The experimental set up consists of metal bar, one end of which is heated by an electric heater while the other end of the bar projects inside the cooling water jacket. A cylindrical shell filled with the asbestos insulating powder surrounds the middle portion of the bar. The temperature of the bar is measured at different sections. Heat Input to the heater is given through variac and measured by Digital Voltmeter & Digital Ammeter. By varying the heat input rates, wide range of experiments can be performed. Water under constant head condition is circulated through the jacket and its flow rate and temperature rise is noted.