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Turbulent heat transfer characteristics and pressure drop in swirling flow at upstream and downstream of an abrupt expansion

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Abstract

This investigation is aimed at studying the heat transfer characteristics and pressure drop for turbulent airflow in a sudden expansion pipe equipped with propeller swirl generator. The investigation is performed for the Reynolds number ranging from 10,000 to 41,000 under a uniform heat flux condition. The experiments are conducted for three locations for the propeller fan upstream the sudden expansion and three locations downstream the sudden expansion (N = 5 blades and blade angle of 45°). The influences of using a freely rotating propeller on heat transfer enhancement and pressure drop are reported. The experimental results indicate that inserting the propeller downstream of the tube provides considerable improvement of the heat transfer rate higher than inserting the propeller upstream the tube. The increase in pressure drop resulting from using the propeller upstream is found to be higher than the downstream swirler. The maximum performance enhancement for the downstream swirler is about 326% while it is about 213% for upstream one. Correlations for relative mean Nusselt number and enhancement performance are presented for different fan locations and different Reynolds numbers.

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Abbreviations

C p :

Specific heat capacity of the fluid, J/kg K

d :

Upstream pipe diameter, m

D :

Test section Pipe diameter, m

h :

Heat transfer coefficient, W/m2 K

H :

Step height, H = 0.5(D − d), m

k :

Thermal conductivity of the fluid, W/m K

L :

Test section pipe length, m

\( \dot{m} \) :

Mass flow rate, kg/s

N :

Blades number

Nu :

Nusselt number

∆P :

Pressure drop, Pa

\( \dot{q} \) :

Heat flux, W/m2

Q :

Heat transfer rate, W

Re :

Reynolds number

T :

Temperature, °C

X :

Distance, m

S :

Swirler position, m

θ :

Swirl generator vane angle, º

η :

Thermal performance

μ :

Viscosity of the fluid, N s/m2

ρ :

Density, kg/m3

b :

Bulk

e :

Exit

fd :

Fully developed

h :

Heated

i :

Inlet

m :

Mean

mr :

Relative mean

o :

Smooth pipe (d/D = 1) without swirl

r :

Relative

s :

Surface

x :

Local

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Authors and Affiliations

  1. Mechanical Engineering Deparment, Tabbin Institute for Metallurgical Studies, Cairo, Egypt

    A. E. Zohir

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Zohir, A.E. Turbulent heat transfer characteristics and pressure drop in swirling flow at upstream and downstream of an abrupt expansion. Heat Mass Transfer 48, 529–539 (2012). https://doi.org/10.1007/s00231-011-0901-x

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  • DOI: https://doi.org/10.1007/s00231-011-0901-x

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