Speed Heat Research Articles

Modeling and Control of an Integrated Self-Heater for Automotive Batteries Based on Traction Motor Drive Reconfiguration

Lithium-ion batteries suffer from substantial capacity and power degradation in cold climates, severely deteriorating electric vehicles’ performance. To solve this issue, internal heating schemes are attractive due to their high efficiency, fast speed, and uniform temperature distribution. Nevertheless, high-cost power converters and large-sized passive components are required to charge/discharge batteries alternatively, challenging onboard implementation of battery heaters. In this study, we develop an integrated battery self-heater (IBSH) based on the topology reconfiguration of traction motor drives, eliminating additional hardware. The theoretical model and operation principle of the proposed IBSH are derived for the first time, providing a feasible design and control baseline for onboard applications. Then, a robust controller is developed to adjust the heating current and cell voltage regardless of nonlinear uncertainties during self-heating. The downscaled experiments demonstrate that the proposed IBSH can effectively preheat automotive batteries with 3.45 °C/min heating speed and 0.201% SOC/°C energy consumption rate.

Oxide/Metal/Oxide 구조의 유연하고 투명한 히터

Optically transparent and electrically conductive films were investigated for the flexible and transparent heaters. Metal (Ag), silver nanowires (AgNWs) and metal oxide (ITO or ZnO) were employed to form the various types of transparent heaters. A single-layered ITO, metal hybrid AgNWs (ZnO/AgNWs) and ZnO/Ag/ZnO composite were manufactured on PET substrates. Each case was tailored by large-scale device (150 mm x 100 mm).BRFor each structure, visible light transmittance, electrical conductivity, and heating performances were investigated to show the enhanced performances from the ZnO/Ag/ZnO composite, which showed the excellent transmittable (77% at wavelength of 550 nm) and outperforming heating performances to reach 146°C with fast heating speed. The improved performances are mainly attributed to the structure of ZnO/Ag/ZnO, where the thin Ag governs the electrical property with good optical feature. This study suggests that the ZnO/Ag/ZnO transparent heater has the excellent optical and electrical properties with good flexibility and affordable scalability to enlighten the large-scale and flexible heating applications.

A Split-Source Self-Heater for Automotive Batteries Based on Traction Drive Reconfiguration

At cold climates, internally preheating batteries are essential and promising to alleviate the performance degradation of electric vehicles because of its rapid heating speed and uniform temperature distribution. To implement onboard internal battery heating, the integrated self-heater is developed to utilize traction motor drive reconfiguration, thereby eliminating extra expensive high-power converters and bulky passive components. However, previous integrated self-heaters introduce excessive voltage stress on dc-link capacitors, arousing a serious concern on the system reliability and safety. In this article, a split-source self-heater (SSSH) is proposed to reconfigure the battery pack as two series-connected sources, where the heating energy can be alternately exchanged via traction motor windings with reduced capacitor voltage stress. The theoretical model and operation principle of the proposed SSSH are deduced for practical controller design and suppression of annoying noises and vibrations. Based on the model, a supertwisting controller is developed to adjust the heating current and cell voltage regardless of nonlinear uncertainties during self-heating. The downscaled experiments verify that the proposed SSSH can preheat automotive batteries with 4.27 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C/min heating speed and 0.24% state of charge/ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C energy consumption rate. The induced torque ripple is reduced by 90%, and the capacitor voltage never exceeds the nominal value during self-heating.

Crossover PC-SAFT equations of state based on White's method for the thermodynamic properties of CO2, n-alkanes and n-alkanols

In order to improve the prediction accuracy of the thermophysical properties of fluid in near critical region, in this work, White's renormalization group (RG) corrections were applied to construct the crossover PC-SAFT EoS (simplified as PC-SAFT-RG). We first fit the three parameters introduced by the crossover process to the experimental data, then the phase behavior as well as derivative properties in the critical region and outside the critical region for several fluids such as CO2, n-alkanes and n-alkanols were investigated using the PC-SAFT EoS and the PC-SAFT-RG. Our results show that the PC-SAFT-RG is able to modify the behavior of the PC-SAFT EoS in the critical region and revert to classic behavior outside the critical region. The PC-SAFT-RG improves the PC-SAFT EoS's performances on the second derivative thermodynamic properties, with the average absolute relative deviations (AADs) of 9.96%, 6.99% and 3.91% for isobaric heat capacity, isochoric heat capacity and speed of sound respectively.

