Heat and Mass Transfer

, Volume 54, Issue 3, pp 727–744 | Cite as

Experimental and numerical study on thermal-hydraulic performance of wing-shaped-tubes-bundle equipped with winglet vortex generators

  • Mohamed A. Abdelatief
  • Sayed Ahmed E. Sayed Ahmed
  • Osama M. Mesalhy
Original
  • 83 Downloads

Abstract

The present work evaluates, experimentally and numerically, by the aid of commercial code FLUENT 6.3.26, the effects of relative locations (∆X or ∆Y), heights (hw), and span-angle (θ) of winglet-vortex-generators (WVGs) on thermal-hydraulic performance enhancement for down-stream and/or up-stream wing-shaped-tubes bundle heat exchangers for air Re ranging from 1.85 × 103 to 9.7 × 103 while water Re = 5 × 102. hw is set as 5 mm, 7.5 mm and 10 mm. For tube down-stream, θ is set as 0° (Base-line-case) and from 5° to 45° clockwise common-flow up (CFUp) and counterclockwise common-flow down (CFDn) while for tube up-stream it is set as −5°, −10° and −15° CFUp. Results show that the increase of θ counterclockwise-(CFDn) or clockwise-(CFUp) leads to increase the values of Nu number. Using WVGs with (+5 ° ≤ θ ≤ +45°) results in increasing Nu number by about from 34 to 48% comparing with that of base-line-case. The lowest values of drag coefficient (f) for tube down-stream are obtained at +5° CFDn and −15° CFUp with respect to the base-line case. For tube up-stream, Nu number increases by increasing θ from 0° to −5° and the values of Nu number for θ varying from −5° to −15° have no significant changes. (f) increases with hw and has negligible effect on ha. Furthermore, optimization analyses of θ and longitudinal fin (LF) are utilized, in four cases, for finding the optimum combination and maximum efficiency. The highest values of heat transfer parameters such as effectiveness (ε), area goodness factor (G) and efficiency index (η) and the lowest values of fluid-flow parameters like (f) and hence the best efficiency, are achieved for −15° CFUp down-stream, (“case 3” of −15° CFUp down-stream and 6 mm LF height) and +5° CFDn down-stream. Correlations of Nu number, (f) and (ε) as a function of θ and Re for the studied cases are performed.

Keywords

WVGs Span-angle Winglet height Relative position Wing-shaped Thermal-hydraulic 

List of symbols

Alphabet- upper case

FR

Air volume flow rate, m3/s

= j/f

Area goodness factor

j

Colburn j factor, j = St.Pr2/3

N

Number of tube rows

Nu

Nusselt number, (h.Deq)/k

P.P.

Pumping power, (∆Pa. FRa), W

Pr

Prandtl number, (μ. cp)/k

f

Drag coefficient, (2.∆P)/(ρaf.Va 2)

Q

Heat transfer rate, W

Re

Reynolds number, (ρ.V.Deq)/μ

Rth

Thermal resistance, K/W

St

Stanton number, Nu/(Re.Pr)

T

Temperature, K

Ts

Tube surface temperature, K

Alphabet- lower case

ha

Heat transfer coefficient, W/m2.K

hf

Fin height, m

hw

Winglet height, m

m

mass flow rate, kg/s

Greek symbols

δf

Fin thickness, m

δw

Winglet thickness, m

μ

Absolute viscosity, Pa.s

ρ

Density, kg/m3

θ

Span angle °

ε

Effectiveness, (ρaf.cpf (Tai-Tae))/ ∆Pa

η

Efficiency Index, (St/Stc)/(Pdc/Pdcc)

ηf

Fin efficiency

ηo

Overall fin efficiency

∆P

Pressure drop, Pa

∆hdyn

Dynamic head difference, m H2O

∆Ta

Air temperature difference, °C

∆Tw

Water temperature difference, °C

ΔTln

Logarithmic mean temperature difference, °C

∆X

Relative distance in X-direction, m

∆Y

Relative distance in Y-direction, m

Subscripts

a

Air

af

Air film

ai

Air inlet

c

Circular

eq

Equivalent

f

Fin

L

Longitudinal

l

Length

s

Surface

T

Transverse

t

Thickness

w

Winglet or Water

Abbreviations

CFDn

Common flow down

CFUp

Common flow up

LF

Longitudinal fin

LFTHE

Longitudinal finned-tube heat exchanger

LMTD

Log mean temperature difference

LVGs

Longitudinal vortex generators

WVGs

Winglet vortex generators

Notes

Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • Mohamed A. Abdelatief
    • 1
  • Sayed Ahmed E. Sayed Ahmed
    • 1
  • Osama M. Mesalhy
    • 1
  1. 1.Mechanical Power Engineering Department, Faculty of engineeringZagazig UniversityZagazigEgypt

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