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In the present paper, augmentation of hear transfer during condensation of R¬22 inside horizontal tubes with helically coiled inserts has been investigated
experimentally. For the sake of
comparison, the data for plain tube were also collected. The experimental set-up which was used in this investigation was basically a well instrumented vapor compression systems. The test condenser consisted of four separate coaxial double pipe condensers assembled in series and called as "test sections". It was a counter¬flow heat exchanger where R-22 would condense inside the inner tube by rejecting heat to the coolant water flowing in the annulus. Experimental data for tubes with coiled wire inserts were obtained for three different wire diameters of 0.65, 1.0 and 1.5 mm with a coil pitch of 10 mm and three different coil pitches of 6.5, 10 and 13 mm for the wire of 1 mm diameter. The results show that, in general, the insertion of a helically coiled wire inside the condenser tube increases the heat transfer coefficient, significantly. The gain in heat transfer coefficient is not very consistent for a particular coiled wire and it is a
complex function of vapor Reynolds number and coiled wire geometry. The best performing roughed tube in the high vapor quality region, increased the sectional heat transfer coefficient by as much as 100% above the plain tube values on a nominal area basis. No correlation exists for prediction of heat transfer coefficient during condensation of vapors inside a tube with coiled wire inserts. A generalized correlation was developed on the basis of the experimental data of this investigation.