Jackson Marcinichen - Academia.edu (original) (raw)

Papers by Jackson Marcinichen

Dynamic Modeling of On-Chip Two-Phase Cooling System with Multiple Micro-Evaporators in Parallel Flow

WORLD SCIENTIFIC eBooks, Aug 30, 2015

Hybrid Two-Phase Cooling Technology For Next-Generation Servers: Thermal Performance Analysis

This paper advances the work presented at ITHERM 2020 where a novel passive two-phase technology ... more This paper advances the work presented at ITHERM 2020 where a novel passive two-phase technology was introduced for more efficient cooling of datacenters compared to air-based cooling solutions (e.g. In-Room, In-Row, etc.). The proposed hybrid two-phase cooling technology uses passive low-height thermosyphons to dissipate the heat generated by high power components inside the servers. The heat is then transferred to multiple rack-level thermosyphons, equipped with one or more overhead compact condensers, which in turn dissipate the total heat from the rack into a room-level water-based or air-based cooling loop. Air-cooling is still used for the low heat-generating components (e.g. memory units, secondary chips, etc.) to make the cooling technology cost effective.This study is focused on a thermal performance analysis of the hybrid two-phase cooling technology applied to a single server (2U HP ProLiant DL180 G6), where low-height thermosyphons are installed to cool the two CPUs, and the remaining server components are cooled via air in forced convection using server-level fans. The thermal performance of the low-height thermosyphons is extracted from previous experimental measurements carried out at Nokia Bell Labs and presented at ITHERM 2020. Additional measurements considering the effect of the refrigerant charge on the thermal resistance and associated chip case temperature are conducted. The air-cooling performance and flow distribution are investigated via CFD simulations performed in COMSOL that characterize the conjugate heat transfer between server components and cooling air. The experimental and numerical results presented here show that, at the maximum server IT load of 587 W, the hybrid two-phase technology ensures sufficient cooling for all the hardware components while significantly reducing the energy consumption of the fans. Specifically, the fan contribution is reduced from 24% (traditional air-cooling) to about 2% of the server effective IT load (hybrid two-phase cooling), demonstrating the potential of the proposed technology to scale existing hardware and build next-generation datacenters, while keeping low costs and being environmentally-friendly.

Experimental Characterization of Different Condenser Technologies in a Passive Two-Phase Cooling System for Thermal Management of Electronics

Passive two-phase, micro-channel cooling for thermal management of electronics represents an effi... more Passive two-phase, micro-channel cooling for thermal management of electronics represents an efficient and viable solution to augment conventional air-cooling systems with the potential for higher power dissipation densities, increased reliability, reduced power consumption and decreased noise levels. This paper focuses on the development of a novel thermosyphon-based cooling system for electronics. The target application is a telecommunications equipment shelf unit that comprises 18 circuit pack cards. The envisioned cooling system presented here is an infrastructure-independent, air-cooled thermosyphon loop consisting of an evaporator (cold plate), manufactured with 18 individual micro-channel zones (one per circuit pack card), and connected via riser and downcomer tubes to an air-cooled condenser. The total height of the thermosyphon loop, from mid-evaporator to mid-condenser, is approximately 50 cm. The main objective of this work is to assess the effect of different condenser technologies on the thermal-hydraulic performance of the thermosyphon; prior work examining the optimal design of the evaporator, riser and downcomer tubes has already been discussed in our previously published studies. A comprehensive experimental program was conducted to evaluate two different air-cooled condensers in a front-to-back air flow configuration: a single-pass, louvered-fin, flat-tube design and a multiple-pass, wavy-fin, circular-tube design. Thermosyphon experiments were carried out with R134a as the working fluid for filling ratios from 45% to 65%, imposed uniform and non-uniform heat loads from 102 W to 1023 W, fan speeds from 7302 min−1 to 15480 min−1, and fan tray configurations ranging from 5 to 7 fans. Test results demonstrate that the louvered-fin flat-tube condenser provides low liquid-side frictional pressure drops and thus high refrigerant mass flow rate in the loop, which is ideal for increasing power densities as it is more conservative with respect to dry-out phenomenon. On the other hand, the multiple-pass, wavy-fin, circular-tube condenser offers low thermosyphon thermal resistances in the entire region of heat loads, primarily due to the low air-side pressure drop.

