Kn. Agrawal et al., HEAT-TRANSFER AUGMENTATION BY COILED WIRE INSERTS DURING FORCED-CONVECTION CONDENSATION OF R-22 INSIDE HORIZONTAL TUBES, International journal of multiphase flow, 24(4), 1998, pp. 635-650
In the present work, heat transfer augmentation by coiled wire inserts
during forced convection condensation of R-22 inside horizontal tubes
has been studied. The test-condenser consisted of four separate coaxi
al double pipe test sections assembled in series. It was a counterflow
heat exchanger where R-22 condensed inside the inner tube by rejectin
g heat to the coolant water flowing in the annulus. Coiled wires with
three different wire diameters of 0.65, 1.0 and 1.5 mm and three diffe
rent coil pitches of 6.5, 10.0 and 13 mm were made and used in full le
ngth of test-condenser. The use of helically coiled wires were found t
o increase the condensing heat transfer coefficients by as much as 100
% above the plain tube values on a nominal area basis. (C) 1998 Elsevi
er Science Ltd. All rights reserved.