Thermal Management Method Research Articles

Rapid calculation method to evaluate thermal management of LED systems based on an improved multi-layer model

An improved laminated structure model of LED systems is proposed. Besides the light-emitting diode (LED) chip, printed circuit board (PCB) substrate, heat sink, etc, additional interface layers are applied to model the non-ideal surface of thermal interface materials (TIMs). And a rapid calculation method is developed for temperature-related calculations. Through comparisons, the method is proved to be valid, and the execution time can be greatly reduced. It is found that the air gap at the TIM surface does hinder heat conduction but the effect is not obvious. The influence of LED chips on system thermal management is comprehensively analyzed. For a single LED chip, the junction temperature shows a linear relationship with its thermal resistance and heat power. The chip size, as well as the aspect ratio between the chip and the PCB substrate, has great effects on the junction temperature. For a multi-chip array, the impact of the chip quantity is suggested to be considered combined with the chip layout. The mutual thermal interaction among LED chips is of most concern, which will become more serious with an increasing number of chips. The work provides a rapid and flexible evaluation method for thermal management of LED systems.

Experimental investigation on thermal management of proton exchange membrane fuel cell stack using micro heat pipe array

• A new PEMFC thermal management method based on MHPA is proposed. • MHPA reduces the temperature of air-cooled PEMFC and improves the internal temperature uniformity. • MHPA realizes the separation of PEMFC reaction air and cooling air, and strengthens the heat dissipation. As a result of the limited air cooling capacity, the heat dissipation problem of air-cooled proton exchange membrane fuel cells (PEMFC) may limit the increase in power generation. In this research, the high-efficiency heat transfer element micro heat pipe array (MHPA) is integrated into the bipolar plate, and it is applied to the thermal management of PEMFC to realize the separation of reaction air and cooling air. A MHPA-PEMFC comprising 50 single cells is designed, and a series of comparative experimental studies are conducted. Results show that MHPA effectively improves the temperature distribution inside PEMFC. Compared with traditional PEMFC, the average temperature, maximum temperature difference, and maximum Index of Uniform Temperature of MHPA-PEMFC are reduced by 11.58 °C, 5.10 °C and 0.97 °C, respectively. When the reaction air flow rate is 160.8 m 3 /h, the maximum output power is 197.3 W higher, and the mass power density and volume power density are increased by 12.2% and 9.5%, respectively. The heat dissipation of MHPA’s cooling channel can account for up to 50.5% of the theoretical heat production, but the proportion decreases with the increase in reaction air flow. The results provided a basis for the application of MHPA to PEMFC thermal management.

An on-site temperature prediction method for passive thermal management of high-temperature logging apparatus

In the downhole oil and gas industry, temperature prediction is an important means to avoid the hazards brought by the high-temperature environment to electronic devices. An improved adaptive Kalman filter (IAKF) temperature prediction method, used here as a virtual sensor, can predict the instrument temperature in real time. It uses the temperature state transfer matrix as a system adaptive discriminant parameter to improve the prediction accuracy of the model. This approach is a data-driven prediction method for practical, field-deployable application, it does not require modeling of heat transfer mechanisms and does not require data sets. Experiments results show that the IAKF model can effectively predict the changing trend of the apparatus in the next 30 min, and the maximum temperature prediction error is within 6.5°C. Its predictions are more stable and accurate than the extended Kalman filter, and it consumes very little CPU resources to run in embedded devices.

Refrigerant flow distribution research for battery cooling coupled with cabin comfort based on dual-evaporator heat pump system for electric vehicle acceleration

Abstract The heat pump system employed with a dual evaporator for battery cooling coupled with cabin comfort is an innovative thermal management method. It can be inferred that the refrigerant thermal load distribution can trigger temperature fluctuations for thermal performance of both battery and cabin. To trade-off between the thermal management demands of battery and cabin, this study proposed a strategy to promote the decreasing of battery temperature and to ensure battery thermal uniformity with a higher priority. Hence a transient refrigerant flow rate distribution scheme with a minimum flow rate to satisfy battery thermal demands was designed. The results showed a significant reduction in the temperature fluctuations for cabin thermal comfort and BTM thermal controlling. It offers a satisfactory reference for refrigerant thermal load distribution strategy applied with the heat pump system connected to the battery and cabin by the dual evaporator.

