Optimal Shape Selection of Heat Exchangers Surfaces during Convective Heat Transfer

2018 ◽  
Vol 284 ◽  
pp. 1337-1341
Author(s):  
V. Konukhov ◽  
S. Mukhanov ◽  
G. Konukhova

The article contains the results of a research in constructing of modern heat exchangers form of heat exchanging surfaces and modes of heat media flux, providing minimum area (size) of heat exchanging apparatus. Decreasing of heat-transferring area is achieved by using different techniques of intensification of convective heat exchange. Intensification of the heat exchange is accompanied by increasing of energy consumption for pumping the coolant. It is concluded that under the conditions of turbulent flow, the transport mechanism does not strongly depend on the shape of the perturbations introduced into the flow, while the tendency to approach the dependences is common to the curves for the considered surfaces, and the experimental data obtained on pipes with a periodic section of the flow cross-section along the length. Using surfaces creating channels with a greater coefficient of hydraulic resistance when creating a compact heat exchangers, which corresponds to surfaces for which the principle of trans-verse flow is realized.

2019 ◽  
Vol 5 (3) ◽  
pp. 91-100
Author(s):  
Vladimir S. Berdnikov

This work is a brief overview of experimental study results for hydrodynamics and convective heat exchange in thermal gravity capillary convection modes for the classic Czochralski technique setup obtained at the Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences. The experiments have been carried out at test benches which simulated the physics of the Czochralski technique for 80 and 295 mm diameter crucibles. Melt simulating fluids with Prandtl numbers Pr = 0.05, 16, 45.6 and 2700 have been used. Experiments with transparent fluids have been used for comparing the evolution of flow structure from laminar mode to well-developed turbulent mode. Advanced visualization and measurement methods have been used. The regularities of local and integral convective heat exchange in the crucible/melt/crystal system have been studied. The experiments have shown that there are threshold Grashof and Marangoni numbers at which the structure of the thermal gravity capillary flow undergoes qualitative changes and hence the regularities of heat exchange in the melt change. The effect of melt hydrodynamics on the crystallization front shape has been studied for Pr = 45.6. Crystallization front shapes have been determined for the 1 × 105 to 1.9 × 105 range of Grashof numbers. We show that the crystallization front shape depends largely on the spatial flow pattern and the temperature distribution in the melt.


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