Research Article Open Access

An Investigation of Solar Concentrator Receiver Designs through Sensible Heat Test

Abstract

A solar receiver system collects solar radiations in a solar concentrator system and transfers the heat to the working fluid of the system for useful thermal application. In the present work two locally fabricated receiver designs are experimentally investigated on a solar parabolic dish concentrator having an aperture area of 7 m² and a rim angle of 56°C. Based on sensible heat test of fluid, two thermal performance parameters, rate of rise of fluid temperature, R_f, and utilizable efficiency of system, η_u, are determined and are recommended for the comparative study of different receivers. The experiments are conducted with two fluid, water, flow rates 8 L/min and 10 L/min for the receivers, flat copper spiral receiver, CSR, and copper conical spiral receiver, CoSR. The R_f for CoSR and CSR receivers are found to be 0.33 and 0.23°C/min, respectively for 8 L/min flow rate. The utilizable efficiency of CoSR and CSR are determined to be 33% and 17%, respectively. The receiver surface temperature of CSR is found higher than CoSR due to less efficiency of CSR. It is found in the experimental observation that the sensible heat test procedure clearly differentiates the performances of receivers and is appropriate to study the thermal performance of different receiver designs.

Nomenclature

A_a Aperture area of the concentrator (m²)

A_r Receiver base area (m²)

C_R Concentration ratio; C_w Specific heat of water (J/kg°C)

D_a Concentrator diameter (m)

I_b Normal beam solar irradiance on concentrator aperture plane (W/m²)

I_s Global solar irradiance on horizontal plane (W/m²)

I_{s, avg} Average global solar insolation at the horizontal surface (W/m²) in time period Δt

M_w Mass of water in the storage tank (kg)

q_a Available rate of heat to the fluid (W)

q_u Utilized rate of heat by the fluid (W)

S Solar flux absorbed in receiver plate (W/m²)

T_a Ambient temperature (°C)

T_r Receiver stagnation temperature (°C)

T_w Water temperature in storage tank (°C)

T_w,f Water temperature in storage tank at the end of heating process (°C)

T_w,I Water temperature in storage tank at the beginning of heating process (°C)

W_s Wind speed (m/s)

Greek symbols

α_r Absorptivity of receiver paint

Δt Time interval (s)

η_u Utilized thermal efficiency of concentrator

ρ_r Specular reflectance of the reflector

θ Average angle of incidence on the horizontal surface (°)

Acronyms

ESPC Economic Solar Paraboloidal Concentrator

SPDC Solar Paraboloidal Dish Concentrator

HTF Heat Transfer Fluid

CSR Copper Spiral Receiver

CoSR Copper Conical Spiral Receiver

CFP Circular Flat Plat

Sunita Mahavar

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