Consider an airplane cruising at an altitude of 30 km where standard atmospheric conditions are (- 50°c) and 26.5 kpa at a speed of 800 km/h. each wing of the airplane can be modeled as a 25m x 3m flat plate, and the friction coefficient of the wings is 0.0016 and its surface temperature is 10°c: a) draw the schematic of the system. b) using the c-c analogy, determine the heat transfer coefficient and the rate of heat transfer for the wings at cruising conditions.

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

During a steady flow process, the change of energy with respect to time is zero. a)- true b)- false

Thermal stresses are developed in a metal when its a) initial temperature is changed b) final temperature is changed c) density is changed d) thermal deformation is prevented e) expansion is prevented f) contraction is prevented