ISSN Online: 2377-424X
ISBN Print: 0-89116-299-2
International Heat Transfer Conference 7
TURBULENT BOUNDARY LAYER HEAT TRANSFER IN THE ENTRANCE REGION OF A PIPE
Abstrakt
In the technical applications treating the intensive cooling, the short channnels with small values of l/d very often appear. In this contribution we solve the
heat transfer in the very short entrance region by l/d = 4 in the circular tube of the inner diameter d = 50 mm in which the air is flowing with Reynolds numbers from 104 to 105. We suggest a simple mathematical model to calculate the temperature T+ and the heat transfer coefficient in the developing thermal turbulent boundary layer. The problem is formulated mathematically
by means of the time-averaged partial differential energy equation for turbulent boundary layer. The fully developed velocity profile is described by the 3-layer
scheme, the turbulent thermal diffusivity by two models. The results are presented in the form of T+ = f(y+) and that of Nu = f (Re) for various lenghts l/d.