Liquid Coolant Research Articles

Thermal management improvement in electric vehicles through design optimization of coolant distributor valves

On battery electric vehicles a precise control of heat flows is required for passenger comfort and for both performance and safety of battery packs. This is typically achieved with a thermal management system which employs some type of liquid coolant to transfer heat. Coolant distributor valves are used to regulate coolant flows through the exchangers, for example to recover heat from hot sources, thus to increase vehicle energy efficiency. The development of this type of component is high-priced and the design is generally complex since several operating functions and manufacturing constraints should be satisfied. Despite this complexity and the positive impact such valves have on the thermal management of electric vehicles, a few works are currently available in the literature on design procedures for this component, where only a partial overview of the topic is provided and a comprehensive design methodology considering the effective operating conditions is still missing. In this work we construct a physical model of the valve for torque, internal leakage and pressure drop, and we build an optimization procedure to improve the global performance of the valve. We compare the obtained designs with a simpler approach that optimizes performance parameters independently and we show that designs which severely under-perform with respect to the uncontrolled performance parameters can be produced if an over-simplified design approach is followed. We then show with a global vehicle thermal model that the impact of valve design on global vehicle performance crucially depends on the thermal exchanges at vehicle level and, thus, on its operating conditions. In particular, the impact is considerable when mixing of cold and hot flows through the valve occurs. For a specific example vehicle evaluated in a type-3a cycle of the Worldwide Harmonized Light Vehicle Test Procedure, a valve determined with the proposed optimization procedure allows us to obtain in this condition an increase of about 1 km in the vehicle driving range with respect to a valve defined with the simpler approach.

Simulations-based investigation of the effectiveness of fire suppression techniques for safe, large-scale storage of Li-ion batteries

Thermal runaway and subsequent fire in Li-ion cells and battery packs is of much concern in the safety of practical electrochemical energy storage systems. While much of the past work in this direction has focused on single cells or small packs, there is a relative lack of understanding of thermal runaway related fire and fire suppression strategies for large-scale systems, for example in storage and transportation of Li-ion cells. This work presents a simulations-based investigation of strategies for effective prevention and suppression of thermal runaway propagation and resulting fire in pallets containing a large number of Li-ion cells. The impact of location, orientation and flowrate in sprinklers supplying a liquid coolant is quantitatively investigated. It is shown that a minimum flowrate is needed for effective fire containment, beyond which, additional flowrate does not offer much incremental benefit. The orientation of sprinklers with respect to the trigger pallet undergoing thermal runaway is found to strongly impact the effectiveness of fire suppression. Fire suppression in the case of vertically stacked pallets is also investigated. Interesting synergistic effects involving a combination of liquid coolant along with one or more suppressant gases is demonstrated. The key output of this work is a computational model that quantitatively predicts the effectiveness of fire suppression techniques for battery transportation and storage. Results presented here offer a fundamental understanding of an important practical problem in battery-based energy storage. Results may form the basis of design and optimization to ensure the safety of large-scale storage and transportation of Li-ion cells.

Two-Phase Liquid Cooling for High-Power Microelectronics via Embedded Micro-Pin Fin Heat Sink

Two-Phase Liquid Cooling for High-Power Microelectronics via Embedded Micro-Pin Fin Heat Sink

Sensitivity Analysis and Optimization of a Liquid Cooling Thermal Management System for Hybrid Fuel Cell Aircraft

The objective of this work is to perform a comprehensive system analysis of a liquid-cooling thermal management system for a hybrid-electric aircraft using fuel cells for general aviation by sizing and optimizing the system with respect to a given objective. A sensitivity analysis on the different design parameters and model assumptions is also performed and their impact on the aircraft and its performances will be assessed. Firstly, the case study is defined and an optimization is run with some initial assumptions leading to a feasibility study for the implementation of this system. The sensitivity analysis is then undergone for the chosen coolant type and fuel cell stack temperature selected after the first optimization. Incorporating the findings of this analysis, a second optimization is run on the thermal management system with improved inputs in order to demonstrate a scenario with reduced penalty on the aircraft. Preliminary results show that implementing this hybrid propulsion system along with its thermal management is feasible with a reduction in payload and range. In addition, it can be concluded that initial assumptions and design choices are shown to have a significant impact on the system’s sizing and should be considered in aircraft sizing design loops.

