Concentrated Solar Thermal Energy Technologies pp 103-114 | Cite as

# Experimental and Computational Investigation of Heat Transfer in an Open Volumetric Air Receiver for Process Heat Application

## Abstract

^{2}per day in Jodhpur only. This solar energy can be harnessed for electricity generation, melting or heat treatment of metals. Use of air as heat transfer fluid offers significant advantages of being nontoxic, freely available and operating temperature beyond 800 °C. Considering these aspects, as a research initiative, open volumetric air receiver (OVAR) is being developed with a peak-power capacity of 4 kW

_{th}. The installed testing facility at IIT Jodhpur includes sub systems, which are thermal energy storage (TES), air–water heat exchanger. In the absence of solar simulator electrical heating is being employed for circumferential (external) heating of the absorbers. In particular, the presented paper presents:

- (a)
Effect of pore diameters (2 and 3 mm) on the average outlet temperature of absorber with porosity (Ɛ) ~52% at \( {\text{POA/MFR}} = 100\;{\text{kJ/kgK}} \), where POA is the equivalent Power-On-Aperture and MFR is mass-flow rate of air;

- (b)
Efficiency performance curve for absorbers with Ɛ ~ 52%;

- (c)
Modeling of heat transfer in absorber with adopted commercial CFD tool FLUENT including returned air circulation;

- (d)
Comparison between CFD analyzed and experimentally obtained temperature for absorbers with Ɛ ~ 42, 52, and 62%;

- (e)
Predictions with incident radiation onto the front surface of porous absorber.

### Keywords

Solar energy Open volumetric air receiver (OVAR) Absorber CFD POA/MFR Local thermal nonequilibrium model (LTNE)### Nomenclature

*ρ*_{f}Density of fluid (kg/m

^{3})- \( v(v_{1},\, v_{2}, \, v_{3})\)
Velocity vector

*E*_{f}Total fluid energy (J)

- \( \eta_{\text{th}} \)
Thermal efficiency

- \( S_{\text{s}}^{\text{h}} \)
Solid enthalpy source term

*T*_{f}Temperature of fluid (K)

*t*Time (s)

*µ*Viscosity of air (kg/m s)

*k*_{f}Thermal conductivity of fluid (W/mK)

- RANS
Reynolds Average Navier–Stokes

*h*_{fs}Heat transfer coefficient for the fluid/solid interface

*T*_{s}Temperature of solid (K)

- Ɛ
Porosity (%)

*p*Static pressure (Pa)

*y*^{+}Nondimensional wall distance

- \( S_{\text{f}}^{\text{h}} \)
Fluid enthalpy source term

*A*_{fs}Interfacial area density, i.e., the ratio of the area of the fluid/solid interface and the volume of the porous zone

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