Post dryout heat transfer in nuclear and cryogenic equipment
Technical Report
·
OSTI ID:4933109
Heat transfer in the liquid deficient region downstream of the dryout location is considered in relation to the performance of steam generating reactors, once-through steam generators, and cryogenic vaporizers. Experimental results are reported on the propagation of dryout for vertical electrically heated tubes of 12.7 mm (0.5'') bore with both uniform and cosine heat flux profiles by up-flow of steam-water mixtures at pressures up to 70 bar (1000 psia). Measurements are given of local wall temperatures as dryout proceeds with increasing power increments. A semi-empirical model of the liquid deficient region has been found to give reasonable agreement with experimental results. This model divides the heat transfer mechanism into two processes; heat transfer from the wall to a superheated boundary layer and evaporation of entrained droplets in the superheated vapour core assumlng no droplet/wall interaction. Tests on a vertical electrically heated U-tube test section 12.8 mm steam pressure of 180 bars (2600 psia) are discussed. Measurements were made of wall temperatures downstream of dryout. The data are compared with existing correlations and analyzed in an attempt to separate the components of droplet deposition and forced convection in the liquid deficient region as droplet/ wall interaction was then significant. A method is proposed whereby the water-side heat transfer characteristics determined using electrically heated tubes may be used to estimate the variation in tube wall temperatures in a sodium-heated steam generator. Analysis of some published data for eryogenic fluids indicates a similar behavior to that for water. Wall temperatures computed from the semi- empirical model development for water systems show moderate agreement with these published experimental profiles. (auth)
- Research Organization:
- UKAEA Research Group, Harwell. Atomic Energy Research Establishment
- Sponsoring Organization:
- Sponsor not identified
- NSA Number:
- NSA-29-002597
- OSTI ID:
- 4933109
- Report Number(s):
- AERE-R--7519
- Country of Publication:
- United Kingdom
- Language:
- English
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