M. A. Lambert

Bio: M. A. Lambert is an academic researcher from San Diego State University. The author has contributed to research in topics: Surface roughness & Conductance. The author has an hindex of 1, co-authored 1 publications receiving 25 citations.

Thermal Contact Conductance of Non-Flat, Rough, Metallic Coated Metals

Abstract: Thermal contact conductance is an important consideration in such applications as thermally induced stress in supersonic and hypersonic flight vehicles, nuclear reactor cooling, electronics packaging, spacecraft thermal control, and gas turbine and internal combustion engine cooling In many instances, the highest possible thermal contact conductance is desired For this reason, soft, high conductivity, metallic coatings are sometimes applied to contacting surfaces (often metallic) to increase thermal contact conductance Two previously developed theoretical models for thermal contact conductance of metallic coated metals have been proven accurate for flat, rough surfaces However, these two theories often substantially over-predict the conductance of non-flat, rough, metallic coated metals In this investigation, a previously developed semi-empirical conductance model for flat and non-flat, rough, uncoated metals is employed in predicting the conductance of flat and non-flat, rough, metallic coated metals The more commonly cited of the previous theoretical models for flat surfaces and the semi-empirical model are compared to experimental thermal contact conductance results from a number of investigations in the literature Results for a number of metallic coating/substrate combinations on surfaces with widely varying flatness and roughness were analyzed Both models agree well with experimental results for flat, rough, metallic coated metals However, the semi-empiricalmore » model is substantially more accurate and more conservative than the theoretical model compared to the majority of experimental results for non-flat, rough, metallic coated metals« less

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

Improved pyroelectric detectors for single crystal adsorption calorimetry from 100 to 350 K

Abstract: The adsorption of atoms and molecules on single crystal surfaces allows one to produce well-characterized atomic, molecular, or dissociated adsorbates. Microcalorimetric measurement of the resulting adsorption energies, i.e., single crystal adsorption calorimetry, allows determination of the standard enthalpies of formation of these adsorbates. Methods are described for making an improved heat detector for such measurements, which greatly improves the signal-to-noise ratio, particularly at low temperatures (down to 100 K). The heat detector is an adaptation of a previously introduced design, based on a metallized pyroelectric polymer (beta-polyvinylidene fluoride), which is pressed against the back of a single crystal during measurement but removed during sample preparation and annealing. The improvement is achieved by selectively etching the metal coating of the polymer, thus reducing the pyro- and piezoelectric noise from all nonessential regions of the polymer. We, furthermore, describe how to achieve a better thermal contact between the sample and the pyroelectric polymer, without increasing the thermal mass of the detector, resulting in significantly improved sensitivities for both 1 and 127 microm thick samples. The result is a detector which, using 1 microm samples, is approximately 40 times more sensitive at 100 K than the traditional polymer-based detector, showing a pulse-to-pulse standard deviation in the heat of adsorption of just 1.3 kJ/mol with gas pulses containing only 1.1% of a monolayer onto Pt(111), for which 1 ML (monolayer) is 1.5x10(15) species/cm(2). For measurements at 300 K, where especially pyroelectric noise is likely of less concern, the new design improves the sensitivity 3.6-fold compared to the traditional detector. These improvements are furthermore used to propose a new detector design that is able to measure heats of adsorption on samples as thick as 127 microm with reasonable sensitivity.

Thermal conductivity of granular porous media: A pore scale modeling approach

Abstract: Pore scale modeling method has been widely used in the petrophysical studies to estimate macroscopic properties (e.g. porosity, permeability, and electrical resistivity) of porous media with respect to their micro structures. Although there is a sumptuous literature about the application of the method to study flow in porous media, there are fewer studies regarding its application to thermal conduction characterization, and the estimation of effective thermal conductivity, which is a salient parameter in many engineering surveys (e.g. geothermal resources and heavy oil recovery). By considering thermal contact resistance, we demonstrate the robustness of the method for predicting the effective thermal conductivity. According to our results obtained from Utah oil sand samples simulations, the simulation of thermal contact resistance is pivotal to grant reliable estimates of effective thermal conductivity. Our estimated effective thermal conductivities exhibit a better compatibility with the experimental data in companion with some famous experimental and analytical equations for the calculation of the effective thermal conductivity. In addition, we reconstruct a porous medium for an Alberta oil sand sample. By increasing roughness, we observe the effect of thermal contact resistance in the decrease of the effective thermal conductivity. However, the roughness effect becomes more noticeable when there is a higher thermal conductivity of solid to fluid ratio. Moreover, by considering the thermal resistance in porous media with different grains sizes, we find that the effective thermal conductivity augments with increased grain size. Our observation is in a reasonable accordance with experimental results. This demonstrates the usefulness of our modeling approach for further computational studies of heat transfer in porous media.

Review of prediction for thermal contact resistance

Abstract: Theoretical prediction research on thermal contact resistance is reviewed in this paper. In general, modeling or simulating the thermal contact resistance involves several aspects, including the descriptions of surface topography, the analysis of micro mechanical deformation, and the thermal models. Some key problems are proposed for accurately predicting the thermal resistance of two solid contact surfaces. We provide a perspective on further promising research, which would be beneficial to understanding mechanisms and engineering applications of the thermal contact resistance in heat transport phenomena.