4 of 9 Q3 (a) Select the correct answer in each of the following three questions [3] Engineering thermodynamics does not

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4 Of 9 Q3 A Select The Correct Answer In Each Of The Following Three Questions 3 Engineering Thermodynamics Does Not 1 (46.03 KiB) Viewed 19 times

4 of 9 Q3 (a) Select the correct answer in each of the following three questions [3] Engineering thermodynamics does not include energy [......] (A) transfer (B) utilisation (C) storage (D) transformation ii. Which of the following would be identified as a control volume? (A)Compression of the air-fuel mixture in a cylinder (B) Filling a tire with air at a service station (C) Compression of the gases in a cylinder (D) The flight of a dirigible iii. In a quasi-equilibrium process, the pressure [......] (A) remains constant (B) varies with location (C) is everywhere constant at an instant (D) depends only on temperature (b) A student stands in a very cold environment at -15 C, wearing clothes that cover the skin almost entirely. The exposed surface area of the clothes is 1.6 m'and has an average surface temperature of 27 °C. The convection heat transfer coefficient is 15 W/mK and the emissivity of the surface of the cloth is assumed to be 0.7. Stephen-Boltzmann constant 5.67 x 10-8 kg s'kt. Answer the following questions: Calculate the total heat loss from the person's body to the environment 14) ii. The person feels cold and therefore puts more cloths on Which mechanism of heat transfer, between the person's body and the environment, is affected by the extra clothes and how does that help the person feel warmer? 14) iii. Without showing any calculation, predict the effect of extra clothes on the average temperature of the exposed surface of the clothes, and briefly explain your reasons. i. (c) A Carnot engine operates between two temperature reservoirs maintained at 200°C and 20 °C, respectively. If the desired output of the engine is 15kW. determine the heat transfer from the high-temperature reservoir and the heat transfer to the low-temperature reservoir. [6] (d) The heat transfer from a 2 m diameter sphere to a 25 °C air stream over a time interval of one hour is 3000 kJ. Estimate the surface temperature of the sphere if the heat transfer coefficient is 10 W/mK. Page 4 of 9 Continued Overleaf