Question

4, Radiation heat transfer is characterized by A) energy transport as a result of bulk fluid motion A) thermal energy transfer as vibrational energy in the lattice structure of the material ) movement of discrete packets of energy as electromagnetic waves D) circulation of fluid motion by buoyancy effects 15. Consider a 0.2m diameter, 1.8 rm long horizontal cylinder in a room at 20°C . If the outer surface temperature of the cylinder is 40° C, the natural convection heat transfer coefficient in W/m c is For air, use k 0.025 88 W/m1" C, Pr 0.7282, v-: 1.608 x 1 0-5 m2 /s 0.387 Ra (i+(0.469/Pr)"167" A) 2.9 B) 3.5 C) 4.1 D) 5.2 E) 6.1 16. Consider an oil-to-oil double-pipe heat exchanger whose flow arrangement is not known. The temperature measurement indicates that the cold oil enters at 20°C and leaves at 55°C, while the hot oil enters at 80°C and leaves at 65°C. Do you think this is a parallel-flow or counter-flow heat exchanger? A) parallel flow only D) shell and tube C) A or B B) counter flow only E) Cross flow 17. In the heat transfer relation Q UA,ΔΙ, for a heat exchanger, What is AT- AT, AT C) D) E) None B) In(AT,/AT log(AT,/AT) 18. Choose the correct statement with respect to a counter flow heat exchanger: A) Both the fluids at inlet are in their coldest state B) Both the fluids at exit are in their hottest state C) Both the fluids at inlet are in their hottest state D) One fluid is hottest and the other is coldest at inlet

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Answer 1