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Heat and Mass Transfer

, Volume 48, Issue 3, pp 555–571 | Cite as

Effect of porous disc receiver configurations on performance of solar parabolic trough concentrator

  • K. Ravi Kumar
  • K. S. ReddyEmail author
Original

Abstract

In this article, heat transfer enhancement of line focus solar collector with porous disc receiver is studied with water and therminol oil. A three dimensional (3-D) numerical simulation of porous disc enhanced receiver is carried out using commercial CFD software Fluent 6.3 to evolve the optimum configuration. The 3-D numerical model is solved by renormalization-group based k-ε turbulent model associated with standard wall function. The effect of porous disc receiver configurations (solid disc at bottom; porous disc at bottom; porous disc at top; and alternative porous disc) on performance of the trough concentrator is investigated. The effect of porous disc geometric parameters (φ, θ, W, H and t) and fluid parameters (Pr and m) on heat transfer enhancement of the receiver is also studied. The numerical simulation results show that the flow pattern around the solid and porous discs are entirely different and it significantly influences the local heat transfer coefficient. The porous disc receiver experiences low pressure drop as compared to that of solid disc receiver due to less obstruction. The optimum configuration of porous disc receiver enhances the heat transfer rate of 221 W m−1 and 13.5% with pumping penalty of 0.014 W m−1 for water and for therminol oil-55, heat transfer rate enhances of 575 W m−1 and 31.4% with pumping penalty of 0.074 W m−1 as compared to that of tubular receiver at the mass flow rate of 0.5 kg s−1. The Nusselt number and friction factor correlations are proposed for porous disc receiver to calculate heat transfer characteristics. The porous disc receiver can be used to increase the performance of solar parabolic trough concentrator.

Keywords

Pressure Drop Nusselt Number Friction Factor Heat Transfer Rate Heat Transfer Enhancement 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

Ac

Cross sectional area of the receiver (m2)

Ap

Aperture area of the solar trough collector (m2)

Ar

Receiver area (m2)

cF

Forchheimer coefficient

cp

Specific heat at constant pressure (J kg−1 K−1)

CR

Concentration ratio of the collector

\( C_{\varepsilon 1} ,C_{\varepsilon 2} ,C_{\mu } \)

Turbulent model constants

di

Inner diameter of the receiver (m)

do

Outer diameter of the receiver (m)

dp

Diameter of the pore in the disc (m)

D

Glass cover diameter (m)

f

Friction factor

H

Height of the porous disc (m)

hf

Heat transfer coefficient at inner surface of the receiver (W m−2 K−1)

Ib

Beam radiation (W m−2)

k

Turbulent kinetic energy (J)

Kp

Permeability (m2)

L

Length of the receiver (m)

m

Mass flow rate (kg s−1)

Nu

Nusselt number

ΔP

Pressure drop (Pa)

Pr

Prandtl number

Q

Total heat transfer (W)

\( q^{\prime \prime } \)

Heat flux (W m−2)

\( q_{ub}^{\prime \prime } \)

Useful heat flux applied at bottom of the receiver (W m−2)

\( q_{ut}^{\prime \prime } \)

Useful heat flux applied at top of the receiver (W m−2)

r

Radius (m)

Re

Reynolds number

S

Magnitude of rate of strain

t

Thickness of the porous disc (m)

T

Temperature (K)

Twi

Inner wall temperature of the receiver (K)

Two

Outer wall temperature of the receiver (K)

u, v, w

Velocity (m s−1)

Ul

Overall heat loss coefficient (W m−2 K−1)

V

Velocity vector (m s−1)

W

Pitch of the porous discs (m)

x, y

Spatial position (m)

Greek symbols

αt

Inverse of Prandtl number

γ

Intercept factor

ε

Turbulent dissipation rate (m2 s−3)

θ

Angle (deg)

λ

Thermal conductivity (W m−1 K−1)

μ

Viscosity of the fluid (Ns m−2)

\( \upsilon_{eddy} \)

Eddy viscosity (m2 s−1)

\( \upsilon_{o} \)

Molecular viscosity (m2 s−1)

\( \upsilon_{t} \)

Turbulent viscosity (m2 s−1)

ρ

Density (kg m−3)

\( \rho_{g} \)

Reflectivity of the glass

φ

Porosity

ψ

Turbulent model constant

\( \left( {\tau \alpha } \right)_{b} \)

Transmissivity-absorptivity product for beam radiation

Subscripts

a

Ambient

CF

Clear fluid

f

Fluid

in

Inlet

int

Interface

i, j

General spatial indices

max

Maximum

PM

Porous medium

ref

Reference

s

Solid

T

Therminol oil

W

Water

WT

Water and therminol oil

Notes

Acknowledgement

The financial support provided by the Department of Science and Technology (DST, Govt. of India), New Delhi through the research project is duly acknowledged.

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Heat Transfer and Thermal Power Laboratory, Department of Mechanical EngineeringIndian Institute of Technology MadrasChennaiIndia

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