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- Flow boiling; Microchannels; Visualization; Flow patterns; Flow reversal; Electronics cooling (2)
- Melting (2)
- Natural Convection (2)
- Paraffin (2)
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- Solid-Liquid Phase Change (2)
- Bubble incipience; Microheater; Homogeneous nucleation (1)
- Coefficient of performance (1)
- Electronics cooling (1)
- Microchannel; Thermally developing; Electronics cooling; Liquid cooling; Heat sink (1)
- Miniature-scale refrigeration system (1)
- Second-law efficiency (1)
- Smallscale compressor (1)
Articles 1 - 11 of 11
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Subcooled Boiling Incipience On A Highly Smooth Microheater, T. Chen, J. F. Klausner, S V. Garimella, J. N. Chung
Subcooled Boiling Incipience On A Highly Smooth Microheater, T. Chen, J. F. Klausner, S V. Garimella, J. N. Chung
CTRC Research Publications
Abstract Subcooled boiling incipience on a highly smooth microscale heater (270 lm · 270 lm) submerged in FC-72 liquid is investigated. Using high-speed imaging and a transient heat flux measurement technique, the mechanics of homogeneous nucleation on the heater are elucidated. Bubble incipience on the microheater was observed to be an explosive process. It is found that the superheat limit of boiling liquid is required for bubble incipience. It is concluded that boiling incipience on the microheater is a homogeneous liquid–vapor phase change process. This is in contrast to recent observations of low-superheat heterogeneous nucleation on metallic surfaces of rms …
Hydrodynamic Loading Of Microcantilevers Vibrating In Viscous Fluids, Sudipta Basak, Arvind Raman, S V. Garimella
Hydrodynamic Loading Of Microcantilevers Vibrating In Viscous Fluids, Sudipta Basak, Arvind Raman, S V. Garimella
CTRC Research Publications
The hydrodynamic loading of elastic microcantilevers vibrating in viscous fluids is analyzed computationally using a three-dimensional, finite element fluid-structure interaction model. The quality factors and added mass coefficients of several modes are computed accurately from the transient oscillations of the microcantilever in the fluid. The effects of microcantilever geometry, operation in higher bending modes, and orientation and proximity to a surface are analyzed in detail. The results indicate that in an infinite medium, microcantilever damping arises from localized fluid shear near the edges of the microcantilever. Closer to the surface, however, the damping arises due to a combination of squeeze …
Energy-Based Model For Electrowetting-Induced Droplet Actuation, V. Bahadur, S V. Garimella
Energy-Based Model For Electrowetting-Induced Droplet Actuation, V. Bahadur, S V. Garimella
CTRC Research Publications
Electrowetting (EW) induced droplet motion has been explored in the past decade in view of its promising applications in the field of microfluidics. This paper demonstrates the potential of energy-based analyses for modeling the performance of EW-based fluid actuation systems. Analyses based on system energy minimization offer simplified modeling tools to predict the overall performance of EW systems while circumventing the need to model the numerous complexities in the system. An analytical model is developed to estimate the actuation force on a droplet moving between two electrodes. The origins and contributions of various components of the actuation force are analyzed. …
Thermally Developing Flow And Heat Transfer In Rectangular Microchannels Of Different Aspect Ratios, Poh-Seng Lee, S V. Garimella
Thermally Developing Flow And Heat Transfer In Rectangular Microchannels Of Different Aspect Ratios, Poh-Seng Lee, S V. Garimella
CTRC Research Publications
Laminar convective heat transfer in the entrance region of microchannels of rectangular cross-section is investigated under circumferentially uniform wall temperature and axially uniform wall heat flux thermal boundary conditions. Three-dimensional numerical simulations were performed for laminar thermally developing flow in microchannels of different aspect ratios. Based on the temperature and heat flux distributions obtained, both the local and average Nusselt numbers are presented graphically as a function of the dimensionless axial distance and channel aspect ratio. Generalized correlations, useful for the design and optimization of microchannel heat sinks and other microfluidic devices, are proposed for predicting Nusselt numbers. The proposed …
Measurements And High-Speed Visualizations Of Flow Boilingof A Dielectric Fluid In A Silicon Microchannel Heat Sink, Tailian Chen, S V. Garimella
Measurements And High-Speed Visualizations Of Flow Boilingof A Dielectric Fluid In A Silicon Microchannel Heat Sink, Tailian Chen, S V. Garimella
CTRC Research Publications
Experiments were conducted to investigate flow boiling heat transfer to a dielectric fluid in a silicon chip-integrated microchannel heat sink. Twenty-four microchannels, each 389 lm · 389 lm in cross-section, were fabricated into the 12.7 mm · 12.7 mm silicon substrate. High-speed visualizations (at 12,500 frames per second) were performed simultaneously with heat transfer and pressure drop measurements to investigate the physics of flow boiling in parallel microchannel arrays. At low heat fluxes, bubbly flow is dominant, with the bubbles coalescing to form vapor slugs as the heat flux is increased. At high heat fluxes, the flow regimes in the …
Experimental Investigation Of A Miniature-Scale Refrigeration System For Electronics Cooling, S. Trutassanawin, E. A. Groll, S V. Garimella, L Cremaschi
