High Heat Generation Research Articles

Development of hybrid cooling method with PCM and Al2O3 nanofluid in aluminium minichannels using heat source model of Li-ion batteries

Lithium ion batteries are considered as the main energy storage option. High temperatures cause capacity fading and can even produce fire. It is, therefore, essential to design an effective thermal management system (TMS) to keep battery temperature in the safe range. In this study, thermal response of lithium ion batteries is investigated in high discharge rates with a new TMS combining active and passive methods. Refined paraffin in blockform (P 42–44 #107150) combined with porous copper metal foam was considered as the passive part and aluminium mini-channel containing coolant flow was regarded as the active part of TMS. The experiments were conducted at three different Reynold numbers in active and hybrid methods and it was shown that at higher flowrates the maximum temperature is lower. The research has also shown that passive cooling was inefficient in keeping the battery temperature below the safety limit of 60 °C in high discharge rates. The hybrid thermal management system (HTMS) reduced the steady-state temperature of batteries by 19.5% compared to active method at a Reynolds number of 340 and heat generation power of 3.7 W. The active method was also ineffective in controlling the battery temperature at high heat generation power levels while HTMS showed an appropriate thermal performance at the same condition. Furthermore, effect of utilizing Al2O3-water nanofluid with two different volume fractions was investigated in both active and hybrid systems. It was shown that, compared to the base case with water flow, nanofluid can reduce the maximum temperature of batteries by 15.5% and 8.5% in active and hybrid methods, respectively.

Effects of rotary ultrasonic bone drilling on cutting force and temperature in the human bones.

Efficacy and outcomes of osteosynthesis depend on various factors including types of injury and repair, host factors, characteristics of implant materials and type of implantation. One of the most important host factors appears to be the extent of bone damage due to the mechanical force and thermal injury which are produced at cutting site during bone drilling. The temperature above the critical temperature (47 °C) produces thermal osteonecrosis in the bones. In the present work, experimental investigations were performed to determine the effect of drilling parameters (rotational speed, feed rate and drill diameter) and techniques (conventional surgical bone drilling and rotary ultrasonic bone drilling) on cutting force and temperature generated during bone drilling. The drilling experiments were performed by a newly developed bone drilling machine on different types of human bones (femur, tibia and fibula) having different biological structure and mechanical behaviour. The bone samples were procured from male cadavers with the age of second to fourth decades. The results revealed that there was a significant difference (p < 0.05) in cutting force and temperature rise for rotary ultrasonic bone drilling and conventional surgical bone drilling. The cutting force obtained in rotary ultrasonic bone drilling was 30%-40%, whereas temperature generated was 50%-55% lesser than conventional surgical bone drilling process for drilling in all types of bones. It was also found that the cutting force increased with increasing feed rate, drill diameter and decrease in rotational speed, whereas increasing rotational speed, drill diameter and feed rate resulted in higher heat generation during bone drilling. Both the techniques revealed that the axial cutting force and the temperature rise were significantly higher in femur and tibia compared with the fibula for all combinations of process parameters.

Thermal-Hydraulics Operation Parameters Modeling and Analysis of KLT-40S Reactor at Steady-State and Transient Condition using RELAP5-3D

One of Floating Nuclear Power Plant (FNPP) designs in the world is currently being built by Russian Federation, named “Academic Lomonosov,” which uses two PWR types, KLT-40S as its power unit. However, too little information regarding its detailed technical specification is available, including its thermal-hydraulics parameters. The objective of this research is to create a thermal-hydraulic model of KLT-40S reactor core use RELAP5-3D and to predict fuel and cladding temperature value at the steady-state condition, and transient condition with a variety of primary coolant mass flow rate and pressure to simulate abnormal event within the reactor. The reactor thermal-hydraulic model is created by dividing 121 coolant channels in the actual nuclear fuel assemblies into two channels: one channel to simulate coolant flow in 120 fuel assemblies with average heat generation, and the other channel to simulate coolant flow in one fuel assembly with highest heat generation in the core. The fuel structure had solid cylinder geometry and made from ceramic-metal UO2 dispersed in the inert silumin matrix. The fuel cladding is made from zirconium alloy. These fuel heat structures generate heat from fission reaction and are modelled as a heat source according to the reactor power technical data, i.e., 150 MWt. The reactor axial power distribution is approximated by cosine distribution. Operation parameter variation that represents the real reactor normal operation condition in this research is a variation that has flow loss coefficient value 8,000, radial power peaking factor 1.1, and axial power peaking factor 1.1 with axial power peaking located in the middle of the fuel rod. The fuel and cladding temperature value at the steady-state condition and several transient conditions are predicted in this research, and there is no temperature value that goes beyond the safety limit.

