Suresh V. Garimella

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

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Publications (368)530.03 Total impact

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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.
    International Journal of Heat and Mass Transfer 09/2015; 88. DOI:10.1016/j.ijheatmasstransfer.2015.04.038 · 2.52 Impact Factor
  • Xuemei Chen, Justin A. Weibel, Suresh V. Garimella
    Journal of Heat Transfer 08/2015; 137(8). DOI:10.1115/1.4030451 · 2.06 Impact Factor
  • 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.
    International Journal of Heat and Mass Transfer 07/2015; 86. DOI:10.1016/j.ijheatmasstransfer.2015.02.067 · 2.52 Impact Factor
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    E-Pubs Purdue, Hao Wang, Zhenhai Pan, Suresh V. Garimella
  • Journal of Solar Energy Engineering 06/2015; 137(3):031012. DOI:10.1115/1.4029453 · 1.13 Impact Factor
  • Journal of Heat Transfer 03/2015; 137(7):071501. DOI:10.1115/1.4029969 · 2.06 Impact Factor
  • Suchismita Sarangi, Justin A. Weibel, Suresh V. Garimella
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    ABSTRACT: The enhancement of pool boiling heat transfer by copper-particle surface coatings is experimentally investigated, using the wetting dielectric fluid FC-72. In one technique, loose copper particles are placed on a heated copper surface to provide additional vapor nucleation sites in the cavities formed at particle-surface and particle–particle contact points, thereby enhancing boiling performance over a polished surface. This ‘free-particle’ technique is benchmarked against the more traditional technique of sintering a fixed layer of copper particles to the surface to enhance boiling heat transfer performance. The effect of particle size on the heat transfer performance is studied for particle diameters ranging from 45 μm to 1000 μm at a constant coating layer thickness-to-particle diameter ratio of approximately 4. The parametric trends in the boiling curve and the critical heat flux are compared between the two techniques, and the dominant boiling mechanisms influencing these trends are compared and contrasted. High-speed visualizations are performed to qualitatively assess the boiling patterns and bubble departure size/distribution, and thus corroborate the trends observed in the boiling curves. The measured wall superheat is significantly lower with a sintered coating compared to the free-particle layer for any given particle size and heat flux. Performance trends with respect to particle size, however, are remarkably similar for both enhancement techniques, and an optimum particle size of ∼100 μm is identified for both free particles and sintered coatings. The free-particle technique is shown to offer a straightforward method to screen the boiling enhancement trends expected from different particulate layer compositions that are intended to be subsequently fabricated by sintering.
    International Journal of Heat and Mass Transfer 02/2015; 81. DOI:10.1016/j.ijheatmasstransfer.2014.09.052 · 2.52 Impact Factor
  • Xuemei Chen, Justin A. Weibel, Suresh V. Garimella
    Advanced Materials Interfaces 02/2015; 2(3). DOI:10.1002/admi.201400480
  • S H Taylor, S V Garimella
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    ABSTRACT: A sensor concept is developed and analyzed for in situ characterization of a thin dielectric layer. An array of long, planar electrodes is flush-mounted into opposing faces of two substrates on either side of the dielectric layer. The substrates are oriented such that the lengthwise dimensions of the opposing electrodes are orthogonal. Capacitance is measured between single electrode pairs on opposite substrates while all other electrodes are grounded. The electric field between the active electrodes is sharply focused at their crossing point, resulting in high sensitivity to void content in a square detection zone of the dielectric layer. For a fixed interfacial gap size, direct proportionality of the capacitance with void fraction within the detection zone is poor for high electrode-to-electrode spacing on the substrates, but improves dramatically as this spacing is reduced. Three methods of deriving a simulation-based sensitivity response of measured capacitance to any arbitrary two-dimensional void geometry are investigated. The best method requires data from simulations of an empty air gap and a TIM-filled gap, and uses a reduced-order superposition technique to predict the normalized capacitance value obtained for any void geometry to within 10% of that predicted by a high-fidelity direct simulation. The sensing technique is demonstrated using manually introduced voids of 250 µm–2000 µm diameter in a 254 µm thick interface material layer with a dielectric constant of 4.7. The relationship of the capacitance to the void fraction is shown to fall within the predicted bounds.
    Measurement Science and Technology 01/2015; 26(1). DOI:10.1088/0957-0233/26/1/015601 · 1.35 Impact Factor
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    ABSTRACT: X-ray micro computed tomography (μ-CT), originally developed for non-destructive biomedical imaging, is increasingly being employed in areas as diverse as materials characterization and reverse engineering. The technique employs computer processed X-rays to produce tomographic images or slices of specific regions of the object under investigation.
    Energy Procedia 12/2014; 45:645-652. DOI:10.1016/j.egypro.2014.01.069
