Browse Topic: Cooling
Engineers from Australia and China have invented a sponge-like device that captures water from thin air and then releases it in a cup using the sun’s energy, even in low humidity where other technologies such as fog harvesting and radiative cooling have struggled.
The initial powder used for the manufacturing of NdFeB permanent magnets is usually prepared through rapid cooling, either by melt spinning or strip casting. The powders produced by these two methods are suitable for different applications: while melt-spun powder is a good initial material for bonded and hot-deformed magnets, strip-cast powder is normally used for sintered magnets. To investigate the suitability of using strip-cast powder to manufacture hot-deformed magnets, NdFeB powder prepared by strip casting was hot pressed (without particle alignment) and compared with melt-spun powder prepared under the same conditions (700 °C, 45 MPa, 90 min). Although the processing parameters are the same (pressed in the same mold), the magnetic properties of the magnets made from the two powders are significantly different. Surprisingly, the magnet made from the strip-cast powder (after ball milling) shows comparable magnetic properties to those of isotropic magnets, with coercivity (HcJ) of 1270 kA/m and remanence (Br) of 0.7 T, while that made from the melt-spun powder exhibits much lower properties: HcJ = 480 kA/m, Br = 0.5 T, although the melt-spun powder initially shows much better magnetic properties than the strip-cast powder. Possible reasons for such a difference in magnetic properties are discussed. It was shown that the particle size of the initial powder plays an important role in determining the final magnetic properties of the hot-pressed magnets.
Battery cell aging and loss of capacity are some of the many challenges facing the widespread implementation of electrification in mobility. One of the factors contributing to cell aging is the dissimilarities of individual cells connected in a module. This paper reports the results of several aging experiments using a mini-module consisting of seven 5 Ah 21700 lithium-ion battery cells connected in parallel. The aging cycle comprised a constant current-constant voltage charge cycle at a 0.7C C-rate, followed by a 0.2C constant current discharge, spanning the useful voltage range from minimum to maximum according to the cell manufacturer. Charge and discharge events were separated by one-hour rest periods and were repeated for four weeks. Weekly reference performance tests were executed to measure static capacity, pulse power capability and resistance at different states of charge. All diagnostics were normalized with respect to their starting numbers to achieve a percentage change over time. Both electrical and thermal dissimilarities were considered by initial cell selection or adjusting the thermal boundary conditions, respectively. The latter was achieved by contrasting air cooling with direct liquid immersion cooling which prevented temperature spikes and ensured more uniform temperature distribution between the cells. For well-clustered cells, the use of immersion cooling reduced the capacity fade noticeably when compared to air cooling. However, when cells are not well clustered, the impact of electrical dissimilarities overshadowed the thermal benefits. Poor cell clustering resulted in a lower discharge resistance increase which itself reflected as smaller changes of the pulse power fade. The results highlighted the importance of cell selection and clustering during research and when building packs for final application and reinforced the benefits of good thermal management. The work did not fully explore the benefits of immersion cooling due to the moderate C-rates used.
As “point of need” additive manufacturing emerges as a priority for the Department of Defense (DoD), Australian 3D printing provider SPEE3D is one of several companies demonstrating that its machines can rapidly produce castings, brackets, valves, mountings and other common replacement parts and devices that warfighters often need in an on-demand schedule when deployed near or directly within combat zones. DoD officials describe point of need manufacturing as a concept of operations where infantry and squadron have the equipment, machines, tools and processes to rapidly 3D print parts and devices that are being used in combat. Based in Melbourne, Australia, SPEE3D provides cold spray additive manufacturing (CSAM) machines that use a combination of robotics and high-speed kinetic energy to assemble and quickly bind metal together into 3D-printed parts without the need for specific environmental conditions or post-assembly cooling or temperature requirements. Over the last two years, the company has participated in military point of need manufacturing challenges and demonstrations with military units from the U.S., UK, Australia and Japan among others.