Thermal Testing of Arrays of PHP Finned Plates for Enhanced Air-Cooling of Electronics

Pulsating Heat Pipe Fin Plates for Enhancing Natural and Forced Convection Cooling of Electronics: Experimental Campaign

2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm), May 31, 2022

Compact and Highly Thermal-Hydraulic Efficient Air-Cooled Closed Loop Thermosyphon Cooling System for High Intense Heat Load Dissipation of Future Microprocessors

A very compact air-cooled loop thermosyphon cooling system (LTS) was designed, prototyped and tes... more A very compact air-cooled loop thermosyphon cooling system (LTS) was designed, prototyped and tested for microprocessor cooling application. It was designed specifically for 2U servers and heat loads up to 400 W in a footprint area of 40 mm per 40 mm. The low pressure and low GWP working fluid R1233zd(E) was used. Tests were done for two ambient temperatures (22 °C and 40 °C) and included optimal charge determination as well as extensive tests at optimal charge. Values of performance ratio, simply defined as heat load divided by fan power consumption, higher than 30 were observed for the maximum heat load of 400 W. The experimental results were also used to validate JJ Cooling Innovation’s inhouse proprietary solver developed to design the LTS and results will be presented.

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

This paper advances the work presented at ITHERM 2019 in which a novel thermal technology has bee... more 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 and the previous papers published by the same authors, heat flux dissipation in telecom servers and high-performance computing servers is following an exponentially increasing trend in order to handle the new requirements of higher data transmission, data processing, data storage and massive device connectivity dictated by the next industrial revolution. This trend translates into the need for upgrading the capacity of existing servers and datacenter racks, as well as building new datacenters around the globe. The envisioned cooling technology, which will improve datacenter energy usage, is based on a novel combination of low-height thermosyphons operating in parallel to passively dissipate the heat generated by the servers and rack-level thermosyphons equipped with an overhead compact condenser, to dissipate the total power from the server rack to the room-level water cooling loop.The present paper is mainly focused on the experimental evaluation of the thermal performance of a 7-cm high liquid-cooled thermosyphon designed to cool a 2-U server with a maximum heat dissipation here of 200 W (but could have gone even higher) over a 4 x 4 cm2 pseudo-chip footprint. A new test setup and filling rig were designed at Nokia Bell Labs in order to accurately evaluate thermosyphon thermal performance over a wide range of heat loads, secondary side mass flow rates and inlet temperatures, using R1234ze(E) as the working fluid. A new extensive database was obtained, capturing the entire thermosyphon characteristic curve, expressed as total thermal resistance as a function of the power. Here, the experimental results are presented and discussed in detail, and they demonstrate that passive two-phase thermosyphon-based approach provides significant advantages in terms of cooling performance, energy efficiency and noise level compared to other datacenter cooling solutions available on the market or under development.

h i g h l i g h t s Novel dynamic modeling of a microchannel-based thermosyphon is presented/vali... more h i g h l i g h t s Novel dynamic modeling of a microchannel-based thermosyphon is presented/validated. A geometry is proposed/simulated for the retrofitting of a commercial 2U-server. Both stable and unstable solutions are found for the steady-state. A riser diameter increase of 30% led up to 60% increase in flow rate. The flow self-redistributes into the highest heat load CPU during parallel cooling.

Air-Cooled Closed Loop Thermosyphon Cooling System Experimental Campaign: Effects of Working Fluid, Heat Load and Air Flow Rate

2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm), May 31, 2022

Two-Phase Mini-Thermosyphon for Cooling of Datacenters: Experiments, Modeling and Simulations

Nowadays, datacenters heat density dissipation follows an exponential increasing trend that is re... more Nowadays, datacenters heat density dissipation follows an exponential increasing trend that is reaching the heat removal limits of the traditional air-cooling technology. Two-phase cooling implemented within a gravity-driven system represents a scalable and viable long-term solution for datacenter cooling in order to increase the heat density dissipation with larger energy efficiency and lower acoustic noise. The present article builds upon the 4-part set of papers presented at ITHERM 2016 for a 15-cm height thermosyphon to cool a contemporary datacenter cabinet, providing new test data over a wider range of heat fluxes and new validations of the thermal-hydrodynamics of our thermosyphon simulation code. The thermosyphon consists of a microchannel evaporator connected via a riser and a downcomer to a liquid-cooled condenser for the cooling of a pseudo-chip to emulate an actual server. Test results demonstrated good thermal performance coupled with uniform flow distribution for the new larger range of operating test conditions. At the maximum imposed heat load of 158 W (corresponding to a heat flux of 70 W cm−2) with a water inlet coolant at 20 °C, water mass flow rate of 12 kg h−1 and thermosyphon filling ratio of 78%, the pseudo mean chip temperature was found to be 58 °C and is well below the normal thermal limits in datacenter cooling. Finally, the in-house LTCM’s thermosyphon simulation code was validated against an expanded experimental database of about 262 data points, demonstrating very good agreement; in fact, the pseudo mean chip temperature was predicted with an error band of about 1 K.

