Al-Tarik Flashcards by Zed D

Self-ignition would occur in the engine using
certain brand of petrol if the temperature due to
compression reached 350°C. Calculate the highest
ratio of compression that may be used to avoid pre
ignition if the law of compression is

PV1.3 = c
PV1.4 = c

Calculate the final pressure in each case. Assuming
inlet conditions of 27°C and 1 bar.

11.36, 6.19, 23.5 bar, 12.8 bar

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A motorist equips his automobile tyres with a relief
type valve so that the pressure inside the tyre will
never exceed 220 kPa (gauge). He starts the trip
with a pressure of 200 kPa (gauge) and a
temperature of 23°C in the tyres. During the long
drive the temperature of the air in the tyres reaches
83°C. each tyre contains 0.11 kg of air. Determine:

a) the mass of air escaping each tyre;
b) the pressure of the air inside the tyre when the
temperature returns to 23°C.

0.0094 kg
183 kPa

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the pressure of the air inside the tyre when the
temperature returns to 23°C

183 kPa

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the mass of air escaping each tyre

0.0094 kg

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Calculate the density of Ethane at 171 bar and
458K; assume for Ethane:

TC = 305 K
PC = 48.80 bar
R = 319.3 J/kg-K

a) Assume it behaves as a perfect gas.
b) Using the compressibility chart.

117 kg/m3
146 kg/m3

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Calculate the density of Ethane at 171 bar and
458K; assume for Ethane:

TC = 305 K
PC = 48.80 bar
R = 319.3 J/kg-K

Assume it behaves as a perfect gas

117 kg/m3

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Calculate the density of Ethane at 171 bar and
458K; assume for Ethane:

TC = 305 K
PC = 48.80 bar
R = 319.3 J/kg-K

Using the compressibility chart

146 kg/m3

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300 kg/minute of steam at 3 MPa and 400°C is
supplied to a steam turbine. Determine the potential
heat released from steam if it is condensed at
constant pressure. Can you deduce the specific heat
of the steam under this condition?

Q = 2133.5 kW
Cp = 4.009 kJ/kg-K

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Self-ignition would occur in an engine using certain
brand of petrol if the temperature due to
compression reaches 350°C; when the inlet
condition is 1 bar, 27°C.

Calculate the highest compression ratio possible in
order to avoid self-ignition, if the compression is
according to
a) Adiabatic, with index of 1.4; and
b) Polytropic, with index of 1.3.

6.2
11.4

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Self-ignition would occur in an engine using certain
brand of petrol if the temperature due to
compression reaches 350°C; when the inlet
condition is 1 bar, 27°C.

Calculate the highest compression ratio possible in
order to avoid self-ignition, if the compression is
according to
Adiabatic, with index of 1.4

6.2

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Self-ignition would occur in an engine using certain
brand of petrol if the temperature due to
compression reaches 350°C; when the inlet
condition is 1 bar, 27°C.

Calculate the highest compression ratio possible in
order to avoid self-ignition, if the compression is
according to
Polytropic, with index of 1.3.

11.4

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An unknown gas has a mass of 1.5 kg contained in a bottle of volume 1.17 m3 while at a temperature of
300K, and a pressure of 200 kPa. Determine the
ideal gas constant and deduce the gas?

R = 520 J/kg-K;
M = Ro/R = 15.99

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A 6 m3 tank contains helium at 400K is evacuated
form atmospheric pressure of 100 kPa to a final
pressure of 2.5 kPa. Determine
a) The mass of helium remaining in the tank;
b) The mass of helium pumped out;
c) If the temperature of the remaining helium falls
to 10°C, what is the pressure in kPa?