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    ABSTRACT: A single molten-salt thermocline tank is a low-cost alternative to conventional multiple-tank systems for concentrating solar power thermal energy storage. Thermocline tanks are typically composed of molten salt and a filler material that provides sensible heat capacity at reduced cost; such tanks are referred to as a dual-media thermocline (DMT). However, inclusion of quartzite rock filler introduces the potential for mechanical ratcheting of the tank wall during thermal cycling. To avoid this potential thermomechanical mode of failure, the tank can be operated solely with molten salt, as a single-medium thermocline (SMT) tank. In the absence of a filler material to suppress formation of tank-scale convection eddies, the SMT tank may exhibit undesirable internal fluid flows in the tank cross-section. The performance of DMT and SMT tanks is compared under cyclic operation, assuming adiabatic external wall boundary conditions. A computational fluid dynamics model is used to solve for the spatial temperature and velocity distributions within the tank. For the DMT tank, a two-temperature model is used to account for the non-thermal equilibrium between the molten salt and the filler material, and Forchheimer's extension of Darcy's Law is added to the porous-medium formulation of the laminar momentum equation. The governing equations are solved numerically using a finite volume approach. For adiabatic external boundaries, the SMT tank yields a percentage point increase in the first and second law efficiencies relative to the DMT tank. Future work is needed to compare the thermocline tank designs with respect to capital cost and storage performance under non-adiabatic wall boundaries.
    Energy Procedia 12/2014; 49:916-926. DOI:10.1016/j.egypro.2014.03.099
  • Zhenhai Pan, Justin A. Weibel, Suresh V. Garimella
    Numerical Heat Transfer Applications 12/2014; 67(1). DOI:10.1080/10407782.2014.916109 · 1.85 Impact Factor
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    ABSTRACT: We investigate hitherto-unexplored flow characteristics inside a sessile droplet evaporating on heated hydrophobic and superhydrophobic surfaces and propose the use of evaporation-induced flow as a means to promote efficient "on-the-spot" mixing in microliter-sized droplets. Evaporative cooling at the droplet interface establishes a temperature gradient that induces buoyancy-driven convection inside the droplet. An asymmetric single-roll flow pattern is observed on the superhydrophobic substrate, in stark contrast with the axisymmetric toroidal flow pattern that develops on the hydrophobic substrate. The difference in flow patterns is attributed to the larger height-to-diameter aspect ratio of the droplet (of the same volume) on the superhydrophobic substrate, which dictates a single asymmetric vortex as the stable buoyancy-induced convection mode. A scaling analysis relates the observed velocities inside the droplet to the Rayleigh number. On account of the difference in flow patterns, Rayleigh numbers, and the reduced solid-liquid contact area, the flow velocity is an order of magnitude higher in droplets evaporating on a superhydrophobic substrate as compared to hydrophobic substrates. Flow velocities in all cases are shown to increase with substrate temperature and droplet size: The characteristic time required for mixing of a dye in an evaporating sessile droplet is reduced by ∼8 times on a superhydrophobic surface when the substrate temperature is increased from 40 to 60 °C. The mixing rate is ∼15 times faster on the superhydrophobic substrate compared to the hydrophobic surface maintained at the same temperature of 60 °C.
    Physical Review E 12/2014; 90(6-1):062407. DOI:10.1103/PhysRevE.90.062407 · 2.33 Impact Factor
  • Stephen H. Taylor, Suresh V. Garimella
    Journal of Electronic Packaging 12/2014; 136(4):041008. DOI:10.1115/1.4028075 · 0.65 Impact Factor
  • Matthew J. Rau, Ercan M. Dede, Suresh V. Garimella
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    ABSTRACT: Local single- and two-phase heat transfer distributions are measured under a confined impinging jet issuing from a cross-shaped orifice. Spatially resolved temperature maps and convection coefficients resulting from the impinging flow are obtained via infrared imaging of a thin-foil heat source. The cooling patterns in single- and two-phase operation are explained by an accompanying numerical investigation of the fluid flow issuing from the orifice; computed velocity magnitudes and turbulence intensities are presented. In single-phase operation, the coolest surface temperatures correspond to areas with high liquid velocities. High velocities and developing turbulence are also shown to increase convective heat transfer along the diagonal outflow directions from the impinging jet. During two-phase transport, boiling preferentially begins in regions of low velocity, providing enhanced heat transfer in the areas least affected by the impingement. The cross-shaped orifice achieves local heat transfer coefficients that exceed the stagnation-point value of a circular jet of equivalent open orifice area by up to 1.5 times, while resulting in an increased pressure drop only 1.1 times higher than that of the circular jet.
    International Journal of Heat and Mass Transfer 12/2014; 79:432–436. DOI:10.1016/j.ijheatmasstransfer.2014.08.012 · 2.52 Impact Factor
  • Matthew J. Rau, Suresh V. Garimella
