Papers by Keyword: Cooling

Abstract: Li-ion batteries generate significant heat during operation, which leads to an increase in temperature and, consequently, a reduction in the battery's efficiency and lifespan. In this study, different cooling methods are simulated for the thermal management of the battery. The cooling using air and liquids is investigated with laminar flow at varying velocities. Results indicated that the use of water/glycol is more effective than air and mineral oil.

Abstract: The housing sector accounts for a high percentage of total energy consumption in Iraq, with most energy usage on air-conditioning systems in summer to provide comfort to residents. This study simulates energy consumption for a typical 200 m², two-story, single-family building in Al Amarah city, Iraq, to compare heating, cooling, and total energy use across three different building configurations. Locally manufactured hollow concrete blocks made with 40 × 20 × 20 cm3 dimensions were adopted to improve their thermal performance by filling the cavities with Polystyrene insulation. The research examined three residential building configurations: (i) a base case built with traditional fired-clay brick, (ii) hollow concrete block walls free of insulation, and (iii) hollow concrete block walls incorporating thermal insulation. Energy simulations using eQUEST software were conducted, utilising the thermal response factor method as the primary tool to analyse the impact of external environmental conditions on cooling and heating loads. The results demonstrated significant annual energy savings for the building with hollow concrete blocks with and without insulation. However, insulated hollow concrete blocks showed reduced annual energy consumption compared to the common brick building system. Specifically, the insulated and uninsulated blocks attained energy savings by 29.4% and 16.08%, respectively, for north-facing orientation.

Abstract: This work numerically studies the thermal management of a Li-ion battery pack using Phase Change Materials (PCMs) with two different modelling approaches. Specifically, the results obtained with the Enthalpy-Porosity method, implemented in the tool STAR-CCM+, are compared with those yielded by the Apparent Heat Capacity formulation, employed by COMSOL Multiphysics. Both models are first validated against benchmark cases found in the literature. The study then focuses on the thermal behaviour of a battery pack composed of four 21700 Li-ion battery cells, cooled using the paraffinic PCM RT35. The numerical results show that, while natural convection in the liquid PCM accelerates the melting process, it leads to a non-uniform temperature distribution, particularly disadvantageous for cells located in the upper part of the battery pack. In addition, although both numerical approaches show good agreement between their results, especially in capturing the overall thermal behaviour, some minor differences in the temperature profiles during the PCM phase change still emerge.

Abstract: The construction, operating principles, and Li-ion battery thermal runaway mechanisms were analyzed. The external mechanical damage to a Li-ion battery with the uncontrolled thermal runaway development was investigated. The battery self-heating temperature regime was determined. A possible reactions set leading to intense materials self-heating and decomposition was considered. The battery self-heating stopping by immersing it in a container with a water excess relative to the stoichiometric amount for the lithium metal maximum mass that can accumulate was investigated. The change in resulting aqueous solution pH was measured, and the hydrogen release was also recorded. Reaction completion time dependences was established. The water required amount to absorb the heat that could be released during the reaction was calculated, which correlated with the experimental data. Possible measures to Li-ion batteries prevent and stop the burning were considered.

Abstract: The paper presents research of the possibility of using potassium carbonate and bicarbonate as inhibitors in the compositions of aqueous fire-extinguishing substances for the elimination of fires associated with the burning of solid and liquid combustible materials. It has been shown theoretically and experimentally that both potassium carbonate and bicarbonate are highly effective in inhibition of chain reactions in the gas phase of flame combustion. Recommendations on the selection of the inhibitory component when creating compositions of aqueous fire extinguishing substances are given.

Abstract: У даному дослідженні представлені можливості використання вогнегасної речовини на основі водорозчинного полімеру для ліквідації пожеж на полігонах ТПВ та полігонах побутових відходів, пожежне навантаження яких утворюється за рахунок твердих горючих матеріалів. Теоретично та експериментально показано, що шляхом зміни концентрації гелеутворювальних добавок можна змінювати в'язкість, що безпосередньо впливає на швидкість випаровування та глибину проникнення вогнегасної речовини в осередок пожежі. Наведено результати експериментальних досліджень ефективності гелевих вогнегасників на основі полімеру ECOFLOC A-07.

