Smooth-and enhanced-tube heat transfer and pressure drop : effect of Prandtl number and the role of transition to turbulence.
An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics in laminar, transitional, and turbulent flow through one smooth tube and twenty-three enhanced tubes. The working fluids for the experiments were air, water, ethylene glycol, and ethylene glycol/water mixtures; Prandtl number (Pr) ranged from 0.7 to 125.3. The smooth-tube experiments were carried out with Pr values of 0.7, 6.8, 24.8, 39.1, and 125.3; Pr values of 0.7, 6.8, and 24.8 were tested with enhanced tubes. Reynolds number (Re) range (based on the maximum internal diameter of a tube) was 200 to 55,000, depending on Prandtl number and tube geometry. The enhanced-tube friction factors are no more than 5.5 times the smooth-tube values. For some tubes, the friction factors are practically the same for 0.7 {<=} Pr {<=} 25, with moderate differences in laminar, transitional, or turbulent flow for some of the tubes. Consistent with the low-pressure-drop characteristics of these enhanced tubes, the increases in heat transfer coefficient are no more than 2.5 times the smooth-tube values for the Re and Pr ranges covered in the study. For most enhanced tubes, heat-transfer coefficients are insensitive to variations in the Prandtl number for liquids. There is a definite connection between the attainable friction or heat transfer and the transition process.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- EE
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 949498
- Report Number(s):
- ANL/ET/JA-41524
- Journal Information:
- Int. J. Heat Exchangers, Journal Name: Int. J. Heat Exchangers Journal Issue: 2 ; Dec. 2002 Vol. 3
- Country of Publication:
- United States
- Language:
- ENGLISH
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