Abstract
An experimental investigation of refrigerant R-134a two-phase flow condensation heat transfer coefficient and pressure drop in condenser tube section of refrigeration system under different operating conditions is presented. The experimental and theoretical investigations are based on test conditions in range of 10 -17 kW/m2 for heat flux, 42-63 kg/m2s for mass flux, vapor quality 1-0.03 and saturation temperature 44 to 49˚C. The experimental tests are conducted on test rig supplied with a test section to simulate the water cooled double pipe heat exchanger, which is designed and constructed in the present work. “The experimental results have revealed that, the heat flux and mass flux have significant impacts on the heat transfer coefficient. “The heat transfer coefficient was increased with increase in heat flux and mass flux at prescribed test conditions, where the enhancement in heat transfer coefficient was about 47% and 14% for relatively higher heat flux and mass flux, respectively. “The enhancement in the heat transfer coefficient was about 51% for relatively lower saturation temperature 45.97˚C and 43% for higher vapor quality 0.88 compared to other values at constant test conditions. “The pressure drop was higher in the range of 12% and 49% for relatively higher mass flux and heat flux respectively. “The present work results have validated by comparison with predictive models and with similar research work results and the comparison has revealed an acceptable agreement.
Highlights
Condensation is a phase change process from vapor to liquid which represents an efficient way of heat removal as the latent heat of condensation provides a high heat transfer coefficient
Condensation of refrigerants inside heat exchanger channels was investigated by many researchers. [1] “investigated experimentally the two-phase heat transfer coefficient of pure R134a condensing inside a smooth tube with inner diameter 8.1 mm and 500 mm length in tube heat exchanger vertical downward flow at high mass flux”
“The results showed that the average heat transfer coefficient increased with the increase of vapor quality, mass flux, and heat flux, but decreased with an inner diameter. [8] studied the condensing flow heat transfer coefficient and pressure drop of a multiport mini-channel aluminium tube with a natural hydrocarbon, propane R290 as working fluid flowing through a square section horizontal tube having an internal diameter of 1.16 mm and a condensing length of 259 mm
Summary
Condensation is a phase change process from vapor to liquid which represents an efficient way of heat removal as the latent heat of condensation provides a high heat transfer coefficient. The results showed that, the experimental heat transfer coefficient increases with the average vapor quality and refrigerant mass flux and decreases with increases of condensation and tube wall temperature difference. [4] developed models to study the pressure drop and heat transfer coefficients for condensation of hydrocarbons in smooth horizontal tubes over a wide range of conditions for pure natural fluids, propane and pentane”. [8] studied the condensing flow heat transfer coefficient and pressure drop of a multiport mini-channel aluminium tube with a natural hydrocarbon, propane R290 as working fluid flowing through a square section horizontal tube having an internal diameter of 1.16 mm and a condensing length of 259 mm. “The tests were conducted at saturation pressure of 2 - 3.5 Mpa with the mass flux of 99 255kg/m2.s and fluid to wall temperature difference of 4.8-20.2 K throughout the vapor quality range. The experimental data were compared with many well-known correlations of condensation heat transfer coefficient and pressure drop”
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