Written in English
|Statement||by Dean Matthew Pachosa.|
|The Physical Object|
|Pagination||xvi, 100 leaves, bound :|
|Number of Pages||100|
First, the onset of nucleate boiling appears for a lower wall superheat in microgravity compared to 1- g with an upward facing plate. In normal gravity, thermal convection cools down the heated plate and delays the onset of nucleate boiling. Then different nucleate boiling regimes are Cited by: This article presents a numerical analysis for the use of a dielectrophoretic (DEP) force on vapor bubbles to sustain nucleate boiling heat transfer in space where the gravity-driven buoyancy force is absent. The analytic and numerical solution procedures for the DEP force are outlined for an infinite-plate and a finite-plate electrode geometry, by: 7. J. N. Chung, An experiment was performed that produced a controlled electrical body force (dielectrophoretic force or DEP force) over the length of a horizontal platinum wire heater during boiling. The DEP force was generated such that it either aided or opposed terrestrial gravity or acted nearly alone in by: The objective of this paper is to analyze experimentally the feasibility of utilizing the dielectrophoretic (DEP) force to sustain boiling in space where the gravity-driven buoyancy force is absent. First, a bubble trajectory experiment is present to determine the magnitude of the DEP force produced at the edge of two diverging-plate electrodes to the highly nonuniform electric field.
In order to maintain steady nucleate boiling in microgravity another force must be imposed onto the boiling process to replace the gravity-driven buoyancy force. Using three electrode geometries it was found that an electric field can provide a replacement force for buoyancy in microgravity. Microgravity experiments offer a unique opportunity to study the complex interactions without external forces, and can also provide a means to study the actual influence of gravity on the pool boiling by comparing the results obtained from microgravity experiments with . Competing Effects of Dielectrophoresis and Buoyancy on Nucleate Boiling and an Analogy With Variable Gravity Boiling Results. J. Heat Transfer (May, ) Dielectrophoresis-Driven Nucleate Boiling in a Simulated Microgravity Environment. J. Heat Transfer (May, ). Nucleate boiling is a type of boiling that takes place when the surface temperature is hotter than the saturated fluid temperature by a certain amount but where the heat flux is below the critical heat water, as shown in the graph below, nucleate boiling occurs when the surface temperature is higher than the saturation temperature (T S) by between 10 °C (18 °F) to 30 °C (54 °F).
Pachosa and Chung were interested in the role of the dielectrophoretic (DEP) force in boiling and its potential to facilitate bubble removal in the microgravity environment. Snyder and Chung  experimentally investigated the effectiveness of a static electric field in replacing the buoyancy force in order to maintain nucleate pool boiling in microgravity. F.M. WANG, CHIN. PAN, in Transport Phenomena in Heat and Mass Transfer, ABSTRACT. Nucleate boiling heat transfer at high heat fluxes is characterized by the existence of a macrolayer between the heating surface and hovering bubble with vapor stems penetrating the layer nourishing vapor to the growing bubble. Heat transfer from the heating surface results in temperature . Long-term steady state nucleate boiling seems to be possible in microgravity, especially in subcooled conditions, though impaired bubble removal and coalescence lead to an increase of void fraction. In the nucleate boiling regime, as mentioned above, under microgravity condition, the vapor bubbles are adhered to the wall since they can't depart with the absence of gravity. Since the contact angle influence the wettability near the wall, the larger contact angle allows more bulk liquid to fill the gap between the vapor bubble and wall, hence increase the heat transfer between the fluid and the wall.