Investigation of flow and heat transfer at the circular fins

Vladimir Mityakov,Andrey Gusakov,Michail Grekov,Vladimir Seroshtanov,A Borodinecs,V Sergeev,N Vatin

doi:10.1051/matecconf/201824506001

Vladimir Mityakov, Andrey Gusakov + Show 5 more

Open Access

https://doi.org/10.1051/matecconf/201824506001

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Abstract

For simultaneous investigation of heat transfer and hydraulic parameters of finned circular tube is proposed to connect PIV (Particle Image Velocimetry) method and thermal imaging with gradient heat flux measurement. In the first series of experiments, the hollow fin was investigated. The hollow fin was heated with saturated water steam and its isothermal surface simulated the ideal (isothermal) fin. The solid fin made of titanium alloy was investigated in similar regimes for comparison. In the second series, the influence of distance between fins on the heat transfer coefficients (HTC) at the circular fin, mounted on a circular cylinder was studied. The unique Gradient Heat Flux Sensors (GHFSs) were installed at different places of the fin surface. Comprehensive method including heat flux measurement, PIV and thermal imaging allows to study flow and heat transfer at the surface of the fin in real time. Possibility of complex study of flow and heat transfer for non-isothermal fins is shown.

Highlights

A number of recuperative heat exchangers use circular tubes whose finning increase their heat transfer surface
Dependence of average heat transfer coefficient (HTC) on Reynolds number for isothermal (a, c) and non-isothermal (b, d) fins of different heights is shown at Fig. 4
It can be seen that HTC decreases in interval of φ = 120 ... 180 °

Summary

Introduction

A number of recuperative heat exchangers use circular tubes whose finning increase their heat transfer surface. Distribution of the heat transfer coefficient (HTC) at the surface of the fin is the main problem here[1, 2]. Heat transfer and hydrodynamics have been studied during separate measurements. The investigation of heat transfer at different surfaces was troubled by the missing of heat flux sensors with the required response time. More often, temperature was measured and HTCs were calculated from similarity equations. For more accurate comparison of flow and heat transfer, a combination of approaches that includes simultaneous measurement of heat flux per unit area and HTC using unique gradient heat.

Heat flux measurement

IR imaging

Experimental model

Results

Conclusions