Experimental Investigation Of A Miniature-Scale Refrigeration System For Electronics Cooling, S. Trutassanawin, E. A. Groll, S V. Garimella, L Cremaschi
CTRC Research Publications
A miniature-scale refrigeration system suitable for electronics cooling applications was developed and experimentally investigated. A detailed review of the literature on refrigeration systems and system simulation models for application to electronics cooling is also provided. Experimental results obtained with the prototype system demonstrate its feasibility for use in cooling compact electronic devices. The cooling capacity of the system investigated varied from 121 to 268 W, with a COP of 2.8 to 4.7, at pressure ratios of 1.9 to 3.2. The effectiveness of the condenser ranged from 52% to 77%, while a thermal resistance of 0.60 and 0.77 C-cm 2/W was …
Experimental And Numerical Investigation Of Melting In A Cylinder, B Jones, D Sun, S Krishnan, S V. Garimella
Experimental And Numerical Investigation Of Melting In A Cylinder, B Jones, D Sun, S Krishnan, S V. Garimella
CTRC Research Publications
Well-controlled and well-characterized experimental measurements are obtained during the melting of a moderate-Prandtl-number material (n-eicosane) in a cylindrical enclosure heated from the side. The study aims to provide benchmark experimental measurements for validation of numerical codes. Experimental results in terms of measured temperatures and melt front locations are reported in both graphical and tabular forms. The melt front was captured photographically and its location ascertained using digital image processing techniques. To facilitate numerical validation exercises, a complete set of experimental results have been made available on a website for public access. An illustrative numerical comparison exercise was also undertaken using …
Effects Of Dissolved Air On Subcooled Flow Boiling Of A Dielectric Coolant In A Microchannel Heat Sink, T. Chen, S V. Garimella
Effects Of Dissolved Air On Subcooled Flow Boiling Of A Dielectric Coolant In A Microchannel Heat Sink, T. Chen, S V. Garimella
CTRC Research Publications
The effects of dissolved air in the dielectric liquid FC-77 on flow boiling in a microchannel heat sink containing ten parallel channels, each 500 mircometers wide and 2.5 mm deep, were experimentally investigated. Experiments were conducted before and after degassing, at three flow rates in the range of 30–50 ml/min. The dissolved air resulted in a significant reduction in wall temperature at which bubbles were first observed in the microchannels. Analysis of the results suggests that the bubbles observed initially in the undegassed liquid were most likely air bubbles. Once the boiling process is initiated, the wall temperature continues to …
Characterization Of Rough Engineering Surfaces For Use In Thermal Contact Conductance Modeling, A. F. Black, S V. Garimella
Characterization Of Rough Engineering Surfaces For Use In Thermal Contact Conductance Modeling, A. F. Black, S V. Garimella
CTRC Research Publications
Most surface properties used in calculating contact conductance are not intrinsic to the surface, but vary with the sampling frequency of the instrument used to characterize the surface. This paper offers a methodology for characterizing a surface based on intrinsic surface characterization properties (the self-affine fractal dimension and topothesy), intrinsic material properties, and applied load. A surface characterization model is developed to predict the wavelengths on a surface that are significant in predicting thermal contact conductance. The surface characterization model is combined with surface deformation and constriction resistance models to predict contact conductance across nominally flat, metallic surfaces. The long-wavelength …
Direct Simulation Of Transport In Open-Cell Metal Foams, S. Krishnan, J. Y. Murthy, S V. Garimella
Direct Simulation Of Transport In Open-Cell Metal Foams, S. Krishnan, J. Y. Murthy, S V. Garimella
CTRC Research Publications
Flows in porous media may be modeled using two major classes of approaches: (a) a macroscopic approach, where volume-averaged semiempirical equations are used to describe flow characteristics, and (b) a microscopic approach, where small-scale flow details are simulated by considering the specific geometry of the porous medium. In the first approach, small-scale details are ignored and the information so lost is represented in the governing equations using an engineering model. In the second, the intricate geometry of the porous structures is accounted for and the transport through these structures computed. The latter approach is computationally expensive if the entire physical …
Analysis And Prediction Of Constriction Resistance Between Coated Surfaces, C. T. Merril, S V. Garimella
Analysis And Prediction Of Constriction Resistance Between Coated Surfaces, C. T. Merril, S V. Garimella
CTRC Research Publications
Well-controlled and well-characterized experimental measurements are obtained during the melting of a moderate-Prandtl-number material (n-eicosane) in a cylindrical enclosure heated from the side. The study aims to provide benchmark experimental measurements for validation of numerical codes. Experimental results in terms of measured temperatures and melt front locations are reported in both graphical and tabular forms. The melt front was captured photographically and its location ascertained using digital image processing techniques. To facilitate numerical validation exercises, a complete set of experimental results have been made available on a website for public access. An illustrative numerical comparison exercise was also undertaken using …