The effect of liquid channels and cold plates on the performance of hybrid thermal management strategies for cylindrical Li-ion cells

In this paper, phase change material (PCM) based hybrid thermal management strategies are proposed for cylindrical Lithium-ion battery modules. Experimental and numerical studies are conducted to analyze the proposed strategies at a high discharge rate of 7 C. Three different types of thermal management configurations are developed. In all the configurations primary coolant is the PCM and secondary coolants are liquid and air. In one of the configuration vertical liquid coolant channels are placed between the PCM and airflow at the top of the cells. Whereas, in the two configurations different designs of cold plates are utilized in place of liquid channels. The experimental studies are conducted to obtain the temperature and heat flux profiles of the battery module. Moreover, a numerical model is developed and validated using the experimental data obtained. Using the numerical model, the thermal performance of the battery module was obtained for the proposed strategies. Based on the results, the maximum temperature of the battery module was limited to 29.1 °C and a high temperature uniformity was achieved by the end of the discharge cycle with the temperature difference limited to 1.2 °C. Additionally, the proposed hybrid thermal management strategy was capable of maintaining the required optimal thermal operating conditions without changing the phase of the PCM. Furthermore, it eliminates the requirement of a pump and reservoir since there is no flow of liquid within the battery module. This reduces the energy required for the operation of the thermal management system, thereby increasing the available energy for propulsion. Additionally, the developed strategy also increases the safety of the battery modules as it is capable of maintaining the required thermal environment in high discharge rates up to 7 C.

A thermoelectric cloud chamber: I. Redesign and operation

Developed by CTR Wilson, the cloud chamber was among the most important experimental apparatuses for observing nuclear phenomena in the first half of the twentieth century. Currently, cloud chambers are used as a didactic resource to teach radiation-matter interactions and other Nuclear Physics phenomena. This paper presents the construction of an electrically cooled cloud chamber. This device enables the observation of several nuclear physics phenomena in places where dry ice and liquid coolants are unavailable. The apparatus comprises a cooling unit based on thermoelectric modules and high-performance heat sinks. The first tracks are observable within 2 min after the instrument is turned on, and it can continue working for long periods, provided that alcohol is replaced. The device enabled the observation of numerous interactions between ionizing radiation and matter using natural and commercial radiation sources.

FeNi steel alloys under effect of molten lead liquid at high temperature 750℃: A molecular dynamics simulation study

Materials that have superior properties are indispensable for technological applications. Steel that has strong, heat- resistant, corrosion-resistant properties is indispensable for application in the design of liquid lead metal-cooled nuclear reactors. One of the steels that need to be studied for superior properties is FeNi alloy steel. In this study, the influence of FeNi steel composition was studied using computational methods of simulating molecular dynamics. The exact composition of FeNi steel to be able to work in liquid lead reactor coolant was analyzed using the CNA (common neighbor analysis) method. Molecular dynamics simulation uses the MOLDY program while the calculation of CNA values uses the OVITO program. From the simulation results, it can be known the effectiveness of variations in Fe and Ni composition that are able to produce the most stable FeNi alloy steel from the influence of liquid lead metal corrosion.

