Boilers

1.81

A waste heat recovery boiler produces 4.8 Mpa(dry saturated) steam from 104°C feedwater. The boiler receives energy from 7 kg/sec of 954°C dry air. After passing through a waste heat boiler, the temperature of the air is has been reduce to 343°C. How much steam in kg is produced per second? Note: At 4.80 Mpa dry saturated, h = 2796.

45.1 KJ/min

Water is boiler in a pan on a stove at sea level. During 10 minutes of boiling, it is observed that 200 grams of water has evaporated. Then the rate of heat transfer to the water is:

2.51 m/sec

Water substance at 70 bar and 65ºC enters a boiler tube of constant inside diameter of 25 mm. The water leaves the boiler tube at 50 bar and 700ºK at velocity of 150 m/s. Calculate the inlet velocity (m/sec).

At 70 bar (7 Mpa) and 65ºC: V1=0.001017m³/kg

At 50 bar (5 Mpa) and 700ºK(427ºC): V2=0.06081m³/kg

1.609 li/sec

Water substance at 70 bar and 65ºC enters a boiler tube of constant inside diameter of 25 mm. The water leaves the boiler tube at 50 bar and 700ºK at velocity of 100 m/s. Calculate the inlet velocity (li/sec).

80.67

23.5 kg of steam per second at 5 Mpa and 400 deg. C is produced by a steam generator. The fedwater enters the economizer at 145 deg. C and leaves at 205 deg. C. the steam leaves the boiler drum with a quality of 98%. The unit consumes 3 kg of coal per second as received having a heating value of 25,102 KJ/kg. What would be the overall efficiency of the unit in percent? At 5 Mpa and 400 deg. C: h = 3195.7  at 5 Mpa; hf = 1154.23, hfg = 1640.1 At 205 deg C: hf = 875.04 at 145 deg. C: hf = 1640.1

853.36 hrs

A water tube boiler has a capacity of 1000 kg/hr of steam. The factor of evaporation is 1.3 boiler rating is 200%, boiler efficiency is 65% heating surface area is 0.91 m^3 per bo.Hp, and the heating value of fuel is 18,400 Kcal/kg. The total coal available in the bunker is 50,000 kg. Determine the no, of hrs to consume the available fuel.

230.80 hrs

Two boilers are operating steadily on 91,000 kg of coal contained in a bunker. One boiler is producing 1591 kg of steam per hour at 1.2 factor of evaporation and an efficiency of 65% and another boiler produced 1364 kg of steam per hour and 1.15 factor of evaporation and an efficiency of 60%. How many hours will the coal in the bunker run the boiler if the heating value of the coal is 7,590 Kcal/kg?

62.70%

The heating value of fuel supplied in a boiler is 40,000 kj/kg. if the factor of evaporation is 1.10 and the actual specific evaporation is 10, what is the efficiency of the boiler?

7,817.16 kg/hr

What is the rate of evaporation of  a water tube boiler if the factor of evaporation is 1.10, percent rating of  200% and the heating surface area is 250 m^2?

12 lb/10⁶ BTU

A boiler plant generates 224,000 lb of steam and burns 13.9 tons of coal per hour. The coal has a heating value of 11400 BTU/lb. A test of particulates leaving the boiler shows that 3804 lb of particulate is being discharged per hour. What is the particulate discharged per million BTU heat input to the furnace?

136.5%

Compute is the percent rating of a water tube boiler if the heating surface area is 500 m2 and the developed boiler horsepower is 750?

1138

The percent rating of water tube boiler is 200 %, factor of evaporation is 1.10, and heating surface is 400 ft². Determine the rate of evaporation, in kg/hr.

5.3 kg/s

A Rankine cycle operates with a thermal efficiency of 40 % and the factor of evaporation of the boiler is 1.15. Determine the mass flow rate of steam if the cycle power output is 5.5 MW.

189.6

A boiler operates at 82 % efficiency while the mass of steam generated is 490 200 kg in 6 hours. The enthalpy of steam is 3187 kJ/kg and feed is 604.83 kJ/kg while the fuel used for boiler has a heating value of 32 567.85 kJ/kg. Find the mass of fuel needed per day in metric tons.

