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Innovative and Advanced Motor Design
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
It should be noted that the development of a new YASA motor design comes with a wide range of technical challenges, especially the thermal challenge that addresses effective motor cooling. Because the windings are buried deep inside the stator and disposed between two rotors, heat generated from the windings becomes difficult to disperse. To solve this issue, several cooling schemes are proposed. Generally, air cooling is preferred for many applications where the heat load is low or moderate. Compared with liquid cooling, air cooling eliminates the risk of coolant leakage and has the simplest form among all cooling schemes. To further enhance the heat dissipation, cooling fins may be casted at the housing outer surfaces and thus heat can be effectively dissipated away by means of these fins. This not only provides the motor a higher heat dissipation capacity to produce greater torque and power, but also allows for a stiffer motor structure. For motors with very high heat loads, indirect liquid cooling may be needed for maximizing power density because water or oil transfers heat much more efficiently than air. Furthermore, liquid cooling makes little noise compared with air cooling. However, a liquid cooling system often requires additional equipment such as pumps and cooling pipes, making the motor structure more complicated. Nevertheless, this cooling scheme can extract the heat from the windings very effectively [15.27].
Temperature and Heat
Published in Daniel H. Nichols, Physics for Technology, 2019
Convection depends on a number of factors: The faster the fluid or air flows, the quicker the heat will be transferred.Increasing the surface area will increase the rate of transfer, that is, big cooling fins mean faster cooling.Fluids or gases with high thermal conductivities transfer heat better.The bigger the temperature difference between the fluid or gas and the object transferring the heat, the faster the heat will get transferred, that is, cold water will cool an object faster than warm water.
Steady One-Dimensional Heat Conduction
Published in Anthony F. Mills, Heat and Mass Transfer, 2018
The proper design of cooling fins is an optimization problem: usually the objective is to minimize the amount of material in the fins in order to minimize either weight or cost. Exercises 2–39 and 2–71 show how optimal dimensions can be found for a given fin shape, and Exercises 2–63 and 2–65 illustrate that there is an optimal fin shape. The engineer is also free to choose the fraction of area covered by fin “footprints.” This is a more difficult problem because as the fins are moved closer to each other, the value of the heat transfer coefficient hc changes in a complicated way. There is always the question of whether fins should be provided at all. Exercise 2–62 shows that when the heat transfer coefficient is large, adding fins can actually reduce the heat loss. The conduction resistance in the fin can exceed the decrease in convective resistance due to the increased surface area. A useful rule is not to use fins unless k/hct > 5.
Optimization of a thermophotovoltaic system for the combi boiler
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
In the TPV system, the high temperature of the cell reduces the cell efficiency. Also, the cells may be under thermal stress at high temperatures. The thermal stress can impair the cells (Mattarolo 2007). In this study, the upper limit of the cell temperature was preferred as 475 K (approximately 200 °C). The cooling fin must have a high thermal conductivity to reduce the cell temperature. The thermal expansion coefficient of the fin should be close to that of the cell to prevent mechanical stress. For this purpose, beryllium oxide and aluminum nitride are used to reduce the cell temperature. In this study, beryllium oxide was used as the cooling fin (cooling plate) due to its high thermal conductivity (250 W/(m.K)) (Mattarolo 2007). Also, the view factor between components must be taken into account in the TPV system. For this purpose, reflectors were placed at the top and bottom of the TPV system to achieve more electric power density (Durisch and Bitnar 2010). Figure 3 shows the schematic cross-section of the TPV model designed to reduce the computational load.
Two-phase refrigerant flow in the evaporator of a stirling cooling system with a thermosyphon loop
Published in Experimental Heat Transfer, 2020
Thermosyphon heat exchangers offer notable advantages in cooling systems that use alternative refrigeration technologies. K. Matsubara et al. [10], developed a loop thermosiphon thermal collector for the waste heat recovery power generation. The effective thermal conductivity of the loop was calculated to be much higher than that of copper. Grooten and Van der Geld [11] performed a heat transfer analysis on long thermosyphons using R-134a as the working fluid. The effect of the saturation temperature on condensation heat transfer enhancement was significant, and the effect on evaporation heat transfer was also substantial for longer thermosyphons. In another study by the same authors [12], the effect of the inclination angle for similar thermosyphon systems using R-134a was investigated. The authors concluded that the heat flux capacity decreased with decreasing inclination angle. The thermosyphon principle held up to 83° of inclination angle with respect to the vertical. Pappas et al. [13] studied the heat transfer performance of a hybrid cooling fin thermosyphon with an airfoil cross-sectional shape. The study revealed details regarding the effect of geometry and fill volume on heat transfer, promoting that an optimum fill volume of heat transfer fluid exists for the thermosyphon system. Lee et al. [14] conducted a flow visualization study using both water and a commercially available working fluid flowing through a thermosyphon, finding that the flow motion becomes more strenuous for both fluids with increasing heat load.