Tubeside evaporation of nonazeotropic refrigerant mixtures from two enhanced surfaces

Conference · Mon Jan 01 04:00:00 EST 1990

OSTI ID:6617608

Conklin, J C; Vineyard, E A

As part of the Building Equipment Research program at Oak Ridge National Laboratory, nonazeotropic refrigerant mixtures (NARMs) are being investigated to replace chlorofluorocarbon compounds. The evaporation of NARMs is not isothermal, and this can improve the heat exchanger effectiveness of an evaporator as well as improve thermodynamic cycle efficiencies. The evaporating heat transfer coefficient for four nonazeotropic mixtures of refrigerants R143a and R124 was investigated for two inside tube surfaces, one having spiral ridged fins and the other a corrugated or fluted surface. Refrigerant R22 was also evaporated for comparison of the finned and fluted enhanced surface performances. The measured pressure drop and the heat transfer coefficient for the complete evaporation from 25% quality to a slight amount of superheat of the NARMs and R22 are presented as a function of mass flux for both enhanced surfaces. Both the heat transfer coefficient and the pressure drop of the fluted tube are higher than those of the finned tube at both a given refrigerant mass flux and a given heat exchanger load for all the refrigerant mixtures. When plotted as a function of the mass fraction of R143a, the heat transfer coefficient for the fluted tube is minimal at approximately 40% (51% by mole) by mass of R143a. However, the heat transfer coefficient for the finned tube did not show a degradation as a function of R143a mass fraction, and it appears to be a linear function of the mass fraction of R143a for a given mass flux. 10 refs., 9 figs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• Sponsoring Organization: DOE/CE
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6617608
• Report Number(s): CONF-901194-2; ON: DE90016037
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320106* -- Energy Conservation
Consumption
& Utilization-- Building Equipment-- (1987-)
42 ENGINEERING
420400 -- Engineering-- Heat Transfer & Fluid Flow
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
DISPERSIONS
ENERGY TRANSFER
FLUIDS
GEOMETRY
HEAT EXCHANGERS
HEAT TRANSFER
MATHEMATICAL MODELS
MATHEMATICS
MIXTURES
PRESSURE DROP
REFRIGERANTS
SURFACE PROPERTIES
SURFACES
THERMAL ANALYSIS
WORKING FLUIDS