Design and Analysis of the Location of Cold and Heat Sources for the Payload’s Active Thermal Control System on the Lunar Surface

The payload of the Chang’e-4 biological experiment is used as an object for designing and analyzing the location of cold and heat sources. The research compares and analyzes the energy consumption and temperature uniformity of cooling and heating sources mounted on different surfaces using Thermal Desktop/Sinda Fluint, which may be used to guide the design and operation of active thermal control systems. The results indicate that when the hot and cold sources are mounted on the payload’s top surface, the total energy consumption of the active thermal control system is minimized and temperature uniformity is improved.

Evaluation of melt quality during polymer extrusion

Polymer materials are widely spread and used in all industry sectors. The operating properties of polymer products make them practically indispensable in various industries. They have acquired widespread popularity and their production volumes are predicted to grow every year. The extrusion of polymers is one of the main methods for their processing. The melt uniformity is one of the main factors that influence the quality of the products and is determined by the level of mixing, i.e., by the redistribution of additives in a dispersion medium when these additives are introduced into the main polymer. The influence of working conditions, geometry of working bodies and other parameters on the melt temperature uniformity was determined. Nowadays, there are a lot of methods for determining the melt uniformity. They can be used indirectly in or after the extrusion process and can be short or long lasting, which in fact determines the acceptability of each of the methods. To determine the melt uniformity, statistical evaluation methods, which have been verified by many experiments and are well known, are often used. The analysis showed that the mixing index is most sensitive among the criteria described. Although statistical criteria of evaluating the melt uniformity are widespread, it is better to use parameters that allow the state of the mixture to be analyzed directly in the work process for the extrusion of polymers, to identify those that depend on the mixing process. Methods and criteria for verifying the melt quality were analyzed and potential use of their temperature uniformity for measuring and evaluating the melt quality directly in the extrusion process, to eliminate the costly sampling process, was determined.

Effects of Thin Film Heat Spreader on Hot Spots Mitigation in Heat Sinks

The effects of graphene platelets and diamond based thin film heat spreaders on maximum temperature of integrated electronic circuits were investigated. A fully three-dimensional conjugate heat transfer analysis was performed to investigate the effects of thin film material and thickness on the temperature of a hot spot and temperature uniformity on the heated surface of the integrated circuit when subjected to forced convective cooling. Two different materials, diamond and graphene were simulated as materials for thin films. The thin film heat spreaders were applied to the top wall of an array of micro pin-fins having circular cross sections. The integrated circuit with a 4 × 3 mm footprint featured a 0.5 × 0.5 mm hot spot located on the top wall which was also exposed to a uniform background heat flux of 500 W cm−1. A hot spot uniform heat flux of magnitude 2000 W cm−2 was centrally situated on the top surface over a small area of 0.5 × 0.5 mm. Both isotropic and anisotropic properties of the thin film heat spreaders made of graphene platelets and diamond were computationally analyzed. The conjugate heat transfer analysis incorporated thermal contact resistance between the thin film and the silicon substrate. The isotropic thin film heat spreaders significantly reduced the hot spot temperature and increased temperature uniformity, allowing for increased thermal loads. Furthermore, it was found that thickness of the thin film heat spreader need not be greater than a few tens of microns

The Effects of Absorbing Materials on the Homogeneity of Composite Heating by Microwave Radiation

When cured in a microwave, flat thin composite panels can experience even heat distribution throughout the laminate. However, as load and geometric complexity increase, the electromagnetic field and resulting heat distribution is altered, making it difficult to cure the composite homogeneously. Materials that absorb and/or reflect incident electromagnetic radiation have the potential to influence how the field behaves, and therefore to tailor and improve the uniformity of heat distribution. In this study, an absorber was applied to a composite with non-uniform geometry to increase heating in the location which had previously been the coldest position, transforming it into the hottest. Although this result overshot the desired outcome of temperature uniformity, it shows the potential of absorbing materials to radically change the temperature distribution, demonstrating that with better regulation of the absorbing effect, a uniform temperature distribution is possible even in non-uniform composite geometries.

Simulation Study on Liquid Cooling of Lithium-ion Battery Pack with a Novel Pipeline Structure

Lithium-ion battery is widely used as the mainstream power source of electric vehicles owing to its high specific energy and low self-discharge rate. However, the performance of the lithium-ion battery is largely hindered by its heat dissipation issue. In this paper, lithium-ion battery pack with main channel and multi-branch channel based on liquid cooling sys-tem is studied. Further, numerical simulation was used to analyze the effects of coolant temperature and flow rate on cooling performance. Based on the original pipeline structure, a new pipeline structure was proposed in the present work. The results show that increasing the cool-ant flow rate not only reduces the maximum temperature of the battery pack, but also reduces the temperature difference. Lowering the coolant temperature could largely decrease the maximum temperature of the battery pack, but it tends to widen the temperature difference and worsen the temperature uniformity. Up-on comparison, maximum temperature is found to be decreased by 0.44K, whereas, the temperature difference of the battery decreased and the temperature uniformity is improved.