課程名稱︰熱力學
課程性質︰必修
課程教師︰陳希立
開課學院：工學院
開課系所︰機械工程學系
考試日期（年月日）︰2009 fall
考試時限（分鐘）：2 堂課
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
第一部分:(50%)
1.(5%)試說明下列物理量之單位(SI制)?並指出為何性質(property)?
(1)密度(2)熱傳率(3)比熱(4)比焓(5)功
2.(5%)試以熱力學第二定律,說明熱與功之區別?
3.(5%)在一密閉系統之固型槽中內放置壓縮液體水,說明以加熱或冷卻何種方式,
此系統會產生水蒸氣?(T-v圖說明)
4.(5%)說明是否有-20(oC) 之過熱水蒸氣?在否存在5(oC)之冰?
5.(5%)空氣以低於音速流過一擴張器(diffuser),試問出口之溫度與壓力會上升或下
降?若經過一毛細管(capillary tube),試問入出口之溫度與壓力會如何變化?
6.(5%)高壓過熱之蒸氣管路旁道以一閥件連接一真空之絕熱容器,當閥件打開,充填
完成之後,容器內蒸氣之溫度會高於或低於管路內之蒸氣溫度?
7.(5%)何謂逆卡諾循環(說明4個過程)?並說明此逆卡諾冷凍機之COP為何?
8.(5%)上題中逆卡諾冷凍機降低高溫熱源溫度1度C與提高低溫熱涵1度C,何者
對逆卡諾冷凍機COP之提升較大?
9.(5%)今有一熱驅動之冷凍機,熱源溫度為Tg,所傳出之熱量為Qq低溫冷凍室溫度
為Tl,吸收熱量為Ql,環境溫度為To,試證明此冷凍機之最佳COP為
COP=Ql/Qg=(1-To/Tg)(Tl/To-Tl)
10.(5%)若上題中熱源溫度為120度C,低溫溫度為-10度C,環境溫度25度C,試計算
上題中之COP為何?
第二部分(50%)
(Air:Gas consant,R=0.287kJ/kg K;specific heat:cp=1.005kJ/kg K,cv0.718kJ/kg K)
11.(10%)Air is contained in a variable-load piston device equipped
with a paddle wheel.Initially,air is at 600 kPa and 300K.The
paddle wheel is now turned by an external electric motor until
20kJ/kg of work has been transferd to air.During this process,
heat is transferrd to maintain a constant air temperatire while
allowing the gas pressure drops to 200kPa. Calculate the required
amount of heat transfer,in kJ/kg.
12.(20%)Steam flows steadily through an adiabatic turbine.The inlet
conditions of the steam are 12.5 470oC, and 100 m/s, and
the exit conditions are 13 kPa,82 percent quality,and 30 m/s
The mass flow rate of the steam is 15 kg/s. Determine (a)(5%)the
change in kinetic energy(in kJ/kg),(b)(10%)the power output
(in MW),and (c)(5%)the turbine inlet area(in cm2).
13.(20%)An insulated vertical piston-cylinder device initially
contains 0.25m3 of air at 250 kPa and 42oC. At this stat, a
linear spring touches the piston but exerts no force on it.The
cylinder is connected by a valve to a line that supplies air at
900 kPa and 42oC. The valve is opened, and air from the
high-pressure line is allowed to enter the cylinder. The valve
is turned off when the pressure inside the cylinder reaches
650 kPa. If the enclosed volume inside the cylinder doubles
during this process, determine (a)(10%)the boundary work
for this process(in kJ)and (b)(10%)the final temperature
of the air inside the cylinder(in oC).
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