The thermoelectric generator (TEG) is commonly used to harvest or scavenge the remnant energy from waste heat sources, such as automotive exhaust systems, cooling line of power plants, ocean temperature difference, human body, and industrial processes. The performance of TEG depends on the thermoelectric material and its structural configuration. To obtain the maximum power from TEG module, the optimal design of heat exchanger is required to realize the full potential of power generating system. The internal structure of heat exchanger plays a critical role to determine the efficiency of TEG by enhancing heat transfer between the hot and cold sides of the TEG module. We studied the effect of internal fin structure in heat exchanger with hot water feeding condition to obtain the best performance of TEG module array by using computational simulations and compared with the experimental results.
The development of electronic components is rapidly progressing due to the recent growth of electronic technology. As a representative example, wearable electronic devices are being widely studied as next-generation electronic devices. Next-generation wearable electronic devices require the development of flexible electronic devices and sophisticated components. Besides, it requires high adhesion between the flexible substrate and electrical components such as multilayer flexible printed circuit boards. Various adhesion processes have been studied to improve adhesion. As a method for increasing the adhesion, the most important factor is to improve the adhesion of the adhesive, but there is additionally a method of improving the adhesion by changing the surface area of the medium. Plasma treatment in electronics, developed for application to multi-layer flexible printed circuit boards for next-generation flexible mobile electronics, can assist to strongly combine different materials by changing the surface area to form a stronger bonding strength between the medium and the adhesive. We conducted on how the adhesion strength is improved depending on the presence or absence of plasma treatment on the medium. Also, as the heat conduction behavior was enhanced due to the miniaturization of electronic components, the heat resistance of the adhesive is also tested. We find that the adhesive strength decreases as the temperature increases, which is explained in this study.
The modeling in this study was conducted to maximize the high performance of adhesive materials. Aluminum nitride (AlN) and epoxy resin were used to model AlN in the form of a sphere and resin in a liquid state. The results are expected to be dependent on the location of the sphere in the resin. First of all, spherical AlN is regularly stacked in the basic form of 3x3. Secondly, the volume ratio of AlN was maximized at a unit volume considered of the packing factor of AlN. Air pockets with the same diameter of AIN can be substantially added inside the resin. Then, the heat transfer coefficient of the air was very low, so it was considered as a factor that could sufficiently affect the heat transfer coefficient of the adhesive material. The modeling was compared the cases with and without the air pockets. Thirdly, the modeling of the same structures showed the larger heat transfer rate when the material was changed to zinc oxide (ZnO), which has the larger heat transfer coefficient than AlN. Finally, the molecular crystal of ZnO can be implemented as a tetrapod type. The ZnO of tetrapod type had the good heat transfer rate because of the greater proportion per unit volume than the sphere.
In order to meet the environmental regulation due to global warming issues, the new energy resource such as ocean temperature between surface and deep see level or wasted heat resources from power plant have received much attentions as a renewable energy, which is not used in conventional power cycle using a water-steam phase change. Instead, organic Rankine cycle (ORC) based on a properly selected refrigerant can be used for power generation by utilizing the relatively hot source from cooling water from conventional power plants, internal combustion engines and industrial processes. To operate ORC cycle in low temperature difference, a proper selection of working fluid is very essential to design the ORC system for industrial application. However, the selection of working fluid is currently very limited due to ozone depletion by CFC as well as global warming issues by CO2 emission. Under new regulations, we should design and select appropriate refrigerants which can meet the environmental regulation for lower global warming potential (GWP) and lower ozone depletion potential (ODP). In this study, the convective heat transfer coefficients of single, binary or ternary refrigerants were studied through a pool boiling test. Also, the selected refrigerants were tested by lab scaled ORC system.
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