Trevor J. Snyder

Dielectrophoresis with application to boiling heat transfer in microgravity. II. Experimental investigation

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. The results showed that the DEP forces measured experimentally are equal to those predicted in Part I to within 10%–15%. Second, the bubble detachment diameter and frequency of bubbles generated with a gold-film, single-bubble heater were measured in microgravity so that the masking effect of gravity could be eliminated. In particular, a comparison is made between the DEP forces produced with a relatively high-electric-field gradient at the edge of two flat-plate electrodes to the DEP forces produced with the relatively low electric-field gradient between two diverging-plate electrodes. It was discovered that the bubble deta...

A second look at electrokinetic phenomena in boiling

In the article by V. Asch [J. Appl. Phys. 37, 2654 (1966)], experiments were performed to study the influence of an electrostatic field on nucleate boiling of Freon-113(R-113). We have found that Asch might not have properly considered the effects of his experimental setup and therefore came to incorrect conclusions concerning electrophoretic and dielectrophoretic forces. Aschs analysis of the electric field distribution led him to conclude that the dielectrophoretic forces were small, however, we show in this article that, in general, there are strong dielectrophoretic forces in the vicinity of the heater wire. This article presents the results from a set of experiments performed with an apparatus similar to that of Aschs with test fluids of R-113 and FC-72. The experimental results show that vapor bubbles can be attracted to either the anode or cathode depending on the potentials with respect to the heater wire on which the boiling takes place. This is contrary to the results obtained by Asch which le...

Dielectrophoresis with application to boiling heat transfer in microgravity. I. Numerical analysis

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, respectively. A simple analysis is presented that describes the limits on the magnitude of the DEP force. A comparison is made between the DEP forces produced near the edges of the finite-plate electrodes (where there is a relatively high-gradient electric field) to the forces produced between the electrodes and away from the edges (where there is a relatively low-gradient electric field). The predicted DEP forces are then used to study the effectiveness of bubble transport for both high and low electric-field gradients in microgravity. To effectively maintain boiling in space with the DEP force, a knowledge of the electric field is required which addresses both t...

Thermal performance of embedded active chips

Electronic circuit density is currently limited by the physical dimensions of the elements which compose the device. Therefore, 3D integration of chips into printed circuit boards is one approach being explored to keep pace with this continuous trend toward miniaturization and densification. Embedded passive components in printed circuit boards have been shown to reduce space requirements by 30% or more, achieve better HF signal integrity and also allow for cost reductions. Work on embedded active components is ongoing and is expected to achieve these same results and should additionally allow higher interconnect density and a dramatic functionality increase while maintain key PCB attributes of component and interconnects. This paper presents a thermal analysis of an enclosure which is intended to hold the PCB boards containing the active discrete chips. A transfer function is generated for this design including the effects of fan flow rate, ambient intake temperature, and geometric location. Finally, the two models are merged together such that the enclosure data is joined with the embedded chip model. A Monte Carlo simulation approach is used to understand and optimize the performance and operation of the combined systems.