Suresh V. Garimella

Purdue University, ウェストラファイエット, Indiana, United States

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Publications (391)543.14 Total impact

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    ABSTRACT: • A cycle-integrated energy storage strategy for vapor compression refrigeration is proposed.
    No preview · Article · Jan 2016 · International Journal of Refrigeration
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    Xuemei Chen · Ravi S. Patel · Justin A. Weibel · Suresh V. Garimella
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    ABSTRACT: Coalescence-induced jumping of condensate droplets from a superhydrophobic surface with hierarchical micro/nanoscale roughness is quantitatively characterized. Experimental observations show that the condensate droplet jumping is induced by coalescence of multiple droplets of different sizes, and that the coalesced droplet trajectories typically deviate from the surface normal. A depth-from-defocus image processing technique is developed to track the out-of-plane displacement of the jumping droplets, so as to accurately measure the droplet size and velocity. The results demonstrate that the highest jumping velocity is achieved when two droplets coalesce. The jumping velocity decreases gradually with an increase in the number of coalescing droplets, despite the greater potential surface energy released upon coalescence. A general theoretical model that accounts for viscous dissipation, surface adhesion, line tension, the initial droplet wetting states, and the number and sizes of the coalescing droplets is developed to explain the trends of droplet jumping velocity observed in the experiments.
    Preview · Article · Jan 2016 · Scientific Reports

  • No preview · Article · Dec 2015 · Journal of Electronic Packaging
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    Hao Wang · Jayathi Y. Murthy · Suresh V. Garimella

    Full-text · Dataset · Dec 2015
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    Hao Wang · Jayathi Y. Murthy · Suresh V. Garimella

