Plate Heat Exchanger with Diffuser Channels
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AND MASS TRANSFER AND PHYSICAL GASDYNAMICS
Plate Heat Exchanger with Diffuser Channels V. G. Lushchika, *, M. S. Makarovaa, **, and A. I. Reshmina, *** a
Institute of Mechanics, Moscow State University, Moscow, Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected]
Received November 23, 2019; revised December 31, 2019; accepted March 10, 2020
Abstract—A numerical simulation of the heat transfer in plate heat exchangers with diffuser channels with small opening angles was performed with a three-parameter differential turbulence model supplemented by the transport equation for a turbulent heat flux. It is shown that the amount of heat transferred from the “hot” coolant to the “cold” increases as compared that in heat exchangers with channels with a constant cross section due to the heat-transfer enhancement in heat exchangers with diffuser channels. DOI: 10.1134/S0018151X2003013X
INTRODUCTION Improvements in the efficiency of heat exchangers due to the intensification of heat-transfer processes is an urgent problem of energy conservation. To date, a large number of various methods of heat-transfer enhancement have been proposed. Their review and analysis has been the subject of extensive literature (e.g., monographs [1–3] and reviews [4, 5]). The most common method of heat transfer enhancement in channels with a single-phase coolant is artificial flow turbulization, which is carried out with corrugated surfaces, annular or spiral grooves, surface finning, spiral or twisted pipes, screws, twisted tapes, holes, etc. [2]. As noted in [2], the creation of separation zones or other organized vortex structures in it is considered to be the most accessible and effective method of controlled action on the structure of turbulent flow. Moreover, almost all known methods of heat-transfer enhancement are associated with an increase in the power required for coolant pumping, which is a drawback of these methods. We should note the method proposed by A.A. Gukhman and V.K. Migai (see [1]) for heat-transfer enhancement with surfaces that form a diffuser–confuser system and create pressure inhomogeneities in the flow. In this case, the expansion angles of the diffusers are selected from the conditions to obtain a flow with unsteady separated vortex zones, which enhance heat transfer. Plates with various types of corrugated surfaces are used in plate heat exchangers; they increase the heatexchange surface by 15–25% [6]. Moreover, the friction coefficients in plate heat exchangers with corrugated plates are much higher than in smooth channels with the same Reynolds numbers.
It was shown [7–9] that heat-transfer enhancement can be realized in a diffuser with virtually no increase in the friction coefficient. The strong influence of expansion in a continuous diffuser with a small opening angle on the flow regime was experimentally confirmed in [10], and the measured velocity and Reynolds stress profiles are in good agreement with calculations performed with the three-parameter differential turb
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