Cooling chip on PCB by embedded active microchannel heat sink

The use of chips is inseparable from printed circuit board (PCB), therefore, it is an effective way to realize microchannel heat sink (MCHS) on PCB to actively cool chip. For improving the integration and cooling efficiency, and reducing the size, energy consumption and coolant consumption of cooling system for thermal management of chips on PCB, the principle and structure of cooling chip on PCB by embedded active microchannel heat sink (EAMCHS) are proposed. EAMCHS is formed by simultaneously integrating MCHS, diffuser/nozzle piezoelectric micropump (PMP) and piezoelectric microvalves with annular boundary on PCB. Chip to be cooled is mounted directly on MCHS. PMP and piezoelectric microvalves enable EAMCHS to drive and control coolant, respectively. The finite element simulation model and theoretical model of cooling chip on PCB by EAMCHS are established to simulate and analyze its heat transfer characteristics and flow characteristics. The manufacturing and assembly based on PCB process are studied and EAMCHS is manufactured. The size and weight of the assembled EAMCHS are small (about 6.5 cm3) and light (about 18.2 g), respectively. Utilizing high temperature co-fired ceramic (HTCC) to simulate chip heating, the working performances of cooling chip on PCB by EAMCHS are experimentally tested and analyzed on the constructed experimental setup. Research results show that EAMCHS can control the temperature of HTCC at 64.0 °C with heat flux of 50 W/cm2 through the flow rate of 30.11 mL/min of coolant. The established theoretical model can describe heat transfer characteristics and flow characteristics of cooling chip by EAMCHS, which will be conducive to its structural design and optimization. The proposed EAMCHS has low energy consumption, small size and light weight, and provides a novel principle, novel method and novel structure for thermal management of chips highly integrated on PCB.

A Review of Battery Thermal Management Methods for Electric Vehicles

Abstract Being one of the core power units of electric vehicles, the lithium-ion batteries (LIBs) are broadly concerned. However, in the cases of abuses, LIBs may counter thermal runaway, threatening the personal and property safety of users. In order to avoid the occurrence of thermal runaway, the battery thermal management system (BTMS) has been introduced to improve the safety, optimize the efficiency and prolong the service life of lithium-ion batteries. In this review, feasible thermal management schemes of LIBs system were summarized chronically, different thermal management schemes were evaluated, and case studies were made. The schemes of controlling the internal reaction control in the battery are highlighted as well. This review offers a comprehensive view of BTMS and proposes a promising future for the employment of lithium-ion batteries.

An Overview on the Use of Phase Change Material (PCM) for PV Cooling

The thermal management processes for PhotoVoltaic (PV) cooling applications, increase PV systems’ overall efficiency and yield to a maximized power generation. Accordingly, this paper investigates recent PV thermal management methods, which involve the use of Phase Change Material (PCM) under the back of PV modules. Compared to other cooling methods (such as air and water based methods) PCM based techniques show less need for maintenance, are environment-friendly, and have a longer life cycle. Since PCM are diverse in nature, and many methods exist to guide their selection procedure, this paper begins by revealing different types of PCM, which are found to be as Organic, Inorganic, Eutectic and Commercial PCM, with the characteristics of each. After acknowledging different PCM natures, a selection process is established based on either the melting temperature, latent heat, or thermal conductivity of PCM. Results have shown that Commercial PCM are the best option followed by Organic PCM, due to their improved chemical aspects when compared with Inorganic and Eutectic PCM. Concerning PCM selection criteria, the easiest yet sufficient process is based on the melting temperature method, due to the simplified calculations when compared to other thermic quantities. At the end, future work recommendations are declared, related to PCM lifecycle assessment and cooling/heating cycles effects on PV entropy.

Impacts of different exhaust thermal management methods on diesel engine and SCR performance at different altitude levels

Exhaust thermal management is important for efficient operation of the diesel engine aftertreatment system to meet emissions requirements at low speed and low load conditions. In order to study the impacts of exhaust thermal management strategies on diesel engine performance and SCR conversion efficiency at different altitudes, the effects of the altitudes (2000, 1000, and 0 m), intake throttling, exhaust throttling, and post injection were experimentally studied with a high-pressure common-rail diesel engine that consisted of a diesel oxidation catalyst (DOC) and a selective catalytic reduction (SCR) aftertreatment device. The results showed that the exhaust temperature and the SCR conversion efficiency were improved by intake or exhaust throttling or post injection at any altitudes. However, the intake or exhaust throttling resulted in engine air flow rate reduction, combustion deterioration, brake specific fuel consumption (BSFC) increase, and NOx emissions decrease. When the intake throttling and the exhaust throttling were compared with the same pressure change amplitude, the intake throttling provided better effects on exhaust temperature enhancement, SCR conversion efficiency increase, while the exhaust throttling provided worse effects on BSFC. As the altitudes increased, the impacts of the intake or exhaust throttling on the SCR conversion efficiency and the BSFC became more prominent. Moreover, increasing post injection fuel quantity or retarding post injection timing made combustion worse, BSFC higher, and NOx emissions lower with benefits of exhaust gas temperature increase and SCR conversion efficiency increase. Therefore, post injection is an effective method of exhaust thermal management and should be adopted first. Then, intake throttling should be used. Finally, exhaust throttling can be considered.

