problem 1: A 3kW electric water heater is a cylindrical element encompassing outside diameter 10mm. The heat transfer among the heater and the surrounding water is 980W/m2K. Find out the length of the heater if the surface temperature must not surpass 95oC when the water is at 65oC.
problem 2: The element comprises an electric resistance heater, diameter 2mm in the centre of the 10 mm diameter stainless steel tube that has a wall thickness of 1mm. The gap among the resistance heater and within of the tube is packed with a ceramic material, Thermal conductivity 2W/mK.
Find out the temperature of electric heater element. You might suppose that the heater element is at uniform temperature and the thermal resistance among the element and the ceramic is negligible. The thermal conductivity of the stainless steel is 16W/mK.