Publications by John Richard Thome

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Two-phase flow boiling of R245fa, R236fa, and R1234ze(E) in 100 × 100 μm2 parallel microchannels for cooling of future 3D-ICs has been investigated. Significant flow instabilities, back flow, and non-uniform flow distribution among the channels were observ ...

Multi-microchannel evaporators with flow boiling, used for cooling high heat flux devices, usually experience transient heat loads in practical applications. These transient processes may cause failure of devices due to a thermal excursion or poor local co ...

This paper advances the work presented at ITHERM 2019 in which a novel thermal technology has been introduced to cool servers and datacenter racks more efficiently compared to the traditional air-based cooling solutions. As reported in the state-of-the-art ...

This paper is the fourth part of the present study on two-phase mini-thermosyphon cooling. As mentioned in the first three parts, gravity-driven cooling systems using microchannel flow boiling can become a long-term scalable solution for cooling of datacen ...

A constructaltree-shaped microchannel network for maximizing the saturated critical heat flux in a disc-shaped planar body has been investigated. n(0) radial channels touch the center and n(p) channels touch the periphery. Designs with no pairing level (n( ...

The development of newer and more efficient cooling techniques to sustain the increasing power density of high-performance computing systems is becoming one of the major challenges in the development of microelectronics. In this framework, two-phase coolin ...

This research focuses on acquiring accurate flow boiling heat transfer data and flow pattern visualization for three refrigerants, R134a, R236fa and R245fa in a 1.030 mm channel. We investigate trends in the data, and their possible mechanisms, for mass fl ...

The scope of the present paper is to provide a brief and concise survey of the most recent experimental and computational studies aimed at characterizing local heat transfer in microchannels in flow boiling conditions. The significant developments in the measurement techniques have allowed detailed flow visualizations and 2D temperature fields to be obtained simultaneously, thus improving the understanding of the microscale flow boiling dynamics and thermal behavior. First of all, flow patterns are seen to

New tendencies envisage 3D Multi-Processor System-On-Chip (MPSoC) design as a promising solution to keep increasing the performance of the next-generation highperformance computing (HPC) systems. However, as the power density of HPC systems increases with the arrival of 3D MPSoCs, supplying electrical power to the computing equipment and constantly removing the generated heat is rapidly becoming the dominant cost in any HPC facility. Thus, both power and thermal/cooling implications play a major role in the

As data centers grow exponentially in size and number worldwide, it appears evident that more efficient and reliable cooling solutions are needed to reduce energy consumption and noise level significantly. Thermosyphon-based systems have been proven to res ...

This article presents new experimental critical heat flux results under saturated flow boiling conditions for a macro/microscale tube. The data were obtained in a horizontal 2.20-mm inside diameter stainless-steel tube with heating lengths of 361 and 154 m ...

Numerous characteristic trends and effects have been observed in published studies on two-phase micro-channel boiling heat transfer. While macro-scale flow boiling heat transfer may be decomposed into nucleate and convective boiling contributions, at the micro-scale the extent of these two important mechanisms remains unclear. Although many experimental studies have proposed nucleate boiling as the dominant micro-scale mechanism, based on the strong dependence of the heat transfer coefficient on the heat fl

This article presents experimental results of heat transfer from two different studies [1, 2] for horizontal flow boiling inside smooth copper tubes with different refrigerants. The main goal of this study was to verify the influence of the saturation temperature on the heat transfer coefficient. The experimental tests were carried for refrigerants R-134a, R-22 and R-404A, at saturation temperatures ranging from 5 to 20°C for two tubes of 12.7 and 13.84 mm ID and three heat fluxes of 5, 7.5 and 17.5 kW/m2.

Curved channels in the form of bends are encountered in many industrial two-phase flow applications, such as U-bends in air-conditioning and refrigeration evaporators and condensers. For engineering design purposes, the evaluation of the pressure loss in t ...

This article highlights the advantages of on-chip microchannel cooling technology, based on first-and second-law analysis and experimental tests on two types of cooling cycles, the first driven by an oil-free liquid pump and the second by an oil-free vapor ...

Microstructured reactors (MSR) with characteristic dimensions below 100 μm are warranted to maintain close to isothermal conditions when carrying out quasi-instantaneous highly exothermic reactions. Unfortunately, such small dimensions increase the risk of clogging, create high pressure drop and are costly to number-up. The multi-injection (MI) MSR, where one of the reactants is added stepwise along the reactor length, allows working with larger dimensions (diameter >500 μm) while maintaining good temperatu

This paper proposes a novel concept for a loop thermosyphon cooling system, designed for the transistor module of a transformer. The thermosyphon uses a free convection cooled condenser, making the system completely passive, i.e. no energy consumption is n ...

Visual observations of two-phase regimes for R134a and R245fa flowing in 0.509 mm and 0.790 mm horizontal tubes are documented and compared to the predictions of the analytical flow regime models available in the literature. Annular flow was found to domin ...

Hot-spots are present in micro-electronics and are challenging to cool effectively. This paper presents highly nonuniform heat flux measurements obtained for a pseudo-CPU with 35 local heaters and temperature sensors cooled by a silicon multi-microchannel ...

Though microreactors provide high heat transfer rates, temperature profiles are formed in case of fast and highly exothermic reactions. A method based on non-intrusive infrared thermometry has been developed to track these profiles quantitatively with a resolution of 250 data points/cm(2) and a precision of 1 degrees C. By placing the microreactor at a pressure of 10(-2) mbar, convective heat losses are efficiently suppressed which assures well defined boundaries and reproducible results. The temperature pr

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Two-phase heat transfer and high-speed visualization of refrigerant flows in 100 × 100 μm2 silicon multi-microchannels

Thermal Response of Multi-Microchannel Evaporators During Flow Boiling of Refrigerants Under Transient Heat Loads With Flow Visualization

Experimental Characterization of a Server-Level Thermosyphon for High-Heat Flux Dissipations

Two-Phase Mini-Thermosyphon Electronics Cooling, Part 4: Application to 2U Servers

Constructal tree-shaped microchannel networks for maximizing the saturated critical heat flux

Flow Boiling Heat Transfer and Pressure Drops of R1234ze(E) in a Silicon Micro-pin Fin Evaporator

Flow boiling heat transfer of R134a, R236fa and R245fa in a horizontal 1.030mm circular channel

Microchannel Flow Boiling Heat Transfer, Update on the Latest Experimental and Numerical Contributions

Towards Thermally-Aware Design of 3D MPSoCs with Inter-Tier Cooling

Implementation of Passive Two-Phase Cooling to an Entire Server Rack

Critical Heat Flux of R134a and R245fa Inside Small-Diameter Tubes

Mechanisms Of Boiling In Microchannels: Critical Assessment

INFLUENCE OF THE SATURATION TEMPERATURE ON THE HEAT TRANSFER COEFFICIENT FOR FLOW BOILING INSIDE HORIZONTAL SMOOTH TUBES

Two-Phase Pressure Drops in Adiabatic Horizontal Circular Smooth U-Bends and Contiguous Straight Pipes (RP-1444)

Advances in Electronics Cooling

Intensification of highly exothermic fast reaction by multi-injection microstructured reactor

Experimental Performance of Completely Passive Single and Recirculating Loop Thermosyphon Cooling Systems using Low GWP R1234ze and R1234yf

Characterization and prediction of two-phase flow regimes in miniature tubes

On-Chip Two-Phase Cooling with Refrigerant 85 mu m-Wide Multi-Microchannel Evaporator Under Hot-Spot Conditions

Infrared imaging of temperature profiles in microreactors for fast and exothermic reactions