NUCLEATE POOL BOILING FROM PLAIN AND ENHANCED SINGLE TUBE TO R12 AND R134a FOR AIR-CONDITIONING EVAPORATORS

Aziz, Mohammed A.; Sayed, Sayed A.; El Refai, A.

doi:10.21608/asat.1999.24910

NUCLEATE POOL BOILING FROM PLAIN AND ENHANCED SINGLE TUBE TO R12 AND R134a FOR AIR-CONDITIONING EVAPORATORS

Document Type : Original Article

Authors

¹ Assoc. Prof. Dpt. of Mech. Power Zagazig University, Zagazig Egypt+

² Department of Mechanical Power Engineering Faculty of Engineering, Zagazig University Zagazig, Egypt.

³ Prof. Dpt. Of Mech. Power Zagazig University, Zagazig Egypt+

⁴ Lect. Dpt. Of Mech. Power Zagazig University, Zagazig Egypt+

10.21608/asat.1999.24910

Abstract

Measurements of pool boiling heat transfer coefficients in pure R12 and R134a are reported for a plain tube (FYI) and three enhanced tubes: (Screen Matrix tube, (SM) and two integral finned tubes: Radial (RF) and longitudinal LF). The data were taken at saturation temperatures of -5, and 5 , and heat flux range from 2 x 103 to 104 W/m2. All enhanced tubes provide higher boiling coefficients than the plain tube does. The slopes of the boiling coefficient vs the heat flux curves for enhanced tubes are smaller than those for the plain tube, indicating the dominating effect of enhanced surfaces conditions. The mechanism describing the generation, growth and separation of bubbles for tested enhanced tubes was elaborated . The highest boiling coefficient was found to belong to the screen matrix tube , having the highest nucleation sites density. Additional achievement was observed when R134a was tested at the considered operating condition. Two correlations for predicting the boiling coefficients from the present considered surfaces were developed with satisfactory accuracy for the design of refrigerant flooded evaporators.

Keywords