Wyniki wyszukiwania - BazTech

1

Numerical study of flow maldistribution in plate heat exchangers used for evaporation process

Pluszka Paweł, Brenk Arkadiusz Patryk, Malecha Ziemowit Miłosz

Archives of Thermodynamics

|

2019

|

Vol. 40, no 3

57--82

EN

Geometry of plate heat exchangers (PHE) is characterized by a complex net of narrow channels. It enhances turbulence and results in better heat transfer performance. Theoretically, larger number of channels (plates) should proportionally increase the PHE heat power capacity. In practice a nonuniform massflow distribution in consecutive flow channels can significantly deteriorate the overall heat exchange performance. The flow maldistribution is one of the most commonly reported exploitation problems and is present in PHE with and without phase-change flows. The presented paper investigates numerically a flow pattern in PHE with evaporation of R410A refrigerant. Various sizes of PHE are considered. The paper introduces a robust methodology to transform the complicated geometry of a real 3D PHE to its 2D representation. It results in orders of magnitude faster calculations and allows for fast evaluation of different geometrical changes of PHE and their effect on flow maldistribution.

2

Pressure drop related to flow maldistribution in a model minichannel plate heat exchanger

Klugmann M., Dąbrowski P., Mikielewicz D.

Archives of Thermodynamics

|

2018

|

Vol. 39, no 2

123--146

EN

The paper describes issues related to pressure drop that accompanies the phenomenon of maldistribution of working fluid between the channels of a model minichannel plate heat exchanger. The research concerns a single exchanger’s plate containing 51 (in every geometry) parallel rectangular minichannels of hydraulic diameters 461 µm, 571 µm, 750 µm, and 823 µm. In addition, more complex geometry has been investigated, equipped with additional diagonal channels (so called extended geometry). The moment of the liquid phase transition through the heat exchanger was recorded at the flow rates ranging from 0.83 g/s to 13.33 g/s in the inlet manifold. The paper discusses the total pressure drop as a function of the flow rate and the characteristic dimension of minichannels, as well as the pressure drop as a function of the time of the fluid passage through the main part of the measuring section in which measurements were done. The resulting profiles correlate with the images of the flow distribution between channels recorded using the fast shutter speed camera, that allows to draw a further conclusions about the specifics of the maldistribution process. The impact of the total pressure drop on the actual range of optimum operating conditions of the heat exchanger was analyzed.

3

Selected studies of flow maldistribution in a minichannel plate heat exchanger

Dąbrowski P., Klugmann M., Mikielewicz D.

Archives of Thermodynamics

|

2017

|

Vol. 38, no. 3

135--148

EN

Analysis of the state of-the-art in research of minichannel heat exchangers, especially on the topic of flow maldistribution in multiple channels, has been accomplished. Studies on minichannel plate heat exchanger with 51 parallel minichannels with four hydraulic diameters, i.e., 461 μm, 574 μm, 667 μm, and 750 μm have been presented. Flow at the instance of filling the microchannel with water at low flow rates has been visualized. The pressure drop characteristics for single minichannel plate have been presented along with the channels blockage, which occurred in several cases. The impact of the mass flow rate and channels’ cross-section dimensions on the flow maldistribution were illustrated.

4

Numerical model of a cross-flow heat exchanger with non-uniform flow of media

Hanuszkiewicz-Drapala M., Bury T., Widziewicz K.

Journal of Power Technologies

|

2013

|

Vol. 93, nr 5

295--302

EN

This paper presents thermal-hydraulic analyses of finned cross flow heat exchangers working in media flow maldistribution conditions. The authors postulate a possibility of performing such analyses through the use of CFD models of recurrent segments of the heat exchangers. Media inflow to each recurrent segment may be individually defined and thus the flow maldistribution in the whole heat exchanger could be considered. The methodology of creating these models, running calculations and results of very initial experimental validation is presented in the paper.