Effect of cooling on pressure losses in U-type wavy pipe flow

Results of pressure drop measurements under adiabatic and nonadiabatic (at T-w const.) flow conditions in U-type wavy pipes having fixed dimensionless radius of centerline curvature 2R/d=6.62 and two dimensionless spacer leng ths l/d=0 and l/d=39.7 are presented. The working fluid was water. The effe cts of cooling and spacer length were investigated. It is shown that coolin g of water increases the friction factor. This increase is plausible attrib uted to the deformation of the velocity distribution resulting from the tem perature dependence of the viscosity and density of water. The experimental data were correlated with the simply equation f = (a + b/ln(Re) + c/Re)*(mu/mu(w))(m) where: a=0.121433-0.00182313*l/d, b =-0.010311+0.00019359*l/d, c=16.68855-0.16757*l/d, m=(-0.62+0.013 Pr(0.84)G r(0.17))*(380/De(n))(0.33). The above equation is applicable in the range of 18<De(n)<3800, 8000<Gr<230 00, 2.95<Pr<4, 0.46<mu/mu(w)<0.72, 0<l/d<40 and for 2R/d=6.62. (C) 2000 Els evier Science Ltd.