Thermal Management Of Equipment Research Articles

Phase change materials encapsulated in graphene hybrid aerogels with high thermal conductivity for efficient solar-thermal energy conversion and thermal management of solar PV panels

Phase change materials (PCMs) have a wide range of applications in latent heat storage and thermal management. However, their practical use is hindered by high leakage rates and low thermal conductivity. To address these issues, polyvinyl alcohol/carboxylated carbon nanotubes/graphene hybrid aerogels (PCG) were carbonized at high temperatures to obtain polyvinyl alcohol/carboxylated carbon nanotubes/graphene carbon aerogels (cPCG). Polyethylene glycol (PEG) was then encapsulated within cPCG to form cPCG@PEG shape-stabilized PCMs (SSPCMs). These cPCG@PEG SSPCMs demonstrated excellent thermal conductivity (0.843 W•m-1•K-1) and superior solar-thermal conversion performance (91.8%). Additionally, the latent heat of cPCG@PEG showed a minimal decrease even after 100 melt-crystallization cycles. An experimental setup was designed to regulate the temperature of solar photovoltaic (PV) panels using cPCG@PEG. The results indicated that cPCG@PEG effectively managed the temperature of solar PV panels under varying light conditions. This study presents a novel approach for enhancing the application of porous PCMs in solar energy utilization and thermal management of equipment.

Experimental and numerical investigations on the intermittent heat transfer performance of rectangular cavity plate fin phase change material based heat sink

Thermal management of equipment in confined spaces is of great importance for the safe operation of equipment. Solid-liquid phase change materials (PCM) can be applied to the thermal management of intermittent electronic equipment because of their large isothermal latent heat absorption capacity. In this paper, experimental and numerical research on the thermal performance of an intermittent rectangular cavity plate fin PCM-based heat sink is carried out, which can be applied to heat dissipation in narrow spaces with high heat flow. The optimal PCM-based heat sink structure is obtained by numerical simulation based on the Taguchi method, and the enthalpy method is used to model the phase change process. Temperature testing and visualization experiments are used to visually present the PCM-based heat sink's internal temperature distribution and validate the numerical model. The effects of fin structure parameters, heating power, cooling air speed and number of intermittent cycles on thermal performance (base temperature, liquid fraction and operating time) are analyzed for different structured PCM-based heat sinks. The results show that the PCM-based heat sink with 8 fins, 15 mm fin height and 2 mm fin thickness has the longest stage C at the critical base temperature of 348 K and reaches the maximum operating time of 1193 s during the charging cycle. The natural convection in stage C of the charging cycle plays a crucial role in prolonging the operating time. Meanwhile, increasing the number of intermittent cycles can result in longer operating time and lower critical base temperature. As the number of intermittent cycles increases from 1 to 8, the temperature difference between the maximum and minimum temperature of the base during the whole cycle is reduced from 48 K to 25 K, and the temperature fluctuations gradually decrease.

Spin-off Companies: A Great Challenge for the Brazilian Space Program

Space science research and development is, by itself, a great challenge for research institutions throughout the world. This is especially true for developing countries such as Brazil, where the expenditures and number of institutions devoted to this field of study are limited. Additionally, because most funding for space research programs often originates from government sources, these are usually one of the first to be cut in times of economic distress. On the other hand, economy studies of the main space programs in the world show that the return on investment to the society in terms of new technologies greatly surpasses the research funds. Therefore, one of the greatest challenges for governments of developing countries with their own space programs is to create favorable conditions, so that the investments become profitable to the population, providing not only technological independence in the space field but also technological solutions to daily problems. Development of the heat pipe technology is a good illustration of the aforementioned tradeoff. Heat pipes are highly efficient, low cost passive heat transfer devices, used for the thermal management of equipment and panels in satellites. The first registered patents are concerned with application of these devices in domestic and bakery applications, dating back to the middle of the 20th century. Although very efficient, this technology was not largely employed until the Cold War, when the major countries intensified their space exploration

Problems of Thermophysics and Thermal Engineering for the New Technologies of the Twenty-First Century

This review article gives an overview of some topics related to classical and modern problems in the theory of heat, its meaning for various branches, and thermal management of equipment. The specific requirements for new technologies involved in the thermal operation of miniaturized instruments, components of equipment, devices, units operating in fast-response regimes, improvement of heat resistance, reliability, and endurance are considered. Special requirements have been put forward for nanotechnologies, where engineering parts, elements of devices, and technological equipment have microscopic and submicroscopic dimensions. Also, the stringent requirements of thermal modes of modern large-scale technologies in such branches of industry as nuclear power engineering and rocket-space engineering have become more important and determining. The thermal modes of these technologies call for new approaches to the design of the thermodynamic state of micro- and macrosystems, high-temperature plasma, and cryogenic temperatures. New results of the study of the mechanism of heat transfer in phase transitions, principally in new approaches to the problem of enhancement of heat transfer in one- and two-phase flows are presented. The importance of studies of thermal processes providing reliable thermal modes of new power plants, microsystems, and nanotechnologies is shown. The significance of advances in the study of thermal processes for developing the theory of heat is discussed. Especially considered are achievements in the theory of heat for its role in the decisions of actual problems of biology, medicine, and environment. This review article cites 105 references, most of them in Russian.