Quenching is a heat treatment process for the rapid cooling of a metallic workpiece in water, oil, or air to obtain certain desired material properties. It is the most critical step in the sequence of heat-treating operations to preserve the solid solution formed at the solution heat-treating temperature by rapidly cooling to near room temperature. Because of the complex interaction between temperature, phase-transformation, and stress/strain relation that depends on the temperature distribution and the microstructure of the workpiece, there is no performance-informed quenching process that can be applied reliably to reduce the high scrap rate of airframe aluminum forging parts with a significant amount of residual stress and distortion. Since large aluminum forging parts are increasingly used in aerospace structures to enable structural unitization, it is important to construct a digital twin modeling approach to mirror the physical quenching process for minimizing scrap rate, increasing production efficiency, and engineers and machine operators' handling of variances in forging operations. A high-fidelity modeling of the coupling of thermal, metallurgical, and mechanical interactions is a key component to creating a digital twin of the physical quenching process. A high-fidelity thermal multi-phase computational fluid dynamics (CFD) model is applied to simulate fluid dynamics and temperature fields in the quenchant tank. The developed immersogeometric modeling approach is used next for an efficient model generation of a 3D workpiece with various dipping orientations. Given the temperature and pressure profiles predicted from the CFD-based heat transfer module, residual stress and distortion prediction modules are developed by including temperature and pressure fields mapping and temperature and strain rate dependent property evolution via Abaqus' user-defined subroutines. Verification and demonstration studies are performed using aluminum coupons dipped into a quenching tank with different orientations. Time histories of the temperature and residual stress fields were predicted to explore the relationship between the process and performance.
This paper has been withdrawn by the publisher.
The automotive sector is evolving both globally and as well as in India. The Indian customer’s expectations from an automobile are also evolving at fast pace. This is resulting in a continuous shrinkage of the time available for vehicle development. To meet customers’ expectation of superior cabin thermal comfort it is important to predict cabin cooling performance at early stage. This can be achieved through thermal simulation. Existing studies of cabin thermal simulation explained the method of co-simulation. Wherein, Input for the cabin was used a grill air temperature which was obtained from the physical test. It showed good correlation for the cabin inside air temperature with actual test. However, cabin cooling performance does not only depend on cabin structure & layout but also, affected by AC system & its component level performance. AC systems and components were not considered in previous studies. As a result, replacing or modifying the AC system components does not allow us to estimate the cabin inside air temperature. Therefore, it is important to link AC system with existing co-simulation methods. This paper explains that, how the AC system is connected to existing co-simulation model and carryout the real-time cabin cooling simulation. Revised co-simulation approach will help in the development of an effective AC system and predict cabin inside air temperature while considering the impact of AC system components on cabin cooling.
A typical modern automobile compressor-driven air conditioner, about powerful enough to cool a house, may not be needed even in very hot, humid climates if we combine insights from comfort theory with innovations in comfort delivery, photonics, and superefficient thermal and air-handling devices. Recent advances can successively minimize unwanted heat gain into the passenger cabin, cool people’s bodies rather than the vehicle, deliver highly effective radiant cooling, passively reject extracted heat to the sky, and, if needed, move air very efficiently and quietly to expand the human comfort range. Together these proven innovations may give automotive occupants excellent hot-weather comfort without refrigerative air conditioning. This substitution could improve climate protection and electric-vehicle range, cut the automobile’s weight and cost, avoid climate and ozone harm from refrigerants, reduce noise and air pollution, make autos more energy-efficient, and save the United States gasoline costing many billions of dollars per year. Prompt experimental tests of such integrative designs are warranted.
