الفهرس 
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Abstract
An experimental apparatus is designed and constructed in the present investigation to study the effect of the lubricating oil on the heat transfer coefficient during flow boiling of refrigerant R-134a.
The measurements include the effect of heat flux. Mass flux and evaporation pressure on the boiling heat transfer coefficient at different at different oil concentrations. The refrigeration cycle used in the experimental work consists of a compressor, condenser, expansion valve, and a test section that simulates the evaporator. The test section is a shell and tube heat exchanger made from copper tubes. The test section is provided with 44 thermocouples distributed along the test section to measure the outside wall temperatures of the refrigerant tube, in addition to two thermocouples used to measure the inlet and the exit temperatures of the hot water passing through the test section.
Experiments were carried out for a range of heat flux of 20 – 100kW/m2,, mass flux ranged 100mm to 200 kg/m2s, oil concentration ranged from 0.5% and foe evaporation pressure of 2.034 – 2.724 bar (29.7 – 39.7 psi). The measurements show that for the same oil concentration, mass flux, and evaporation pressure the heat transfer coefficient increases as the heat flux increases.
Also the measurements showed that the constant heat flux, mass flux, and evaporation pressure as the oil concentration increases the heat transfer coefficient decreases.
It was indicated from the measurements also, that at a certain oil concentration and for constant heat flux and evaporation pressure as the mass flux increases the heat transfer coefficient increases.
Also the measurements indicated that as the evaporation pressure decreases the heat transfer coefficient decreases, for constant heat flux, mass flux, and oil concentration. The results were compared with the available data in the recent existing literature. The present results showed a good agreement with the previous investigations.
A computer program written in VISUAL BASIC is used to compute the heat transfer coefficient at different oil concentration, evaporation pressure, heat and mass flux.
A mathematical correlation equation is deduced to relate the heat transfer coefficient with oil concentration, evaporation pressure, heat and mass fluxes, with a maximum deviation of ±10%.