0.018 kg;
0.704 kg;
1763 Pa

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A 6 m3 tank contains helium at 400K is evacuated
form atmospheric pressure of 100 kPa to a final
pressure of 2.5 kPa. Determine
The mass of helium remaining in the tank

0.018 kg

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A 6 m3 tank contains helium at 400K is evacuated
form atmospheric pressure of 100 kPa to a final
pressure of 2.5 kPa. Determine
The mass of helium pumped out

0.704 kg

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A 6 m3 tank contains helium at 400K is evacuated
form atmospheric pressure of 100 kPa to a final
pressure of 2.5 kPa. Determine
If the temperature of the remaining helium falls
to 10°C, what is the pressure in kPa?

1763 Pa

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The gas in an internal combustion engine, initially
at a temperature of 1270°C; expands polytropically
to five times its initial volume and one-eight its
initial pressure. Calculate:
a) The index of expansion, n, and
b) The final temperature

1.292
698K

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1.292

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698K

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Determine using Steam Tables, the volume
occupied by 2 kg of steam at 500 kPa, under the
following conditions and specify the state of steam.
a) Pure liquid state
b) When it is in a pure vapour state
c) 20% moisture content
d) 20% dry

0.00218 m3
0.7498 m3
0.557 m3
0.152 m3

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Determine using Steam Tables, the volume
occupied by 2 kg of steam at 500 kPa, under the
following conditions and specify the state of steam.
Pure liquid state

0.00218 m3

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Determine using Steam Tables, the volume
occupied by 2 kg of steam at 500 kPa, under the
following conditions and specify the state of steam.
20% moisture content

0.557 m3

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Determine using Steam Tables, the volume
occupied by 2 kg of steam at 500 kPa, under the
following conditions and specify the state of steam.
When it is in a pure vapour state

0.7498 m3

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Determine using Steam Tables, the volume
occupied by 2 kg of steam at 500 kPa, under the
following conditions and specify the state of steam.
20% dry

0.152 m3

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The model ‘6SE-TCA3 Perkins’ diesel engine have a stroke of 190 mm and a bore of 160 mm. If its clearance volume is 5% of the swept volume, determine the pressure and temperature at the end of compression when the inlet condition is 1 bar, 27°C. Assume n = 1.38

67.2 bar 956K

An adiabatic steam turbine expands steam from a pressure of 6 MPa and a temperature of 500°C to a pressure of 10 kPa. The isentropic efficiency of the turbine is 0.82 and changes in kinetic and potential energy may be neglected. Determine the state of the steam at exit from the turbine and the specific work transfer.

Mixed phase with dryness factor x = 0.917; 849 kJ/kg

A closed rigid container has a volume of 1 m3 and holds air at 345 kPa and 20°C. heat is added until the temperature is 327°C. determine the change in Internal energy: Using an average value of the specific heat

932 kJ

A closed rigid container has a volume of 1 m3 and holds air at 345 kPa and 20°C. heat is added until the temperature is 327°C. determine the change in Internal energy: a) Using an average value of the specific heat b) Taking into account the variation of specific heat with temperature

932 kJ 1018.7 kJ

A closed rigid container has a volume of 1 m3 and holds air at 345 kPa and 20°C. heat is added until the temperature is 327°C. determine the change in Internal energy: Taking into account the variation of specific heat with temperature

1018.7 kJ

A steam turbine receives steam at 2 MPa and 250°C, and exhausts at 0.1 MPa, 0.85 dry. a) Neglecting heat losses and changes in ke and Pe, estimate the work output per kg stream. b) If, when allowance is made for friction, radiation, and leakage losses, the actual work obtained is 80% of the heat estimated in (a), calculate the power output of the turbine when consuming 600 kg of steam per minute.

539 kJ/kg 4.31 MW

steam turbine receives steam at 2 MPa and 250°C, and exhausts at 0.1 MPa, 0.85 dry. Neglecting heat losses and changes in ke and Pe, estimate the work output per kg stream

539 kJ/kg

Steam at 1.0 MPa, 0.95 dry is throttled to kPa. What is the quality of the steam after throttling?