53.08%

The heating value supplied in a boiler is 41000 KJ/kg if the factor of evaporation is 10 kg of steam/kg fuel. What is the efficiency of the boiler?

615

What is the water rate in kg/hr of an auxiliary boiler which produces steam at .80 Mpa and 98% dry from feedwater at 43 degC. The fuel calorific value is the equivalent to that of 1.2 metric tons/day. Assume an efficiency of 70%.

0.9317

Two boiler of equal steaming capacity generate steam to a common header of 15 Mpa pressure. One boiler produces wet steam. If the mixture is saturated steam, find the quality of the steam in the second boiler. @1.5 Mpa & 250 degC   h = 2925 KJ/kg  @1.5 Mpa , hf = 845 KJ/kg  hfg = 1947 KJ/kg.

3.08%

Steam leaves an industrial boiler at 827.4 kPa and 171.6 oC. A portion of the steam is passed through a throttling calorimeter and is exhausted to the atmosphere when the calorimeter pressure is 101.4 kPa.  How much moisture does the steam leaving the boiler contain if the temperature of the steam at the calorimeter is 115.6 oC? At 827.4 kPa (171.6 oC) hf = 727.25 kJ/kg  hfg = 2043.2 kJ/kg. From table 3: at 101.4 kPa and 115.6oC h2 = 2707.6 kJ/kg.

2 x 10⁶ kJ

A 10 m³ vessel contains 5 m³ of liquid water and 5 m³ of saturated water vapor at 100kpa. Calculate the internal energy of the system using the steam tables.

24.9 ft³

3.0 lbm of air are contained at 25 psia and 100 °F. Given that R_air = 53.35 ft-lbf / lbm-°F, what is the volume of the container?

1124 cal

Twenty grams of oxygen (O₂) are compressed at a constant temperature of 30°C to 5 % of their original volume. What work is done on the system?

3.16 kg

A vessel with a volume of 1 cubic meter contains liquid water and water vapor equilibrium at 600 kPa. The liquid water has a mass of 1 kg. Using the steam tables, calculate the mass of the vapor.

-432 kJ/kg

A cylinder and a piston arrangement contains saturated water vapor at 110 °C. The vapor is compressed in a reversible adiabatic process until the pressure is 1.6 MPa. Determine the work done by the system per kilogram of water.

0

Ideal Oxygen is throttled at 140degF from 10 atm to 5 atm. What is the temperature change?

8 kJ

Gas is enclosed in a cylinder with a weighted piston as the top boundary. The gas is heated and expands from a volume of 0.04 m³ at a constant pressure of 200 kPa. Calculate the work done by the system.

6.74 x 10^-20 J

Assume the total heat of vaporization (per gram) of water can be used to supply the energy needed to tear 1 g of water molecules apart from each other. How much energy is needed per molecule for this purpose?

230.4 BTU/lbm

An isobaric steam generating process starts with saturated liquid at 20 psia. The change in entropy is equal to the initial entropy. What is the change in enthalpy during the process? (Hint: Not all liquid is vaporized.)

The device violates the 1st law of thermodynamics.

A steam generator produces saturated steam at 100 psia from saturated liquid at 14.7 psia. If the heat source is a bath at 340F that produces 800 BTU/lbm, which of the following is true?

13.3 ft³/lbm

If air is at a pressure, ρ , of 3200 lbf/ft², and at a temperature, T , of 800°R, what is the specific volume, v? (R = 53.3 ft-lbf/lbm-°R, and air can modeled as an ideal gas).

100,000 kJ

A 5m³ vessel initially contains 50 kg of liquid water and saturated water vapor at total internal energy of 27,3000 kJ. Calculate the heat requirement to vaporize all of the liquid.

100 J

A copper can of negligible heat capacity contains 1 kg of water just above the freezing point. A similar can contains 1 kg of water just below the boiling point. Two cans are brought to into thermal contact. Find the change in entropy of the system?