Optimization and Control of a Z-Source, Ultrafast Mechanically Switched, High-Efficiency DC Circuit Breaker

A novel design of the Z-source circuit breaker topology is presented to minimize on -state losses of the protection device. An ultrafast mechanical switch is proposed to commutate the fault current and improve the controllability of the circuit breaker. Replacing the power thyristor in the Z-source circuit breaker and integrating an advanced control scheme reduces energy losses with a low-resistance mechanical contactor. The proposed design facilitates bidirectional current flow, enhances control capability for distributed energy resources, and improves ride-through capabilities during load transients. Z-source circuit breakers utilize an impedance network to create a forced current zero crossing in the event of a fault, allowing the inline thyristor to isolate the fault from the source through reverse bias. However, full load current flows through the thyristor, resulting in high loss and heat generation. The concept is validated, and a proper control scheme is developed for this circuit breaker through an analytical estimation model of the system dynamics during a fault. Simulation and modeling are performed in power systems computer aided design (PSCAD) and piecewise linear electrical circuit simulation (PLECS). Finally, an experimental laboratory prototype is tested to validate the analytical and simulation models and certify the control logic.

Development of luminescent atacamite nanoclusters for bioimaging and photothermal applications

Fluorescent atacamite nanoclusters (FANCs) have been developed and modified with silica for Drosophila salivary gland tissue imaging and photothermally induced cell death of osteosarcoma MG-63 cells. FANCs were synthesized with Moringa oleifera leaf extract without using any hazardous reducing and external capping agents. FANC was further used to evaluate light absorption, fluorescence emission, band gap, and magnetic properties as the first report on such nanoclusters. Upon excitation with a 350 nm light source, FANCs exhibited fluorescence at 460 nm, with a relative quantum yield of 0.3%. Besides, silica-encapsulated fluorescent atacamite nanoclusters (SEFANC) manifested remarkable improvement in emission, quantum yield (1.7%), shelf-life (15 d), biocompatibility, and photostability. Concomitantly, it has also increased the absorption in the near-infrared region and demonstrated high heat generation potential (42 °C → 50 °C). The above results suggest that FANC can be a potential candidate in the area of nanomedicine for a number of applications such as bioimaging, photothermal therapy, etc.

Experimental investigation and optimization of loop heat pipe performance with nanofluids

High heat generation from electronic devices needs to cool down properly to prevent overheating. Loop heat pipe (LHP) is one of the excellent cooling devices for high heat generation of electronic devices. Nanofluid is a working fluid which has nanoparticle dispersed in based fluid. Nanofluid is proven to have better thermal performance compared with conventional fluids. In this paper, we investigate on the thermal performance of loop heat pipes using different types of nanofluids. The desired nanofluids used in this study are diamond nanofluid, aluminium oxide (Al2O3) nanofluid and silica oxide nanofluid (SiO2) with 0–3% of mass concentrations. The results showed that as the mass concentration of nanofluids increased, the thermal resistance for diamond nanofluid and Al2O3 nanofluid decreased, but SiO2 nanofluid results show the opposite trend of thermal resistance with increasing mass concentration. The lowest thermal resistance is 3.0872 °C W−1, 3.1465 °C W−1 and 3.2816 °C W−1 for diamond, Al2O3 and SiO2, respectively. Moreover, all types of nanofluids show better heat transfer performance compared with water. Diamond nanofluid also had higher heat capacity than Al2O3 nanofluid as it had a lower vapour line temperature reading. Optimization result also shows that diamond nanofluid has better thermal enhancement than Al2O3 with 1.19% of mass concentration.

