Question

(b) High voltage electric power transmitted to a city is dropped to a low voltage in a transformer before use. To keep the transformer at a steady temperature, heat (called the Joulean power dissipation) needs to be transferred to an ambient. Assuming the transfomer to be a vertical cylinder with a diameter of 0.4 m and height of 1 m, the walls are kept at 90°C in a stagnant fluid bath Determine the allowable heat dissipation if the fluid is water kept at 30°C i) ii) Determine the allowable heat dissipation if the fluid is oil kept at 30°C. ii) Explain why oil is used rather than water in commercial transformers iv) Determine the allowable heat dissipation if the transformer is now horizontal and tho fluid is water kept at 30°C (20 marks)

Answer 1

(b) +5.36hwabes (e) eil has more Conuection Goafficient ie, disiptes more heat Gaficient ie, diss

D. As long as the surface area of contact remains same, the dissipated heat would be same.