الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Two-phase flow is incorporated in all thermal equipments which involve flow boiling. The aim of this investigation is to throw some additional lights on the question of the effect of varying different parameters as : inlet sub cooling, inlet pressure, flow rate and heat flux on heat transfer coefficient and pressure DROP in two-phase flow in the region of nucleate bolling. To carry out the experimental study in this work a test rig has been constructed to investigate the effect of the different mentioned parameters. The test section is a vertical 3 tube-bundle connected electrically in parallel. They are arranged in triangular shape. Each tube is 10/12 mm diameters, and 200 cm in length. The bundle is fixed inside a stainless steel tube having 63.5/69.5 mm diameters, and 220 cm in length.
In this work a computer program is also proposed for determination of pressure DROP and heat transfer coefficient according to the data obtained experimentally.
from the evaluation of the obtained experimental results, it is concluded that the two-phase heat transfer rate can be improved by raising the operating heat flux ( in the region of subcooeld and low quality nucleate boiling). In addition boiling heat transfer rate increase by decreasing both inlet subcooling and mass flow rate.
For all performed experiments the average nucleate boiling heat transfer coefficient is found to be 2.5 * 10 3 W/m2.c.
The total pressure DROP in the two-phase flow is found to increase with increasing void fraction (quality). The frictional term in the two-phase flow region is found to be higher than the corresponding term in the single-phase flow region. In addition, it was found that the deviation between both experimental and theoretical pressure DROP lies in the range from -2 to + 20%. In comparison with other previous results, a well agreement is found.