The helium core flash is a very short time event
a. True
b. False
Indicate whether the statement is true or false
True
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When viscous dissipation is appreciable, the conservation of energy [Eq. 5.6] must take into account the rate at which mechanical energy is irreversibly converted to thermal energy due to viscous effects in the fluid. This gives rise to an additional term, Ø , on the right-hand side, the viscous dissipation where
Apply the resulting equation to laminar flow between two infinite parallel plates, with
the upper plate moving at a velocity U. Assuming constant physical properties [p, cp, k,
?], obtain expressions for the velocity and temperature distributions. Compare the
solutions with the dissipation term included with the results when dissipation is
neglected. Find the plate velocity required to produce a 1 K temperature rise in
nominally 40°C air relative to the case where dissipation is neglected.
GIVEN
Laminar flow between two infinite parallel plates
Upper plate moves at a velocity U?
The viscous dissipation term given above must be used in the conservation of energy equation
FIND
(a) Expression for velocity and temperature distributions
(b) Compare these to solutions without the dissipation term
(c) Plate velocity that gives a 1 K rise in 40°C air relative to the case without the dissipation term
ASSUMPTIONS
Steady state
Constant physical properties
The plates are at constant temperatures, T1, T2
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 28, for dry air at 40°C
Thermal conductivity (k) = 0.0265 W/(m K)
Absolute viscosity (?) = 19.1 x 10–6 N s/m2
Standing Waves on a String: A stretched string is observed to have four equal segments in a standing wave driven at a frequency of 480 Hz. What driving frequency will set up a standing wave with five equal segments?
A. 600 Hz B. 360 Hz C. 240 Hz D. 120 Hz
In the above image, the text on the right is written to ensure ______.
A. SEO B. RWD C. scannability D. searchability
Why weren't many elements heavier than helium produced during the nucleosynthesis era?
What will be an ideal response?