Experimental study of heat transfer enhancement for ammonia condensing on vertical fluted tubes
Experiments were run to determine heat transfer performance of single vertical tubes with ammonia condensing on the outside. The four test tubes (aluminum) were of 1-in. nominal diameter and 4-ft length with 0 (smooth), 24, 48, and 60 external flutes. Test parameter ranges are given. The condensing heat transfer coefficients are reported as composite coefficients that include the resistance of both the condensing side and the tube wall. The composite condensing coefficients ranged from 720 to 9600 Btu/hr . ft/sup 2/ . /sup 0/F. All parameters were based on total condensing surface area. The data show that, for a given heat flux, a fluted tube can increase condensing coefficients by up to 7.2 times smooth tube values. The condensing temperature difference (composite) varied from 0.3 to 23/sup 0/F in the experiments; and the data show that, for a given condensing temperature difference, a fluted tube can accommodate heat loads up to 5.4 times the smooth tube values. Alternatively, for a given heat load, a smooth tube requires condensing temperature differences up to 9.7 times the fluted tube values. Tests were also run to evaluate the effect of tube length on the heat transfer performance of fluted tubes; however, no appreciable effect was detectable in going from an ''effective'' condensing length of 4 ft to 2 ft.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5266451
- Report Number(s):
- ORNL-5356
- Country of Publication:
- United States
- Language:
- English
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