Leroy S. Fletcher

Bio: Leroy S. Fletcher is an academic researcher from Texas A&M University. The author has contributed to research in topics: Thermal contact conductance & Thermal conductivity. The author has an hindex of 28, co-authored 153 publications receiving 2862 citations. Previous affiliations of Leroy S. Fletcher include Texas A&M University System & University of Virginia.

Recent Developments in Contact Conductance Heat Transfer

Abstract: The characteristics of thermal contact conductance are increasingly important in a wide range of technologies. As a consequence, the number of experimental and theoretical investigations of contact conductance has increased. This paper reviews and categorizes recent developments in contact conductance heat transfer. Among the topics included are the theoretical/analytical/numerical studies of contact conductance for conforming surfaces and other surface geometries; the thermal conductance in such technological areas as advanced or modern materials, microelectronics, and biomedicine; and selected topics including thermal rectification, gas conductance, cylindrical contacts, periodic and sliding contacts, and conductance measurements. The paper concludes with recommendations for emerging and continuing areas of investigation.

Contact heat transfer: the last decade

Abstract: Resistance d'une simple constriction; resistance thermique de points de contact multiples dans le vide; correlations pour la conductance de contact thermique dans le vide

Micro-heat-pipe catheter

Abstract: A micro-heat-pipe catheter provides a hyperthermia or hypothermia source for the treatment of cancerous tumors or other diseased tissue. The heat-pipe is about the size of a hypodermic needle and is thermally insulated along a substantial portion of its length. The heat-pipe includes a channel, partially charged with an appropriate working fluid. Active or passive heat control tailors the delivery or removal of thermal energy directly to or from the tumor or diseased tissue site.

Heat Transfer Through Falling Film Evaporation and Boiling on Horizontal Tubes

Abstract: Evaporation and boiling heat transfer coefficients are presented for thin, distilled water films flowing over the outside of horizontal, electrically heated brass tubes. Tests were conducted with a thin-slot water distribution system for 2.54- and 5.08-cm-dia smooth tubes. Both local and average heat transfer data were obtained for nonboiling and boiling conditions corresponding to feedwater temperatures ranging from 49 to 127C and heat-flux values ranging from 30 to 80 kW/m{sup 2}. Feedwater flow rates ranged from 0.135 to 0.366 kg/s per meter length per side of the tube. Both nonboiling and boiling correlations of the average heat transfer coefficients were developed and compared.

Review of Models for Thermal Contact Conductance of Metals

Abstract: Thermal contact conductance is a topic of great relevance to such applications as electronics packaging, satellite thermal control, nuclear reactor cooling, aerodynamic heating of supersonic aircraft and missiles, and turbine and internal combustion engine design. A fundamental problem in this discipline concerns the contact of metals in a vacuum environment for which gap and radiative conductance are negligible and only contact (solid spot) conductance is appreciable. A number of conductance models for metals are compiled and compared to experimental data from the literature. Theoretical models have been developed that accurately predict contact conductance for the two bounding cases of flat, rough surfaces and nonflat (spherical), smooth surfaces. However, these do not agree with most results for arbitrarily nonflat, rough surfaces, those usually obtained from common manufacturing processes. Empirical and semiempirical correlations, although many are developed for nonflat, rough surfaces, also suffer from limited applicability. The few theoretical models for nonflat (spherical), rough surfaces are computationally intensive and are not readily applied to design.

Medical probe device and method

Abstract: A medical probe device comprises a catheter having a stylet guide housing with one or more stylet ports in a side wall thereof and a stylet guide for directing a flexible stylet outward through the stylet port and through intervening tissue at a preselected, adjustable angle to a target tissue. The total catheter assembly includes a stylet guide lumen communicating with the stylet port and a stylet positioned in said stylet guide lumen for longitudinal movement from the port through intervening tissue to a target tissue. The stylet can be an electrical conductor enclosed within a non-conductive layer, the electrical conductor being a radiofrequency electrode. Preferably, the non-conductive layer is a sleeve which is axially moveable on the electrical conductor to expose a selected portion of the electrical conductor surface in the target tissue. The stylet can also be a microwave antenna. The stylet can also be a hollow tube for delivering treatment fluid to the target tissue. It can also include a fiber optic cable for laser treatment. The catheter can include one or more inflatable balloons located adjacent to the stylet port for anchoring the catheter or dilation. Ultrasound transponders and temperature sensors can be attached to the probe end and/or stylet. The stylet guide can define a stylet path from an axial orientation in the catheter through a curved portion to a lateral orientation at the stylet port.

Thermal conductivity enhancement of suspensions containing nanosized alumina particles

Abstract: Various suspensions containing Al2O3 nanoparticles with specific surface areas in a range of 5–124 m2 g−1 have been prepared and their thermal conductivities have been investigated using a transient hot-wire method. Nanoparticle suspensions, containing a small amount of Al2O3, have substantially higher thermal conductivity than the base fluid, with the enhancement increasing with the volume fraction of Al2O3. The enhanced thermal conductivity increases with an increase in the difference between the pH value of aqueous suspension and the isoelectric point of Al2O3 particle. For the suspensions using the same base fluid, the thermal conductivity enhancements are highly dependent on specific surface area (SSA) of nanoparticle, with an optimal SSA for the highest thermal conductivity. For the suspensions containing the same nanoparticles, the enhanced thermal conductivity ratio is reduced with the increasing thermal conductivity of the base fluid. The crystalline phase of the nanoparticles appears to have no ...

System and method for delivering thermally sensitive and reverse-thermal gelation materials

Abstract: A catheter for injecting a thermally sensitive gelation material to remote sites within a patient's body by maintaining the thermally sensitive gelation material in a liquid state until it is delivered to a target area within the body.

Thermal Interface Materials: Historical Perspective, Status, and Future Directions

Abstract: With the continual increase in cooling demand for microprocessors, there has been an increased focus within the microelectronics industry on developing thermal solutions. Thermal interface materials (TIMs) play a key role in thermally connecting various components of the thermal solution. Review of the progress made in the area of TIMs in the past five years is presented. The focus is on the rheology-based modeling and design of polymeric TIMs due to their widespread use. Review of limited literature on the thermal performance of solders is also provided. Merits and demerits of using nanoparticles and nanotubes for TIM applications are also discussed. I conclude the paper with some directions for the future that I feel are relatively untouched and potentially very beneficial

Multiple antenna ablation apparatus and method

Abstract: A multiple antenna ablation apparatus includes an electromagnetic energy source, a trocar including a distal end, and a hollow lumen extending along a longitudinal axis of the trocar, and a multiple antenna ablation device with three or more antennas. The antennas are initially positioned in the trocar lumen as the trocar is introduced through tissue. At a selected tissue site the antennas are deployable from the trocar lumen in a lateral direction relative to the longitudinal axis. Each of the deployed antennas has an electromagnetic energy delivery surface of sufficient size to, (i) create a volumetric ablation between the deployed antennas, and (ii) the volumetric ablation is achieved without impeding out any of the deployed antennas when 5 to 200 watts of electromagnetic energy is delivered from the electromagnetic energy source to the multiple antenna ablation device. At least one cable couples the multiple antenna ablation device to the electromagnetic energy source.