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Sādhanā

, 44:241 | Cite as

Numerical investigation to predict optimum attack angle combination of longitudinal vortex generators in compact heat exchangers for thermo-hydraulic heightened performance

  • Mohd Zeeshan
  • Sujit NathEmail author
  • Dipankar Bhanja
Article

Abstract

The current 3-D numerical analysis explores the effect of combinations of rectangular winglet pairs (RWPs) having different attack angles (i.e. 5°, 15° and 25°) along a row of the tube array, on the performance of the fin and tube heat exchanger (FTHE). The considered airside Reynolds number Re ranges from 500 to 900. In total, six combinations of three attack angle vortex generators (VGs) have been numerically analysed namely 5°-15°-25°, 5°-25°-15°, 15°-5°-25°, 15°-25°-5°, 25°-5°-15° and 25°-15°-5°. The performance of the FTHE is represented by area goodness factor. The performance rankings of the FTHEs are also obtained by the MOORA method. Finally, 5°-25°-15° case provides the best thermal hydraulic performance for which heat transfer coefficient (h) is increased by 68.20% at Re = 500 and 81.78% at Re = 900, with a significant pressure drop penalty.

Keywords

Fin and tube heat exchanger rectangular vortex generators area goodness factor MOORA method 

Nomenclature

AT

total heat transfer surface area (m2)

Amin

minimum flow area (m2)

cp

specific heat (J kg−1 K−1)

D

outer tube diameter (m)

Dh

hydraulic diameter, Dh = 4AminL/AT

f

friction factor

Fp

fin pitch (m)

Ft

fin thickness (m)

h

air-side heat transfer coefficient (W m−2 K−1)

H

channel height (m)

Hw

winglet height (m)

j

Colburn j-factor

L

flow length (m)

m

mass flow rate (kg/s)

Nu

average Nusselt number

p

pressure (Pa)

Pf

fan power (W)

Pr

Prandtl number

Pl

longitudinal tube pitch (m)

Ps

span wise tube pitch (m)

Q

heat transfer capacity (W)

Re

air side Reynolds number

St

Stanton number

T

temperature (K)

Tout

outlet temperature (K)

Tw

wall temperature (K)

\( \bar{T} \)

bulk average temperature (K)

Tin

inlet temperature (K)

∆Tm

mean value of temperature

\( \bar{p} \)

bulk average pressure (Pa)

∆p

air side pressure drop (Pa)

U

free stream velocity (ms−1)

u

velocity in x-direction (ms−1)

v

velocity in y-direction (ms−1)

Vm

mean velocity at Amin (m s−1)

w

velocity in z-direction (m s−1)

Greek symbols

μ

dynamic viscosity (Pa.S)

ρ

density (kg m−3)

λ

thermal conductivity (W m−1K−1)

ηf

fan efficiency

Abbreviations

FTHE

finned tube heat exchanger

MOORA

multi-objective optimization on the basis of ratio analysis

RWP

rectangular winglet pair

LVG

longitudinal vortex generators

CFD

common flow down

CFU

common flow up

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Copyright information

© Indian Academy of Sciences 2019

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringNational Institute of Technology SilcharSilcharIndia

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