Unformatted text preview: ENGR 225 Name KE Y
October 31, 2007 Please Check One Recitation: 8:3 0__;10: 1 5; mlzlS Short answer (2 pts. Each, for 27F and multiple choice circle the best answer at the choices given, ﬁll in the blank must be completed
with a meaningﬁtl word or phrase) 1. For ﬂow in a pipe, the mass ﬂow rate is the product of the density of the fluid, the cross sectional area perpendicular to the
direction of ﬂow and then. 01mg velocity of the ﬂuid 2. @F For steady state ﬂow, 2 m= 2 m is always true. 014‘! 3. Flow work
a) is the same as ﬂow energy
b) is the product of pressure and volume
0 has the same units as kinetic energy
@ all of the above
e) none of the above 4. For an open system, energy can be transported 112p“ and out of the system by both of the mechanisms that operate for closed
systems. In addition for open systems Mass can transfer energy in or out. . _ V2 V2
5. @ F The expression, Q — W = 2 m[h + g + gz] - 2 m[h + 7 + g1] is the ﬁrst law ofthermodynamics applied to our in steady ﬂow through an open system. 6. For ﬂow through an adiabatic throttling valve as illustrated .1 I ,2 to the right,
the energy balance given in question 5 simpliﬁes to —P a) Q = W
b). ml(h1 + HZ) = m2[h2 + VZZ) @ hl=h2 d) none of the above 7. A turbine rem “5 energy from moving ﬂuid.
8. @ F When a process is cyclic, the cycle is closed only when the ﬂuid returns to its original state. 9. All heat engines in the real world
a move energy from a low temperature source to a high temperature sink reject heat to the surroundings
c) require TlnPl
d) can be run backwards 10. A refrigerator requires the input of energy in the. form of W° ‘4“ to operate.
ll. T a Compressed air engines (like the one demonstrated in class) operate on a cycle. 12. The second law of thermodynamics can be stated as a) it is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce a net amount
of work b) it is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a
lower-temperature body to a higher-temperature body c) work can be completely converted to heat, but heat cannot be completely converted to work (1) heat spontaneously moves from hot to cold, but not from cold to hot @ all of the above ...
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