Evaporation heat transfer and pressure drop of refrigerant R-134a in a plate heat exchanger

Journal Article · Mon Feb 01 04:00:00 EST 1999 · Journal of Heat Transfer

DOI:https://doi.org/10.1115/1.2825924· OSTI ID:343651

Yan, Y Y; Lin, T F ^[1]

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1. National Chiao Tung Univ., Hsinchu (Taiwan, Province of China). Dept. of Mechanical Engineering

Plate heat exchangers (PHE) have been widely used in food processing, chemical reaction processes, and other industrial applications for many years. Particularly, in the last 20 years plate heat exchangers have been introduced to the refrigeration and air conditioning systems as evaporators or condensers for their high efficiency and compactness. Here, the evaporation heat transfer coefficient and pressure drop for refrigerant R-134a flowing in a plate heat exchanger were investigated experimentally in this study. Two vertical counterflow channels were formed in the exchanger by three plates of commercial geometry with a corrugated sine shape of a chevron angle of 60 deg. Upflow boiling of refrigerant R-134a in one channel receives heat from the hot downflow of water in the other channel. The effects of the mean vapor quality, mass flux, heat flux, and pressure of R-134a on the evaporation heat transfer and pressure drop were explored. The quality change of R-134a between the inlet and outlet of the refrigerant channel ranges from 0.09 to 0.18. Even at a very low Reynolds number, the present flow visualization of evaporation in a plate heat exchanger remains turbulent. It is found that the evaporation heat transfer coefficient of R-134a in the plates is much higher than that in circular pipes and shows a very different variation with the vapor quality from that in circular pipes, particularly in the convective evaporation dominated regime at high vapor quality. Relatively intense evaporation on the corrugated surface was seen from the flow visualization. Moreover, the present data showed that both the evaporation heat transfer coefficient and pressure drop increase with the vapor quality. At a higher mass flux the pressure drop is higher for the entire range of the vapor quality but the evaporation heat transfer is clearly better only at the high quality. Raising the imposed wall heat flux was found to slightly improve the heat transfer, while at a higher refrigerant pressure, both the heat transfer and pressure drop are slightly lower. Based on the present data, empirical correlations for the evaporation heat transfer coefficient and friction factor were proposed.

• Sponsoring Organization: USDOE
• OSTI ID: 343651
• Journal Information: Journal of Heat Transfer, Journal Name: Journal of Heat Transfer Journal Issue: 1 Vol. 121; ISSN 0022-1481; ISSN JHTRAO
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
AIR CONDITIONERS
EVAPORATION
FRICTION FACTOR
GEOMETRY
HEAT EXCHANGERS
HEAT TRANSFER
PRESSURE DROP
REFRIGERANTS
REFRIGERATING MACHINERY
TWO-PHASE FLOW