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Li-ion batteries have experienced a widespread deployment due to the strong interest in electrochemical devices capable of storing a large amount of energy in small volumes and supplying high powers when required. However, besides those advantages, this technology still presents several unsolved issues, especially regarding the safety aspects. These devices can, in fact, experience thermal runaway if the generated thermal power is not adequately dispersed, and this can occur when the cell / battery is subjected to abuse conditions (mechanical, electrical or thermal abuses). The experimental study was carried out using a full-scale hardware simulator, capable of simulating the thermal behavior of a battery pack, where electrically heated elements replaced real Li-ion cells. This expedient guarantees a high reproducibility of the working conditions and consequently a higher reliability of the measured data. The hardware simulator allows to reproduce the thermal behavior under normal operating conditions, and under abuse conditions which can lead to thermal runaway. The present work reports the results of the tests that have been carried out by reproducing the abuse conditions in one cell inside a battery module; the abused cell is heated with a high power (from 100 to 500 W for cells with a maximum heat loss of 30 W under normal operating conditions) and the efficiency of different cooling systems is checked both in limiting the temperature of the abused cell and in preventing the propagation of heat to the adjacent cells. In particular, different fluids, different fluid speeds and different mitigation methods have been tested.

This paper describes a set of experimental tests carried out to better understand the thermal behavior of Lithium-ion batteries under load and the capability of various cooling fluids in maintaining the working conditions within a safe range for the cells. Despite several theoretical models are available in the literature, very few experimental data are reported. Different types of cells have been analyzed. The generation of hot spots has sometimes been registered, their occurrence being independent of cell geometry and size; instead, the battery's history and age, appeared the main factors in determining the onset of hot spots on the surface of the cell. Two experimental rigs have been set up to test the capability of different cooling fluids in removing the surplus heat generated in a Li-ion battery module, where the cells of interest have been replaced with electrically heated elements with the same thermal characteristics of the cells. It was thus possible to safely investigate “extreme” operating conditions, where the occurrence of a thermal runaway is possible. Among the tested fluids, air was unable to adequately limit the surface temperature increase, while a perfluorinated polyether, allowed to work within the optimal temperature range, even under severe operating conditions.

Temperature control is one of the most significant factors to improve the performance and extend the cycle life of a battery. It is, therefore, important to design and implement an effective battery thermal management system (TMS). Phase change materials (PCMs) can be used as a cooling means for batteries. In the present paper, a preliminary analysis of the thermal behavior of PCMs used to cool down a heated metal surface was carried out. Tests have shown that pure PCMs are able to limit the temperature increase, but only for relatively low-heat fluxes. At higher values of the heat produced, the thermal conductivity of the PCM was increased by using solid foams characterized by higher thermal conductivity; it was, thus, possible to keep the surface temperature within safe limits for longer times. A computational fluid dynamics (CFD) model of the composite material (PCM + solid foam) was also developed, which allowed to predict the temperature trend within the system under different boundary conditions. However, the average thermal conductivity of the composite system that best fitted the experimental results was found to be much lower than that theoretically predicted by using common semiempirical correlations.

In the present work an analysis of experimental data obtained exposing metallic targets to the flow of a number of nanofluids has been carried out. The investigated suspensions were composed of typical nanometer-sized solid particles, such as TiO2, Al2O3, SiC, and ZrO2 at different concentrations, suspended in different base fluids. The effects of the flow of these nano-materials on three reference targets made of commercial metals (aluminum, copper, and stainless steel) have been assessed. An accurate analysis of the results showed that, where present, the observed damages are caused by chemical corrosion rather than by mechanical erosion, the pH of the suspension being the most important parameter. Conversely, no influence of the particles' nature and content was found, even at high concentrations of nanoparticles (up to 20% by weight). This is believed to be a useful information about the practical feasibility of advanced systems, like in heat transfer applications, based on the use of these relatively new fluids. © 2015 The Institution of Chemical Engineers.

In the present paper the results of an experimental investigation on the advantages of using nanofluids for heat transfer operations have been reported. The nanofluid systems varied both in terms of type of particles and their concentration, and of base fluid, for a total of 23 different system configurations. The experimentally derived heat transfer coefficients for these systems, for single-phase forced convection inside tubes, have been compared with those of water or of the corresponding base fluid. The trends identified have been reported as a function of different operating parameters (Re number and fluid average velocity) and the analysis showed that the advantage often claimed for nanofluids actually occurs only under a limited number of hydrodynamic conditions and at the expense of a much higher pumping energy. At the same time, the most commonly adopted correlations for the prediction of the heat transfer coefficient of homogeneous mixtures have been applied to the investigated systems, to check whether it is possible to predict the heat transfer capability of a nanofluid with the ordinary equations by simply introducing the average physical properties of the mixture. It has been found that with the exception of Al2O3 suspensions, in most of the cases the heat transfer coefficient can be actually predicted with a rather good level of accuracy. © 2014 by Begell House, Inc.

The results of an experimental study on the effects of the flow of nanofluids (water-based suspensions of nanometer-sized solid particles) on metal surfaces are presented. Either different nanofluids (containing TiO2, Al2O3, ZrO2, and SiC, respectively) and different target materials (aluminum, copper, stainless steel) have been investigated, under similar operating conditions. Different behaviors were observed depending on the specific combination nanofluid-target material, which in some cases led to severe damaging of the tested target, thus highlighting the need for an adequate preliminary investigation of the possible interactions between the selected nanofluid and the apparatus materials, before its adoption as heat transfer fluid. © 2013 The Institution of Chemical Engineers.