Grinding performance by applying MQL technique: an approach of the wheel cleaning jet compared with wheel cleaning Teflon and Alumina block

Characterized by the high heat generation, grinding has great difficulty in dry machining. As an alternative, it is proposed to apply abundant cutting fluid (conventional method) or a minimum amount of lubrication, which in turn dispenses with disposal costs and drastically reduces the volume of cutting fluid application during machining compared with the conventional technique. Despite this, the application of cutting fluids in MQL can cause clogging of the grinding wheel, damaging the workpiece quality. Against this, one of the techniques explored in the literature is the application of grinding wheel cleaning jet (WCJ), removing part of the layer adhered to the surface of the grinding wheel. Also, the present work proposes the cleaning of the cutting surface of the grinding wheel through the mechanical contact between Alumina (WCAB), and Teflon (WCTB) blocks with the cutting surface of the CBN grinding wheel, during cylindrical grinding of AISI 4340 steel hardened. Feed rates of 0.25; 0.50; 0.75, and 1 mm/min were applied under the following lubri-refrigeration conditions: conventional, MQL, and MQL with WCJ, WCAB, and WCTB. The parameters studied were roughness, roundness deviation, diametrical wheel wear, grinding power, acoustic emission, and microstructural analysis. The results showed that the WCAB and WCTB could improve grinding conditions compared with MQL without cleaning, mainly when applied with Alumina block. However, WCJ is the better condition associated with MQL. However, the conventional flood lubricant application remains with better results, indicant that it is necessary more effort to improve the MQL technique.

Thermal effects in H2O and CO2 assisted direct carbon solid oxide fuel cells

Thermal effects in a H2O and CO2 assisted tubular direct carbon solid oxide fuel cell (DC-SOFC) are numerically investigated. Parametric simulations are further conducted to study the effects of operating potential, the distance between carbon and anode, inlet gas temperature, and anode inlet gas flow rate on the thermal behaviors of the fuel cell. It is found that the fuel cell with H2O as gasification agent performs considerably better than the cell with CO2 as gasification agent in all cases. It is also found that the temperature field of the fuel cell is highly uneven. The breakdown of the heat sources in the fuel cell shows that the H2O assisted DC-SOFC has much higher heat generation and consumption than the CO2 assisted cell. Interestingly, a thermal neutral voltage is observed, at which no heating or cooling of the cell is needed. In addition, the distance between the anode and the carbon layer is required to be as small as possible, which improves the temperature uniformity of the fuel cell. The results of this study demonstrates the importance of thermal effects in DC-SOFCs and form a solid foundation for DC-SOFC thermal management.

Low carbon containing Al2O3-C refractories with nanocarbon as the sole carbon source

The functional refractories used in the continuous casting process of steel are mostly made up of alumina (Al2O3) - carbon (C) system. Graphite is used as the main carbon source because of the properties it offered. Generally, these refractories contain about 30% residual carbon after coking. But the use of high carbon content leads to several disadvantages like carbon pickup by steel, high heat loss and generation of higher extent of COx gases, etc. Hence, the development of low carbon Al2O3-C refractories without conceding any beneficial properties is the challenge to the refractory technologists. Such a challenge is intended in current study with the use of nanocarbon as a complete alternative for graphite. The variation in physical, mechanical and thermo-mechanical properties with variation in amount of nanocarbon in the composition is studied. Phase analysis and microstructural developments are also evaluated along with the oxidation resistance at different temperatures. Because of its high reactivity, nanocarbon helps to form in-situ ceramic phases at much lower temperatures thereby enhances strength and other properties. But the increase in amount of nanocarbon above 2% found to deteriorate the properties.

Numerical Investigations of Mini-Channel Heat Sink for Microprocessor Cooling: Effect of Slab Thickness

High heat generation in microelectronics devices is an inevitable consequence of high processing loads. One of the important factors in design of electronic devices is to design a smart cooling system to remove the generated heat well in time for a reliable and longer life. Water-cooled heat sinks are replacing air-cooled heat sinks with the rapid compactness and high process requirements. In this work, we introduced a slab in mini-channel and evaluated the thermal performance of mini-channel heat sink. The boundary layer separately develops in upper and lower portions of channel, which enhanced the heat transfer. We changed the thickness of slab from 0.2 to 1.6 mm for fin spacing of 0.5 mm and 1 mm, respectively, to determine the effects of thickness on overall thermal performance of heat sink. The computed values were then compared with the data available in the literature without slab. The minimum base temperatures recorded for 0.2-mm-thick slab with fin spacing of 0.5 mm and 1.0 mm were 40.1 °C and 42.4 °C, respectively. This represents a reduction of 12.5% and 16.2%, respectively, in the base temperature as compared to the base temperature without a slab.

