Changes in the intensity of heat transfer following a flow turn in ducts

It is shown experimentally that heat transfer in an elbow can be approximately calculated by using empirical relationships for coil pipes with similar geometrical flow characteristics. The presence of a turn at the inlet of a heat transfer pipe significantly intensifies heat transfer in the straight section following the turn, which has to be taken into account in heat transfer calculations. An expression is presented for calculating the intensification of heat transfer in a straight section following an elbow for relative lengths (l/d) of the straight section up to 35.