Superheated condition

A boiler receives feed water at 40°C and delivers steam at 2 MPa and 500°C. if the furnace is oil fired, the calorific value of oil being 42000 kJ/kg and 4000 kg oil are burned while 45000 kg of steam are produced, determine: a) The heat supplied in the boiler. b) The efficiency of the boiler. Assume the values of enthalpies at the two state points as: h1 = hf@40°C = 169.33 kJ/kg at 2 MPa, 500°C, h2 = 3467.6 kJ/kg

1.484x108 kJ; 88%

A boiler receives feed water at 40°C and delivers steam at 2 MPa and 500°C. if the furnace is oil fired, the calorific value of oil being 42000 kJ/kg and 4000 kg oil are burned while 45000 kg of steam are produced, determine: The heat supplied in the boiler. Assume the values of enthalpies at the two state points as: h1 = hf@40°C = 169.33 kJ/kg at 2 MPa, 500°C, h2 = 3467.6 kJ/kg

1.484x10^8 kJ

A boiler receives feed water at 40°C and delivers steam at 2 MPa and 500°C. if the furnace is oil fired, the calorific value of oil being 42000 kJ/kg and 4000 kg oil are burned while 45000 kg of steam are produced, determine: The efficiency of the boiler. Assume the values of enthalpies at the two state points as: h1 = hf@40°C = 169.33 kJ/kg at 2 MPa, 500°C, h2 = 3467.6 kJ/kg

88%

30 kg/s steam at 3 MPa, 300°C expands isentropically in a turbine to a pressure of 100 kPa. If the heat transfer from the casing to surrounding air represents 1 per cent of the overall change of enthalpy of the steam, calculate the power output of the turbine. Assume exit is 2 m above entry and that initial velocity of steam is 10 m/s whereas exit velocity is 1 m/s.

W = +19 kW

An air compressor receives air at 27°C and delivers it to a receiver at the rate of 0.5 kg/s. It is driven by an electric motor which absorbs 10 kW and the efficiency of the drive is 80%. Water jacket cooling is used at the rate of 6 kg/min while its temperature rises from 10°C and 20°C. Estimate the temperature of the air delivered. Data: Cpw = 4.186, and Cpa = 1.005 kJ/kg-K

43.5°C

Air at 27°C receives heat at constant volume until its temperature reaches 927°C. Determine the heat added per kilogram? Assume for air Cv = 0.718 kJ/kg-K

646.2 kJ/kg

An ideal gas occupies a volume of 0.5 m3 at a temperature of 340 K and a given pressure. The gas undergoes a constant pressure process until the temperature decreases to 290 K. Determine a) The final volume. b) The work if the pressure is 120 kPa.

0.426 m3; -8.88 kJ

A piston and cylinder mechanism contains 2 kg of a perfect gas. The gas expands reversibly and isothermally from a pressure of 10 bar and a temperature of 327°C to a pressure of 1.8 bar. Calculate: a) The work transfer; b) The heat transfer and; c) The specific change in enthalpy of the gas. Take R = 0.3 kJ/kg-K and n = 1.4

617 kJ; 617 kJ; 0

An insulated, constant-volume system containing 1.36 kg of air receives 53 kJ of paddle work. The initial temperature is 27°C. Determine a) The change of internal energy. b) The final temperature Assume a mean value Cv = 0.718 kJ/kg-K

+ 53 kJ; 81.3°C

The gas expanding in the combustion space of a reciprocating engine has an initial pressure of 50 bar and an initial temperature of 1623°C. The initial volume is 50000 mm3 and the gas expands through a volume ratio of 20 according to the law pV1.25 = constant. Calculate a) The work transfer and b) Heat transfer in the expansion process Take R = 270 J/kg-K and Cv = 800 K/kg-K.