Tepelné samovznietenie ako najčastejšie sa vyskytujúce fyzikálno-chemické samovznietenie

Self-ignition and self-heating are processes when the heat required for ignition of a substance arises in the substance itself as a result of chemical, physical or biological processes. The term autoignition should be nderstood not only as self-ignition, the ignition of a substance but as a complex, spontaneously occurring process, from the first moment of temperature rise (self-heating temperature) to reaching autoignition temperature, as a result of chemical, physical or biological processes. The result of the self-ignition process is the ignition and subsequent burning of the substance or material in a flameless or flameless manner (smouldering, incandescence). Thermal spontaneous combustion is among the most common cases of physicochemical spontaneous combustion. Thermal autoignition is a thermooxidation process that is anifested by burning (flame or flameless) after previous self-heating of substances that are heated to a temperature at which the released heat of reaction exceeds the amount and speed of heat removed to the environment.

Entropy generation analysis of MHD hybrid nanofluid flow due to radiation with non-erratic slot-wise mass transfer over a rotating sphere

Flow over rotating spheres has serious applications in fiber coating, rotating machinery design and parts, and projectile missions. Therefore, the current study investigates the flow and entropy generation of a radiative magneto-hybrid nanofluid flow over rotating sphere. Further, the temperature-sensorial water properties in studying water-based nanofluids are ignored, though this erratic behavior of water characteristics influences the physical characteristics of the corresponding hybrid nanofluid. Hence the current framework is one of the foremost projects to introduce the variable nature of water properties in the water-hosted hybrid nanofluid flow analysis. The investigation is accomplished in the account of the modified Buongiorno model (MBM). The flow separation in this kind of flow geometry is controlled by using non-erratic slot-mass transfer. The mathematical representations of the physical principles of the flow are solved using (i) congenial transformation (ii) quasilinearization (iii) methods of finite differences to form a block matrix system, and (iv) Varga’s iterative algorithm. Some of the major outcomes are: The flow separation can be significantly delayed using slot suctions, precisely appointing them downstream with higher strengths; heat transport performance drastically subsidies for high viscous dissipation (Ec), entropy produces at higher rate for viscous heating (Br) and high angular speed (Ω).

Optimization of Wear Parameters of Cryogenic and Heat-treated Al 6101 Closed-cell Foam using Taguchi Technique

Objectives: This study deals with the optimization of wear properties of Al 6101-alloy foam treated with different temperature zones such as Untreated (UT), Heat Treated (HT), Cryogenic Treated (CT), and Cryogenic Heat Treated (CHT), respectively. The results of this study concerning confirmation tests enable us to validate the proposed optimization findings for the coefficient of friction and specific wear. Methods: The Al 6101 foam samples used in this study are exposed to different heat and cryogenic treatments as well as wear tests using the pin-on-disk apparatus setup with the Taguchi optimization technique. The wear parameters are enhanced further using the Analysis of variance (ANOVA) technique, and this model is processed using the MINITAB software. The Al 6101 foam samples are evaluated using important wear testing parameters like Heat Zone, Load (N), Speed (rpm), and Sliding Distance (m), as well as the output parameters such as coefficient of friction and specific wear (mm3/Nm). Findings: The optimum combination of the coefficient of friction and specific wear, according to the graphic and analytical results of Taguchi’s optimization, is with 40 N load, 400 rpm speed, and 1500 m distance for a cryogenic zone and 40 N load, 400 rpm speed, and 2000 m distance for a cryogenic heat zone, respectively. The interaction of sliding distance, load, and speed, which has probabilities of 17.42, 8.95, and 7.74, respectively, is followed by the coefficient of friction, which has a greater probability percentage of 48.01 for the heat zone. The ANOVA for the specific wear has a higher probability percentage of 48.82 for the load and is followed by the interaction of heat zone, sliding distance, and speed, which have probabilities of 37.59, 6.02, and 2.85, respectively. Novelty: Considering Al 6101 foam, which is mostly a nonferrous material, this experiment once again confirmed that novel cryogenic treatment has a noteworthy improvement in coefficient of friction and specificwear. Additionally, Taguchi’s optimization and ANOVA analysis proved that the Al 6101 closed-cell foam specimen in the CHT zone exhibited optimal results when compared with other heat zones. The results confirmed that the CHT processing improves the wear resistance of the Al 6101 closed-cell foam effectively when examined with other different heat zones. Keywords: Al 6101 ClosedCell Foam; Cryogenic Treatment; Taguchi Technique; Coefficient Of Friction; Specific Wear; Wear Graph; Surface Morphology; L16 Orthogonal Array; ANOVA