Tribological studies of EN31 steel and Ti-6Al-4V alloy materials using pin-on-disc tribometer

Mechanical parts in modern machining systems are often subjected to friction and wear causing high heat generation at the contact zones leading to reduced lifecycle and increased power consumption of machinery. Coolants, despite controlling this high contact zone heat, are uneconomical due to their high cost. Various researchers across industries have been focusing towards replacing coolants by developing newer lubricants to obtain environmental and economic benefits. The current work presents an experimental investigation to evaluate tribological characteristics of bearing steel (EN 31) and Ti-6Al-4V alloy using MoS2 as solid lubricants. Friction and wear properties were measured on a pin-on-disc tribometer at different sliding conditions. Solid lubricant was effectively supplied to the pin-disc interface zone through a specially designed experimental set-up namely minimum quantity solid lubricant (MQSL). The obtained results are compared with the dry and wet environmental conditions. The results indicate a significant improvement in the tribological performance of steel and alloy materials under MQSL when compared with dry and wet environment conditions. The work presented here provides a good understanding of methods to cool/lubricate the sliding zones, reduce temperature at sliding interface to make the machining of difficult-to-cut materials more efficient and economic.

Multifunctional Grid-Connected Voltage Source Inverter to Drive Induction Motor Operating With High-Inertia Load

This paper proposes a novel multifunctional topology for a grid-connected voltage source inverter to control the speed and power flow of a squirrel-cage induction motor. For high-inertia loads during startup, the issues faced include a large transient current and high heat generation. However, the solutions proposed by existing startup methods are inadequate. The topology presented in this study not only addresses the problems related to these methods, i.e., creating a smooth startup, but also presents a flexible alternative for power factor correction using capacitor banks. First, the proposed technique accelerates the motor smoothly to its operating point through the sinusoidal voltage provided by an inverter with an LC filter in its output. In the second step of the control method, after achieving stability in the desired operating point, a converter with an LC filter is assigned the task of power factor correction. Thus, the proposed topology achieves a smooth startup and unity power factor. It includes a new control strategy in which the rotor field-oriented control method is employed for the speed control mode. Finally, the validity of the proposed theory is verified.

Study the performance of solid lubricants during hard turning of AISI 4340 steel

Hard turning process is widely used in manufacturing industries. The main problem associated with hard turning is the high frictional heat generation. Traditionally cutting fluids are used to control the heat generation. However, the major drawback related with the use of cutting fluids is the environmental pollutions. The use of solid lubricants during machining is another alternative technique to control the heat generation. It is environmental as well operator friendly. Therefore, in this research work, an experimental study has been conducted to investigate the performance of solid lubricants assisted hard turning. The hexagonal boron nitride (h-BN) and zinc sulfide (ZnS) were taken as a solid lubricating medium. The cutting speed, feed rate, workpiece hardness and tool nose radius were selected as process parameters. The cutting force and chip tool interface temperature were taken as performance indicators. The experiments were performed by using central composite design. The significance of process parameters was analyzed by performing analysis of variance (ANOVA). The second order mathematical models of cutting force and chip tool interface temperature were formulated. The optimal value of the process parameters which provides minimum cutting force and chip tool interface temperature was suggested. The experimental results were compared with dry and wet conditions of machining. The results indicate that solid lubricants have shown better machining performance when compared to dry and wet conditions.

