Session: 11-01: Micro/Miniature Two-Phase Devices/ Systems

Paper Number: 132015

132015 - Experimental Investigation of Two-Phase Flows in Printed Circuit Heat Exchangers 

Abstract: 

Printed Circuit Heat Exchangers (PCHE) as a type of efficient and compact heat exchanger have been successfully applied in various industrial fields such as electric power, petrochemical engineering, aviation and aerospace, with broad development potential. At present, there is more research on single-phase flow in PCHEs, but the study of two-phase flow is still in the initial stages. The microchannel heat dissipation of the PCHE stands out in dealing with small-sized devices and high heat flux density compared to conventional-sized channels, especially when two-phase flow occurs within the channels, improving thermo-hydraulic performance. This paper establishes a visual experimental platform for single-layer PCHE microchannel heat exchangers with channel structures of rectangular, semi-circular, honeycomb, parallel fins, and staggered fins. It employs high-speed cameras to observe two-phase flow patterns, interfaces, and bubble behaviors inside the single-layer PCHE microchannels. Combined with MATLAB image processing technology, the study analyzes the evolution of gas-liquid flow patterns within the channels, bubble shapes, and the distribution characteristics of void fraction, examining the effects of different PCHE channel structures and experimental operational parameters on the two-phase flow patterns and the pressure drop in PCHE microchannels. Experimental results indicate that bubble flow with smaller diameters occurs in the inlet header, and in semi-circular and rectangular straight channels, the flow patterns are primarily bubble flow and slug flow of varying lengths. In the middle channels of parallel and staggered fin channels, annular flow is dominant, whereas slug flow occurs in the side channels. In biomimetic honeycomb channels, bubble flow predominates, due to long bubbles at the entrance continuously breaking into smaller slugs along the flow direction. The distribution of void fraction in straight channels is typically higher in the middle and lower on the sides. With an increase in air velocity, the distribution of void fraction becomes more apparent, with a greater number of channels exhibiting peak void fraction values and more pronounced differentiation between them. For parallel and staggered fin channels, the distribution of void fraction shows significant variation, with the middle channels having noticeably higher void fraction than the side channels. However, in biomimetic honeycomb channels, the distribution of void fraction is much more uniform, with larger differences at the inlet decreasing along the flow direction among the channels. Under the same inlet conditions, the order of pressure drop from highest to lowest is as follows: honeycomb, rectangular, semi-circular, parallel fin, and staggered fin channels. As the inlet velocity of both gas and liquid phases increases, the pressure drop in each structured channel also increases.

Presenting Author: Jingzhi Zhang Shandong University

Presenting Author Biography: Zhang Jingzhi, male, born in August 1989, doctor, associate professor.From September 2006 to March 2017, he received his bachelor's, master's and doctor's degrees from Shandong University and Zhejiang University respectively.From April 2017 to September 2020, he worked as an assistant researcher in the School of Energy and Power Engineering of Shandong University, and from September 2020 to now, he has worked as an associate professor.From September 2019 to September 2020, he went to Lund University in Sweden as a visiting scholar to conduct research on microchannel multiphase flow in the Department of Energy Sciences.He has published more than 70 SCI/EI papers, which have been cited more than 700 times, with an H-factor of 16.
The research focuses on the problems of flow heat transfer in the fields of energy, chemical industry and microelectronics, mainly using numerical simulation and experimental methods to study the coupling mechanism of single-phase/multiphase flow and heat transfer in conventional and micro-channels, as well as flow pattern regulation and heat transfer enhancement technology, including:
1) Multiphase flow heat transfer mechanism and strengthening technology in new industrial heat exchangers;
2) Phase-change heat transfer mechanism and flow pattern control in multi-scale coupled heat exchange element;
3) Development of high-efficiency chemical and pharmaceutical microreactors and microfluidic technology;
4) High heat flux/high power device thermal management technology.

Authors:

Liangliang Zhang Shandong University
Jingzhi Zhang Shandong University
Li Lei Shandong University
Wei Li Zhejiang University