Experimental investigations on thermo-stamping of carbon fiber reinforced polyamide 6 hat-shaped components with self-resistance electrical heating: Influence on microscopic and macroscopic properties from temperature related processing parameters

Thermo-stamping is a widely used forming process for automotive components made from fiber reinforced thermoplastic composites, but it still suffers from a variety of challenges such as long cycle time and high energy consumption. In this paper, self-resistance electrical (SRE) heating, an internal efficient heating method with the advantages of rapid heating speed and low energy consumption, was introduced into thermo-stamping for the rapid manufacturing of carbon fiber reinforced polyamide 6 (CFR-PA6) hat-shaped components. The impacts of the temperature related process parameters, preheating temperature (90 °C ∼ 220 °C) and mold temperature (20 °C ∼ 130 °C) on the shape accuracy, surface quality, microscopic morphology and mechanical properties of obtained hat-shaped components were investigated through experimental characterization. Besides, the energy-saving effect of SRE heating was also revealed compared with radiant heating, an external heating method. It is found that the defects such as fiber bundle cracks, matrix cracks and interface cracks caused by SRE heating are more serious than those caused by radiant heating, which is attributed to the effect of Joule heating, Lorentz force and dielectric breakdown. However, a high mold temperature can reduce these defects owing to the reconsolidation behavior of the hat-shaped component during the thermo-stamping process. The results show that the hat-shaped components possess a good formability and forming quality at a preheating temperature at 200 °C and mold temperature at 130 °C. Moreover, the total cycle time of thermo-stamping with SRE heating is less than 1 min and the energy consumption by SRE heating is about 9.86 % ∼12.09 % compared with radiant heating, which provides a more energy-efficient option for industrial production.

Gradient-Harmonizing-Based Deep Learning for Thermophysical Properties of Carbon Dioxide

Carbon dioxide presents many unique advantages for cooling and power cycles under supercritical or near-critical conditions, where the characterization of thermophysical properties is a daunting task. The present study proposes different deep feedforward neural network (DFNN) models for property evaluations of carbon dioxide. The all-in-one DFNN model appears acceptable for enthalpy, entropy, and thermal conductivity, but it exhibits poor performance in density, speed of sound, viscosity, and constant-pressure specific heat. The specific DFNN model presents limited improvement in the near-critical and pseudoboiling regions, where steep property gradients occur. To alleviate the situation, the sampling data are divided into easy samples and hard samples. Easy samples are data that have small-gradient norm and can be well fitted, whereas hard samples are those with large-gradient norms and are difficult to fit. The gradient-harmonizing method is proposed to solve the imbalance between hard and easy samples by rectifying their gradient contribution and assigning different weights. The resultant models show significantly improved performance as compared to the existing methods in the literature, with less than 0.4% in absolute average relative errors for the studied properties. The gradient-harmonizing algorithm can potentially be adopted to property evaluations of other substances involved in aerospace propulsion.

