Abstract
The paper presents results of numerical and experimental analyses of a fin-and-tube air-water heat exchanger. The analysed device is a one-row heat exchanger with finned elliptical tubes. The aim of the analyses is to investigate the impact of a controlled non-uniform inflow of air on the heat exchanger performance. The heat exchanger was modelled numerically using the ANSYS Fluent program. The developed model was applied to simulate the heat exchanger operation in the conditions of the uniform inflow of air. Cases of an uncontrolled non-uniform inflow of gas were investigated experimentally, using a purpose-designed test station. On the experimental test station the effect of a controlled non-uniform air inflow was also achieved by placing appropriately shaped inserts in the air inlet duct, directing the air partially to the region of the water inlet header. By controlling the gas inflow, it was possible to significantly enhance the heat exchanger performance. The results of the multivariate numerical analyses conducted for the adopted parameters of the mediums (air and water volumetric flow rates and water temperature) show that the heat exchanger performance can be improved by up to almost 5% compared to a variant with a natural non-uniform air inflow taking place in the exchanger under consideration.
Highlights
Heat exchangers functioning as devices transferring heat between two or more fluids are the main elements of very many industrial systems
The mass, size and cost limitations do not allow the use of a big-sized heat exchanger to achieve a better heat exchange. This is the reason for which several heat transfer enhancement methods are considered to improve the heat transfer efficiency without increasing the heat transfer area
It should be noted that the application of any passive method improving the heat exchange efficiency increases the pressure drop on the device
Summary
Heat exchangers functioning as devices transferring heat between two or more fluids are the main elements of very many industrial systems. The mass, size and cost limitations do not allow the use of a big-sized heat exchanger to achieve a better heat exchange. This is the reason for which several heat transfer enhancement methods are considered to improve the heat transfer efficiency without increasing the heat transfer area. Passive methods are of big interest as they do not require any external energy supply Such methods are based on geometry modifications or turbulating inserts (turbulators) to enhance the heat exchanger performance. It should be noted that the application of any passive method improving the heat exchange efficiency increases the pressure drop on the device. Many researchers point to another problem affecting the heat exchanger operation – the non-uniform flow of mediums through the device [4,5,6]
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