On thermal management of pouch type lithium-ion batteries by novel designs of wavy minichannel cold plates: Comparison of co-flow with counter-flow

The liquid cooling technique is the most preferred technique among the common methods of battery thermal management (BTM) due to its greater compactness and better efficiency. The temperature uniformity within batteries, mainly when they operate under extreme conditions (thermal runaways) is of utmost importance because a uniform temperature distribution can noticeably affect the performance, safety, and lifetime of batteries. Concerning this issue, novel wavy minichannel cold plates are proposed to establish better thermal management and temperature uniformity in pouch type lithium-ion batteries. The considered cases have variable wave amplitudes, which are varied in each wavelength of the wavy minichannels. These cases are investigated for the co-flow and the counter-flow patterns to improve conventional wavy cold plate temperature gradient problems in the laminar flow regime. The results indicate that replacing the conventional wavy cold plate with novel designs can improve temperature uniformity and decline the corresponding factor by 38.7%. It is found that a cold plate with the counter-flow pattern has a better temperature uniformity than the case with the co-flow pattern. Moreover, it is worth mentioning that the temperature distribution and uniformity of the conventional model are considerably influenced by the flow pattern compared to the novel cases. Using a counter-flow pattern in the conventional case leads to 73.1% decline in the maximum temperature difference compared to the co-flow pattern.

Investigation of engine's thermal management based on the characteristics of a map-controlled thermostat

New concepts and strategies are continually being investigated to meet fuel efficiency targets for new generations of internal combustion engines. Thermal management methods can reduce fuel consumption by up to 4%. One approach for thermal management is a map-controlled thermostat. In the current work, this concept is investigated through a benchmarking approach and a methodology for deriving the response time curve for this type of thermostat. To better explore the benchmarking idea, characteristics of map-controlled thermostats for two different engines are identified, analyzed, and compared. Finally, the effects of two separate map-controlled thermostats on the average fuel consumption of engines are investigated for a driving cycle using one-dimensional simulation. It is shown that using a map-controlled thermostat can reduce average vehicle fuel consumption by about 1.7% relative to current vehicles with ordinary wax-type thermostats.

Theory and Practices of Li-Ion Battery Thermal Management for Electric and Hybrid Electric Vehicles

This article surveys the mathematical principles essential for understanding the thermal management of Li-ion batteries, the current technological state of the art, and the solution. Since the thermal management of electric drive vehicles has environmental, economic, and safety impacts, this review focuses on the efficient methods of battery thermal management (BTM) that were proposed to overcome the major challenges in the electric vehicle industry. The first section examines the perspective of battery-driven vehicles, the principles of Li-ion batteries with a thermal runaway, and their implication for battery safety. The second section discusses mathematical approaches for effective BTM modeling, including the thermal-fluidic network model, lumped capacitance model, spatial resolution lumped capacitance model, equivalent circuit model, impedance-based model, and data-driven model. The third section presents the current state-of-the-art technologies, including air-based, liquid-based, PCM-based, in situ BTM methods, and heat pipe and thermoelectric module-based methods. The conclusion section summarizes the findings from existing research and the possible future directions to achieve and employ better thermal management techniques.

Simultaneous application of active and passive methods in cooling of a cylindrical lithium-ion battery by changing the size of the elliptical cavity filled with nano phase change materials

This article performs the numerical study of thermal management of a battery pack using active and passive thermal management methods. For the active method, a forced and laminar airflow is used in the battery pack. For the passive one, phase change material (PCM) is employed around all battery cells placed in the enclosure. The enclosure filled with PCM is elliptical. Four different enclosure models are examined by changing their small diameter. This study is performed when the passive method does not work by melting all PCMs and the active method works. The numerical study method is finite element method and the study is transient. The results demonstrate that the maximum temperature of the battery first enhances and then decreases by employing the active method. The time of the change in the battery temperature trend depends on the enclosure model. The quantity of liquid PCM and the ambient air temperature are also lowered when the active technique is utilized. The temperature of the battery and the quantity of molten PCM are reduced by using enclosures with smaller minor axes. Using cavities with bigger minor axes, on the other hand, increases the quantity of molten PCM and the battery temperature. Also, the air outlet temperature from the enclosure with larger dimensions is higher than other enclosure models.