1.66 x 10^-24  g/atom

The atomic weight of hydrogen is 1gram per gram-atom. What is the mass of hydrogen atom?

755 mmHg

In a gaseous mixture of 20 deg. C the partial pressures of the components are as follows: Hydrogen, 200 mmHg; Carbon Dioxide, 150 mmHg; Methane, 320 mmHg; Ethylene, 105 mmHg. What is the total pressure of the mixture?

-94.8 BTU/lbm

Air undergoes an isentropic compression from 14.7 psia to 180.6 psia. If the initial temperature is 68 °F and the final temperature is 621.5 °F, calculate the work done by the gas.

7.33 kJ

Gas is enclosed in a cylinder with a weighted piston as the top boundary. The gas is heated and expands from a volume 0.04 m³ to 0.1 m³. The pressure varies such that PV = C, and the initial pressure is 200 kPa. Calculate the work done by the system.

1.79 kJ/kg.°C

From the steam tables, determine the average constant pressure specific heat (Cp) of steam at 10 kPa and 45.8°C.

2.39 J/moleK

For an ideal gas, what is the specific molar entropy change during an isothermal process in w/c the pressure changes from 200 kPa to 150 kPa?

Zero

What is the value of the work done for a closed, reversible, isometric system?

2585 psia

If 1 lbm of steam at 14.7 psia, 63 % quality is heated isentropically, at what pressure will it reach the saturated vapor state?

348.0 cal/K

200g of water are heated from 5C to 100C and vaporized at a constant pressure. The heat of vaporization of water at 100C is 539.2 cal/g. The heat capacity at constant pressure, Cp is 1.0 cal/gK. Determine the total change in entropy.

n = 0

What is true about the polytropic exponent, n , for a perfect gas undergoing an isobaric process?

0.91

On a hot day, the temperature rises from 50F early in the morning to 99F in the afternoon. What is the ratio of the concentration (in moles/ft³ of helium in a spherical balloon in the afternoon to the concentration of helium in the balloon in the morning?

4.18 kW

Cool water at 9 deg. C enters hot-water from which warm water at a temperature of 80 deg. C is drawn at an average rate of 300 g/min. How much average electric power does the heater consume in order to provide hot water at this rate?

0.357 K/s

Water (specific heat c_v = 4.2 kJ/kg-K) is being heated by a 1500W heater. What is the rate of change in temperature of 1 kg of the water?

700 kJ

Calculate the change in enthalpy as 1 kg of nitrogen is heated from 1000 K to 1500 K, assuming the nitrogen is an ideal gas at a constant pressure. The temperature-dependent specific heat of nitrogen is:

c_p = 39.06 - 512.79T^-1.5 + 1072.7T^-2 - 820.4T^-3

c_p is in kJ/Kmole-K and T is in K.

-0.689 BTU/lbm-°R

Helium is compressed isothermally from 14.7 psia and 60 °F. The compression ratio is 4. Calculate the change in entropy of the gas given that R_He = 0.4961 BTU/lbm-°R.

75.4 K

One kilogram of water (c_v = 4.2 kJ/kg-K) is heated by 300 BTU of energy. What is the change in temperature, in K?

6.095 in³

In an isentropic compression, p₁ = 200 psia, p₂ = 300 psia, V₁ = 10 in³, and  k= 1.4. Find V₂.

179.3 ml

200 mL of oxygen are collected over water at 23C and a pressure of 1 atmosphere. What volume would the oxygen occupy dry at 273K and 1 atmosphere?

7.28 atm

A gas has a density of 0.094 lb/ft³ at 100degF and 2 atm. What pressure is needed to change the density to 0.270 lb/ft3 at 250degF?

8.342 psia

If atmospheric air 14.7 psia and 60degF at sea level, what is the pressure at 12000 ft altitude if air is incompressible. Note: @ 60degF; the density of air is 0.0763 lbm/ft³; P1 = 14.7 psia.

23.57 psia

A cold tire contains 1000 in.3 of air at 24 psia and 32degF. What pressure in the tire is needed if the temperature and volume are increased to 35degF and 1020 in.3 respectively?