    Full-text · Dataset · Dec 2015
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    Xuemei Chen · Justin A. Weibel · Suresh V. Garimella
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    ABSTRACT: Omniphobic surfaces with reentrant microstructures have been investigated for a range of applications, but the evaporation of high- and low-surface-tension liquid droplets placed on such surfaces has not been rigorously studied. In this work, we develop a technique to fabricate omniphobic surfaces on copper substrates to allow for a systematic examination of the effects of surface topography on the evaporation dynamics of water and ethanol droplets. Compared to a water droplet, the ethanol droplet not only evaporates faster, but also inhibits Cassie-to-Wenzel wetting transitions on surfaces with certain geometries. We use an interfacial energy-based description of the system, including the transition energy barrier and triple line energy, to explain the underlying transition mechanism and behaviour observed. Suppression of the wetting transition during evaporation of droplets provides an important metric for evaluating the robustness of omniphobic surfaces requiring such functionality.
    Preview · Article · Nov 2015 · Scientific Reports
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    Zhenhai Pan · Justin A Weibel · Suresh V Garimella
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    ABSTRACT: High-fidelity simulation of flow boiling in microchannels remains a challenging problem, but the increasing interest in applications of microscale two-phase transport highlights its importance. In this paper, a volume of fluid (VOF)-based flow boiling model is proposed with features that enable cost-effective simulation of two-phase flow and heat transfer in realistic geometries. The vapor and liquid phases are distinguished using a color function which represents the local volume fraction of the tracked phase. Mass conservation is satisfied by solving the transport equations for both phases with a finite-volume approach. In order to predict phase change at the liquid-vapor interface, evaporative heat and mass source terms are calculated using a novel, saturated-interface-volume phase change model. This phase change model is formulated to anchor the interfacial temperature at saturation within each iteration, and thereby acts as a robust constant-temperature boundary condition. Unlike other available phase-change models, the source terms are coupled with the local temperature explicitly; therefore, numerical oscillations around the interface temperature are not observed during iterations within a time step, which reduces the numerical cost. In addition, the reference frame is set to move with the vapor slug to artificially increase the local velocity magnitude in the thin liquid film region in the relative frame. This reduces the influence of numerical errors resulting from calculation of the surface tension force, and thus suppresses the development of spurious currents. As a result, non-uniform meshes may be used which can efficiently resolve high-aspect-ratio geometries and flow features. The overall numerical expense is significantly reduced. The proposed saturated-interface-volume model is first validated against a one-dimensional Stefan problem, and then used to simulate the growth of a vapor bubble flowing in a heated, 2D axisymmetric microchannel. The bubble motion, bubble growth rate, liquid film thickness, and local heat transfer coefficient along the wall are compared against previous numerical studies. A three-dimensional flow boiling problem is studied to demonstrate the cost effectiveness of the present approach and to highlight the transport mechanisms it can reveal in more complex domains.
    Full-text · Article · Oct 2015 · International Journal of Heat and Mass Transfer
  • Yashwanth Yadavalli · Justin A. Weibel · Suresh V. Garimella
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    ABSTRACT: Heat pipes and vapor chamber heat spreaders offer a potential solution to the increasing thermal management challenges in thin-form-factor mobile computing platforms, where efficient spreading is required to simultaneously prevent overheating of internal components and formation of hot regions on the device exterior surfaces. Heat pipe performance limitations unique to such ultrathin form factors and the key heat transfer mechanisms governing the performance must be characterized. A thermal resistance network model and a detailed 2-D numerical model are used to analyze the performance of heat pipes under these conditions. A broad parametric study of geometries and heat inputs using the reduced-order model helps delineate the performance thresholds within which the effectiveness of a heat pipe is greater than a comparable solid heat spreader. A vapor-phase threshold unique to ultrathin heat pipes operating at low-power inputs is observed. At this threshold, the vapor-phase thermal resistance imposed by the saturation pressure/temperature gradient in the heat pipe causes a crossover in the thermal resistance relative to a solid heat spreader. The higher fidelity numerical model is used to assess the accuracy of the resistance network model and to verify the validity and applicability of each assumption made regarding the transport mechanisms. Key heat transfer mechanisms not captured by the reduced-order thermal network models are identified. These include the effects of boundary conditions on the interface mass flux profile, convective effects on the vapor core temperature drop, and 2-D conduction on smearing of evaporation/condensation mass flux into the adiabatic section.
    No preview · Article · Oct 2015 · IEEE Transactions on Components, Packaging, and Manufacturing Technology
  • Stephen H. Taylor · Suresh V. Garimella
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    ABSTRACT: A new electrical capacitance tomography (ECT) image reconstruction method, termed Sensitivity Factor Regularization (SFR), is developed. The SFR method provides an explicit formulation for solving the image reconstruction problem that performs better than other explicit methods, such as linear back-projection and Tikhonov regularization, while providing the same computational efficiency. The computational ease of the SFR method renders it an attractive option for ECT where real-time imaging is required and theoretical statistical evaluation of proposed electrode configurations may readily be performed. A statistical study is conducted using SFR image reconstructions for investigating the impact of electrode density on image quality for a symmetric ECT system characterizing a square cross-section. A larger number of smaller electrodes allows more data to be gathered for use in image reconstruction, but degrades signal-to-noise ratio in the measurements. The statistical study using SFR clearly identifies a theoretical optimum electrode density that minimizes reconstructed image error for a given level of measurement noise.
    No preview · Article · Oct 2015 · Flow Measurement and Instrumentation
  • Andrea Diani · Karthik K. Bodla · Luisa Rossetto · Suresh V. Garimella
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    ABSTRACT: Direct numerical simulation of transport in foam materials can benefit from realistic representations of the porous-medium geometry generated by employing non-destructive 3D imaging techniques. X-ray microtomography employs computer-processed X-rays to produce tomographic images or slices of specific regions of the object under investigation, and is ideally suited for imaging opaque and intricate porous media. In this work, we employ micro-CT for numerical analysis of air flow and convection through four different high-porosity copper foams. All four foam samples exhibit approximately the same relative density (6.4–6.6% solid volume fraction), but have different pore densities (5, 10, 20, and 40 pores per inch, PPI). A commercial micro-computed tomography scanner is employed for scanning the 3D microstructure of the foams at a resolution of 20 μm, yielding stacks of two-dimensional images. These images are processed in order to reconstruct and mesh the real, random structure of the foams, upon which simulations are conducted of forced convection through the pore spaces of the foam samples. The pressure drop values from this μCT based CFD analysis are compared against prior experimental results; the computational interfacial heat transfer results are compared against the values predicted by an empirical correlation previously reported, revealing excellent agreement between the numerical and experimental/empirical hydraulic and thermal results, thus highlighting the efficacy of this novel approach.
    No preview · Article · Sep 2015 · International Journal of Heat and Mass Transfer
  • Stephen H. Taylor · Suresh V. Garimella
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    ABSTRACT: Capacitance tomography is performed on a ∼1 mm thick planar domain. A square array of electrodes is used on one side (bottom) and a single large electrode on the opposing side (top). Dielectric anomalies of interest are empty pockets (voids) in a dielectric material filling the domain. Capacitance is measured between neighboring electrodes on the bottom side, as well as between bottom electrodes and the top electrode. Because regions of sensitivity are highly localized, information regarding the 3D structure of a void must be ascertained from relatively few measurements involving the electrodes near the void. Solutions that are strictly binary are desired for the reconstructed image without incurring excessive computational expense. A new image-reconstruction algorithm is developed that is tailored to capacitance tomography of sparsely characterized domains, entitled the shape-energy evolutionary reconstruction (SEER) algorithm. The algorithm creates binary images by sequentially composing a list of occupied voxels, guided by a knowledge of the spatial sensitivity of each measurement and a voxel-to-voxel energy regularization which prefers adjoining groups of occupied voxels. Detection and reconstruction of void structures in a 1.27 mm layer of thermal gap filler material is demonstrated experimentally. Basic three-dimensional characteristics of voids are distinguished. The reconstructed images provide a means of visualizing and interpreting void characteristics, such as their volume or proximity to a substrate wall.
    No preview · Article · Aug 2015 · Sensors and Actuators A Physical
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    Xuemei Chen · Justin A. Weibel · Suresh V. Garimella