Battery thermal management for electric vehicles have gained significance over recent years, especially for the present lithium-ion batteries. However, high operating temperature and uneven temperature distribution inside the battery cell can significantly reduce capacity and lifetime. The temperature difference between the battery cells needs to be minimized to avoid premature aging of specific cells exposed to a higher temperature. The most common way to dissipate heat from the battery cells is to use air or liquid cooling. Air cooling is less complex than liquid cooling, but the extremely high ambient temperature dramatically limits the usage of air cooling. This paper developed a thermal connector that could be repeatedly assembled and disassembled between the battery cell. The thermal connector can effectively dissipate the heat into the refrigeration cycle while providing constant thermal resistance among the battery cells, which can be as lower as 0.115°C/W. Heat transfer through the thermal connector and refrigeration cycle were then calculated by applying different two-phase heat transfer correlations. Our results indicated that the overall heat transfer coefficient is around 7000.69 W/m2·K, which can be used to dissipate the heat of 20.01 kW. This research can provide the application of thermal connector with refrigeration cycle design in battery thermal management.
Camels keep cool while conserving water in a scorching desert environment via a thick coat of insulating fur. Applying essentially the same approach, researchers have developed a system that could help keep things like pharmaceuticals or fresh produce cool in hot environments without the need for a power supply.
A systematic and comprehensive first law analysis of a cooled gas turbine cycle subjected to vapor compressor inlet air cooling (VC-IAC) has been conducted in our study. Film air cooling technique has been implemented to cool the gas turbine (GT) buckets. The gas turbine is subjected to variation of various operating and ambient parameters and the corresponding effect is analyzed to find out the optimal one. The integration of VC-IAC has been reported to further enhance the plant specific work and plant efficiency of gas turbine cycle, the enhancement being higher in regions having a hot and dry climate. This increase in cycle performance due to VC-IAC has been found superior in case of bucket cooled GT cycle when compared to uncooled one. It has further been witnessed that the plant specific work increases by more than 0.35 % and the plant efficiency increases by little above 0.1 % for every 1o C drop in CIT. The work ratio representing the excess of work of turbine over work of compression has been observed to improve when the ratio of inlet temperatures (rIT) is increased or pressure ratio (rp, c.) is decreased. For every turbine inlet temperature , an optimal rp,c has been reported to exist at which, the plant efficiency is maximized.
Overheating of the brake disc is a major concern in the brake performance. Overheating is the main cause of a reduction in braking efficiency, especially if a vehicle is fully loaded. The heat dissipation rate for Solid rotors is very low. In order to increase the heat dissipation rate, the disc must be used with ventilation provided on it. Further in ventilated disc rotors, the ribs in between the rotors provide cooling. The ribs allow the flow of heat and pull out the air in between the rotors for efficient cooling. In this research, four different brake disc namely, Solid Disc (SL), Cross-drilled disc (CD), Cross-slot disc (CS) and Hybrid disc (CD-CS-SG) which is a combination of Cross drilled and slot with side groove have been analyzed at various brake conditions in the form of heat generation and thermal stresses. The temperature gradient over the surface is studied using the thermal numerical simulations and the stress generated within the structure core of hybrid rotor is studied using the thermo-structural coupling. These results of the optimized hybrid rotor are compared with the results of the primitive design of solid, cross-slotted and curved vane ventilated disc rotors. The results when compared at a given constant angular velocity, the hybrid ventilated brake disc rotor with a side groove proves to be superior to the primitive types in mechanical and thermal properties. It is also been observed that the disc surface temperature was increased with an increase in braking time. Whereas, heat dissipation was found to be maximum in the hybrid brake disc as compared to all configurations. More thermal stresses were observed in hybrid brake disc especially at the corners as compared to solid disc.
This specification, in conjunction with the general requirements for steel heat treatment covered in AMS2759, establishes the requirements for heat treatment of precipitation-hardening corrosion-resistant, maraging and secondary hardening, steel parts. Parts are defined in AMS2759. Parts made from steels other than those specified in this specification may be heat treated in accordance with the applicable requirements herein using processing temperatures, times, and other parameters recommended by the material producer unless otherwise specified by the purchaser. General ordering instructions are specified in AMS2759.
Common cooling methods such as air conditioners are expensive, consume significant amounts of energy, require ready access to electricity, and often require coolants that deplete ozone or have a strong greenhouse effect. An alternative to these energy-intensive cooling methods is passive daytime radiative cooling (PDRC), a phenomenon where a surface spontaneously cools by reflecting sunlight and radiating heat to the colder atmosphere. PDRC is most effective if a surface has a high solar reflectance that minimizes solar heat gain and a high thermal emittance that maximizes radiative heat loss to the sky.
