課程名稱︰熱力學
課程性質︰機械系大二必修
課程教師︰馬小康
開課學院：工學院
開課系所︰機械工程系
考試日期（年月日）︰101/11/13
考試時限（分鐘）：60
是否需發放獎勵金：是
試題：
(25%) (1)Please explain the following terms:
(a) Intercooling of pump
(b) Carnot heat engine cycle
(c) Clausius Statement
(d) Two entropy change of ideal gases
.
(e) What is the definition of s in the following term?
┌ 2 . .
│ Cp(T)/T dT = s2 - s1
┘ 1
(20%) (2) An ideal gas undergoes with constant heat capacities undergoes the
reversible cycle.
The process making up the cycles are
1-2 is a constant volume process
2-3 is an isothermal process
3-4 is an adiabatic process
4-1 is a constant pressure process
(a) Please plot the T-S diagram
(b) Calculate the network, W
net
(15%) (3) It is claimed that the efficiency of a completely reversible heat
engine can be doubled by doubling the temperature of the energy resource.
Justify the validity of this claim.
(20%) (4) A 50-kg iron block and a 20-kg copper block, both initially at 80 C,
are dropped into a large lake at 15 C.
Thermal equilibrium is established after a while as a result of heat transfer
between the blocks and the lake water. Determine the total entropy generate in
this process.
The specific heats of iron and copper at room temperature are C =0.45kJ/kg.C
and C =0.386kJ/kg.C iron
copper
(20%) (5) It is desired determine the unknown volume of the tank(Tank B) in a
operating process. It is not possible either to measure directly the volume of
the tank or to weigh its contents. However, tank B may be evacuated and then
connected to a second tank (Tank A) of known volume which contains steam at
known P and T. (The lines and valve connecting the two tanks are assumed to
have negligible volume and to be perfectly insulated.)
Assumption:
The steam in a 1 m3 tank (x=0.6) is released from 400kPa until the pressure
in the tank A reduces to 200kPa. Please determine the mass withdrawn from
tank A and the unknown volume of a tank B.
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