Consider a vertical cylindrical kettle of diameter 1m filled with liquid that is constantly stirred and the vertical surface of the kettle heated with steam. The steam maintains the kettle wall at 110C. The initial uniform temperature of the fluid is 40C and the stirring produces a heat transfer coefficient of 200W/m2K. The density and specific heat of the fluid are 950kg/m3 and 4.1kJ/kgK, respectively. Calculate the time it will take for the average temperature of the fluid to reach 1) 109C, 2) 109.9C. 3) Compare the two answers. Hint: Use the lumped parameter approach, replacing the solid temperature by the mass average temperature of the liquid. Ans: 1) 5.746h; 2) 8.86h