SIMULATION OF THE EFFECTS OF OIL ON HEAT TRANSFER DURING CONDENSATION OF REFRIGERANTS R-12 AND R-134a

The evaporation heat transfer coefficients and pressure drops of R-410A and R-134a flowing through a horizontal-aluminium rectangular multiport mini-channel having a hydraulic diameter of 3.48 mm are experimentally investigated. The test runs are done at refrigerant mass fluxes ranging between 200 and 400 kg/m2s. The heat fluxes are between 5 and 14.25 kW/m2, and refrigerant saturation temperatures are between 10 and 30 °C. The effects of the refrigerant vapour quality, mass flux, saturation temperature and imposed heat flux on the measured heat transfer coefficient and pressure drop are investigated. The experimental data show that in the same conditions, the heat transfer coefficients of R-410A are about 20–50% higher than those of R-134a, whereas the pressure drops of R-410A are around 50–100% lower than those of R-134a. The new correlations for the evaporation heat transfer coefficient and pressure drop of R-410A and R-134a in a multiport mini-channel are proposed for practical applications.

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Experimental study on time periodic evaporation heat transfer of R-134a in annular ducts due to wall heat flux oscillation

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2016.10.103 ◽

2017 ◽

Vol 106 ◽

pp. 1232-1241 ◽

Cited By ~ 4

Author(s):

C.A. Chen ◽

T.F. Lin ◽

Wei-Mon Yan

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Heat Flux ◽

Wall Heat Flux ◽

Evaporation Heat ◽

Evaporation Heat Transfer ◽

R 134A ◽

Time Periodic

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Nucleate Pool Boiling Heat Transfer Coefficients of Distilled Water (H2O) and R-134a/Oil Mixtures From Rib-Roughened Surfaces

Journal of Heat Transfer ◽

10.1115/1.2824079 ◽

1997 ◽

Vol 119 (1) ◽

pp. 142-151 ◽

Cited By ~ 16

Author(s):

Shou-Shing Hsieh ◽

Chun-Jen Weng

Keyword(s):

Heat Transfer ◽

Boiling Heat Transfer ◽

Pool Boiling ◽

Distilled Water ◽

Transfer Coefficients ◽

Pool Boiling Heat Transfer ◽

Heat Transfer Coefficients ◽

Oil Mixtures ◽

R 134A ◽

Rib Roughened

Measurements of pool-boiling heat transfer coefficients in distilled water and R-134a/oil mixtures with up to 10 percent (by weight) miscible EMKARATE RL refrigeration lubricant oil are extensively studied for a smooth tube and four rib-roughened tubes (rib pitch 39.4 mm, rib height 4 mm, rib width 15 mm, number of rib element 8, rib angle 30 deg–90 deg). Boiling data of pure refrigerants and oil mixtures, as well as the influences of heat flux level on heat transfer coefficient, are presented and discussed. A correlation is developed for predicting the heat transfer coefficient for both pure refrigerants and refrigerant-oil mixtures. Moreover, boiling visualizations were made to broaden our fundamental understanding of the pool boiling heat transfer mechanism for rib roughened surfaces with pure refrigerants and refrigerant-oil mixtures.

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