Tensile and wear behaviour of friction stir welded AA5052 and AA6101-T6 aluminium alloys: effect of welding parameters

To improve the performance and effectiveness of cost, constructing lightweight structure is the important factor for automobile, naval and aerospace industries. AA5052 and AA6101-T6 aluminium alloys are widely applied in transport industries, due to their lightweight and high strength and hence, joining of these two are unavoidable. Friction stir welding is an unconventional welding method, which is developed for constructing lightweight structures. This work describes the detailed study of friction stir welded dissimilar AA5052 and AA6101-T6 alloys. AA5052 and AA6101-T6 plates are welded with rotation rates of 765–1400 rpm and offset distances at advancing side of 0–2 mm. For this purpose, four levels of welding parameters based on Taguchi L16 orthogonal array are chosen. To determine the optimum combinational levels and identify the effect of above-mentioned parameters on tensile and wear properties, Signal to Noise ratio and ANOVA respectively are used. From the results, it is observed that the combination of 1 mm offset distance at advancing side and 1400 rpm rotating speed produces better tensile and wear properties, which is due to high heat generation, sufficient flow of materials and balanced precipitation and strain hardening effects. On the other hand, the combination of 2 mm tool offset at advancing side and 765 rpm rotational rate exhibits poor properties, which is associated with low heat input, defects formation, precipitate coarsening and lesser strain hardening effects.

Effect of micro-EDM machining parameters on the accuracy of micro hole drilling in Zr-based metallic glass

Micro drilling of metallic glass is a technologically important research due to recent development of metallic glass and their technological niche applications in field of micro nozzles, micro-electro mechanical systems (MEMS) and bio-implants. Micro drilling of metallic glass is a challenging work because of in situ crystallization of resultant workpiece due to localized high heat generation during machining. However, micro-electrical discharge machining (Micro-EDM) eludes the limitations of conventional machining methods and offers precise machining of metallic glass with good surface properties. Micro-EDM machining parameters exerts a big influence on the machined features and their surface properties. A study of effect of micro-EDM machining parameters on machined geometry’s features and optimization of machining parameters for accurate machining of metallic glasses are very essential owing to the recent advancements in the applicability of Micro-EDM for processing of metallic glass parts. In present work micro-EDM is used for precision drilling of micro holes in metallic glasses. The levels of input micro-EDM machining parameters such as capacitance, voltage, tool revolutions per minutes (RPM) for optimum accuracy of micro holes and minimum machining time are identified. Resultant of present work culminated to the establishment of micro holes with exceptional accuracy using micro-EDM. The tool RPM is found to be a key parameter for increasing hole accuracy as well as reducing machining time. Outcome of present work may pave application of metallic glasses products based on precision engineering.

Investigation on the thermal behavior of Ni-rich NMC lithium ion battery for energy storage

Heat generation is the primary factor for the safety and performance of lithium-ion battery. While the Ni-rich NMC lithium-ion battery has a much worse safety performance compared to other batteries. Hence, it is important to investigate the thermal behavior of the battery. In this paper, a pseudo two dimension (P2D) electrochemical model coupled with 3D lumped thermal model (ECT) was developed to investigate the thermal behavior of large format Ni-rich nickel-cobalt-manganese oxide (NCM) pouch type lithium-ion battery. The charge/discharge performance, heat generation (including total heat generation and polarized/ohmic/reversible heat generation) and temperature rise at different temperatures and different C-rates were numerically investigated to analyze the overall battery performance at the adiabatic condition. The results show that battery can only normally charge/discharge at quite low C-rate at extremely low temperature (−20 °C) with a much high total heat generation (40.02 kJ/36.12 kJ). The total heat generation and temperature rise increase with the decreasing temperature. The highest heat generation and temperature rise occur at the ambient temperature of −5 °C (at the charge rate of 3C) and 0 °C (at the discharge rate of 3C). At low temperatures (<0 °C), the ohmic heat generation mainly contributes to total heat generation, and as the ambient temperature is higher than 5 °C, the polarized heat generation becomes the main heat generation aspect. While the reversible heat generation is relatively small and almost no change at different C-rates.