Разработка методики для расчета теплопередачи потолочных водяных капиллярных систем низко-температурного отопления

The purpose of this work is development of the heat transfer calculation method of a water low-temperature ceiling capillary heating system for heating rectangular rooms. Recently, such systems have become widespread due to their advantages over traditional heating devices: the use of a coolant with a low temperature potential, high heating speed rate of the internal air, low temperature gradient in the height of the room, absence of noticeable air masses movement and dust flows, ability to work in cooling mode. However, such systems are still incompletely studied, and constructive calculations or calculations of thermal and hydraulic modes are carried out according to formulas obtained empirically, thus, calculations do not always have high accuracy. The paper proposes a heat transfer process calculation method from the considered low-temperature heating system, which allows determination of the heat flow value with high accuracy. It`s revealed that in the considered configuration of the system location (on the ceiling), a significant proportion of heat transfer is infrared radiation, and the convective component is very small. Therefore, it was very important to accurately describe the radiant heat exchange by mathematical equations. The calculation of the radiant component of heat transfer was carried out with the theory of radiation view factors. Experimental test of the studying object was carried out to find the missing values, as well as to verify the results obtained using the proposed calculation method. The calculation results had a slight deviation from the results obtained experimentally (the error was 6 %).

Comparison of Urban Heat Island Diurnal Cycles under Various Atmospheric Conditions Using WRF-UCM

The rapid growth of urbanization significantly influences local atmospheric conditions and life quality of residents living in urban areas by creating a localized phenomenon known as an urban heat island. Urban heat island characteristics are strongly formed by prevailing atmospheric conditions influencing their magnitude and intensity. In this study, we used the Weather Research and Forecasting model to investigate the effects of different airmass and windspeed characteristics on the diurnal cycle of the urban heat island phenomenon during four real weather situations presenting typical scenarios with clear sky conditions. The scenarios consisted of warm dynamic and non-dynamic situations and cold dynamic and non-dynamic situations identified with respect to temperature profiles, humidity and wind speed. The comparison of urban heat island intensity between all four scenarios showed a significant effect of wind speed on urban heat island characteristics and intensity as well as the role of humidity and airmass temperature in diurnal changes. The results showed that urban heat island is best defined by conditions with strong radiative heating and weak wind speed regardless of temperature. Air humidity appears to have significant influence on UHII with cold non-dynamic situations in dry air showing a very high UHII amplitude during the daylight period and high intensity during the night. The comparison of warm and cold dynamics situations showed the influence of vertical heat exchange with strong mixing of air between near-surface levels and lower levels of the troposphere with a mild effect on UHII during the warm situation and strong influence on decreasing UHII during the cold scenario.

Formation mechanism of basin-like depression defect in electric upsetting process of Ni80A superalloy

A kind of surface instability, basin-like depression defect companied by mixed grain structure at the bottom of large-scale valve during electric upsetting process, would significantly influence the microstructures and mechanical properties of components. In order to analyze the forming process of the basin-like depression defect, a finite element model for the electric upsetting process of Ni80A superalloy was developed using multi-field and multi-scale coupling analysis method. Subsequently, a series of parameters loading path schemes for force and current were designed by varying the initial value, peak value and value level, and their effects on basin-like depression and mixed grain structure were simulated and uncovered. It is concluded that the changes of heating speed and pressurization speed result in the different flow velocities between the inner and outer layers of billet, thus exerting the basin-like depression. Simulation results also indicate that these defects can be optimized through the parameter coordination between force and current. Finally, the validity and reliability of the finite element model were verified by physical experiments in electric upsetting process.

A rapid self-heating strategy of lithium-ion battery at low temperatures based on bidirectional pulse current without external power

Polarization is a major problem for lithium-ion batteries (LIBs) at low temperatures. To realize rapid preheating of LIBs at low temperatures, a self-heating strategy based on bidirectional pulse current without external power is proposed. Four inductances and one direct current/direct current (DC/DC) converter are applied to the system. An electrothermal coupling model of LIBs and a performance evaluation model of the system are established to investigate the effects of circuit parameters and initial state-of-charge (SOC) on the heating performance, including the heating time, SOC utilization ratio (SUR), and heating efficiency. The results show that the LIBs can be warmed up from −10 °C to 0 °C in approximately 120 s. It is concluded that reducing the discharge inductance can increase the heating rate, SUR, and heating efficiency. However, the excessive reduction of the discharge inductance would cause a significant voltage drop, which will reduce the voltage to below the cut-off voltage. In addition, a comparative study shows that when the initial SOC values of the two battery packs are different, the heating time will be reduced. A higher initial SOC for one battery pack can increase the heating speed and SUR at the expense of the heating efficiency.

