Heat Transfer HEAT GENERATIONHowever, the rate of increase will vary along with the linear heat flux of the channel. The powerdensity and linear heat rate will follow the neutron flux shape. However, the temperaturedistributions are skewed by the changing capacity of the coolant to remove the heat energy.Since the coolant increases in temperature as it flows up the channel, the fuel cladding and, thus,the fuel temperatures are higher in the upper axial region of the core.A radial temperature profile across a reactor core (assuming all channel coolant flows are equal)will basically follow the radial power distribution. The areas with the highest heat generationrate (power) will produce the most heat and have the highest temperatures. A radial temperatureprofile for an individual fuel rod and coolant channel is shown in Figure 17. The basic shapeof the profile will be dependent upon the heat transfer coefficient of the various materialsinvolved. The temperature differential across each material will have to be sufficient to transferthe heat produced. Therefore, if we know the heat transfer coefficient for each material and theheat flux, we can calculate peak fuel temperatures for a given coolant temperature.Figure 17 Radial Temperature Profile Across aFuel Rod and Coolant ChannelRev. 0 Page 49 HT-02
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