Heat Transfer Performance of Copper Foam-Based Vapor Chamber Composite Liquid Cooling System Under Double-Sided Heating

Heat Transfer Performance of Copper Foam-Based Vapor Chamber Composite Liquid Cooling System Under Double-Sided Heating

Lithium Battery Thermal Management Based on Lightweight Stepped-Channel Liquid Cooling

Abstract This study proposes a stepped-channel liquid-cooled battery thermal management system based on lightweight. The impact of channel width, cell-to-cell lateral spacing, contact height, and contact angle on the effectiveness of the thermal control system (TCS) is investigated using numerical simulation. The weight sensitivity factor is adopted to evaluate the effect of TCS weight (mTCS) on the maximum temperature (Tmax) of battery pack. Results suggest that the channel width plays the most critical role, followed by cell-to-cell lateral spacing and contact angle, while the contact height has minimal influence. Four parameters that affect the thermal balance performance of battery pack, including the number of channels, and baffles, baffle angle, and coolant inlet velocity, are presented using orthogonal experiment. Results indicate that the number of channels and baffle angle have a significant influence on the thermal balance of battery pack, while thermal performance is largely insensitive to coolant inlet velocity and the number of baffles. Based on the analysis stated in this work, an improved design of the TCS is presented that reduces weight by 54.08% while increasing Tmax only by 2.52 K.

Atomistic modelling of the Pb-Bi system from a constructed bond order potential

Lead-bismuth eutectic (LBE) alloys are currently considered one of the most promising liquid metal coolants for fast reactors, and especially accelerator-driven systems (ADS). An analytical bond-order potential (BOP) of Pb-Bi has been constructed to account for the electronic interactions and angular contribution of Pb-Bi system. The newly developed BOP has been validated to show a better performance than the Pb-Bi potentials already published in the literature. Molecular dynamics simulations based on current BOP has been adopted to investigate various properties of Pb-Bi binary system. It accurately predict the heats of formation, density, and thermal expansion coefficient of liquid LBE at 700 K. The diffusion coefficient and viscosity of liquid Pb44.5Bi55.5 are calculated, which are in good agreement with experimental observations in the literature. These findings provide a foundation for future design of Pb-Bi eutectic alloys for use in ADS and heavy-metal-cooled fast nuclear reactors.

Thermodynamic features of corrosion processes in liquid lead coolant in the presence of dissolved oxygen

In this work, the thermodynamic formalism of the law of acting masses is used to analyze the chemical equilibrium in a lead-based liquid metal solution in the case when iron and oxygen are present in the melt as impurities. The calculations were carried out using iron as an example, since it is this chemical element that is the main component of steels, which are currently regarded as the most promising container material for lead liquid-metal systems. The technology for controlling oxygen activity comes down to the fact that while maintaining the required oxygen concentration, lead becomes less chemically aggressive towards iron. By ensuring the constant required amount of oxygen in the liquid lead coolant, it is possible to maintain the basis of protective films on the surface of steel, which include iron and chromium oxides.

A comparison of neutronic studies on 400 MW thermal fast reactor with modified CANDLE burn-up schemes using helium gas, lead bismuth eutectic and liquid sodium coolants

A comparison of neutronic studies on 400 MW thermal fast reactor with modified CANDLE burn-up schemes using helium gas, lead bismuth eutectic and liquid sodium coolants

A comparison of neutronic studies on 400 MW thermal fast reactor with modified CANDLE burn-up schemes using helium gas, lead bismuth eutectic and liquid sodium coolants

A comparison of neutronic studies on 400 MW thermal fast reactor with modified CANDLE burn-up schemes using helium gas, lead bismuth eutectic and liquid sodium coolants

CFD Analysis of using Deionized Water in Radiator to Enhance the Efficiency for Sustainable Growth

Conventional liquid coolant used in automotive radiators is often used as an engine coolant. Heating systems in automotive air chambers are commonly used to cool circulating fluids, usually water or an aqueous combination of antifreeze agents such as ethylene glycol (EG). This study examines the benefits and issues of the usage of deionized water in all radiators. Deionized (DI) water has received attention as a possible alternative to chemical coolants generally used in automobile air conditioners. Automotive engineers are addressing the demanding situations of intense freezing by developing special garage systems to optimize engine overall performance and limit environmental impact. Compared to conventional refrigerants, the usage of deionized water has lesser environmental consequences, consisting of decreased corrosion and mineral production, which extends radiator lifestyles and improves cooling efficiency. Moreover, DI-water poses several challenges, which include the capability to freeze and compatibility with some radiator materials. Ultimately, this study investigates using deionized water as a refrigerant while used in radiators inside the inlet water. Additionally, it explores the impact of deionized water on engine performance, durability, heat transfer overall performance, corrosion resistance, and potential overheating, at the same time as additionally addressing environmental problems.

