The Effect of Surface Roughness on the Heat Exchange and Pressure-Drop Coefficients; INFLUENCE DES RUGOSITES DE PAROI SUR LES COEFFICIENTS D'ECHANGE THERMIQUE ET DE PERTE DE CHARGE
The effect of various types of roughness on the wall of an axial tube in an annular space of 15 to 25 mm cooled by an air-flow was studied in the case of steady turbulence. Roughness for assurance of the boundary layers was set up using triangular threads of 0.2 to 0.4 mm thickness machined in the tube itself, or brass or glass wire wound on a smooth tube. Tests were also carried out using the roughness provided by regularly spaced pyramids 0.4 mm high. The results obtained showed that the heat exchange increased because of the presence of this roughness. A maximum in the heat exchange and pressure-drop coefficients was observed when the pitch equaled about eight times the height of the thread. An analytical method was developed and experiments were carried out in which the two walls of the annular space were heated in such a way as to transmit unequal heat flows. The region considered is limited to Reynolds' numbers of between 5 x 10/ sup 3/ and wall temperatures of under 250 deg C. (auth)
- Research Organization:
- France. Commissariat a l'Energie Atomique. Centre d'Etudes Nucleaires, Saclay
- NSA Number:
- NSA-18-005463
- OSTI ID:
- 4131515
- Report Number(s):
- CEA-2283
- Country of Publication:
- France
- Language:
- English
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