Evaluation of surface and sub-surface integrities of a mold steel under different grinding conditions

In a context where there is a continuous search for more environmentally friendly machining processes (for example, the implementation of the minimum quantity of lubrication—MQL—cooling–lubrication technique) and the constant concern with the high heat generation during the grinding process, there is still a lack of information about grinding of steel for molds and dies. Thus, the present work sought to evaluate the performance of tangential surface grinding of a steel for plastic injection molds, testing by two types of conventional abrasives (green silicon carbide and white aluminum oxide) under three different equivalent chip thicknesses. The performance of the MQL cooling–lubrication technique compared to the conventional one (flood coolant) was also evaluated. The output parameters to assess the surface integrity were the surface roughness (Ra parameter), residual stresses and SEM images of the ground surfaces, as well as microhardness below the machined surface. The results shown that both conventional abrasives types have potential to be used in grinding of this steel, once low surface finish values (Ra < 0.2 μm) and workpieces free of damages were fabricated. Silicon carbide (SiC) grinding wheel in general outperformed the aluminum oxide (Al2O3) one in terms of surface roughness after machining under severest conditions (Ra < 0.35 μm). Residual stresses were predominantly compressive irrespective of the cooling–lubrication technique and type of abrasive employed. Despite lower surface roughness and compressive residual stresses generated after grinding with the Al2O3 grinding wheel, drop in hardness below the machined surface was observed, unlike when machining with SiC grinding wheel. MQL technique proved to be more effective than conventional coolant technique under the conditions investigated, irrespective of the grinding wheel used, and in some situations, it outperformed the conventional technique.

An optimal internal-heating strategy for lithium-ion batteries at low temperature considering both heating time and lifetime reduction

Low-temperature preheating of batteries is fundamental to ensure that electric vehicles exhibit excellent performance in all-climate conditions. Direct current for discharge is presented to rapidly preheat batteries due to its simple implementation and high heat generation compared to alternating current. Experimental results reveal that the heating time is significantly reduced while capacity degradation is dramatically increased, with the decreasing discharge heating voltage. A simple fade model to capture battery capacity loss is proposed and accurately demonstrated under direct-current discharge heating. Pareto front for dual crucial yet conflicting objectives, heating time and capacity loss, is obtained using the multi-objective genetic algorithm and the effect of weighting coefficient on heating performance is discussed, thus proposing an optimal internal-heating strategy. The battery is rapidly heated from −30 °C to 2.1 °C within 103 s and the capacity loss is only 1.4% after 500 repeatedly heating, implying substantially no lifetime deterioration. At 0.8 state-of-charge, the heated battery can offer 8.7/32.7 times the discharge/charge power and 62.46 times the discharge energy of the unheated battery, indicating a significant performance boost. The proposed optimal heating method, thanks to short heating time and no substantial lifetime reduction, yields great potential to rapidly boost battery performance in extremely cold conditions.

Aging investigation of an echelon internal heating method on a three-electrode lithium ion cell at low temperatures

Abstract An echelon internal heating method based on alternating current has exhibited many advantages of high heat generation rate and thermal uniformity for fast battery heating at low temperatures. However, inappropriate parameter settings for the echelon internal heating method are prone to risk battery health due to side reactions. To address this problem, a three-electrode cell is fabricated to investigate the effect of the echelon internal heating method on cell health at low temperatures. A fractional order circuit model is used to determine the optimal current amplitude and frequency of alternating current at different temperatures for preheating the cell. After many cycles of preheating the cell, capacity calibration results and incremental capacity curves show no apparent detrimental effect of the proposed heating method on cell health.

Corrosion behavior of surface induced by wire EDM on 316L stainless steel: an experimental investigation

Wire electric discharge machining is an efficient technique among the available nonconventional machining process and is mostly used for machining complex shapes and hard materials. This process also acts as a form of surface modification technique. The discharge energy of machining process influences the nature of the machined surface to a very high degree due to high heat generation and deposition of wire electrode material. 316L stainless steel is widely used in engineering, marine and medical applications. Although 316L SS is a corrosion resistant material, there is a lot of research going on to improve its corrosion resistance by different surface modification techniques due to its applications. Investigation on the effect of WEDM parameters on the corrosion behavior of 316L SS material is carried out. Corrosion studies were carried out by Potentiodynamic polarization test and phase analysis was carried out by using XRD. Significant enhancement in the corrosion resistance of WEDMed surface is observed with the variation in pulse on time and peak current. Pulse on time and peak current are the significant parameters influencing the amount of discharge energy. Low level of discharge energy enhanced the corrosion resistance of WEDMed surface.