rea | = | Reynolds number of air |
| V | = | Wind velocity (m/s) |
| νa | = | Kinematic viscosity of air (m2/s) |
| h r, r-a | = | Radiative heat transfer coefficient (W/m2. 0C) |
| ε | = | Thermal emittance |
| σ | = | Stefan-Boltzmann constant (5.6697 x 10 8 W/(m2 K4) |
| UL | = | Overall heat loss coefficient (W/m2. 0C) |