Heat Transfer in Pipe Flow at High Speeds

Abstract

Measurements have been made of adiabatic friction and of heat transfer for air flowing in pipes at speeds up to 1·6 times that of sound for conditions closely approaching established pipe flow in the range of Reynolds numbers Re = 1·24 to 4·35 × 105, free stream air temperatures Tb = 190 to 286 deg. K., and wall to free stream temperature ratios Tw/Tb = 1·08 to 1·73. The heat transfer results agreed within ±5 per cent with the formula and frictional data were some 4 per cent above The above formulae were obtained by a method, first suggested by von Kármán (1935), of allowing for compressibility effects by replacing, in formulae for incompressible fluids, the fluid properties computed at bulk temperature by those at wall temperature, and then transforming to terms of these properties at bulk temperature, using the laws of variation of physical properties with temperature as obtained from N.B.S.-N.A.C.A. Tables (1949-50). Separate tests were made of the heat transfer in the presence of a plane shock-wave in the heated length of the test pipe, and the values of Stanton number were found to be up to 30 per cent higher than for shockless flow. A subsonic test with a similar adverse pressure gradient over the heated length also showed considerably increased heat transfer. The recovery factors calculated from the adiabatic runs were close to √ Pr, that is, 0·84.