Thermodynamics i i Add

7/25/2019 Thermodynamics i i Add

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Theoretical Question

1- How are steam power plants classified?2- What are the essential requirements of steam power station design?

3- What are the advantage and disadvantage of diesel power Plants?

4-

State the application of diesel power plants.5- What are the major fields of application of gas turbine?

6- State the limitation of gas turbine.7- State the advantage and disadvantage of gas turbine power plants

over diesel and thermal power plants.

8- How are gas turbine power plants classified?9- Discuss briefly the methods employed for improvement of thermal

efficiency of open cycle gas turbine plant.10- List the advantage of combined cycle?

11- What is the difference between open and closed gas turbine?

12-

State the method of increasing the thermal efficiency ofRankin cycle?

13- State the advantage and disadvantage of regenerative cycleover simple Rankine cycle.

14- Prove the efficiency of the Otto cycle is:

ratioExpansionrr

Otto:

11

1=

Obtain the same expressions for work and mean effect pressure.

15- Repeat the 14 for Diesel cycle. (obtain the same expressions)

16- Repeat the 14 for Dual cycle. (obtain the same expressions)

Define new parameters such as r in the question 15 & 16 and

then solve the problem.


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(Combined Binary Gas Turbine Cycle and Vapor Cycles)

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Duct Burner

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9/13

(

. kPa C kg/s/

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) A regenerative gas turbine power plant is shown in Figure. Air enters the

compressor at 1 bar, 27 oC and is compressed to 4 bar. The isentropic efficiency of

the compressor is 80% and the regenerator effectiveness is 90%. All the power

developed by higher-pressure turbine is used to run the compressor and lower-

pressure turbine provides the net power output of 97 kW. Each turbine has isentropic

efficiency of 87% and temperature at the inlet to the high-pressure turbine is 1200K.

Determine:

a) The mass flow rate of air into the compressor, in kg/s

b) The thermal efficiency

c) The temperature of the air at the exit of the regenerator, in K.

d) T-S Diagram


10/13

)Figure shows a steam jet refrigeration system that produces chilled water in a flash

chamber. The chamber is maintained at a vacuum pressure by the steam ejector,

which removes the vapor generated by entraining it in the low-pressure jet and

discharging into the condenser. The vacuum pump removes air and other

noncondensable gases from the condenser shell. For the conditions shown on the

figure, determine the make-up water and cooling water flow rates, each in kg/h.

) Figure shows the schematic diagram of a vapor-compression refrigeration system

with two evaporators usingRefrigerant 12 as the working fluid. This arrangement is

used to achieve refrigeration at two different temperatures with a single compressor

and a single condenser. The low-temperature evaporator operates at -18 oC with

saturated vapor at its exit and has a refrigerating capacity of 3 tons. The higher-temperature evaporator produces saturated vapor at 3.2 bar at its exit and has a

refrigerating capacity of 2 tons. Compression is isentropic to the condenser pressure

of 10 bar. There are no significant pressure drop in flows through the condenser and

two evaporators, and the refrigerant leaves the condenser as saturated liquid at 10 bar.

Calculate:

a) the mass flow rates of refrigerant through each evaporator, in kg/min

b) the compressor power input, in kW.

c) the rate of heat transfer from the refrigerant passing through the condenser, in kW.


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d) h-s and T-S diagrams

) An ideal vapor-compression refrigeration cycle is modified to include a counter

flow heat exchanger, as shown in figure. Refrigerant 12 leaves the evaporator as

saturated vapor at 1.4 bar and is heated at constant pressure to 20 oC before entering

the compressor. Following isentropic compression to 12 bar, the refrigerant passes

through the condenser, exiting at 44 oC, 12 bar. The liquid then passes through the

heat exchanger, entering the expansion valve at 12 bar. If the mass flow rates of

refrigerant is 6 kg/min, determine:

a) the refrigeration capacity, in tons of refrigeration.

b) the compressor power input, in kW.

c) the coefficient of performance

d) h-s and T-s diagrams

Discuss possible advantage and disadvantage of this arrangement.


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) A vapor-compression refrigeration system using Refrigerant 134a is being

designed for a household food freezer. The refrigeration system must maintain a

temperature of -17 oCwithin the freezer compartment when the temperature of theroom is 32 oC. Under these conditions, the steady-state heat transfer rate from the

room into the freezer compartment is 440 kW. Specify operating pressure and

temperature at key points within the refrigeration system and stimate the refrigerant

mass flow rate and compressor power required.

Note: 1 bar= 100 kPa, 1 Ton=12000 Btu/hr= 3516.07137624894 watts


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Thermodynamics i i Add