527 J; 136 J

Air, which may be considered a perfect gas, enters an adiabatic nozzle with negligible velocity. The entry pressure is 6 bar and the exit pressure is 1 bar; the entry temperature is 760 K. The flow throughout the nozzle is reversible and the mass flow rate is 2 kg/s. Calculate the exit velocity. Take Cp = 1004.5 J/kg-K and n = 1.4

782 m/s

A reciprocating steam engine cylinder contains 2 kg of steam at a pressure of 30 bar and a temperature of 300°C. The steam expands reversibly to a final pressure of 2 bar, according to the law pv1.2 = c. Calculate: a) The final state of the stream b) The work transfer and c) The heat transfer in the process

0.875; 884 kJ; -63.4 kJ

3 kg/s of steam enters an adiabatic condenser at a pressure of 100 kPa with dryness fraction 0.80, and the condensate leaves the condenser at a temperature of 30°C. The condenser is cooled by water which enters at a temperature of 5°C and leaves at a temperature of 25°C. Calculate the mass flow rate of cooling water required if all changes in kinetic and potential energy may be neglected. Assume Cp = 4.2 kJ/kg-K, and the enthalpy at 100 kPa and 30°C = 125 kJ/kg.

75 kg/s

Steam at a pressure of 6 MPa and a temperature of 500°C enters an adiabatic turbine with a velocity of 20 m/s and expands to a pressure of 50 kPa, and a dryness fraction of 0.98. The steam leaves with a velocity of 200 m/s. The turbine is required to develop 1 MW. Determine a) The mass flow rate of steam required, when KE is neglected, and b) What is the effect of KE on the answer?

1.216 kg/s; 1.187 kg/s or an error of 2.4%

A reciprocating compressor delivers 0.1 kg/s of air at a pressure of 12 bar. The air enters the compressor at a pressure of 1 bar and a temperature of 15°C. Calculate the delivery temperature of the air, the work transfer rate and the heat transfer rate in the compression process for; i. Reversible polytropic compression, PV1.2 = constant; ii. Reversible adiabatic compression; iii. Reversible isothermal compression. Air – R = 0.287 kJ/kg-K, Cp = 1.005 kJ/kg-K, Cv = 0.718 kJ/kg-K and n = 1.4

i. 435.7 K, -21.2 kW, -10.6 kW; ii. 585.5 K, -21.36 kW, 0; iii. -20.5 kW, -20.5 kW

A reciprocating compressor delivers 0.1 kg/s of air at a pressure of 12 bar. The air enters the compressor at a pressure of 1 bar and a temperature of 15°C. Calculate the delivery temperature of the air, the work transfer rate and the heat transfer rate in the compression process for; Reversible adiabatic compression Air – R = 0.287 kJ/kg-K, Cp = 1.005 kJ/kg-K, Cv = 0.718 kJ/kg-K and n = 1.4

585.5 K, -21.36 kW, 0

A reciprocating compressor delivers 0.1 kg/s of air at a pressure of 12 bar. The air enters the compressor at a pressure of 1 bar and a temperature of 15°C. Calculate the delivery temperature of the air, the work transfer rate and the heat transfer rate in the compression process for; Reversible polytropic compression, PV1.2 = constant Air – R = 0.287 kJ/kg-K, Cp = 1.005 kJ/kg-K, Cv = 0.718 kJ/kg-K and n = 1.4

435.7 K, -21.2 kW, -10.6 kW

A reciprocating compressor delivers 0.1 kg/s of air at a pressure of 12 bar. The air enters the compressor at a pressure of 1 bar and a temperature of 15°C. Calculate the delivery temperature of the air, the work transfer rate and the heat transfer rate in the compression process for; Reversible isothermal compression. Air – R = 0.287 kJ/kg-K, Cp = 1.005 kJ/kg-K, Cv = 0.718 kJ/kg-K and n = 1.4

-20.5 kW, -20.5 kW

A reciprocating internal combustion engine has a clearance volume of 0.0001 m3 and a compression ratio (volume ratio) of 10. The pressure and temperature of the combustion gases when the piston is at top dead centre are 4000 kN/m2 and 1800°C respectively. Assuming that the expansion process follows PV1.3 = constant, calculate: a) The work transfer in this process; and b) The temperature of the gases at the end of the process.