Analysis of Pyrolysis Kinetic Parameters Based on Various Mathematical Models for More than Twenty Different Biomasses: A Review

Today, energy use is an important and urgent issue for economic development worldwide. It is expected that raw material in the form of biomass and lignocellulosic residues will become increasingly significant sources of sustainable energy in the future because they contain components such as cellulose, hemicellulose, lignin, and extractables with high energy-producing potential. It is then essential to determine the behavior of these materials during thermal degradation processes, such as pyrolysis (total or partial absence of air/oxygen). Pyrolyzed biomass and its residual fractions can be processed to produce important chemical products, such as hydrogen gas (H2). Thermogravimetric (TGA) analysis and its derivative, DTG, are analytical techniques used to determine weight loss as a function of temperature or time and associate changes with certain degradation and mass conversion processes in order to evaluate kinetic properties. Applying kinetic methods (mathematical models) to degradation processes permits obtaining several useful parameters for predicting the behavior of biomass during pyrolysis. Current differential (Friedman) and integral (Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, Starink, Popescu) models vary in their range of heating speeds (β) and degree of advance (α), but some (e.g., Kissinger’s) do not consider the behavior of α. This article analyzes the results of numerous kinetic studies using pyrolysis and based on thermogravimetric processes involving over 20 distinct biomasses. The main goal of those studies was to generate products with high added value, such as bio-char, methane, hydrogen, and biodiesel. This broad review identifies models and determines the potential of lignocellulosic materials for generating bioenergy cleanly and sustainably.

Investigation on the thermoelastic response of a nanobeam in modified couple stress theory considering size-dependent and memory-dependent effects

For nano/micro-scale structures, the classical continuum mechanics can’t properly depict the size-dependent effect arising in them anymore. In addition, Fourier’s law is limited in describing the heat transfer process in nano/microstructures due to its nature of predicting infinite heat speed. To amend such defects, the non-classical continuum mechanics based on the nonlocal elasticity theory and the modified couple stress theory incorporating the non-Fourier heat transfer model with memory-dependent effect is formulated to characterize the thermoelastic behaviors in micro/nano-scale system in the present work. Then, the model is used to study the dynamic response of an Euler-Bernoulli nanobeam subjected to a ramp-type heating. The corresponding governing equations are derived and then solved by Laplace transform method and its numerical inversion. The distributions of the non-dimensional transverse deflection, temperature and displacement are obtained and illustrated graphically. In calculation, the influences of the ramp heating time parameter, the material length parameter, the nonlocal parameter, the time-delay factor and the kernel functions on the considered physical quantities are examined and discussed in detail.

Fast self-heating battery with anti-aging awareness for freezing climates application

Lithium-ion batteries (LIBs) need to be heated before use at low temperatures to avoid poor electric vehicle performance. In this study, a self-heating method for LIBs at low temperatures is proposed, where the influence of various heating parameters on heating performance is explored experimentally. To make the balance between heating speed and capacity degradation while achieving efficient preheating, a lumped parameter thermal model and an empirical capacity fade model are established to determine appropriate duty ratio and external resistance, which can predict the corresponding time required for LIBs to be heated to the target temperature and reveal the capacity loss of LIBs quantitatively after repeated heating. A multi-objective optimization method based on non-dominated sorting genetic algorithm II (NSGA-II) is employed to obtain the Pareto optimal front between heating speed and capacity degradation, which leads to the selection of the optimal electrical parameters with the help of K-means clustering algorithm and three newly defined heating performance indicators. Finally, the duty ratio and external resistance are preferably 80% and 203.98 mΩ through the NSGA-II method, respectively. The experimental results verify the optimal heating strategy which can heat the LIB quickly from – 20.56 °C to 0 °C within 70 s. This optimal heating strategy is applied to heat the LIB for 200 times, the battery capacity degradation is only about 7.72%.

