Heat transfer limitation in a vertical annular closed two-phase thermosyphon with small fill rates
✍ Scribed by S. Rösler; M. Takuma; M. Groll; S. Maezawa
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 470 KB
- Volume
- 7
- Category
- Article
- ISSN
- 0890-4332
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✦ Synopsis
A thermosyphon with R113 as the working fluid employing fill ratios between 0.02 and 0.4, i.e. 2 and 40% of the evaporator volume, was experimentally and theoretically investigated. A critical heat flux (for which dry-out occurs) was measured which increases from about 104 W m -2 at 5% fill ratio to about 5 x 104Win -2 at 40% fill ratio. The theoretical predictions are in close agreement with the experimental results. NOMENCLATURE A area [m 2] d droplet C exp. constant in equation (3) e evaporator d diameter [m] g glass tube g gravitational acceleration [m s -2] h heat transfer surface he latent heat of vaporization [kJ kg-i] hyd hydraulic L length [m] 1 liquid L* liquid pool depth [m] m average m mass flux (kgm-2s -'] max maximum mass flow rate [kg s-t] v vapor q heat flux [W m -z] Dimensionless numbers u velocity [m s -t] pvu~z V + fill ratio We ffix axial coordinate [m] z characteristic length [m] 4F F specific mass flow rate [kgm -t s -t] Rel=--6 film thickness [m] t~t # dynamic viscosity [kg mt s-q mdhy d p mass density [kg m -~] Rev = -¢ surface tension [N m -l] /~,A 40t/4)(dt 2 -d~)~ Subscripts duff ~ .] C condenser To Vacuum Copper Insert S. R6st~R et al.