Problem 1: An experiment had been carried out to investigate the convection coefficient of an external flow pass through a cylindrical tube. The heater is embedded in the metallic material cylindrical tube with diameter and length of 20mm and 100 mm, respectively. The cylindrical tube is heated internally when the heater is switched on. The average surface temperature of the cylindrical tube is estimated to be 130C and it is subjected to a crossflow of cooling air inside a wind tunnel with velocity of 10m/s and temperature of 25C. (a) Determine the total rate of heat transfer from the hot water to the cooling air via the following correlation methods. (i) Hilpert correlation ( 8 marks) (ii) Zukauskas correlation ( 8 marks) (ii) Churchill and (8 marks) Bernstein correlation (b) The average convection heat transfer coefficient obtained in the experiment is approximately 50 W/m2K, predict the variation of the estimated heat transfer from the pipe surface to surrounding for these three correlation methods with reasonable explanation. (8 marks) (c) Evaluate and compare the requirements for the methods of Hilpert correlation, Zukauskas correleation and and Churchill and Bernstein correlation in predicting the average convection heat transfer coefficient. (8 marks)