Enhancement of heat transfer rates by coiled wires during forced convective condensation of R-22 inside horizontal tubes

In this work, heat transfer augmentation by coiled wire inserts during forc ed convection condensation of R-22 inside horizontal tubes has been studied . The test-condenser consisted of four separate coaxial double pipe test se ctions assembled in series. It was a counter flow heat exchanger where R-22 condensed inside the inner tube by rejecting heat to the coolant flowing i n the annulus. Coiled wires with different wire diameters and coil pitches were made and used in full length of test-condenser. The use of helically c oiled wire was found to increase the condensing heal transfer coefficients by as much as 100 percent above the plain tube values on a nominal area bas is. An empirical correlation to predict the enhanced heat transfer coeffici ents of this investigation was developed and presented.