Fuzzy modelling and metaheuristic to minimize the temperature of lithium-ion battery for the application in electric vehicles

The recent progress in the electric vehicles requires developing an efficient battery that can be fast charged and having a longer lifetime. Proper thermal management of the battery systems plays a key factor in the performance and lifetime of batteries. Liquid cooling is one of the feasible methods for effective thermal management of battery systems. In this work, the optimal size of double-layer reverting channel is determined using fuzzy modelling and modern optimization. A novel application of the Slime mould algorithm (SMA) is suggested to find the best size of double-layer cooling channel that can simultaneously minimize battery's temperature, better uniform of battery's temperature, and lower energy consumption. For first time, an accurate fuzzy model of the double-layer channel in terms of four dimensions parameters (width ratio, length ratio of x axis, length ratio of y axis, and thickness of all channels) is successfully obtained. The average coefficient of determination values are 1.0 and 0.8214 respectively for training and testing. Also, the average RMSE values 9.32E-06 and 0.018 respectively for training and testing High coefficient-of-determination values and low for RMSE values both training and testing phases confirmed the accuracy of the model. Then, SMA is used to determine optimal size of the cooling channel to minimize simultaneously the temperature, surface standard deviation, and pressure drop. The results confirmed the accuracy of the proposed fuzzy model in addition to the performance improvement. The overall performance is improved by 7.8% through minimizing the maximum temperature and well thermal distribution.

Radiative Cooling and Solar Heating Janus Films for Personal Thermal Management

Hot and cold seasonal temperature fluctuations pose a serious public health threat. Radiative thermal management has been shown to be an effective method for personal thermal management. However, the currently available materials cannot maintain human thermal comfort against the hot and cold seasonal temperature fluctuations, such as heating in cold weather or cooling in hot weather. Here, a Janus film that integrates the two opposite requirements of heating and cooling into one functional dual-mode film is fabricated. In cooling mode, the Al backing and embedded silicon dioxide (SiO2) microparticle can achieve a high solar reflectivity (∼0.85) and high IR emissivity (∼0.95) to induce a temperature drop of ∼2 °C. In contrast, the embedded carbon nanotubes (CNTs) can improve solar absorption (∼0.95) and induce a temperature increase of ∼7 °C. Owing to its radiative cooling and solar heating capability and compatibility with large-scale production, this Janus film is promising to bring new insights into the design of the next-generation functional textiles.

Parametric Investigation on the Performance of a Battery Thermal Management System with Immersion Cooling

Lithium-ion batteries will generate a large amount of heat during high-rate charging and discharging. By transferring the heat to the environment in time, the batteries can be kept in a suitable temperature range. This allows them to work normally, prolongs their cycle life, and reduces the risk of thermal runaway. Immersion cooling is a simple and efficient thermal management method. In this paper, a battery thermal management system (BTMS) with immersion cooling was designed by immersing the lithium-ion cells in the non-conductive coolant—dimethyl silicone oil. The electric–thermal coupled model was adopted to obtain the heat production and temperature distribution of the cell during discharging, and the performance of the system was obtained by numerical calculation. It was found that, compared with natural cooling, immersion cooling could significantly reduce both the maximum temperature (MAT) of the cell and the temperature of the tabs during the 3C discharging process. However, the maximum temperature difference (MATD) of the cell was significantly increased. To solve this problem, the effects of the flow rate, viscosity, specific heat capacity, and thermal conductivity of the coolant on the performance of immersion cooling were further investigated and discussed, including the MAT and MATD of the cell, and the pressure drop of the coolant. The method and results could provide references for the design and application of the BTMS with immersion cooling in the future.

Thermomechanical Topology Optimization of Three-Dimensional Heat Guiding Structures for Electronics Packaging