With the exception of thermal storage heat sinks, the term heat sink is a misnomer. Standard heat sinks for electronics cooling are actually heat exchangers, taking the heat from the electronics, and transferring it to a fluid, either air or coolant. Phase Change Material (PCM) heat sinks are the only heat sinks that actually act as a (temporary) sink for heat. They are emerging in the thermal management realm to solve thermal problems in systems where active solutions cannot be used. When there is no place to dissipate the heat generated by electric components, a PCM heat sink is capable of absorbing the generated waste heat [1] .
This specification, in conjunction with the general requirements for steel heat treatment covered in AMS2759, establishes the requirements for heat treatment of precipitation-hardening corrosion-resistant, maraging and secondary hardening, steel parts. Parts are defined in AMS2759. Parts made from steels other than those specified in this specification may be heat treated in accordance with the applicable requirements herein using processing temperatures, times, and other parameters recommended by the material producer unless otherwise specified by the purchaser. General ordering instructions are specified in AMS2759.
Professor Hopkins and University of Virginia colleagues — in collaboration with materials scientists at Penn State, the University of Maryland, and the National Institute of Standards and Technology — have studied a material that can dynamically regulate its thermal properties, switching back and forth between insulating and cooling based on the amount of water that is present.
The integration of inlet air cooling to gas turbine based power utilities is a well accepted practice as this modification to the utility delivers superior utility performance. However, application of inlet-air cooling to drive turbines and specifically to marine mobility sector is rare in literature. Marine vessels are generally propelled by diesel engines, however large marine vessels specifically cruise ships and high speed naval vessels may have requirements of higher speeds and on-board power requirements which can fulfilled by gas turbine driving the propellers while on-board power needs can be met by steam turbine power generated from gas turbine exhaust heat. Such gas-steam combined cycles have the potential to become popular for high capacity marine vessels. The choice of gas turbine based combined cycle power plant for marine vessels in comparison to diesel engine powered vessel is also superior due to lower emission from the former. Higher ambient temperatures are known to negatively affect gas turbine and hence also marine combined cycle performance. The present article discusses the prospects of using an evaporative inlet air cooled combined cycle as a prime mover for marine application. A parametric study of the effect of compressor pressure ratio, turbine inlet temperature, ambient relative humidity and ambient temperature on energy, exergy and emission performance of combined cycle used in marine application has been carried out. Evaporative inlet cooling integrated to cooled gas-turbine based combined-cycle has been observed to improve the power output by 10.25% and efficiency by 1.55%. This improvement has been observed to be higher at higher ambient temperature and lower ambient relative humidity. Inlet air cooling has also observed to improve emission performance with lower NOX and CO emission. The overall cycle exergy destruction has also been observed to reduce due to the addition of inlet air cooling to a gas turbine propelled/powered based combined cycle.
This specification, in conjunction with the general requirements for steel heat treatment in AMS2759, establishes requirements for thermal stress relief treatments of parts manufactured from the following materials: a Carbon and low alloy steels b Tool steels c Precipitation hardening, corrosion resistant and maraging steels d Austenitic corrosion resistant steels e Martensitic corrosion resistant steels
This specification, in conjunction with the general requirements for steel heat treatment covered in AMS2759, establishes the requirements for heat treatment of precipitation-hardening corrosion-resistant, maraging and secondary hardening, steel parts. Parts are defined in AMS2759. Parts made from steels other than those specified in this specification may be heat treated in accordance with the applicable requirements herein using processing temperatures, times, and other parameters recommended by the material producer unless otherwise specified by the purchaser. General ordering instructions are specified in AMS2759.
