Evaporative Heat Transfer and Pressure Drop Characteristics of Refrigerant-Oil Mixtures

Shimon, R.L.

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https://hdl.handle.net/2142/11111 Copy

Description

Title

Evaporative Heat Transfer and Pressure Drop Characteristics of Refrigerant-Oil Mixtures

Author(s)

Shimon, R.L.

Contributor(s)

• Chato, J.C.
• Villaneuva, T.C.
• DeGuzman, N.M.
• Ponchner, M.
• Sweeney, K.A.
• Rhines, N.L.
• Allen, D.G.
• Hershberger, T.T.

Issue Date

1995-08

Keyword(s)

• geometric variables
• R-22 alternatives
• refrigerant-side evaporation condensation studies

Abstract

This study investigates flow boiling heat transfer and pressure drop characteristics of mixtures of R-134a and an ester based lubricant. Nominal oil concentrations of 1 %, 3%, and 5% are tested. Experimental heat transfer coefficients and pressure drops are collected over a wide range of flow conditions. The two-phase flow regime is observed visually. The oil has a significant impact on both heat transfer and pressure drop. Small concentrations of oil enhance the heat transfer coefficient. The enhancement is observed for all oil concentrations tested; however, the enhancement is decreasing at an oil concentration of 5%. The enhancement is attributed to several factors including the promotion of an annular-type flow pattern at low to moderate flow rates, the degradation of the nucleate boiling contribution at the same flow rates, and foaming at higher flow rates. The presence of small amounts of oil also increases the pressure drop. This increase is seen at all oil concentrations tested. The magnitude of the increase continues to rise with oil concentration. Factors influencing the pressure drop are the increase in the mixture viscosity, the promotion of an annular-type flow pattern, and foaming. Mixture properties are used in both a heat transfer correlation and a pressure drop correlation to determine the effects of the thermophysical property changes of the mixture. The results indicate that in order to accurately predict refrigerant-oil data, effects other than just property variations must be taken into account. General correlations must properly account for the flow regime effects and foaming.

Publisher

Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.

Series/Report Name or Number

Air Conditioning and Refrigeration Center TR-84

Type of Resource

text

Language

en

Permalink

http://hdl.handle.net/2142/11111

Sponsor(s)/Grant Number(s)

Air Conditioning and Refrigeration Center Project 37

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