Consider an opaque horizontal plate that is well insulated on its back side. the irradiation on the plate is 2500 w/m2, of which 500 w/m2 is reflected. the plate is at 227 c and has an emissive power of 1200 w/m2. air at 127 c flows over the plate with a heat transfer convection coefficient of 15 w/m2 k. determine the emissivity, absorptivity, and radiosity of the plate. what is the net heat transfer rate per unit area?

Explain the difference laminar and turbulent flow. explain it with the shear stress and the velocity profiles.

When at a point two solid phase changes to one solid phase on cooling then it is known as a) eutectoid point b) eutectic point c) peritectic point d) peritectoid point

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?