On the estimation of maximum surface temperature for cells

In paperwork is presented the estimation of the maximum surface temperature of cells exposed to specific tests for the intrinsic safety type of protection. Particularly, it presents the thermal resistance of the short-circuit test-stand results. The first part introduces the aspects regarding the risk of explosion. The risk of explosion occurs due to the presence of technical equipment in areas where flammable substances may occur. The second part itemizes the requirements for the testing of cells. Also, is introduced the stand configuration and performance aspects. The third part of the paper has been dedicated to the presentation and the discussion of the obtained results. The analysis of the test results highlighted the range of thermal resistance. This result could help estimation of the surface temperature of cells based on their capacity and internal resistance. The convection coefficients were determined. The process of deep discharge destroys the inner electrochemical of the cell system. Therefore, it permits energy recovery lower than a fraction of a tenth.

An Experimental Study on Thermal Runaway Behavior for High-Capacity Li(Ni0.8Co0.1Mn0.1)O2 Pouch Cells at Different State of Charges

Lithium-ion cells normally operate during 0% and 100% state of charge (SOC), therefore thermal runaway can occur at any SOC. In this paper, the 74 Ah lithium-ion pouch cells with the Li(Ni0.8Co0.1Mn0.1)O2 cathode were thermally abused by lateral heating in a semi-open chamber. The differences of thermal runaway behavior were investigated under six SOCs. Characteristic parameters such as triggering time and triggering temperature for thermal runaway show a negative correlation with SOCs, while maximum surface temperature and maximum surface temperature rise rate show a strongly positive correlation. Besides, mass loss ratio increases exponentially with equivalent specific capacity statistically, which implies that the pouch cells with high specific energy density and high capacity may eject more violently. Furthermore, the impact on the surroundings caused by high-temperature ejections was studied, and maximum ambient temperature and maximum ambient pressure in the chamber reached a plateau at middle SOCs. Based on the thermal impact on the surroundings, a theoretical method is proposed to evaluate the deterioration of heat dissipation by venting, and simplified to quantitatively calculate the deterioration under above SOCs. The results can provide guidance for battery safety management strategies and structure design of the battery pack.

INVESTIGATION OF INFLUENCE OF PLASMOCHEMICAL MODIFICATION ON MACRO- AND MICROSTRUCTURE OF SURFACE LAYER OF AUTOCLAVE WALL MATERIALS

studies of the high-temperature effect of a plasma torch on the formation of a multilayer structure of the protective and decorative coating of autoclave wall materials are presented. The tasks of the work included studies: a temperature gradient in a multilayer protective-decorative coating; chemical composition of the fused, intermediate and deep layers of the protective and decorative coating; influence of sodium liquid glass on the formation of macro- and microstructures of protective and decorative coatings under the influence of plasma; processes of thermal diffusion and redistribution of oxides in the fused, intermediate and deep layers. It was found that when the plasma torch was treated with autoclave wall materials, the surface layer was heated to a depth of 3000 μm, and the maximum surface temperature reached 2000 °C. The pattern of the change in the structure of the fused and intermediate layer is revealed. It is shown that the preliminary impregnation of the surface of silica brick during plasma treatment due to the formation of a low-melting melt eliminates microcracks in its deep layers, and high plasma temperatures promote intensive evaporation of sodium and calcium oxides from the fused layer.

Determining the maximum surface temperature for non-electrical equipment aiming at explosion prevention at protection

Non-electrical equipment has been used for over 150 years in industries with potentially explosive atmospheres and great experience has been gained with regard to the application of protective measures to reduce the risk of ignition down to an acceptable safety level. The use of non-electrical equipment in explosive atmospheres required the development of specific requirements with regard to the concept of protection against the ignition of explosive atmospheres, which to clearly define protection measures and to include the experience gained and extended over the years. The practical studies, laboratory research and methods for assessing and testing the hazard of ignition by hot surfaces presented within the paper have as main purpose the improvement of ignition hazard assessment in different operating conditions.

Thermoelastic Rolling Contact Problem of an FGM Layered Elastic Solid

This study focuses on the thermo-elastic rolling contact problem of a graded coating/substrate system. The problem is formulated under the plane thermoelasticity framework. Assuming an exponential variation of the shear modulus within the coating, the governing singular integral equations are extracted by means of the Fourier transform. The solution to problem is provided via the Gauss-Chebyshev integration method. The sensitivity of the contact stresses as well as the surface temperature rise to the stiffness ratio, the coating thickness and the non-dimensional speed is investigated. The results indicate that the thermal expansion ratio substantially affects the contact stresses. Also, the softening coatings will result in maximum surface temperature rise. The coating thickness can alter the surface temperature rise such that an increase of the coating by a factor of 1.6 may result in 50% reduction of the maximum surface temperature.

Influence of the Initial Temperature on the Clutch Hot Judder

In order to explore the effects of the initial temperature on the clutch hot judder, the thermodynamic analysis was conducted during the clutch engagement process. The finite element analysis was adopted to explore the contact pressure based on the consideration of the concentrated reactive force on the circlip. A 4-degree-of-freedom torsional vibration model was established to evaluate the hot judder behavior. The results demonstrated that the closer the surface was to the circlip, the greater the friction torque generated on friction surfaces was. Moreover, the higher the initial temperature was, the shriller the clutch hot judder was. The increased initial temperature not only resulted in the increase in the maximum surface temperature, but also could make the clutch engagement much shorter.