Reduction of precise machining centre column thermal deformations caused by changes in ambient temperature by means of liquid cooling

This paper describes various internal cooling methods and conditions aimed at reducing the displacements of the vertical jig centre column as an isolated unit caused by fluctuations in machining room temperature. The column's internal walls with horizontal and vertical ribs were cooled by the flow of liquid coolant from top to bottom. The cooling process was studied changing the rate of coolant flow and the method of flow generation. The interactions between the thermal phenomena occurring in the column and the conditions prevailing in the machine tool operating room and those occurring in the column areas cooled by the forced flow of liquid coolant are discussed. The FEA Abaqus System and numerical simulations were used to study the heat transfers and to accurately model the displacements. The results of the computations were experimentally validated in industrial operating conditions. On the basis of this study a precise model of the behaviour of the column in cooling conditions was created and the effectiveness of the considered ways of cooling the ribbed internal walls of the jig centre column was evaluated.It has been shown that the division of the column channel into several sections and the spraying of cooling liquid in combination with gravity flow significantly increases the cooling efficiency.

Investigation of Liquid Cooling Plate for Server CPUs Based on Topology Optimization

Investigation of Liquid Cooling Plate for Server CPUs Based on Topology Optimization

Comparison of the Peltier Effect Cooled Liquid Cooling System Developed for Computers Operating in Harsh Environment Conditions with the Fan Cooling System

Günümüzde kullanım alanları artan bilgisayar sistemleri çeşitli sorunları da beraberinde getirmiştir. Yüksek işlem gücü elde etmek için işlemcilerin elektronik bileşenleri daha sıkı yapılar haline getirilmektedir. Bu durumda ısının uzaklaştırılması önemli bir sorundur. Yarıiletken malzemelerin sıcaklıklarının artması daha yüksek güç tüketimlerine ve kararlı yapılarının bozulmasına sebep olmaktadır. Bilgisayar işlemcilerinin soğutulması amacıyla geliştirilen fanlı soğutma sistemleri bilgisayarın bulunduğu ortamın toz ve sıcaklık gibi çevresel şartlarından etkilenmektedir. Klimalı soğutma sistemlerinin çevreye zararlı gazlar yayması bilgisayar soğutma sistemlerinin geliştirilmesinde araştırmacıları yeni yöntemlere yönlendirmiştir. Bu çalışmada; peltier etki ile soğutulan sıvı soğutma sisteminin, fanlı soğutma sistemine göre 2511 MHz saat hızında %40, 2745 MHz saat hızında %24 oranında soğutma verimliliği sağladığı görülmüştür. Yapılan deneylerde peltier etkisi ile soğutulan sıvı soğutma sisteminin fanlı soğutma sistemine göre %32,85 oranında daha fazla güç tükettiği tespit edilmiştir.

Liquid Cooling Systems for Batteries of Electric Vertical Takeoff and Landing Aircraft

Batteries are the lynchpin of electric vertical takeoff and landing (eVTOL) aircraft, and the high discharge rates pose a critical challenge to the battery thermal management system (BTMS). This work presents a channeled liquid cooling technology-based BTMS for eVTOL aircraft. During the flight, the heat generated from the batteries is partly extracted by circulating liquid coolant within a wavy channel (WC) attached firmly to the battery cells. The heat is then transported into a plate-fin compact heat exchanger (HEX), where all the heat is dissipated into the atmosphere. We report sensitivity analyses of the HEX model to shed light on the impact of the relevant design parameters on the BTMS size, weight, and power. We also examine critical parameters of the coupled WC-HEX BTMS in a one-dimensional off-design analysis. We demonstrate that the liquid cooling system can maintain the battery operating temperature within acceptable levels with a mass of less than 20% of the battery pack mass. Battery degradation using the liquid cooling system is reduced by over three times compared to an air-cooled system for both tilt-wing and lift+cruise eVTOL aircraft.

