Estimation of the Thermohydraulic Efficiency of Heat Exchanging Apparatuses with Twisted Tubes

Abstract

The paper presents generalizing relations to calculate heat transfer and hydraulic resistance in longitudinal flow of heat-transfer agents in the cavities of a heat exchanger with twisted tubes and the results of comparison of the thermohydraulic efficiency of the heat-transfer surfaces of the twisted tubes with the surfaces of smooth tubes and tubes having other heat-transfer intensifiers. It has been found that in the flow transition region Reynolds-related regimes with an advanced increase in the heat-transfer coefficient in comparison with the increase in the coefficient of hydraulic resistance is implemented. In a longitudinal flow past twisted tubes, a 1.5−3.5-fold increase in the heat-transfer coefficient is ensured, as compared to flow in smooth straight tubes. The estimation of the thermohydraulic efficiency of heat exchangers made by the method of effective parameters and the analysis of the efficiency of various heat-transfer surfaces made it possible to find the flow regions where the heat-exchange apparatuses with flow swirling by twisted tubes are advantageous over heat exchangers involving other methods of heat-transfer enhancement.