Papers by Keyword: Cooling

Abstract: The performance of a Lithium-ion (Li-ion) battery is highly dependent on its operating temperature. Therefore, the Li-ion battery cooling system needs to be investigated when designing a battery pack. The cooling system must be able to maintain the operating temperature of the battery without exceeding its maximum temperature, so that the performance and safety of the battery pack can be guaranteed. This study aims to determine the effect of C-Rate variations on the operating temperature of the NMC battery through a numerical investigation. Lithium-Ion 18650 batteries arranged in a battery module with a 5×5 configuration is evaluated using a forced-liquid cooling system, with water as the coolant. Numerical simulations were run using the ECM heat generation model at different discharge rates of 1C, 2C, 3C, 4C, and 5C for 720 s. The results obtained indicate that the increase in battery pack temperature is directly proportional to the increase in C-Rate. The operating temperature for the five discharge rates is still in the range of safe operating conditions for the battery pack with the maximum temperature difference is below 5°C.

Abstract: The objective of the current work is to analyze the influence of water cooling of high density polyethylene (HDPE) sheet welding by friction stir process (FSW) on mechanical strength, based on microhardness tests. In the present work, the process using the conventional tool (C-FSW) is presented with the new procedure developed for FSW for HDPE, called water conventional friction stir welding (W-FSW). Test results for water-cooled and non-cooled welded samples were compared. HDPE sheets were initially welded by FSW process, and intensive water cooling was performed to weld after the tool exceeded the initial welding position by 30mm. The tool rotation speed of 1100 rpm and welding speed of 26 mm/min was used. The results were compared and evaluated with the hardness tests. A decrease in the hardness was observed when the sheets were treated by quenching, especially in the weld cores. It was found that the average hardness was much lower than that of untreated welded plates. Additionally, there is a region outside the core that has more or less the same stiffness value. The use of intensive quenching and conventional tooling has proven to be of great importance in improving surface finish, reducing defects, and increasing the mechanical strength of welds. The resulting recrystallization modified the hardness and thus increased the efficiency of the joint. These findings indicate the welding quality of the studied polyethylene.

Abstract: Widely used to preserve foods for long-term preservation, freezing is a standard method of preserving food goods. This technique is highly energy-intensive and time-consuming. Utilising shock freezing techniques helps to accelerate the process. The current paper analyses information regarding the technology and application of shock-freezing technologies, including those utilising electromagnetic and electric fields. The results of experiments conducted using a refrigerator equipped with an electromagnetic system are reported. In order to achieve the research objectives, coils were installed in the refrigerator to induce an alternating electromagnetic field with an electromagnetic induction value of up to 0.6 mT. Preliminary experiments were carried out using sodium chloride solutions with various concentrations found in perspective frozen food products.

Abstract: The work theoretically substantiated and practically implemented the technical solution for supplying the components of gel-forming system (GFS). This allows implementing the concept of using gels to protect tanks with oil products from thermal emission. The response time in case of fire at the unloading-loading racks is determined. Criteria for supplying GFS components for cooling the walls of railway tanks have been developed. The ejection method for supplying GFS components is defined as promising. A device that allows supplying GFS components without structural changes in standard firefighting equipment has been developed and manufactured.

Abstract: The continuous demand focused on optimizing titanium machining techniques in the aerospace industry, makes improving machining processes in this area of great interest to the industry. The contamination produced by the coolants used to machine titanium is a major problem to be addressed, since it is a material that requires cooling due to its strength, physical qualities and low thermal conductivity. That is why the implementation of a RHVT cooling system can improve the current situation. The aim of this work is to compare the final quality of the drilling by applying the system of RHTV (Ranque Hilsch Vortex Tube) cooling techniques and to see the advantages of its application with the dry machining process. This cooling system is expected to reduce drilling temperatures, thereby increasing the environmental performance of the manufacturing process. It is expected to set up a preliminary study based on a comparison between dry drilling and drilling assisted by the application of RHTV. Macro and microgeometric defects will be evaluated to determine the cooling system efficiency, as well as the machining temperatures reached.

Abstract: У даній роботі представлено спосіб створення гелевої вогнегасної речовини на основі гідроксиду алюмінію з використанням карбонату калію. Показано переваги запропонованого способу порівняно з відомим способом створення гелевої вогнегасної речовини на основі гідроксиду алюмінію з використанням карбонату натрію. Наведено результати експериментальних досліджень ефективності гелевогнегасних речовин на основі гідроксиду алюмінію.