    Full-text · Article · Aug 2015 · Journal of Heat Transfer
  • Ravi S. Patel · Justin A. Weibel · Suresh V. Garimella
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    ABSTRACT: A new measurement technique is developed for quantitatively mapping the liquid–gas interface profiles of air bubbles in an adiabatic microchannel slug flow environment. Water seeded with 0.5 μm-diameter fluorescent polystyrene particles is pumped through a single acrylic microchannel of 500 μm × 500 μm square cross section. A periodic slug flow is achieved by the controlled injection of air into the channel. Particles are constrained to the liquid phase, and their distribution in the flow is visualized through an optical microscope in an epifluorescent configuration with pulsed laser illumination to resolve the instantaneous liquid–gas interface profile to within ±2.8 μm in the focal plane.
    No preview · Article · Jul 2015 · International Journal of Heat and Mass Transfer
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    Zhenhai Pan · Justin A Weibel · Suresh V Garimella
    [Show abstract] [Hide abstract]
    ABSTRACT: High-fidelity simulation of flow boiling in microchannels remains a challenging problem, but the increasing interest in applications of microscale two-phase transport highlight its importance. In this paper, a volume of fluid (VOF)-based flow boiling model is proposed with computational expense-saving features that enable cost-effective simulation of two-phase flow and heat transfer in realistic geometries. The vapor and liquid phases are distinguished using a color function which represents the local volume fraction of the tracked phase. Mass conservation is satisfied by solving the transport equations for both phases with a finite-volume approach. In order to predict phase change at the liquid-vapor interface, evaporative heat and mass source terms are calculated using a novel, saturated-interface-volume phase change model that fixes the interface at the saturation temperature at each time step to achieve stability. Numerical oscillation of the evaporation source terms is thus eliminated and a non-iterative time advancement scheme can be adopted to reduce computational cost. The reference frame is set to move with the vapor slug to artificially increase the local velocity magnitude in the thin liquid film region in the relative frame, which reduces the influence of numerical errors resulting from calculation of the surface tension force, and thus suppresses the development of spurious currents. This allows use of non-uniform meshes that can efficiently resolve high-aspect-ratio geometries and flow features and significantly reduces the overall numerical expense. The proposed model is used to simulate the growth of a vapor bubble in a heated 2D axisymmetric microchannel. The bubble motion, bubble growth rate, liquid film thickness, and local heat transfer coefficient along the wall are compared against previous numerical studies.
    Full-text · Conference Paper · Jul 2015
  • Richard A. Simmons · Suresh V. Garimella

    No preview · Article · Jul 2015
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    E-Pubs Purdue · Hao Wang · Zhenhai Pan · Suresh V. Garimella

