課程名稱︰熱力學
課程性質︰系必修
課程教師︰陳瑤明
開課學院：工學院
開課系所︰機械系
考試日期（年月日）︰2012/11/8
考試時限（分鐘）：120分鐘
是否需發放獎勵金：
（如未明確表示，則不予發放）
試題 :
1.Please answer the following questions:(30%)
(a)What is the concept of continum?When is the assumption of continum
valid?
(b)What is the zeroth law of thermodynamics?How do we use it?
(c)The kelvin is a unit of measurement for temperature.Please give its
definition.
(d)Whar are the mechanisms of heaT transfer? What is Fourier's law?
What is Newton's law of cooling?
2.Nitrogen gas is expanded in a polytropic process with n=1.45 from 2MPa and
1200K to 200kPa in a piston-cylinder device. How much work is produced and
heat is transferred during this expansion process,in kJ/kg?
The properties of nitrogen are:R=0.2986kJ/kg.K
and Cv=0.743 kJ/kg.K(20%)
3. An insulated rigid tank is initially evacuated. A valve is opened, and
atmospheric air at 95kPa and 17度C enters the tank until the pressure
in the tank reaches 95kPa,at which point the valve is closed.Determin the
final temperature of the air in the tank.Assume constant specific heats,
and the specific heat ratio of air at room temperature is k=1.4.(15%)
4.An ideal gas expands in an adiabatic turbine from 1200K and 900kPa to
700K.Determine the turbine inlet volume flow rate of the gas,in 立方公尺/
sec ,required to produce turbine work output at the rate of 350kW.
The average values of the specific heats for this gas over the temperature
range and the gas constant are Cp=1.13kJ/kg.K ,Cv=0.83kJ/kg.K
and R=0.30kJ/kg.K(15%)
5. A constant pressure R-134a vapor separation unit separates the liquid and
vapor portions of a saturated mixture into two separate outlet streams.
Determine the flow power needed to pass 6L/s of R-134a at 320 kPa and 55%
quality through this unit.What is the mass flow rate of the two outlet
streams?(20%)
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※ 編輯: manuarg2008 來自: 140.112.214.155 (11/08 17:27)