The Use of the Axial Heat Conduction of the Wall for Increasing the Effectiveness of Heat Exchangers

IF 1.1 4区 物理与天体物理 Q4 PHYSICS, APPLIED
E. P. Valueva, Yu. V. Sabirov
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Abstract

The effect of heat transfer in the wall in the direction of the flow of heat carriers on the effectiveness of heat exchangers is considered for the cases when the wall ends are not thermally insulated from the environment. Use is made of the analytic solution to the problem of parallel-plane flow of heat carriers, which has been considered earlier. The solution depends on the following parameters: ratio of coefficients α of heat transfer from heat carriers; ratio of thermal equivalents β of heat carriers (it is assumed that α = β = 1); number Ntu of heat-transfer units; parameter CA characterizing the axial heat conduction of the wall; the Biot number determining the relative heat transfer from the wall ends to the environment, and the temperatures of the media contacting the wall ends. The effect of the heat conduction the wall increases with decreasing CA. The following two cases are considered: (case I) the temperatures of the environment are assumed to be equal to the inlet and outlet temperatures of the hot heat carrier; (case II) these temperatures are equal to the inlet and outlet temperatures of the cold heat carrier. It is shown that for large Biot numbers (Bi > 1), the effectiveness of using of one of heat carriers can be elevated due to the effect of the axial heat conduction of the wall; in this case, the temperature of the other heat carrier during its flow in the heat exchanger varies insignificantly. The boundaries of the beginning of the effect of the axial heat conduction of the wall on the effectiveness of the heat exchanger are determined.

Abstract Image

利用壁面轴向导热来提高换热器的效率
考虑了壁面端部与环境不隔热的情况下,壁面沿热载体流动方向的换热对换热器效率的影响。利用了先前考虑过的热载体平行平面流动问题的解析解。求解取决于以下参数:热载体传热系数α的比值;热载体的热当量比β(假设α = β = 1);传热单位数Ntu;表征壁面轴向热传导的参数CA;确定从壁端到环境的相对传热的Biot号,以及与壁端接触的介质的温度。壁面热传导的影响随着CA的减小而增大。考虑以下两种情况:(情形1)假定环境温度等于热载体的进出口温度;(情形二)这些温度等于冷热载体的入口和出口温度。结果表明,对于较大的Biot数(Bi >;1)由于壁面轴向导热的影响,可以提高其中一种热载体的使用效率;在这种情况下,其他热载体在热交换器中流动时的温度变化不大。确定了壁面轴向导热对换热器效能影响的起始边界。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Technical Physics
Technical Physics 物理-物理:应用
CiteScore
1.30
自引率
14.30%
发文量
139
审稿时长
3-6 weeks
期刊介绍: Technical Physics is a journal that contains practical information on all aspects of applied physics, especially instrumentation and measurement techniques. Particular emphasis is put on plasma physics and related fields such as studies of charged particles in electromagnetic fields, synchrotron radiation, electron and ion beams, gas lasers and discharges. Other journal topics are the properties of condensed matter, including semiconductors, superconductors, gases, liquids, and different materials.
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