Experimental investigation on heat transfer in laminar, transitional and turbulent circular pipe flow

• Heat transfer in circular pipe flow with dh/l = 0.0118.
• Prandtl and Reynolds numbers in the range of 7 < Pr < 41 and 500 < Re < 23000.
• Transitional flow regime is determined to occur between 2300 < Re < 4000.
• Fully turbulent flow is determined to occur for Re > 4000.
• Gnielinski’s calculation method is checked especially for 1000 < Re < 4000.

Experimental investigations on heat transfer in a circular pipe for laminar, transitional and turbulent flow are presented. Reliable prediction of heat transfer coefficients for transitional flows is still a challenging task. While methods for predicting laminar and turbulent heat transfer coefficients are widely established in literature, the proposed methods and the validity for calculating according values for the transition region and even the definition of this region itself remains a field of ongoing development. One aspect in this picture is the scarce availability of experimental data on heat transfer coefficients in circular pipe flow for Reynolds numbers in the range of 1000