DEVELOPMENT AND STUDY OF DEVICES FOR AIR COOLING OF THE ROTATING SHAFT IN HIGH-TEMPERATURE FURNACE FAN OF MULTI-DISC TYPE

The design of the device for air cooling of the shaft of a multi-disc furnace fan is developed. The dependences of convective heat transfer from the surface of this device to the environment of three standard sizes are obtained. It was established that the heat transfer during the motion of air in the inter-disc spaces of rotating cooling devices with different frequencies is similar to the heat transfer process in the case of its turbulent flow along the flat surface and is described in general by the power law dependence. The found values of the proportionality coefficients in this dependence take into account the design features of the studied devices and differ from the known values by 1.4 – 1.7 times. With the application of rules for thermal processes modeling, the obtained regularities can be used in the calculation of multi-disc cooling devices and for other designs of high-temperature furnace fans. The effect of changing the device external diameter on its cooling capacity was studied. It was established that a reduction in diameter from 313 to250 mmleads to an increase in the uniformity of the distribution of air flow in the inter-disc space and contributes to an increase in the average heat transfer coefficient from a surface unit by 1.6 to 1.7 times in the comparable conditions. The possibility of increasing the uniformity of air blowing of the discs surface in devices with large diameters (MD-313 and MD-290) due to the increase in the dimensions of the inlet openings is limited according to the reduction in heat removal from the fan shaft due to the reduction in the cross-section area of blades material in the zone of cylindrical surface passing through their axes. The maximum heat flow from the fan shaft is provided by the device with a diameter of290 mm, where two parameters are optimally combined: the value of the heat exchange surface and the intensity of its air blowing. Application of the developed devices allows the removed heat flow to be increased by 20 to 30 times compared to cooling of the surface of an open rotating shaft in a free environment in the comparable conditions. The presented materials can be used for the development of high-temperature fans for heating and thermal furnaces. 

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