Flow Boiling and Condensation within an Ultra-Compact Microchannel Heat Exchanger

WORLD SCIENTIFIC eBooks, May 18, 2018

Recent Advances in On-Chip Cooling Systems: Experimental Evaluation and Dynamic Modeling

Proceedings of the 15th International Heat Transfer Conference, 2014

Experimental Characterization of a Compact Thermosyphon Cooling System Operating with R1234ze(E) and R1233zd(E) Low-GWP Refrigerants

2022 21st IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm), May 31, 2022

Novel Air-Cooled Thermosyphon Cooling System for Desktop Computers

The trade-off between efficient cooling and low power consumption is a goal that has always been ... more The trade-off between efficient cooling and low power consumption is a goal that has always been very desirable in electronics cooling, especially nowadays that power densities of processing units are increasing. Conventional cooling solutions do not have the necessary cooling capacities for these power densities or require significant power consumption. In this study, a novel air-cooled thermosyphon cooling system for desktop computers is presented and experimentally tested. The thermosyphon comprises a vertical micro-channel cold plate as the evaporator and a horizontal air-cooled multiport coil as the condenser. The thermosyphon has a total height of 12 cm and operates with a fan speed of 1700 RPM. The working fluid selected for the thermosyphon loop is R1234ze(E), chosen for its advantageous thermophysical properties and nearly zero-GWP (Global Warming Potential). The test results presented in this paper aim to analyze thermosyphon’s thermal and hydraulic performance by studying the trends of thermal resistance and mass flow rate as a function of different operating conditions. The maximum heat rejection under safe conditions is 250 W, corresponding to a heat flux of about 18 W/cm2.

Experimental Validation and Design Simulations of a Passive Two-Phase Cooling System for Datacenters

Thermosyphon cooling systems represent the future of datacenter cooling, and electronics cooling ... more Thermosyphon cooling systems represent the future of datacenter cooling, and electronics cooling in general, as they provide high thermal performance, reliability and energy efficiency, as well as capture the heat at high temperatures suitable for many heat reuse applications. On the other hand, the design of passive two-phase thermosyphons is extremely challenging because of the complex physics involved in the boiling and condensation processes; in particular, the most important challenge is to accurately predict the flow rate in the thermosyphon and thus the thermal performance. This paper presents an experimental validation to assess the predictive capabilities of JJ Cooling Innovation’s thermosyphon simulator against one independent data set that includes a wide range of operating conditions and system sizes, i.e. thermosyphon data for server-level cooling gathered at Nokia Bell Labs. Comparison between test data and simulated results show good agreement, confirming that the simulator accurately predicts heat transfer performance and pressure drops in each individual component of a thermosyphon cooling system (cold plate, riser, evaporator, downcomer (with no fitting parameters), and eventually a liquid accumulator) coupled with operational characteristics and flow regimes. In addition, the simulator is able to design a single loop thermosyphon (e.g. for cooling a single server’s processor), as shown in this study, but also able to model more complex cooling architectures, where many thermosyphons at server-level and rack-level have to operate in parallel (e.g. for cooling an entire server rack). This task will be performed as future work.

Experimental Analysis of the Condenser Design in a Thermosiphon System for Cooling of Telecommunication Electronics

IEEE Transactions on Components, Packaging and Manufacturing Technology, Jun 1, 2020

