Influence of the wetting state of a heated surface on heat transfer and pressure loss in an evaporator tube
The influence of the wetting state of a heated surface on heat transfer and pressure loss in an evaporator tube was investigated for a parameter range occurring in fossil-fired steam generators. Included in the analysis are quantities which determine the wetting state in steady and transient flow. The experimental work consists of the following: Occurrence of critical heat flux (CHF) and post-CHF heat transfer in a vertical upflow evaporator tube; influence of pressure and enthalpy transients on heat transfer in the unwetted region; influence of pipe orientation on heat transfer; and two phase flow pressure loss in wetted and unwetted region. Based on these experiments a method of predicting CHF for a vertical upflow evaporator tube was developed. The heat transfer in the unwetted region was newly formulated taking into account thermal nonequilibrium between the water and steam phases. Wall temperature excursions during pressure and enthalpy transients are interpreted with the help of the boiling curve and the Leidenfrost phenomenon. A method is developed by means of which it is possible to determine the influence of the pipe orientation on the location of the boiling crisis as well as on the heat transfer in the unwetted region. The influence of the wetting state of the heated surface on the two phase flow pressure loss is interpreted as ''Wall effect'' and is calculated using a simplified computer model. 68 refs., 83 figs.
- Research Organization:
- US Nuclear Regulatory Commission (NRC), Washington, DC (United States). Office of Nuclear Regulatory Research; Kraftwerk Union A.G., Erlangen (Germany, F.R.)
- OSTI ID:
- 5236497
- Report Number(s):
- NUREG/IA-0003; ON: TI87900030
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
DRYOUT
HEAT TRANSFER
TEMPERATURE EFFECTS
EVAPORATORS
PRESSURE DROP
TUBES
HEAT FLUX
ORIENTATION
ENTHALPY
FILM BOILING
FLUID MECHANICS
FOSSIL-FUEL POWER PLANTS
PARAMETRIC ANALYSIS
PRESSURE EFFECTS
STEAM GENERATORS
STEAM QUALITY
TEST FACILITIES
TRANSIENTS
TWO-PHASE FLOW
VELOCITY
WETTABILITY
BOILERS
BOILING
ENERGY TRANSFER
FLUID FLOW
MECHANICS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POWER PLANTS
THERMAL POWER PLANTS
THERMODYNAMIC PROPERTIES
VAPOR GENERATORS
200104* - Fossil-Fueled Power Plants- Components
420400 - Engineering- Heat Transfer & Fluid Flow