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Numerical simulation of effective efficiency of a discrete multi V-pattern rib solar air channel

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Abstract

The use of artificial roughness in the form of repeated ribs has been found to be an efficient method of improving the heat transfer to fluid flowing in the channel. In this study, performance of solar air channel as a function of discrete multi V-pattern rib shapes has been investigated. The e/D was varied from 0.022 to 0.043, Gd/Lv was varied from 0.24 to 0.80, g/e was varied from 0.5 to 1.5, α was varied from 30° to 75°, P/e was varied from 6.0 to 12.0 and W/w was varied from 1.0 to 10.0. A methodology has been developed for the prediction of effective efficiency. Based on the values of effective efficiency, an optimization has been carried out to determine the set of data of roughness shapes parameters that correspond to better effective efficiency for given values of operating parameters of the air channel. Design plots have been represent to depict the data of individual roughness shapes parameters that characterize the optimum condition as a function of performance parameter and intensity of radiation. It was observed that the maximum values of effective efficiency for e/D of 0.043, Gd/Lv of 0.69, g/e of 1.0, α of 60°, P/e of 8.0 and W/w of 6.0. Discrete multi v-rib shape has been found to be better thermohydraulic performance (effective efficiency) as comparison to other rib shapes solar air channels.

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Abbreviations

A p :

Area of absorber plate (m2)

e :

Rib height (m)

e/D :

Relative roughness height

F′:

Plate efficiency factor

F R :

Heat removal factor

f :

Friction factor of roughened channel

fs :

Friction factor of smooth channel

G :

Global irradiation (W/m2)

Gd :

Discrete or gap distance (m)

Gd/Lv :

Relative gap distance

g :

Gap or discrete width (m)

g/e :

Relative gap or discrete width

H :

Depth of channel

h :

Convective heat transfer coefficient (W/m2 K)

h e :

Effective heat transfer coefficient (W/m2 K)

h w :

Wind convective heat transfer coefficient (W/m2 K)

I :

Solar intensity (W/m2)

k :

Thermal conductivity of air (W/m K)

K i :

Thermal conductivity of insulation (W/m K)

L :

Test section length (m)

L g :

Fluid gap between heated plate and glass cover

Lv :

Length of single V-shaped rib (m)

m :

Mass stream rate (kg/s)

N :

Number of glass covers

Nu :

Nusselt number of roughened channel

Nu s :

Nusselt number of smooth channel

P :

Pitch of the rib (m)

P/e :

Relative roughness pitch

P m :

Pumping power (W)

Qu :

Useful heat gain rate (W)

Re :

Reynolds number

T a :

Ambient temperature (K)

T f :

Mean temperature of air (K)

T i :

Inlet temperature of air (K)

T O :

Outlet temperature of air (K)

ΔT :

Temperature rise (K)

ΔT/I :

Temperature rise parameter (K m2/W)

t i :

Thickness of insulation (m)

t g :

Thicknesses of glass cover (m)

V :

Velocity of air (m/s)

V w :

Wind velocity (m/s)

W :

Width of channel (m)

w :

Width of single V-shaped rib (m)

W/w :

Relative roughness width

α :

Angle of attack (degree)

ɛ g :

Emissivity of glass cover

ɛ p :

Emissivity of absorber plate

ɛ s :

Emissivity of selective surface

η :

Thermo-hydraulic performance parameter

η eff :

Effective efficiency

τ :

Transmissivity of glass cover

μ :

Dynamic viscosity of fluid

(τα):

Transmittance-absorptance product for absorber-cover combination

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Authors and Affiliations

  1. School of Mechanical Engineering, Kyungpook National University, Daegu Metropolitan City, 702701, South Korea

    Anil Kumar

  2. School of Mechanical and Civil Engineering, Shoolini University, Solan, Himachal Pradesh, 174212, India

    Anil Kumar

  3. Alternate Hydro Energy Centre, IIT Roorkee, Roorkee, Uttarakhand, 247667, India

    R. P. Saini

  4. Mechanical and Industrial Engineering Department, IIT Roorkee, Roorkee, Uttarakhand, 247667, India

    J. S. Saini

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  1. Anil Kumar
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  2. R. P. Saini
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  3. J. S. Saini
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Correspondence to Anil Kumar.

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Kumar, A., Saini, R.P. & Saini, J.S. Numerical simulation of effective efficiency of a discrete multi V-pattern rib solar air channel. Heat Mass Transfer 52, 2051–2065 (2016). https://doi.org/10.1007/s00231-015-1712-2

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  • DOI: https://doi.org/10.1007/s00231-015-1712-2

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