高等工程热力学试卷和答案

1True or false(20pts)

1) Mass can cross the system boundary in the Open system .(T)

2) Heat and work can not cross in the Closed system. (F)

3)Intensive property is a property that is independent of the extent or mass of the system.(T)

4)Heat exchangers are devices that transfer energy between fluids at different temperatures.(T)

5) Heat engine can have a thermal efficiency of 100%. (F)

6)Heat Engines are Devices that are used to convert heat to work.(T)

7)The decrease in quality is always accompanied by an increase in entropy.(T)

8)Reversible processes actually can occur in nature.F)

9)Energy can be neither created or destroyed;it can only change forms.（T）

10)Both Heat and Work are associated with a process and a state.(F)

11)Once the temperature equality is established,the heat transfer stops.(T)

12)The direction of heat transfer is always from the lower temperature body to the higher temperature.body.(F)

13)Work is not a property of a system or its surroundings.(T)

14)Closed Feedwater Heaters require a separate pump for each heater.(F)

15)The reheat process in general can significantly change the cycle efficiency.(T)

2Chosing a correct answer(30pts)

1) A thermodynamic system generally has a boundary, this boundary （b）

a)can be personally defined from your own interests

b)can only be defined following certain roles

c)is depend on the physical boundaries

d)is independent on the physical as well as personal wills

2) A system is called a closed system when （c）

a)there is only heat exchange between the system and its surroundings

b)there is only work interactions between the system and its surroundings

c)there are both heat exchange and work interactoins between the system and its surroundings

d)there are neither heat exchange nor work interactions between the system and its surroundings

3)The specific internal energy,u,other than U,of a system is determined by the（c）of the system

a) volume b) pressure c) temperature d) mass

4) An example of internal property of a system is （c？）

a)mass b)total volume c)pressure d)enthalpy

5) A steady state process is related to （a ？）

a) a closed system with invarible properties

b) a control volume with its property changes

c) an open system keeping its properties constant

d) a closed system having its properties changed

6) A good approximation for a stream flowing through a porous plug is （a ）

a) h in = h out b) P in = P out c)T in = T out d) a and b e) b and c

7) Δ T= 0 is true （d ）

a) for an adiabatic process. b) if no work is done.

c) for an isentropic process. d) for a reversible process.

8) Characteristics of Heat Engines include （e ）

a) They receive heat from a high-temperature source.

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