Passive two-phase cooling systems are an efficient and viable alternative to conventional air-coo... more Passive two-phase cooling systems are an efficient and viable alternative to conventional air-cooling schemes for thermal management of electronics due to their capability of dissipating higher power densities with lower power consumption and noise levels. This article aims to assess the performance of a novel two-phase air-cooled thermosyphon for cooling shelf-level telecommunications equipment that is designed with 18 line cards. In particular, the main objective is to investigate the effect of the condenser technology on the thermal-hydraulic performance of the cooling system. The thermosyphon consists of a multimicrochannel evaporator with 18 individual microchannel zones (one per card) connected to an air-cooled condenser via riser and downcomer tubes. The total height of the loop, from midevaporator to midcondenser, is approximately 50 cm. Two different condenser designs have been tested: a single-pass louvered-fin flat-tube condenser, and a multipass wavy-fin, circular-tube condenser. An extensive experimental campaign is performed to evaluate the performance of these two air-cooled condensers in a front-to-back airflow configuration. The experiments are carried out with R134a as the working fluid, varying filling ratios from 45% to 60%, and heat loads from 102 to 1023 W under uniform and nonuniform conditions. The influence of the air-side fan configuration is also investigated by varying the fans speed from 10 548 to 15 480 min−1 and by increasing the fan-tray height from 65 to 103 mm. The results demonstrate that the single-pass louvered-fin flat-tube condenser provides lower liquid-side frictional pressure drops and consequently higher refrigerant mass flow rate in the loop. This leads to a higher critical heat flux value, which is ideal for increasing power densities and limiting dry-out occurrence. On the other hand, the multiple-pass wavy-fin, condenser offers lower thermal resistances over a larger range of dissipated heat loads. This is mainly attributed to its lower air-side pressure drop.

Design of Passive Two-Phase Thermosyphons for Server Cooling

The main objective of this paper is to utilize an improved version of the simulator presented at ... more The main objective of this paper is to utilize an improved version of the simulator presented at InterPACK 2017 to design a thermosyphon system for energy-efficient heat removal from 2-U servers used in high-power datacenters. Currently, between 25% and 45% of the total energy consumption of a datacenter (this number does not include the energy required to drive the fans at the server-level) is dedicated to cooling, and with a predicted annual growth rate of about 15% (or higher) coupled with the plan of building numerous new datacenters to handle the “big data” storage and processing demands of emerging 5G networks, artificial intelligence, electrical vehicles, etc., the development of novel, high efficiency cooling technologies becomes extremely important for curbing the use of energy in datacenters. Notably, going from air cooling to two-phase cooling, not only enables the possibility to handle the ever higher heat fluxes and heat loads of new servers, but it also provides an energy-efficient solution to be implemented for all servers of a datacenter to reduce the total energy consumption of the entire cooling system. In that light, a pseudo-chip with a footprint area of 4 × 4 cm2 and a maximum power dissipation of 300 W (corresponding heat flux of about 19 W/cm2), will be assumed as a target design for our novel thermosyphon-based cooling system. The simulator will be first validated against an independent database and then used to find the optimal design of the chip’s thermosyphon. The results demonstrate the capability of this simulator to model all of the thermosyphon’s components (evaporator, condenser, riser and downcomer) together with overall thermal performance and creation of operational maps. Additionally, the simulator is used here to design two types of passive two-phase systems, an air- and a liquid-cooled thermosyphon, which will be compared in terms of thermal-hydraulic performance. Finally, the simulator will be used to perform a sensitivity analysis on the secondary coolant side conditions (inlet temperature and mass flow rate) to evaluate their effect on the system performance.

Two-phase liquid cooling system for electronics, part 1: Pump-driven loop

An experimental study to analyse the thermal performance of a two-phase pump-driven loop for elec... more An experimental study to analyse the thermal performance of a two-phase pump-driven loop for electronics cooling is presented, with the target application being a telecommunications equipment shelf having multiple circuit pack cards each dissipating several hundred Watts of power. The upward flow boiling heat transfer and pressure drop of R134a within an evaporator prototype fabricated with 18 individual microcooling zones to cool multiple electronics heat sources was investigated. The electronic heat sources were emulated by multiple copper heater blocks with embedded cartridge heaters, where each heat source was capable of dissipating more than 100 W, for a total power dissipation larger than 1800 W. Experimental results demonstrated the best cooling capability at a mass flow rate of 140 kg/h, uniform heat load of 1800 W to the 18 microcooling zones, system pressure of 600 kPa and inlet subcooling of 2 K in which the temperature difference between the evaporator and coolant inlet was 7.1 K with a uniform flow distribution within the evaporator.

International Journal of Refrigeration-revue Internationale Du Froid, May 1, 2016

Thermal performance of CO 2 gas coolers  Reduction in volume and working fluid charge  Methods ... more Thermal performance of CO 2 gas coolers  Reduction in volume and working fluid charge  Methods for supercritical CO 2 cooling  Effects of tube size, air volumetric flow, fin type and miscible oil concentration  Volume and refrigerant charge reduced by at least 14%