Abstract: The contributions balance of isolation and cooling effects relative to the liquids surface to slow down their evaporation and to achieve safe vapor concentrations is determined. The influence of liquids characteristic temperatures and their water solubility on this process is considered. It is proven that the long-term effect of such means is provided by systems based on closed-pore floating solid materials (for example, foam glass). It is proposed to increase the foam glass low isolation and cooling capacity either by coating it with an inorganic gel or by wetting it with water. Smaller evaporation retardation coefficients by gel were obtained for liquids with the higher water solubility. A 5–6 times greater cooling capacity of the wet foam glass than dry foam glass was obtained for both polar and non-polar liquids. A smaller cooling effect is observed for liquids with a higher vaporization heat and is similar for both the use of the dry and wet foam glass. It was found that for low-boiling non-polar liquids, the evaporation slowing down is more effectively achieved by using isolation effects, and for high-boiling polar and non-polar liquids - by using cooling effects. It is proved that the fire extinguishing effect by applying the foam glass layer on the flammable liquid surface occurs in a similar way for liquids with close equivalent cluster lengths and not flash temperatures.

Abstract: The data center industry consumes between 196 and 400 terawatt-hours annually, between 1% and 2% of the world's energy consumption. A high percentage of data center energy consumption is associated with air conditioning and cooling systems. The optimization of the data center cooling process can occur at multiple scales, being one of the most relevant to the generation and heat transfer processes within servers. In this approach, we must study the temperature fields of each server’s components and understand airflow behavior within the server chassis. The present work, in its first stage, performs a thermal and cooling analysis for a two-unit rack server (2U-Rack) using computational fluid dynamics (CFD) techniques via Ansys Fluent code. A geometric server model was developed, considering heat generation in the main electrical components and heat and air mass transfer with the data center. The model was validated by comparing simulation results with the server's sensor values and the results of thermography testing. Following CFD simulation, airflow velocity fields, temperature contours, and sensitivity scenarios were obtained, with the goal of proposing an optimization model that would allow us to improve server heat transfer processes in the following steps.

Abstract: Extinguishing fires in ecosystems has features compared to extinguishing fires in residential and industrial buildings, due to the composition and structure of combustible materials, which can form many foci of smoldering and have the ability to re-ignite, have a relatively low fire load compared to man-made ones. All this leads to high costs of water for extinguishing, carrying out operations for additional extinguishing of fires that occur after the main extinguishing and sets special requirements for aqueous extinguishing agents for their extinguishing.The paper analyzes the current state of the availability and trends of development in the world and domestic practice of effective water extinguishing agents and technologies for their use. Possible ways to improve recipes and increase the efficiency of fire extinguishing substances are outlined, taking into account, first of all, the criteria of efficiency, economy and environmental friendliness.It is noted that the main direction of increasing the fire extinguishing capacity of water is to create combined fire extinguishing solutions that can combine several methods of extinguishing in one technological operation: cooling, isolation and inhibition, which, other things being equal, reduces fire extinguishing consumption and extinguishing efficiency. An integrated direction of increasing the fire-extinguishing capacity of water can be considered to increase the coefficient of active use of water by reducing the surface tension of the fire-extinguishing solution, increasing the wettability and viscosity of water by introducing appropriate additives, obtaining optimal droplet dispersion.

Abstract: Aluminum alloys in the 7000 series are high-strength alloys that are used in a wide variety of products in the transportation equipment and aerospace fields to reduce weight. In particular, the A7075 alloy has the highest strength and is expected to find further applications in a wide range of fields such as aircraft parts and sporting goods. However, low productivity is a problem due to its high deformation resistance, tendency to produce surface defects called tearing on the product surface, and short tool life. Tearing tends to occur under high temperature and high speed conditions, and is thought to be caused by local melting of Zn, an additive element, due to heat generation in processing. In this study, to improve the productivity of A7075 alloy, the profile was cooled during extrusion to prevent recrystallization of extrudate surface grains due to processing heat and to prevent processing heat during forming. In order to investigate the cooling effect, hot extrusion simulation was conducted. The cooling effect successfully suppressed the occurrence of tearing. These results indicate that cooling the extrudate during forming reduces the effect of heat generation during forming and prevents recrystallization of the extrudate surface grains and local melting of Zn.