Performance Evaluation of the Electric Machine Cooling System Employing Nanofluid as an Advanced Coolant

In this paper, the overall performance of an electric machine cooling system was examined in terms of heat transfer and fluid flow. The structure of the cooling system was based on the cooling jacket method. The cooling jacket contains spiral channels surrounding the stator and end-windings of the electric machine. Al2O3-water nanofluid is used inside the channels as the cooling fluid. The concentration of nanoparticles and the geometric structure of the cooling system have special effects on both aspects of heat transfer and fluid flow. Therefore, in this paper, the overall performance of the cooling system was evaluated by considering these effects. This study compared the importance of heat transfer and fluid flow performances on the overall performance of the cooling system. Numerical analyses were performed by 3D computational fluid dynamics and 3D fluid motion analysis. The analyses were carried out based on the 3D finite element method using the pressure-based solver of the Ansys Fluent software in steady mode.

Development of a Technique for Calculating the Temperature of the Multi-Fuel Nozzle Inner Wall in order to Prevent Sedimentation and Overheating

The article presents the results of a theoretical study on obtaining the formula for calculating the temperature of the inner wall of the multi-fuel nozzle cooling jacket. The problem of overheating these nozzles, as well as the formation of carbon-containing deposits in liquid hydrocarbon fuels and coolants, is discussed. The different ways of dealing with sediment formation, including cooling the fuel channel wall to 373 K are considered. In the case of multi-fuel nozzles, several fuels and coolers can be effectively used at once. The properties of some coolants, including TS-1 kerosene and natural gas, have been investigated. Based on the obtained formula for determining the temperature of the multi-fuel nozzle cooling jacket, a theoretical calculation of the internal temperatures of nozzles of the same mass with several coolants was carried out. An analysis of the results of a theoretical study showed that multi-fuel nozzles are cooled better than single-fuel nozzles and allow predicting fuel consumption in order to achieve the required wall temperature, prevent overheating and sediment formation.

Numerical Investigation on the Thermal Behaviour of a LOx/LCH4 Demonstrator Cooling System

Reliability of liquid rocket engines is strictly connected with the successful operation of cooling jackets, able to sustain the impressive operative conditions in terms of huge thermal and mechanical loads, generated in thrust chambers. Cryogenic fuels, like methane or hydrogen, are often used as coolants and they may behave as transcritical fluids flowing in the jackets: after injection in a liquid state, a phase pseudo-change occurs along the chamber because of the heat released by combustion gases and coolants exiting as a vapour. Thus, in the development of such subsystems, important issues are focused on numerical methodologies adopted to simulate the fluid thermal behaviour inside the jackets, design procedures as well as manufacturing and technological process topics. The present paper includes the numerical thermal analyses regarding the cooling jacket belonging to the liquid oxygen/liquid methane demonstrator, realized in the framework of the HYPROB (HYdrocarbon PROpulsion test Bench) program. Numerical results considering the nominal operating conditions of cooling jackets in the methane-fuelled mode and the water-fed one are included in the case of the application of electrodeposition process for manufacturing. A comparison with a similar cooling jacket, realized through the conventional brazing process, is addressed to underline the benefits of the application of electrodeposition technology.

Improvement of the tube mold to ensure uniform primary cooling of the ingot

For centering the cooling jackets of CCM tube molds relative to the tube, bolts twisted into the jacket are used. The adjustment is made manually, as a result the annular gap between the sleeve and the jacket can have a significant deviation from the specified values. The gap function is to cool the structure by passing water. Taking into account that almost all the modern CCMs for casting long, bloom and round billets are equipped with tube molds, creating a mold design in which the gap between the tube and the cooling jacket is formed with a high degree of accuracy, ensuring uniform heat removal from the walls of the tube is an urgent task. This is necessary to ensure a uniform thickness of the shell of the solidifying billet. The conditions were considered for the formation of a uniform shell of a solidifying ingot in a mold and the production of a billet that meets the requirements for its surface and geometric dimensions, the absence of internal and external cracks of thermal origin. It was shown that the violation of the alignment of the cooling jacket and the tube surfaces results in violation of the uniformity of the cooling water flow. The difference in the volume of water flowing in various parts of the gap between the tube and the jacket can reach 40%. When casting billets with diameters of 600 and 550 mm, the difference in heat flows due to misalignment in existing molds can be 30–40% and 25–35% respectively, and with a cross section of 300×400 mm – 13–23%. In order to eliminate these shortcomings, a new design of the tube mold was developed in VNIIMETMASH (Moscow), in which the gap between the sleeve and the cooling jacket is formed with high accuracy, ensuring uniform heat removal from the walls of the tube and obtaining a uniform thickness of the shell of the solidifying ingot. This will ensure that the casted billet meets the requirements for its quality parameters and geometric dimensions. The diagram of the designed mold for the bloom CCM, which produces billets with a cross section of 340×380 mm is presented.

Cooling Between Exercise Bouts and Post-exercise With the Fan Cooling Jacket on Thermal Strain in Hot-Humid Environments

This study investigated the effects of cooling between exercise bouts and post-exercise with a commercially available fan cooling jacket on thermal and perceptual responses during and following exercise in hot-humid environments. Ten male athletes completed two 30 min cycling bouts at a constant workload (1.4 watts⋅kg–1 of body mass) with a 5 min recovery period in between. Exercise was followed by a 10 min recovery period. In an environmental chamber (33°C, 65% relative humidity), participants performed two trials with (FCJ) or without (CON) the fan cooling jacket on a T-shirt during the 5 min inter-exercise and 10 min post-exercise recovery periods. Mean, chest and upper arm skin temperatures, and thermal sensation and comfort were lower in FCJ than CON trial during and following exercise (P < 0.05). Thigh and calf skin temperatures, infrared tympanic temperature and heart rate were lower in FCJ than CON trial during the experimental trials (P < 0.05). The rates of fall in mean, chest and upper arm skin temperatures, infrared tympanic temperature and thermal sensation and comfort were faster in FCJ than CON trial during both recovery periods (P < 0.05). There were faster rates of fall in thigh and calf skin temperatures and heart rate in FCJ than CON trial during the post-exercise recovery period (P < 0.05). No difference was observed between trials in the rating of perceived exertion (P > 0.05). This study indicates that cooling between exercise bouts and post-exercise with the fan cooling jacket would effectively mitigate thermal strain and perception/discomfort during and following exercise in hot-humid environments. This garment would reduce whole-body skin temperature quickly while promoting falls in lower-body as well as upper-body skin temperatures.