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    ABSTRACT: Confined jet impingement with boiling offers unique and attractive performance characteristics for thermal management of high heat flux components. Two-phase operation of jet impingement has been shown to provide high heat transfer coefficients while maintaining a uniform temperature over a target surface. This can be achieved with minimal increases in pumping power compared to single-phase operation. To investigate further enhancements in heat transfer coefficients and increases in the maximum heat flux supported by two-phase jet impingement, an experimental study of surface enhancements is performed using the dielectric working fluid HFE-7100. The performance of a single, 3.75 mm-diameter jet orifice is compared across four distinct copper target surfaces of varying enhancement scales: 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. The heat transfer performance of each surface is compared in single-and two-phase operation at three volumetric flow rates ( 450 ml/min, 900 ml/min, and 1800 ml/min); area-averaged heat transfer parameters and pressure drop are reported. The mechanisms resulting in enhanced performance for the different surfaces are identified, with a special focus on the coated pin fins. This hybrid surface showed the best enhancement of all those tested, and resulted in an extension of critical heat flux (CHF) by a maximum of 2.42 times compared to the smooth flat surface at the lowest flow rate investigated; no increase in the overall pressure drop was measured.
    Journal of Heat Transfer 10/2014; 136(10):101503. DOI:10.1115/1.4027942 · 2.06 Impact Factor
  • Susan N. Ritchey, Justin A. Weibel, Suresh V. Garimella
    09/2014; 5(3):95-108. DOI:10.1260/1759-3093.5.3.95
  • Stephen H Taylor, Suresh V Garimella
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    ABSTRACT: A near-field focusing capacitance sensor consists of an array of long, coplanar electrodes offset by a small interface gap from an identical orthogonal array of electrodes. The sensor may be used to characterize permittivity inhomogeneities in thin dielectric layers. The sensor capacitance measurements represent a tessellated matrix of integral-averaged values describing void content in a series of zones corresponding to the electrode crossing points (junctions) of the sensor. The sensor does not lend itself to computed tomography because the individual capacitance measurements do not represent overlapping regions of sensitivity. An evolving level-set algorithm is proposed to reconstruct a binary permittivity distribution. A mathematical construct, based on the physics of inverse-square fields, is used to approximately reconstruct shape features too small to be captured by the raw measurements. The method accommodates the non-uniform area-sensitivity of the junction capacitance measurement. Effective use of the algorithm requires active management of the convergence criterion and evolution rate. The algorithm is demonstrated on a series of phantoms as well as measurements of a voided dielectric thermal interface material using a near-field focusing sensor.
    Measurement Science and Technology 08/2014; 25(10):105602. DOI:10.1088/0957-0233/25/10/105602 · 1.35 Impact Factor
  • Zhenhai Pan, Justin A Weibel, Suresh V Garimella
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    ABSTRACT: Prediction and manipulation of the evaporation of small droplets is a fundamental problem with importance in a variety of microfluidic, microfabrication, and biomedical applications. A vapor-diffusion-based model has been widely employed to predict the interfacial evaporation rate; however, its scope of applicability is limited due to incorporation of a number of simplifying assumptions of the physical behavior. Two key transport mechanisms besides vapor diffusion-evaporative cooling and natural convection in the surrounding gas-are investigated here as a function of the substrate wettability using an augmented droplet evaporation model. Three regimes are distinguished by the instantaneous contact angle (CA). In Regime I (CA ≲ 60°), the flat droplet shape results in a small thermal resistance between the liquid-vapor interface and substrate, which mitigates the effect of evaporative cooling; upward gas-phase natural convection enhances evaporation. In Regime II (60 ≲ CA ≲ 90°), evaporative cooling at the interface suppresses evaporation with increasing contact angle and counterbalances the gas-phase convection enhancement. Because effects of the evaporative cooling and gas-phase convection mechanisms largely neutralize each other, the vapor-diffusion-based model can predict the overall evaporation rates in this regime. In Regime III (CA ≳ 90°), evaporative cooling suppresses the evaporation rate significantly and reverses entirely the direction of natural convection induced by vapor concentration gradients in the gas phase. Delineation of these counteracting mechanisms reconciles previous debate (founded on single-surface experiments or models that consider only a subset of the governing transport mechanisms) regarding the applicability of the classic vapor-diffusion model. The vapor diffusion-based model cannot predict the local evaporation flux along the interface for high contact angle (CA ≥ 90°) when evaporative cooling is strong and the temperature gradient along the interface determines the peak local evaporation flux.
    Langmuir 08/2014; 30(32). DOI:10.1021/la501931x · 4.38 Impact Factor
  • Susmita Dash, Aditya Chandramohan, Suresh V. Garimella
    Journal of Heat Transfer 08/2014; 136(8):080917. DOI:10.1115/1.4027535 · 2.06 Impact Factor

Publication Stats

6k Citations
530.03 Total Impact Points

Institutions

  • 2000–2015
    • 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
  • 2008
    • University of Houston
      • Department of Mechanical Engineering
      Houston, TX, United States
  • 2003
    • Technische Universität Dresden
      Dresden, Saxony, Germany
    • Georgia Institute of Technology
      Atlanta, Georgia, United States
  • 1993–2001
    • University of Wisconsin - Milwaukee
      • Department of Mechanical Engineering
      Milwaukee, Wisconsin, United States