ISSN Online: 2377-424X
ISBN Print: 1-56032-797-9
International Heat Transfer Conference 11
CONVECTIVE HEAT TRANSFER IN A WAVY PIPE FLOW
Resumo
This communication presents results of measurements of the average convective heat transfer for the wavy and straight pipe flows. Experiments were performed with the "pipe in pipe" water heat exchangers and the heat energy balance technique. The two test copper pipes (straight and wavy) of d=3.91 mm in diameter and 333.9 diameters in length were used. The straight pipe was used as a reference pipe. The wavy pipe had 33 bends (18°) and the dimensionless bend curvature radius was 2R/d = 6.62. The heat transfer and pressure drop in a wavy pipe flow show smooth transition from laminar to turbulent region. The Nusselt number in the Dean number range from 50 to 4000 can be described with the equation.
Nuw=(0.032De0.88- 0.30) Pr0.4 (Pr/Prw)0.11.
In turbulent region the heat transfer for the wavy pipe compare with the straight one is about 24% higher. For the Reynolds numbers Re < 500 we did not observe any significant increase of the average heat transfer for the wavy pipe. Presumably, at low Reynolds numbers in a straight pipe flow we had strong disturbance effects produced by the entrance and the buoyancy forces.
Nuw=(0.032De0.88- 0.30) Pr0.4 (Pr/Prw)0.11.
In turbulent region the heat transfer for the wavy pipe compare with the straight one is about 24% higher. For the Reynolds numbers Re < 500 we did not observe any significant increase of the average heat transfer for the wavy pipe. Presumably, at low Reynolds numbers in a straight pipe flow we had strong disturbance effects produced by the entrance and the buoyancy forces.