Abstract
All heat transfer processes are connected with flow structure. It is important to know both heat transfer and flow characteristics. For the first time it is proposed to connect Particle Image Velocimetry (PIV) method with gradient heat flux measurement and thermal imaging for complex study of hydrodynamics and heat transfer at the surface of a single circular cooling fin. The hollow fin is heated with saturated water steam; meanwhile its isothermal external surface simulates the ideal fin. Flow and heat transfer at the surface of the solid fin of the same size and shape, and made of titanium alloy is investigated in the same regimes. Gradient Heat Flux Sensors (GHFS) were installed at different places of the fin surface. Velocity field near the fin, temperature field at the surface of the fin and heat flux were obtained. Comprehensive method including heat flux measurement, PIV and thermal imaging allows to study the flow and heat transfer at the surface of the fin in real time regime. The possibility of complex study of flow and heat transfer for non-isothermal fins is shown.
Highlights
A number of recuperative heat exchanger designs use finned cylinder tubes to increase the heat transfer surface
Despite wide prevalence of finned heat exchangers, there is no universal method for calculation
For a more accurate comparison of flow and heat transfer, a combination approach that includes simultaneous measurement of heat transfer parameters using unique gradient heat flux sensors (GHFS), velocity fields using Particle Image Velocimetry (PIV) method and temperature fields visualized by thermal imaging is proposed
Summary
A number of recuperative heat exchanger designs use finned cylinder tubes to increase the heat transfer surface. Despite wide prevalence of finned heat exchangers, there is no universal method for calculation. This fact is due to the uneven distribution of the heat transfer coefficient at the surface of the fin [1,2,3,4]. The investigations of heat transfer at different surfaces are troubled by the unavailability of heat flux sensors with required response time. Due to this situation, the temperature is often measured and the heat transfer coefficients are calculated from similarity equations. For a more accurate comparison of flow and heat transfer, a combination approach that includes simultaneous measurement of heat transfer parameters (heat flux per unit area and heat transfer coefficient) using unique gradient heat flux sensors (GHFS), velocity fields using PIV method and temperature fields visualized by thermal imaging is proposed
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