Thermacore (United Kingdom)

This work presents a numerical comparative study of the melting and solidification processes of two medium temperature phase change materials (PCMs) for latent heat thermal energy storage (LHTES) applications. The PCMs compared are an inorganic solar salt and a Sn-based metal alloy, with the phase change temperatures around 220C. The numerical comparative study was conducted in a 2D rectangular unit model with constant heat flux, the simulations were conducted deploying the enthalpy method in Ansys FLUENT software. The numerical results were validated using experimental results for one of the phase change materials studied. The charging and discharging times of the designed LHTES were studied for both phase change materials, finding that the metallic PCM LHTES showing superior performance. The charging and discharging time obtained for the solar salt LHTES, duplicate the time required using metallic PCM LHTES. Moreover, the final average temperature for the solar salt LHTES, shows significantly compare with the phase change temperature.

Conventional cooling approaches that target either a singular tab or outer surface of common format cylindrical lithium-ion battery cells suffer from a high cell thermal resistance. Under an aggressive duty cycle, this resistance can result in the formation of large in-cell temperature gradients and high hot spot temperatures, which are known to accelerate ageing and further reduce performance. In this paper, a novel approach to internal thermal management of cylindrical battery cells to lower the thermal resistance for heat transport through the inside of the cell is investigated. The effectiveness of the proposed method is analysed for two common cylindrical formats when subject to highly aggressive electrical loading conditions representative of a high performance electric vehicle (EV) and hybrid electric vehicle (HEV). A mathematical model that captures the dominant thermal properties of the cylindrical cell is created and validated using experimental data. Results from the extensive simulation study indicate that the internal cooling strategy can reduce the cell thermal resistance by up to 67.8 ± 1.4% relative to single tab cooling, and can emulate the performance of a more complex pack-level double tab cooling approach whilst targeting cooling at a single tab.

The performance and ageing of lithium-ion cells are particularly sensitive to the battery operating temperature and in-cell temperature gradient. To mitigate adverse ageing whilst maximising performance, thermal management systems are required to maintain the cell operating temperature within its optimum range. In this paper, an aggressive duty cycle representative of track racing conditions for a performance electric vehicle (EV) is used as an input into a 1-D electrochemical-3-D thermal model which is validated against experimental data with a peak error of 10.6%. The simulated temperature response of the cell during the duty cycle is analysed under 4 minimal cooling conditions. The results indicate that natural convection with air is ineffective in limiting the peak cell temperature rise during the cycle to 20 °C and a more involved cooling method is necessary.

Tool wear of machine tools and large usage of cutting fluids is one of the major problems in manufacturing. Cutting fluids are used to cool down the tool and have been shown to cause environmental problems in machine shops. Tool life and temperature have an inverse relationship, namely that the higher the temperature at the tool-chip interface is, the lower the tool life will be, and vice-versa. In this paper an innovative approach was taken to create an analytical solution to the effect of the embedded heat pipe on temperature of the tool and tool life. It has been well documented in the industry that the major factors that contribute to tool wear are the material properties of the tool insert and the work piece, cutting speed, depth of cut and feed rate. The analytical approach taken in this project is unique because it does not only take into account the complex boundary conditions of heat transfer but also the aforementioned factors and variety of possible cutting conditions. The analytical solution is in the form of set of equations which were developed to simulate the behavior of the tool insert under normal cutting conditions. Both cases, with and without heat-pipe were considered. The predicted temperature data was then compared to the existing experimental data, with very good results. In the end the project yields a quantitative evaluation on influence of mechanical properties of insert, work piece, heat pipe and cutting conditions on tool wear.

<div class="htmlview paragraph">The current trend in military avionics design is to physically move electronics closer to the components they control. This saves on weight, increases component maintainability, reduces aircraft manufacturing costs, and reduces the amount of electromagnetic shielding required. A disadvantage to this trend is the difficulty in achieving thermal control of these remotely located electronics.</div> <div class="htmlview paragraph">Accordingly, this thermal control issue is being addressed through the development of a loop heat pipe cold plate (LHPCP). The LHPCP is different than previous hardware of its kind by the fact that it operates in any orientation. The prototype LHPCP that was fabricated and tested was 30 inches long and weighed 1.2 pounds and was able to transport a minimum of 160 watts in any orientation.</div> <div class="htmlview paragraph">Future LHPCPs will be made flexible to allow relative motion between the package to be cooled and the heat sink. It also will permit cooling to be provided to surfaces in awkward locations relative to the heat sink. Connections to the heat sink can be anything from convective air cooled fins to solid plates bolted on the aircraft's structure.</div>