숙명여자대학교 비교과통합관리시스템

Invited Seminar

Department of Mechanical Systems Engineering

Convective boiling of refrigerants near the micro-

macroscale transition inside plate heat exchangers

날짜    2019년 10월 24일 목요일

시각   12시 – 13시

장소   르네상스 406호

신청   SNOWAY 비교과프로그램(마일리지 2000점 부여)

대상    공개강의 (타과생 환영합니다^^)

연사    김현진 박사

약력  Present Postdoctoral Scholar in Mechanical Engineering, Stanford University

2019 PhD in Mechanical Engineering, University of Illinois at Urbana-Champaign

2014 MS in Mechanical Engineering, University of Illinois at Urbana-Champaign

2011 BA in Visual Arts, Rice University

This work focuses on the refrigerant flow morphology and its impact on evaporative heat transfer and pressure drop during plate heat exchanger (PHE) operation at low mass flux conditions. Some industrial practitioners and academic researchers suggest PHE channel designs are intended to induce turbulence for mixing and enhanced convection; previous PHE thermal performance correlations have typically been based on semi-empirical approaches assuming turbulent flows in conventional macroscale passages. However, the prevailing two-phase flow regimes at low-mass-flux operation, with bubble confinement effects which are usually found in microscale channels, are at low Reynolds numbers and might not be turbulent. Through flow visualization and thermal-hydraulic analyses, results from this research support the existence of microscale flow regimes in PHE flows. Refrigerant bubbles can grow large without breaking up, and they can be fully confined in the PHE channel to be deformed or elongated as shown in Error! Reference source not found.. These large non-spherical bubbles with surrounding thin liquid films characterize the two-phase flow morphology in microchannels. In this flow regime, effective heat transfer can be achieved by evaporating the thin liquid film surrounding the bubbles, rather than fully relying on mixing and convection; instead of being solely in one regime or the other, microscale and macroscale flows can coexist in PHEs, due to the non-uniform, complex flows in the heat exchangers.

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