Dielectric properties analysis of dough and further microwave baking for cookies

Microwave heating is gaining relevance for cooking processes with faster heating speeds, shorter processing times and lower environmental impact than traditional heating (gas or electric ovens for bakery products). Dielectric properties of cookies dough (16.9% moisture content and 19.5% fat content, w.b., density of 650 kg/m3) were analysed for temperature (18-80°C) and microwave frequency (0.5-2.5 GHz). The penetration depth was calculated, and with the obtained results, the maximum thickness values for the cookies were 1.61 and 0.73 cm for 915 and 2450 MHz, respectively, to ensure enough wave penetration. The dough was cut into 8 cm diameter and 0.7 cm of thickness pieces and MW-baked at 360 W for 1.5 min. MW-baked cookies were compared with cookies from the same dough baked in an electric oven at 160°C for 12 min, being similar. MW baking time was shorter, which means the method has potential for this kind of dough.

Frequency-Variable Resonant Self-Heating Technique for Lithium-Ion Batteries at Low Temperature

This article presents a frequency-variable resonant self-heating technique for improving the heating speed of lithium-ion batteries at very low temperatures. In contrast to the conventional heating method with a fixed current and frequency, the proposed technique can increase the battery heating current by determining the minimum impedance of the lithium-ion batteries. Then, through a variable charging/discharging frequency operation, this technique can increase the heating speed without inducing a temperature plateau because of impedance reduction. A lithium-ion battery with improved self-heating performance at low temperatures was developed and used to verify the proposed self-heating technique. A simulation model and self-heating device (dc/dc converters) were also designed and tested at –30-°C ambient temperature. The proposed frequency-variable resonant self-heating technique achieved a heating speed four times faster (from 2784 s to 717 s) than the conventional self-heating technique. Thus, lithium-ion batteries can be used at cryogenic temperatures (–30 °C) by quickly raising the battery temperature with this technique.

Ergonomic design and evaluation of carbon nanotube film (CNTF) and metal wire based flexible electrically heated gloves

Electric heating gloves are essential for people working in severe cold environments which could protect their hands warm efficiently. Existing electric heating gloves, however, tend to restrict the movement of the fingers and have limited thermal protection, affecting the working efficiency of the wearers. Here, we report on the development and evaluation of carbon nanotube film (CNTF) and metal fiber based electric heating gloves. The electric heating elements were placed in the back of the gloves, and we tested the electric heating properties of the gloves. They showed great electrothermal performance and it had a certain repeatability and stability through multiple experiments. Then the electro-thermal and ergonomic performance of the gloves were evaluated under the severe cold outdoor environment of −20 ± 2°C. In comparison with conventional single layer polar fleece gloves and carbon fiber electric heating gloves that purchased from the market, CNTF based gloves and metal fiber-based gloves demonstrated outstanding advantages in terms of faster heating speed, great warmth retention, and enhanced finger agility, which is attributed to the electrothermal properties of CNTF and metal fiber as well as the structural design of the gloves.

Fast Diesel Aftertreatment Heat-Up Using CDA and an Electrical Heater Between 1.2 and 5.0 kW

Commercial vehicles require fast aftertreatment heat-up in order to move the selective catalytic reduction catalyst into the most efficient temperature range to meet upcoming NOX regulations while minimizing CO2. This study is a follow-up study using an electric heater upstream of a LO-SCR followed by a primary aftertreatment system having an engine equipped with cylinder deactivation. The focus of this study is to minimize the maximum power input to the e-heater without compromising tailpipe NOX and CO2. A system solution is demonstrated using a heavy-duty diesel engine with an end-of-life aged aftertreatment system targeted for 2027 emission levels using various levels of controls. The baseline layer of controls includes cylinder deactivation to raise the exhaust temperature more than 100°C in combination with elevated idle speed to increase the exhaust mass flow rate through the aftertreatment system. The engine load is adjusted to compensate for generating electrical power on the engine. The combination of electrical heat, added load, cylinder deactivation, and elevated idle speed allows the aftertreatment system to heat up in a small fraction of the time required by today’s systems. This work was quantified over the cold federal test procedure, hot FTP, low load cycle (LLC), and the U.S. beverage cycle showing improved NOX and CO2 emissions. The improvement in NOX reduction and the CO2 savings over these cycles are highlighted.