Investigation of the Effect of Graphite Bipolar Plate Flow Channel Inhomogeneities and Faults on HT-PEM Fuel Cell Stack Performance

Bipolar plates are a key component of fuel cell stacks. Bipolar plates have multiple functions. They connect the single cells of the stack electrically and must be therefore electrically conductive. They separate oxidant and fuel gases and distribute them on each side over the membrane-electrode-assembly (MEA). Bipolar plates separate coolant liquid too. Fuel cell stack is cooled by coolant liquid which is flowing through the cooling flow channels in the middle of bipolar plates.Especially the bipolar plates for HT-PEM must endure a low pH environment, continuous electrical potential, and higher temperatures up to 200°C. The focus here is on investigations of anode and cathode side flow channels of graphite bipolar plates. Inhomogeneities and faults of flow channels are examined and their effects on fuel cell stack performance are analyzed. The analyses are based on optical scan data of flow channel geometry and measurement data of a HT-PEM fuel cell full stack consisting of 120 cells operated on a testbed under different variations. Inlet pressure and stoichiometry of both anode and cathode were varied, anode was fed with pure hydrogen and with different reformate gas compositions consisting of hydrogen, nitrogen, carbon dioxide and carbon monoxide. For each variation point, polarization curves between 0 A/cm2 – 0,55 A/cm2 in step of 0,05 A/cm2 were recorded.With an on testbed installed cell voltage monitoring (CVM) system voltages of every cell were measured and logged. Enormous amount of optical scan data consisting of width and depth information of flow channels was merged to certain statistical data for anode and cathode bipolar plates. Correlations between statistical data and cell voltages are still being investigated. It is planned to repeat the measurements with another 120 cells HT-PEM fuel cell full stack and compare the results.

High Temperature Corrosion Behavior of 15-15Ti Cladding Tube Material in Contact with Liquid Lead, Outside, and Cs2MoO4, Inside

Lead-Cooled Fast Reactors are one of the emerging new technologies connected to the Generation IV reactor designs. Even though the reactor features are extensive and beneficial, some technical and regulatory difficulties remain that hinder the deployment. One of them is the corrosion behavior of fuel claddings in high burn-up and elevated temperatures, as fuel claddings are a part of accident barriers. In this study, 15-15Ti austenitic steel was the investigated cladding material.As this cladding would be used in a tube form, corrosion attack from both sides, inside and outside is studied in contact to their respective environments. From the outside of the tube, the proposed coolant liquid lead is the corrosive substance. At the inside of the tube, the major corrosive species in our test setup is, for simplicity reasons, Cs2MoO4. However, this choice has been made from some considerations regarding the fuel evolution upon burn-up.In a high burn-up situation, the generated fission products would start to accumulate to the gap between the fuel pellet and the cladding tube. These accumulated products are the so-called “Joint-Oxide Gain” (JOG) phases, and they are the corrosive substances in question when discussing the corrosion attack from the inside of a cladding tube. Cs2MoO4 has been identified as one of the main components of JOG phases and thus will be focused on in this study.A new capsule was designed to investigate the dual-atmosphere corrosion of cladding tubes. Unexposed capsule parts (a) and the basic schematic of the assembled capsule (b) can be seen in the Figure below. The cladding tube material itself is used as the container for JOG as it is filled with Cs2MoO4 and sealed on both ends. This assembly is then placed inside a bigger capsule, which is filled with lead powder to submerge the cladding tube assembly. All assemblies were done in Ar-filled glovebox. The capsules were then exposed to 600-1000 oC for 52 to 168 hours, which was followed by cutting and epoxy embedding to investigate the cross-sections. Figure 1