An instant water heater consists of 9.1 mm inner diameter tube through which water flows at the rate of 18.4 kg/h entering at 30°C. The tube is externally wound over by a nichrome resistance wire with...

An instant water heater consists of 9.1 mm inner diameter tube through which water flows at the rate of 18.4 kg/h entering at 30°C. The tube is externally wound over by a nichrome resistance wire with a heating capacity of 400 W per metre tube length, after which it is insulated. (a) Determine the length of tube required to raise the temperature of water to 75°C. (b) Find the maximum temperature of water at the outlet. (c) What should be done so that there is no boiling in any part of flow. For water at 52.5°C,
 = 984 kg/m³,
 = 0.5410^–3
kg/ ms, k = 0.6445 W/m K and c_p
= 4187 J/kg K.