Abstract
In this study, computational fluid dynamics (CFD) analysis was performed to investigate the cause of the thermal stratification in the channel and the temperature non-uniformity of the plate heat exchanger. The flow velocity maldistribution of the channel and the merging parts caused temperature non-uniformity in the channel width direction. The non-uniformity of flow velocity and temperature in the channel is shown in Section 1 > Section 3 > Section 2 from the heat exchanger. The non-uniform temperature distribution in the channel caused channel stratification and non-uniform outlet temperature. Stratification occurred at the channel near the merging due to the flow rate non-uniformity in the channel. In particular, as the mass flow rate increased from 0.03 to 0.12 kg/s and the effectiveness increased from 0.436 to 0.615, the cold-side stratified volume decreased from 4.06 to 3.7 cm3, and the temperature difference between the stratified area and the outlet decreased from 1.21 K to 0.61 K. The increase in mass flow and the decrease in temperature difference between the cold and hot sides alleviated the non-uniformity of the outlet temperature due to the increase in effectiveness. Besides, as the inlet temperature difference between the cold and the hot side increases, the temperature non-uniformity at the outlet port is poor due to the increase in the stratified region at the channel, and the distance to obtain a uniform temperature in the outlet pipe increases as the temperature at the hot side increases.
Highlights
The amount of heat transfer increases from 1081 W to 1528 W in plate heat exchangers when the inlet temperatures of the hot and cold sides are constant at 283.15 K and 313.15 K, and the mass flow rate on the cold side increases from 0.03 kg/s to 0.12 kg/s
The temperature non-uniformity in Sections 1 and 2 of the channels of the cold side decreased to 0.0061–0.0028 and 0.0041–0.0034 as the mass flow rate of the cold side increased from 0.03 kg/s to 0.12 kg/s, whereas the temperature non-uniformity in Section 3 was instead increased to 0.0054–0.0064
As a result of the analysis, it was confirmed that the fluid temperature in the distribution and merging parts of the channel had non-uniformity in the width direction of the plate heat exchanger
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The decrease in heat transfer performance due to non-uniformity of flow distribution for each channel or location is due to inlet velocity distribution, flow configurations such as U-type (parallel flow) and Z-type (reverse flow), flow resistance, and header shape. About this problem, parallel flow heat exchangers studied the flow distribution of single-phase flow through experiments and analysis. This study makes it possible to reduce errors in performance prediction due to the maldistribution of the flow rate in a large plate heat exchanger and contribute to accurate performance evaluation through proper temperature measurement at the outlet of the heat exchanger
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