Parametric study and improvement of phase separation in intermediate headers of microchannel condensers

Jun Li, Pega Hrnjak

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Phase separation has been proven to be beneficial to aircooled parallel flow microchannel condensers for air conditioning systems. The inlet to the condenser with phase separation is located at the middle of the condenser height. After the first pass, in the vertical second header of the condenser, vapor phase separates from liquid phase mainly due to gravitational effects. In ideal case vapor should go to the top exit and liquid to the bottom exit, resulting in increased heat transfer. Due to interaction between vapor and liquid, separation is not perfect, expressed through the separation efficiency. This paper presents a parametric study of phase separation efficiency in the intermediate headers, with the target to improve separation efficiency. Header prototypes which have two exits are made with transparent PVC to simulate the real header and provide visual access. Using R-134a as a baseline, the measurement of separation efficiency and its general trend will be shown first. The results are compared to those of a mechanistic model based on flow regime and force balance analysis. Inlet mass flux in simulation is controlled at 87 kg·m -2 ·s -1 - 311 kg·m -2 ·s -1 and inlet quality at 0.05 - 0.25. The observed flow patterns in header are compared with the modeling results as well. Then, the header diameter is increased, which effectively improves the separation efficiency due to reduction of vapor velocity in header. Finally, R245fa and R32 are modeled in comparison with R-134a to discuss the effect of fluid properties on separation efficiency.

Original languageEnglish (US)
Title of host publicationFluids Engineering
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791852101
DOIs
StatePublished - 2018
EventASME 2018 International Mechanical Engineering Congress and Exposition, IMECE 2018 - Pittsburgh, United States
Duration: Nov 9 2018Nov 15 2018

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Volume7

Conference

ConferenceASME 2018 International Mechanical Engineering Congress and Exposition, IMECE 2018
CountryUnited States
CityPittsburgh
Period11/9/1811/15/18

ASJC Scopus subject areas

  • Mechanical Engineering

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