In today’s automotive industry, the A/C (Air-conditioning) system is emerging into a high level of technological growth to provide quick cooling, warm up and maintaining the air quality of the cabin during all-weather conditions. In HVAC system, TXV plays vital role by separating high side to low side of vapor compression refrigeration system. It also regulates the amount of refrigerant flow to the evaporator based on A/C system load. The HVAC system bench laboratory conducts the test at different system load conditions to evaluate the outputs from tests during initial development stage to select the right TXV in terms of capacity and Superheat set point for a given system. This process is critical in HVAC developmental activity, since mule cars will be equipped with selected TXV for initial assessment of the system performance. The TXV tuning is conducted in system bench lab using defined test load cases which is developed using combination of given input boundary conditions and tests were conducted based on that. In this paper, major focus is laid on understanding potential importance of each system parameter, identify bench test boundary conditions that are critical for TXV set point decision making and understand internal stakeholder’s requirement. The whole process started with conducting personal interviews with internal stakeholders and suppliers to collect raw voices of customers. The DFSS tools were used to capture internal customer voices and translate into technical measures to provide insight of the data required for TXV selection. Tools used such as voice affinity, HOQ, Pugh Matrix, and Function tree diagram etc. The raw voices from interviews are translated into most important voice and mapped with current process using HOQ approach. The main purpose of house of quality is to derive the measurable targets to meet customer requirement. This study helps us to reduce the number of physical testing by approx. 35% without affecting TXV selection process and use objective approach to study system parameters.
This paper provides a review on state-of-art modern cooling systems employed for thermal cooling of electric motors for vehicle applications. In recent years, the pursue of a more sustainable and ecofriendly mobility has pushed the research towards the development of electric vehicle powertrain systems. Besides the evident advantages of the adoption of electric traction systems in terms of pollution and efficiency, the need of an effective cooling system for the electric machine components gained more and more importance in order to maintain high efficiency and ensure high durability. In fact, it is known that high temperatures can be harmful for the electric motor: besides the evident damages for mechanical parts, the influence on the permanent magnet properties is not negligible [1] [2]. In this fast-evolving environment, different solutions for the thermal problem have been researched and adopted, each one with its own pros and cons. Those who face the development of a PM machine can found plenty of these solutions in literature; so, the purpose of this paper is to draw a first qualitative comparison among the most important mechanisms available to extract heat from the electric machine and to guide the reader to an efficient and effective solution. Various methodologies for heat extraction are here described: resilient thermal pads for a conductive cooling; forced air and liquid loops, spray cooling and hollow rotor shaft for gases/fluids convective cooling methods. Finally, it is provided a table for a qualitative comparison among the various cases.
Hyundai's new engine is developed which optimize the cooling efficiency for knocking improvement and friction reduction. The cooling concepts for this purpose are 1) equalizing the temperature among cylinders by flow optimization, 2) cooling the required area intensively, 3) adopting ‘active flow control’ and 4) enlarging fuel economy at high speed range. In order to realize the cooling concept, 1) cross-flow, 2) compact water jacket & exhaust cooling, 3) flow control valve and 4) cylinder head with integrated exhaust manifold are considered. Improvement of knocking and friction reduction by increased cooling water temperature makes fuel efficiency possible. On the other hand, in order to strengthen the cooling around the combustion chamber and to reduce the deviation among the combustion chamber of cylinders, it is required to design the head water jacket shape accordingly. It is a very important task to decide the appropriate cooling water capacity in water jacket and to secure the cooling flow in the main parts through smooth cooling water flow. Increasing engine cooling is an effective way to improve knocking but excessive engine cooling performance creates unnecessary cooling losses so it is important to configure the combustion chamber ambient cooling appropriately.
(These definitions were prepared by the Joint Committee on Definitions of Terms Relating to Heat Treatment appointed by the American Society for Testing and Materials, The American Society for Metals, the American Foundrymen's Association, and the SAE.) This SAE revision emphasizes the terms used in heat treating ferrous alloys, but also includes for reference some non-ferrous definitions at the end of the document. This glossary is not intended to be a specification, and it should not be interpreted as such. Since this is intended to be strictly a set of definitions, temperatures have been omitted purposely.
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