a) An electric wire heater is used to boil water in a container exposed to the atmosphere, as shown in Figure Q- 2 a. What is the boiling regime if the wire surface temperature is at 120°C and 250°C? Show these points on the boiling curve.[4 marks] Which is more efficient; film condensation or dropwise condensation? Why? c) Two parallel coaxial disks, a of 20 cm diameter, b of 40 cm diameter and10 cm apart, as shown in Figure Q- 2 c.Determine the view factors Fab and Fpa.[4 marks] d) Air at 25°C is blown over aluminium finned walls as shown in Figure Q- 2 d.The assembly has 8 fins which are 1.5 mm thick and spaced 9 mm apart between the walls. The walls are 75 mm high. The depth of the wall and the fins is 75 mm. Both walls are at a constant temperature of 60°C. The convection heat transfer coefficient between the hot surfaces and the airflow is 50 W/m?K, and the thermal conductivity of the aluminium is 200 W/mK. The fin efficiency. i.The heat transfer rate from one fin. iii.The maximum possible heat transfer from one fin to the ambient. iv.The heat transfer rate from the un-finned surfaces in x-direction. [ V.The temperature of the fin at the centre point.

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