Investigation into the mechanism for nucleate boiling in thin falling water films

Thesis/Dissertation · Sat Jan 01 04:00:00 EST 1983

OSTI ID:5891785

Cerza, Jr, M R

The growth rate of a bubble in a falling superheated liquid film is shown experimentally to be much larger than the growth rate that would result from film surface evaporation alone. The base of the falling bubble is believed to lie deeply imbedded in the film. In addition, the bubble travels faster than the fluid beneath its base. The leading semicircular edge of the bubble base is, therefore, in continuous contact with new superheated liquid as the bubble traverses the film. This superheated liquid flashes down to saturation temperature at the leading semicircular edge. This creates a large thermal gradient that causes the evaporation of fluid at the bubble base interface to occur at a larger rate than that caused by the wall to film surface gradient. Bubble growth can also be sustained for a long period of time under this newly proposed mechanism. This mechanism is decidedly different from that of its pool boiling counterpart. A mathematical model for bubble growth in a falling laminar film proposes that bubble growth is governed by transient conduction through the bubble base as the bubble is swept downstream by the liquid film. Heat transfer data and flow characteristics of the laminar thermal entry length for the falling film are also presented for film Reynolds numbers of 640 to 5000 and for wall heat fluxes of 6 to 78 kW/m/sup 2/. Saturation temperatures in the experiments were 90 and 100C.

• Research Organization: Rutgers--the State Univ., New Brunswick, NJ (USA)
• OSTI ID: 5891785
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420400* -- Engineering-- Heat Transfer & Fluid Flow
BOILING
BUBBLE GROWTH
DATA
FILMS
FLUID FLOW
HEATING
HYDROGEN COMPOUNDS
INFORMATION
KINETICS
LAMINAR FLOW
MATHEMATICAL MODELS
NUCLEATE BOILING
NUMERICAL DATA
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SUPERHEATING
THEORETICAL DATA
WATER