Abstract Heterogeneous and complex electronic packages may require unique thermomechanical structures to provide optimal heat guiding. In particular, when a heat source and a heat sink are not aligned and do not allow a direct path, conventional thermal management methods providing uniform heat dissipation may not be appropriate. Here we present a topology optimization method to find thermally conductive and mechanically stable structures for optimal heat guiding under various heat source-sink arrangements. To exploit the capabilities, we consider complex heat guiding scenarios and three-dimensional (3D) serpentine structures to carry the heat with corner angles ranging from 30 deg to 90 deg. While the thermal objective function is defined to minimize the temperature gradient, the mechanical objective function is defined to maximize the stiffness with a volume constraint. Our simulations show that the optimized structures can have a thermal resistance of less than 32% and stiffness greater than 43% compared to reference structures with no topology optimization at an identical volume fraction. The significant difference in thermal resistance is attributed to a thermally dead volume near the sharp corners. As a proof-of-concept experiment, we have created 3D heat guiding structures using a selective laser melting technique and characterized their thermal properties using an infrared thermography technique. The experiment shows the thermal resistance of the thermally optimized structure is 29% less than that of the reference structure. These results present the unique capabilities of topology optimization and 3D manufacturing in enabling optimal heat guiding for heterogeneous systems and advancing the state-of-the-art in electronics packaging.

Estimation of the thermohydraulic performance of a microchannel heat sink with gradual and sudden variation of the flow passage

Microchannel heat sink (MCHS) is used as an efficient method of thermal management in a miniaturized, high performance electronic devices. However, high pumping power and uneven distribution of temperature are two major limitations of such MCHS. In this work, efforts are made to optimize these limitations through modification of channel geometry. Three sequential computational analyses have been performed for a MCHS. In the first analysis, the channel cross-section reduces to a minimum one (at the throat) and then increases. For five different throat positions are considered for this analysis. None of the channel configuration achieves the overall performance more than 1. Next, sudden contraction and expansion are introduced in the channel passage. Three different cross-sections are used. The sudden expansion recovers the pressure gradually, whereas, at sudden contraction, the pressure drops instantaneously. The overall performance index (OPI) improves when two channel sections with larger cross-sectional area is connected by a channel with smaller cross-section. The OPI of such configuration is found to be greater than 1. Finally, multiple sudden expansion and sudden contraction are introduced sequentially in the channel cross-section. It is observed that the heat transfer performance and pressure drop both increases with increase in number of expansion and contraction.

Experimental investigation and performance evaluation of thermal energy management arrangements for robots

AbstractIn this study, thermal energy management systems with the choices of three different thermal insulating materials are experimentally investigated for robotic applications. These insulating materials are stone wool, fiberglass and extruded polyurethane with air cooling and heating system which are evaluated in the low and high temperature environments to really assess the thermal behavior and performance in such extreme ambient conditions. In this regard, thermodynamic and heat transfer modeling studies are undertaken to investigate various performance parameters, including energy and exergy efficiencies. The experimental results showed that energy efficiencies of the thermal management methods are obtained 46.34% for stone wool, 31.15% for fiberglass, and 44.3% for air cooling system at 40°C. Moreover, the exergy efficiencies are 12.6% for stone wool, 15.08% for fiberglass, 18.91% for extruded polyurethane, and 3.86% for air cooling system.

Measuring Irreversible Heat Generation in Lithium-Ion Batteries: An Experimental Methodology

Lithium-ion battery research has historically been driven by power and energy density targets. However, the performance of a lithium-ion cell is strongly influenced by its heat generation and rejection capabilities which have received less attention. The development of adequate thermal metrics able to capture the anisotropic thermal conductivity and uneven internal heat generation rates characteristic of lithium-ion cells is therefore paramount. The Cell Cooling Coefficient (CCC), in W.K−1, has been introduced as a suitable metric to quantify the rate of heat rejection of a given cell and thermal management method. However, there is no standardised methodology defining how to measure the heat generation capabilities of a cell. In this study, we applied the CCC empirical methodology to evaluate the rates of irreversible heat generation at various operation conditions, providing maps which give a complete insight into cell thermal performance. The maps derived show how the most important operational variables (frequency, C-rate, SOC and temperature) influence the cell thermal performance. These maps can be used along with the CCC by pack engineers to optimise the design of thermal management systems and to down select cells according to their thermal performance.

Research of Thermal Behaviour of Li-ion Battery Module Based on Liquid Cooling

An effective battery thermal management system (BTMS) is crucial to ensure the battery temperature in an appropriate range and prolong the battery life. In this paper, a liquid cooling thermal management method for a li-ion battery module which is consisting of 12 prismatic batteries is set up, three circuitous channels embedded with a cooling plate are studied. Meanwhile, the performance evaluations of the battery module by considering different cooling conditions and battery arrangement are investigated numerically. The effects of the flow area of cooling plate and mass flow rate of coolant on the peak temperature and temperature difference of the battery module during charge/discharge process are examined. The larger flow area is experienced with a lower maximum temperature. Increases of maximum temperature and temperature difference are shown at lower mass flow rate. This paper provides guidance for the design and optimization of the module and thermal management.