A large high-power transformer is installed and operated in an electric-power distribution station. To maintain transform efficiency and prevent its failure (burnout), the transformer oil is cooled via a water-cooled, coiledtube heat exchanger and circulated through the transformer winding module. For one such application, transformer oil, with a flow rate of 0.3 kg/s, is to be cooled to 30°C while flowing through the coiled thin walled metallic tubing. The tube has an inner diameter of 5.0 cm, and its surface is maintained uniformly at a temperature of 20°C. If the oil enters the heat exchanger tube at a temperature of 50°C, and if the coil effects can be ignored and tube modeled as a straight circular pipe, what is the tube length required for this heat exchanger? What is the expected pressure drop across the tube length? Also, if the tube surface temperature increases to 25°C, determine the outlet temperature of transformer oil for the calculated pipe length.