An initial guess at the solid tempe

An initial guess at the solid temperature mid-height along the pedestal (Tp,mid) is made by taking the average of the adiabatic wall temperature and inlet coolant temperature. The convective efficiency of the double-wall geometry is calculated by using the number of transfer units (NTU) method, where the NTU is defined in equation 21 and requires the ratio of overall internal heat transfer coefficient to the coolant heat capacity. The internal convective efficiency can consequently be obtained as per equation 22 where the average solid temperature is taken to be that midway along the pedestal. With knowledge of the heat flows, Q1 – Q3, the temperatures of the film wall and impingement wall can be obtained as shown in equations 29 and 30 respectively based on the thermal circuit. Consequently, the definition of overall cooling effectiveness (see equation 31) can be used to determine the cooling performance of the geometry at a particular coolant mass flow rate. It is noted, in the below validation work, the wall temperature used in defining overall effectiveness was the film wall temperature (TFW) due to its significance in being the surface subjected to the hot core flow.