66.7 J; 1039 K

A mass of gas occupying 0.08 m3 at 6 kN/m2 and 80°C is expanded reversibly in a non-flow process according to a law PV1.2 = constant. The pressure at the end of expansion is 0.7 kN/m2. The gas is then heated at constant pressure to the original temperature. The specific heat capacities at constant pressure and constant volume are 1.00 and 0.74 kJ/kg-K, respectively. Determine: a) The work transfer in the expansion process b) The heat transfer in the expansion process c) The volume at the end of the heating process d) The change in internal energy during the heating process.

+0.723 kJ; +0.312 kJ; 0.685 m3; -0.411 kJ

A reciprocating steam motor is supplied with dry saturated steam at a pressure of 1.6 MPa (specific volume = 0/1238 m3/kg. The stroke of the motor is 0.9 m and the bore is 0.3 m. The clearance volume is negligible. The steam enters the cylinder, expands at constant pressure for ¼ of the stroke and then expands reversible according to a law PV = constant, til the end of the stroke. Calculate a) The mass of the steam b) The work transfer and the heat transfer in the process?

0.114 kg; 31.3 kJ, 31.3 kJ

An ideal centrifugal air compressor takes in air at 1 bar, 15°C and compresses it reversible and adiabatically to a pressure of 4 bar. a) Calculate the delivery temperature of the gas. b) If kinetic energy and potential energy changes are negligible calculate the specific work transfer in the compression process. Air may be assumed to be a perfect gas with specific heat capacity at constant pressure Cp = 1.005 kJ/kg K and n = 1.4.

428 K; -140.7 kJ/kg

A piston and cylinder mechanism has its piston fixed so that the volume contained is 0.0025 m3. The mechanism is filled with wet steam at a pressure of 2 bar. The steam is heated until it reaches the critical point. The piston is released and the steam expands adiabatically to a pressure of 2 bar and a volume of 0.5 m3. Calculate: a) The mass of steam in the mechanism, b) The dryness fraction of the steam after expansion.

0.788 kg; 0.715

A reversible adiabatic air turbine drives a small generator which requires a power of 2 kW. The air supply for the turbine is provided by a reservoir and the pressure and temperature at turbine entry maybe considered constant at 9 bar, 20°C respectively. The velocity of the air at inlet to the turbine is small and may be neglected but at exit the velocity is 55 m/s. The exit pressure is 1.2 bar. Calculate: a) The air temperature at exit from the turbine; and b) The mass flow rate of air stating any assumption made. Air may be considered a perfect gas for which the specific heat capacity at constant pressure Cp = 1.005 kJ/kg-K and n = 1.4.

164.76 K; +0.0157 kg/s

Steam at a pressure of 2 MPa and a temperature of 240°C enters a nozzle with a velocity of 15 m/s. The steam expands reversibly and adiabatically in the nozzle to a pressure of 100 kPa and a dryness fraction of 0.9. Calculate the velocity of the steam at exit from the nozzle.

715 m/s

The cylinder of an engine has a stroke of 300 mm and a bore of 250 mm. The volume ratio of compression is 14:1. Air in the cylinder at the beginning of compression has a pressure of 96 kN/m2 and a temperature of 93°C. The air is compressed for the full stroke according to the law PV1.3 = C. Determine the work transfer per unit mass of air. Assume air R = 287 J/kg-K.

-424 kJ/kg

A mass of air at 330°C, contained in a cylinder expanded polytropically to fuve times its initial volume and 1/8th its initial pressure which is 1 bar. Calculate: a) The value of the expansion index; b) The work transfer per unit mass.