Abstract: The wrought magnesium alloy AZ80, comprising 8 wt% aluminum, underwent fabrication via permanent steel mold casting (PSMC), involving three distinct stages with wall sizes measuring 6 mm, 10 mm, and 20 mm. The numerical simulation of the solidification showed that the cooling rate of the step casting increased, when the wall size decreased. The as-cast alloy's microstructure underwent scrutiny through optical microscopy and scanning electron microscopy (SEM), complemented by energy dispersive spectroscopy (EDS) analysis. Findings from the microstructure examinations unveiled the presence of primary Mg phase across all three sections of the cast AZ80 alloy, accompanied by micron and nanosized Mg-Al-Zn intermetallic phases, as well as micron-sized Al-Mn intermetallic phases. But the intermetallic contents increased, and the dendrite sizes and the porosity levels decreased, as the wall sizes reduced. The tensile testing results revealed significant findings regarding the ultimate tensile strength (UTS), yield strength (YS), modulus, resilience, and toughness, increased, when the wall sizes decreased to 6 from 20 mm. The negative effect of large casting wall sizes on ductility was demonstrated. Exceptional tensile properties of the thin wall resulted from fine dendritic structure, high intermetallic content, and minimal porosity level.

Abstract: This research investigates the thermal performance of earth bricks made with different percentages of wastewater sludge additive (0%, 1%, 3%, 7%, 15%, 20%) in terms of cooling and heating loads, time lag and decrement factor. The simulation of a reference house (2.5m,10m,6m) using TRNSYS software allows for the evaluation of these parameters, external wall thicknesses, bulk density, thermal conductivity, and specific heat capacity are employed as inputs in dynamic thermal inertia model. The results showed that the use of bricks with higher sludge additive percentages resulted in a drop in cooling and heating loads, the lowest cooling and heating loads of 1720 KWH and 1534 KWH respectively were recorded with the highest percentage of wastewater sludge additive of 20% and the biggest wall thickness of 30cm, it was also noted that the use of higher wastewater sludge additive percentages and bigger wall thicknesses led to higher time lags and lower decrement factor, the highest time lag of 15 hours and the lowest decrement factor of 0.019 were as well recorded with the highest wastewater sludge additive of 20%, and the biggest wall thickness of 30cm. These results were attributed to the higher specific heat capacity, and lower thermal conductivity of the bricks with higher wastewater sludge additive percentages.

Abstract: The article analyzes the cooling systems that have become stuck during the operation of high-power electric machines, the importance of using water-cooling systems for them has been dubbed. The main part of the research is devoted to the consideration of nutritional and detailed methods of rational cooling of turbogenerators based on the use of innovative environment protection technologies, namely metal hydride hydrogen storage technologies as an environmentally friendly alternative to motor fuel. It is shown that an alternative to the traditionally used devices for cooling of electric machines with hydrogen is the use of hydrides of intermetallic compounds to implement the working processes of thermosorption compressors, which is due to the ability of reversible hydrides of intermetallic compounds to repeatedly sorb and desorb hydrogen at significantly different pressures, the value of which is determined by the temperature potential of the thermal effect, i.e. thermochemical compression of hydrogen. The methods of calculating the parameters used in the designing such devices have been analyzed, and the method of determining the parameters of phase equilibria of hydrides of intermetallic compounds has been suggested. Mathematical modeling of hydrogen sorption by intermetallic compounds, performed on the basis of the mathematical apparatus of the thermodynamic perturbation theory improved in the study and on the example of the intermetallic hydride LaNi₅, based on the application of the lattice gas model for metal hydrides. At the same time, due to the presence of an unchanged crystal structure of the metal, an increase in the volume of the crystal lattice in the process of hydrogen sorption was taken into account, which leads to the appearance of additional components in the potential energy, and the interaction between absorbed hydrogen atoms has also been taken into account. The calculated temperature dependences of the pressure on the plateau of the hydrogen solubility isotherm are in good agreement with the experimental data available in the literature. The operation of the metal hydride cooling system of TG excludes the occurrence of fire and explosive situations, and it also significantly increases the level of ecological safety indicators.

Abstract: In this paper, the cooling of a passenger car alternator’s stator winding is investigated with the help of computational fluid dynamics. The main heat sources are determined to be the stator winding and the diodes. Their respective heat loss is calculated and applied in the CFD software. In the first step, the CAD model is simplified in a way to enable a fine-quality numerical mesh generation, while keeping the important geometric features that could have significant effects on the results. In the next step, independence studies are carried out for the mesh, time-step size, and flow volume. A comparison is also presented between the steady “frozen rotor” approach and the transient “moving mesh” approach.After conducting the transient simulations at multiple operating points, the simulation results are evaluated with the help of contours and quantitative properties. An experimental comparison is presented which shows a good correlation between the simulated and the measured data, furthermore, the possible reasons for the deviations are eventually discussed. Finally, the benefits of the future applications of the simulation model are introduced briefly.