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Cooling
Published in Fang Zhu, Baitun Yang, Power Transformer Design Practices, 2021
Due to high velocity of forced air, heat exchange on the air side increased. Compared to natural air cooling, with the same amount of loss to be dissipated, the oil will be cooled further, the oil temperature rise, ΔΘoil in wdg, will decrease and branch C-D will be somewhat more curvedly bended, as shown in Figure 7.4 case (a). It is said that by changing from natural air cooling to forced air cooling, the cooling can be improved about 2.6 times at the same ambient temperature [3]. The effect of radiator altitude on oil rises is same as the ONAN case since the nature of oil flow doesn’t change.
Thermal Management of Switched Reluctance Machines
Published in Berker Bilgin, James Weisheng Jiang, Ali Emadi, Switched Reluctance Motor Drives, 2019
Yinye Yang, Jianbin Liang, Elizabeth Rowan, James Weisheng Jiang
The transfer of heat generated within an SRM to an external heat sink depends on various factors, such as the mode of heat transfer, the effective heat transfer area and geometry, the working fluid used for cooling, the flow rate, and temperature of the cooling media. The simplest cooling technique is dissipating the heat to ambient by natural convection. Typically, the heat dissipation can be improved by increasing the heat transfer surface area with added fins on the housing. A more complicated forced air-cooling system can be used to further increase the heat dissipation. For example, a shaft mounted fan can be employed to enhance the heat transfer from the housing fins, the end windings, and rotor surfaces. However, for high current densities, using air as the cooling fluid may not be sufficient, and some form of liquid cooling may be required for better removal of heat. Typical rules of thumb for cooling techniques and associated heat transfer coefficients are listed in Table 14.1 [12]. Higher heat transfer coefficients enable higher current density and, hence, higher machine output power; however, at the expense of higher system complexity and energy cost.
Lubrication and cooling
Published in Andrew Livesey, Practical Motorsport Engineering, 2019
Air cooling has the advantages of not using a liquid coolant (water) and using fewer moving parts. Having no water, it cannot freeze or leak. However, air-cooled engines tend to be more noisy than liquid-cooled ones. The air-cooling system operates by air entering through the flap valve. The fan, which is driven by the crankshaft pulley, forces the air over the fins on the cylinders. The air is then discharged back in to the atmosphere. The flap valve is controlled by the thermostat, this opens when the engine is hot so allowing air to enter. The flap valve is closed when the engine is cold; this restricts the airflow to give the engine a quick warm up to operating temperature.
Recent advancement on thermal management strategies in PEM fuel cell stack: a technical assessment from the context of fuel cell electric vehicle application
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Dinesh Kumar Madheswaran, Arunkumar Jayakumar, Edwin Geo Varuvel
Air cooling is a compact and inexpensive system; however, owing to its parasitic losses, has poor heat removal capability, and is targeted for small stacks (<5 kW) (Raźniak et al. 2018). For a PEMFC (1–5 kW), natural convection at the BPP surface would be enough for heat dissipation (Yin et al. 2021). The air channel size has a strong influence on the performance of air cooling. In a study by Matian, Marquis, and Brandon (2011), the BPP with larger air channels offers uniform temperature distribution because more airflows through the channels and more heat could be dissipated. The effect of different channel configurations (serpentine, parallel, spiral, divided spiral, and distributed spiral) on thermal traits of air-cooled PEMFC was examined by Ravishankar and Arul Prakash (2014). The divided-spiral design has maximum channel bends, provided high-pressure drop. The distributed serpentine design exhibited excellent uniform distribution of heat.
Heat Generation and Thermal Transport in Lithium-Ion Batteries: A Scale-Bridging Perspective
Published in Nanoscale and Microscale Thermophysical Engineering, 2019
Rajath Kantharaj, Amy M. Marconnet
Novel approaches to enhance heat dissipation in battery packs and improve cell-cell thermal stability in the packs include phase change materials (PCM), liquid cooling, and air cooling. Air cooling is easy to implement, but less effective than liquid-based cooling, which requires an extra heat exchanger and associated piping/fittings [70]. In theory, PCMs could be an ideal thermal management strategy as they possess high latent heat and can prevent spikes in temperature, but their low thermal diffusivity poses difficulty in spreading the heat dissipated from the battery. A novel approach to internally cooling cylindrical battery exploits the high effective axial thermal conductivity in such cells and uses the mandrel (a cell component often included at the center of cylindrical cells for safety reasons such as providing a pathway for gases to flow out and for mechanical integrity [71]) at the core as the heat pipe [72], but in practice, this reduces the energy density and increases the system mass. A similar approach using internal cooling for 26650 cells demonstrated that either air or liquid cooling significantly reduces core temperature and prevents risk of thermal runaway, but manufacturing difficulties dominated [73]. Pack/system level cooling is briefly addressed in Section 6.1 and its advantages towards bridging scales in battery thermal analysis are noted.