AN EXPERIMENTAL INVESTIGATION OF THE HEAT TRANSFER COEFFICIENTS FOR BOILING AND CONDENSING HYDROGEN FILMS
Relationships between boiling, condensing, and over-all heat transfer coefficients of hydrogen and the variables of temperature difference and heat flux were investigated. The apparatus utilized a smooth, vertical brass tube. Film condensation of hydrogen vapors took place within the tube whereas nucleate boiling of liquid hydrogen occurred on the outside of the tube. The hydrogen boil-off rate served as a measure of the heat transferred. Individual film temperature differences were obtained from thermocouple readings and thermal resistance calculations. Boiling heat transfer coefficients were determined for a DELTA t of 0.06 to 1.17 deg F and a heat flux range of 23 to 978 Btu/hr-ft/sup 2/ of boiling surface area. The values of the boiling coefficients obtained varied from 360 to 800 Btu/hr-ft/sup 2/- deg F. Of the various theoretical and empirical equations for predicting boiling coefficients that were examined, the Forster-Zuber theory agreed within l2% with the data obtained at a temperature difference of 1.17 deg F. Other theories examined, however, showed less agreement with the experimental values. Condensing heat transfer coefficients were determined for the steady-state condensation of hydrogen vapor under laminar flow conditions. The range in DELTA t studied was 0.31 to 4.69 deg F and the corresponding heat flux range was 31 to 1310 Btu/hr-ft/sup 2/ based on the condensing surface area. The resulting condensing film coefficients varied from 90 to 300 Btu/ hr-ft/sup 2/- deg F and were all lower than those predicted by Nusselt's theory over this same DELTA t range. This is not surprising, however, since compliance with all of the numerous, idealized assumptions of Nusselt' s theory may not have been completely possible in this investigation. Over-all heat transfer coefficients were determined for a temperature range of 0.38 to 6.06 deg F and a heat flux range of 23 to 978 Btu/hr-ft/sup 2/, based on the boiling surface area. These experimental values ranged from 44 to 146 Btu/hr-ft/ sup 2/- deg F and were approximately 16% larger than those predicted by a combination of the Forster-Zuber and Nusselt theories.
- Research Organization:
- Univ. of Colorado, Boulder
- NSA Number:
- NSA-16-027204
- OSTI ID:
- 4818403
- Journal Information:
- Dissertation Abstr., Journal Name: Dissertation Abstr. Vol. Vol: 22
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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