A magnetar is a type of ____
a. hypernova
b. neutron star
c. black hole
d. jet
e. X-ray burster
b
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What is a mineral?
What will be an ideal response?
Erosion performed by flowing water alone is known as
A. weathering. B. abrasion. C. hydraulic action.
Concave spherical mirrors produce images which
A) are always smaller than the actual object. B) are always larger than the actual object. C) are always the same size as the actual object. D) could be smaller than, larger than, or the same size as the actual object, depending on the placement of the object.
Two infinitely large black plane surfaces are 0.3 m apart and the space between them is filled by an isothermal gas mixture at 811 K and atmospheric pressure consisting of 25% CO2, 25% H2O, and 50% N2 by volume. If one of the surfaces is maintained at 278 K and the other at 1390 K respectively, calculate
(a) the effective emissivity of the gas at its temperature
(b) the effective absorptivity of the gas to radiation from the 1390 K surface
(c) the effective absorptivity of the gas to radiation from the 278 K surface
(d) the net rate of heat transfer to the gas per square meter of surface area
GIVEN
Two infinitely large black plane surfaces with an isothermal gas mixture between them
Distance between surfaces (s) = 0.3 m
Gas mixture temperature (Tm) = 811 K
Gas mixture pressure = 1 atm
Gas contents: 25% CO2, 25% H2O, 50 % N2 by volume
Surface temperatures
T1 = 278 K
T2 = 1390 K
FIND
(a) The effective emissivity of the gas at its temperature (? mix)
(b) The effective absorptivity of the gas to radiation from A1
(c) The effective absorptivity of the gas to radiation from A2
(d) The net rate of heat transfer to the gas per square meter of surface are (qm/A)
ASSUMPTIONS
Steady state
Convection is negligible
SKETCH