    Full-text · Dataset · Jun 2015
  • Carolina Mira-Hernández · Scott M. Flueckiger · Suresh V. Garimella
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    ABSTRACT: A molten-salt thermocline tank is a low-cost option for thermal energy storage (TES) in concentrating solar power (CSP) plants. Typical dual-media thermocline (DMT) tanks contain molten salt and a filler material that provides sensible heat capacity at reduced cost. However, conventional quartzite rock filler introduces the potential for thermomechanical failure by successive thermal ratcheting of the tank wall under cyclical operation. To avoid this potential mode of failure, the tank may be operated as a single-medium thermocline (SMT) tank containing solely molten salt. However, in the absence of filler material to dampen tank-scale convection eddies, internal mixing can reduce the quality of the stored thermal energy. To assess the relative merits of these two approaches, the operation of DMT and SMT tanks is simulated under different periodic charge/discharge cycles and tank wall boundary conditions to compare the performance with and without a filler material. For all conditions assessed, both thermocline tank designs have excellent thermal storage performance, although marginally higher first- and second-law efficiencies are predicted for the SMT tank. While heat loss through the tank wall to the ambient induces internal flow nonuniformities in the SMT design over the scale of the entire tank, strong stratification maintains separation of the hot and cold regions by a narrow thermocline; thermocline growth is limited by the low thermal diffusivity of the molten salt. Heat transport and flow phenomena inside the DMT tank, on the other hand, are governed to a great extent by thermal diffusion, which causes elongation of the thermocline. Both tanks are highly resistant to performance loss over periods of static operation, and the deleterious effects of dwell time are limited in both tank designs.
    No preview · Article · Jun 2015 · Journal of Solar Energy Engineering
  • Matthew J. Rau · Suresh V. Garimella · Ercan M. Dede · Shailesh N. Joshi
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    ABSTRACT: The effect of a variety of surface enhancements on the heat transfer achieved with an array of impinging jets is experimentally investigated using the dielectric fluid HFE-7100 at different volumetric flow rates. The performance of a 5×5 array of jets, each 0.75mm in diameter, is compared to that of a single 3.75mm diameter jet with the same total open orifice area, in single-and two-phase operation. Four different target copper surfaces are evaluated: a baseline smooth flat surface, a flat surface coated with a microporous layer, a surface with macroscale area enhancement (extended square pin-fins), and a hybrid surface on which the pin-fins are coated with the microporous layer; area-averaged heat transfer and pressure drop measurements are reported. The array of jets enhances the single-phase heat transfer coefficients by 1.13-1.29 times and extends the critical heat flux (CHF) on all surfaces compared to the single jet at the same volumetric flow rates. Additionally, the array greatly enhances the heat flux dissipation capability of the hybrid coated pin-fin surface, extending CHF by 1.89-2.33 times compared to the single jet on this surface, with a minimal increase in pressure drop. The jet array coupled with the hybrid enhancement dissipates a maximum heat flux of 205.8W/cm2 (heat input of 1.33kW) at a flow rate of 1800ml/min (corresponding to a jet diameter-based Reynolds number of 7800) with a pressure drop incurred of only 10.9kPa. Compared to the single jet impinging on the smooth flat surface, the array of jets on the coated pin-fin enhanced surface increased CHF by a factor of over four at all flow rates.
    No preview · Article · Mar 2015 · Journal of Heat Transfer
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    ABSTRACT: Increasingly stringent fuel economy and emissions regulations alongside efforts to reduce oil dependence have accelerated the global deployment of advanced vehicle technologies. In recent years, original equipment manufacturers (OEMs) and consumers have generally been successful in mutually deploying cleaner vehicle options with little sacrifice in cost, performance or overall utility. Projections regarding the challenges and impacts associated with compliance with mid- and long-term targets in the U.S., however, incur much greater uncertainty. The share of existing new vehicles that is expected to comply with future regulations, for example, falls below 10% by 2020. This article explores advanced technologies that result in reduced fuel consumption and emissions that are commercially available in 2014 Model Year compact and midsize passenger cars. A review of the recent research literature and publicly available cost and technical specification data addressing correlations between incremental cost and fuel economy is presented. This analysis reveals that a 10% improvement in the sales-weighted average fuel economy of passenger cars has been achieved between 2011 and 2014 at costs that are at or below levels anticipated by the regulations by means of reductions in weight, friction, and drag; advancements in internal combustion efficiency; turbocharging combined with engine downsizing; transmission upgrades; and the growth of hybrids. Benefit-cost analyses performed on best-selling models in the selected classifications reveal that consumers thus far are not substantially incentivized to purchase fuel economy. Under baseline conditions, benefit-cost ratios are above a breakeven value of unity for only 6 of 28 models employing improved fuel-economy technologies. Sales-weighted data indicate that the “average” consumer that elected to invest in greater fuel economy spent $1490 to realize a 17.3% improvement in fuel economy, equating to estimated savings of $1070. Thus savings were, on average, insufficient to cover technology costs in the baseline scenario. However, a sensitivity analysis reveals that a majority of new technologies become financially attractive to consumers when average fuel prices exceed $5.60/gallon, or when annual miles traveled exceed 16,400. The article concludes with techno-economic implications of the research on future fuel economy regulations for stakeholders. In general, the additional cost consumers incur in exchange for a given level of fuel economy improvement in the coming years will need to be steadily reduced compared to current levels to ensure that the expected benefits of fuel savings are financially warranted.
    No preview · Article · Mar 2015 · Applied Energy
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    Xuemei Chen · Justin A. Weibel · Suresh V. Garimella
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    ABSTRACT: Hierarchical micro/nanostructured super­hydrophobic surfaces are developed to control the nucleation, growth, and departure of condensate droplets on copper substrates. The microscale roughness elements on the hierarchical surface yield a 40% higher droplet growth rate and a 300% increase in cumulative droplet departure volume as compared to superhydrophobic surfaces with nanostructures alone.
    Full-text · Article · Feb 2015 · Advanced Materials Interfaces

Publication Stats

8k Citations
543.14 Total Impact Points

Institutions

  • 2000-2016
    • Purdue University
      • • School of Mechanical Engineering
      • • Cooling Technologies Research Center (CTRC)
      ウェストラファイエット, Indiana, United States
  • 2010
    • Sony Corporation
      Edo, Tōkyō, Japan
    • Tsinghua University
      Peping, Beijing, China
  • 1993-2001
    • University of Wisconsin - Milwaukee
      • Department of Mechanical Engineering
      Milwaukee, Wisconsin, United States