A laboratory wind tunnel has a test section 25 cm square and 50 cm long. With nominal air speed U1 =25m=s at the test section inlet, turbulent boundary layers form on the top, bottom, and side walls of the tunnel. The boundary-layer thickness is δ1 =10 mm at the inlet and δ2 =30 mm at the outlet from the test section. The boundary-layer velocity profiles are of power-law form, with u=U =ðy=δÞ1=7. Evaluate the freestream velocity, U2, at the exit from the wind-tunnel test section. Determine the change in static pressure along the test section.

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?

Burgers vector is generally parallel to the dislocation line. a)-true b)-false

For each of the following process: a) sketch the p-v diagram, b)sketch t-s diagram, c) sketch t-v diagram, d) sketch the boundary work on one of the diagrams (a, b or c) and e) sketch the reversible heat transfer on one of the diagrams (a, b or c): 1- isobaric process from compressed liquid to superheated vapor 2- isothermal process from compressed liquid to superheated vapor 3- isentropic process from compressed liquid to superheated vapor