1.292; +222 kJ

Steam at a pressure of 10 bar and dryness fraction of 0.96 expands adiabatically to a pressure of 2 bar according to PV1.2 = constant. Determine the work done during expansion per unit mass of steam.

246 kJ/kg

A one pass steam generator receives saturated water at 20 bar, and converting it into steam at 400°C. The mass flow rate of steam is 1200 kg/h, calculate the heat transfer in the generator.

149.667 kW

1 kg of gas occupies a volume of 0.4 m3 at a pressure of 100 kN/m2. The gas is compressed isothermally to a pressure of 450 kN/m2. Determine the work of compression, and the change in entropy of the gas during the compression. Assume for the gas R = 300 J/kg-K.

-60 kJ; -0.451 kJ/kg-K

A nuclear reactor generates 3000 MW of heat. The heat is transferred in a heat exchanger of energy transfer efficiency 75% into steam which is expanded in a turbine in order to produce a power output. The steam is condensed in a condenser, releasing 1800 MW of heat, and pumped back through the heat exchanger by a feed pump which requires 3% of the power output from the turbine. Determine: a) The net power output from the plant. b) The power output from the turbine. c) The overall thermal efficiency of the plant.

463.9 MW; 450 MW; 15%

Milk initially at 30°C is to be kept in a chilled tank at 5°C. If the total volume of milk is 100 litres, its density is 1100 kg/m3 and the specific heat capacity of 4.2 kJ/kg-K. a) Determine the heat extraction rate assuming the chiller to be perfectly insulated. b) What would be the chiller consumption if heat transfer through the chiller body is? i. + 5 kW gain in summer ii. – 5 kW loss in winter

a) 11.55 kW; b) i. 16.55 kW; ii. 6.55 kW

A gas contained in a closed system at a pressure of 1 bar and temperature of 15°C. A mass of 0.9 kg of the gas is heated at constant pressure to raise its temperature from 15°C to 250°C. Determine the work done, and during the process. R = 0.185 kJ/kg K.

+39.1 kJ

Steam enters a cylinder fitted with a piston at a pressure of 20 MN/m2 and a temperature of 500 deg C. The steam expands to a pressure of 200 kN/m2 and a temperature of 200 deg C. During the expansion there is a net heat loss from the steam through the walls of the cylinder and piston of 120 kJ/kg. Determine the displacement work done by one kg of steam during this expansion.

168.6 kJ/kg

During the working stroke of an engine the heat transferred out of the system was 150 kJ/kg of the working substance. If the work done by the engine is 250 kJ/kg, determine the change in internal energy and state whether it is decrease or increase.

-400 kJ/kg, decrease

A closed rigid system has a volume of 85 litres contains steam at 2 bar and dryness fraction of 0.9. Calculate the quantity of heat which must be removed from the system in order to reduce the pressure to 1.6 bar. Also determine the change in enthalpy and entropy per unit mass of the system.

-38 kJ

2 kg of air is heated at constant pressure of 2 bar to 500oC. Determine the change in its entropy if the initial volume is 0.8 m3.

2.04 kJ/K

You have a 200 gram cup of coffee at 100°C, too hot to drink. a) How much will you cool it by adding 50 gm of water at 0°C? b) How much will you cool it by adding 50 gm ice at 0°C? For ice: assume hi = -333.5 and hf = 417 kJ/kg-K

80°C; 64°C

Determine for a unit mass of air, the change in enthalpy when heated from zero°C to 100°C if: i. Cp = 1 kJ/kg-K constant ii. Cp = 0.95 + 0.00002T – 0.03x10-6 T2

100 kJ/kg; 96.09 kJ/kg

A burner heats air from 20 to 40°C at constant pressure. Determine the change in entropy for a unit mass of air going through the heater, assuming that for air Cp = 1 kJ/kg-K.

0.03356 kJ/kg-K

Al-Tarik Flashcards

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