Answer Happy

QUESTION 1 (b) State TRUE or FALSE for the following statement. If FALSE, write the correct statement. (i) Most metals are good conductors of heat because of the migration of neutrons from hot end to cold end. (ii) Thermal conductivity is defined as the heat flow per unit time across unit area when the temperature gradient is unity. (iii) For a given Nusselt number, the convective coefficient is inversely proportional to the thermal conductivity of the fluid. (iv) The ratio of heat transfer by convection to that by conduction is called Biot number. (v) On a heat transfer surface, fins are provided to decrease the surface area to enhance the rate of heat transfer. [C2, SP1][8 marks] Superheated steam at an average temperature 200°C is transported through a steel pipe with diameter, D. = 8 cm and D, = 6 cm with 20 m length. The pipe is insulated with a 4 cm thick layer of gypsum plaster as in Figure Q1(b). The insulated pipe is placed horizontally inside a warehouse where the average air temperature is 10°C. By using thermal conductivity, Ksteel = 50 W/m.ºC and Kp = 0.5 W/m.°C and heat transfer coefficient, hsteam = 800 W/m². °C and hair = 200 W/m².°C. Determine: Steel pipe Superheated steam Insulator L Figure Q1(b) Insulated pipe
(i) Total thermal resistance with the aid of a series circuit schematic diagram. [C4, SP3][12 marks] (ii) The daily rate of heat transfer from the superheated steam. [C3, SP3][2 marks] (iii) The temperature on the outside surface of the gypsum plasters insulation. [C3, SP3][3 marks]