1.67

Determine the specific gravity of carbon dioxide gas (molecular weight = 44) at 150degF (66degC) and 20 psia (138 kPa).

7544 ft³

An empty polyethylene telemetry balloon and payload have a mass of 500 lbm. The balloon is charged with helium when the atmospheric conditions are 60degF and 14.8 psia. The specific gas constant of helium is 386.3 ft-lbf/lbm-R. What is the volume of helium is required?

12.12 kJ/K

What is the change in entropy of 2 kg water molecules when transformed at constant pressure of 1 atmosphere from water at 100degC to steam at the same temperature?

0.026

In a gaseous mixture of 20 deg. C the partial pressures of the components are as follows: Hydrogen, 200 mmHg; Carbon Dioxide, 150 mmHg; Methane, 320 mmHg; Ethylene, 105 mmHg. What is the mass fraction of Hydrogen ( m(H₂) = 2, m(CO₂) = 44, m(meth) = 16 and m(eth) = 30 kg/mol)?

13.1

Assume the total heat of vaporization (per gram) of water can be used to supply the energy needed to tear 1 g of water molecules apart from each other. What is the ratio of energy needed per molecule to kT where k = 1.38 x 10^-23 J/K?

3300 lbf-ft/lbm

Steam at 1000 lbf/ft² pressure and 300°R has a specific volume of 6.5 ft³/lbm and a specific enthalpy of 9800 lbf-ft/lbm. Find the internal energy per pound mass of steam.

1.1577 BTU/lbm-°R

Calculate the entropy of steam at 60 psia with a quality of 0.6.

15.7 BTU

Find the change in internal energy of 5 lbm of oxygen gas when the temperature changes from 100°F to 120°F. c_v = 0.157 BTU/lbm-°R.

-74.49 BTU/lbm

Determine the change in enthalpy per lbm on nitrogen gas as its temperature changes from 500°F to 200°F. c_p = 0.2483 BTU/lbm-°R.

28.6 psia

What is the resulting pressure when one pound of air at 15 psia and 200°F is heated at constant volume to 800°F?

108 Hp

What horsepower is required to isothermally compress 800 ft³ of air per minute from 14.7 psia to 120 psia?

3050 kJ

Calculate the work done by a system in which 1 kg mole of water completely evaporates at 100°C and 1 atmosphere pressure.

W = mRTln V₂/V₁

What is the equation for a work done by a constant temperature system?

3768 ft-lbf

A piston-cylinder system contains a gas which expands under a constant pressure of 1200 lbf/ft². If the piston is displaced during the process, and the piston diameter is 24”, what is the work done by the gas on the piston?

Both: heat transfer = 0; Isentropic: reversible.

How does an adiabatic process compare to an isentropic process?

786 °R

In an adiabatic, isentropic process, p₁ = 200 psia, p₂ = 300 psia, and T₁ = 700 °R. Find T₂, using  γ= 1.4.

12.9

Nitrogen is expanded isentropically. Its temperature changes from 620 °F to 60 °F. Find the pressure Ratio (p₁/p₂).

99.22 BTU/lbm

Nitrogen is expanded isentropically. Its temperature changes from 620 °F to 60 °F. The volumetric ratio is V₂/V₁ = 6.22 and the value of R for nitrogen is 0.0787 BTU/lbm-°R. What is the work done by the gas?

III

A device that is meant to extract power from waste process steam starts w/ steam of 75% quality at 100 psia. The exit conditions of the steam are 70% quality at 14.7 psia. Which of the following statements are true?

I. The device violates the 1st law of thermodynamics.

II. The device violates the 2nd law of thermodynamics.

III. The device generates positive net power

IV. The device generates no net power.

I and II

An engineer devices a scheme for extracting some power from waste process steam. The steam enters a device at 100 psi and quality 75% and exits at 14.7 psia and 65% quality. Which of the following statements are true?

I. The produces 155 BTU/lbm of work.

II. The device violates 2^nd law of thermodynamics.

III. The device violates the 1st law of thermodynamics.

5.98 g

A bicycle tire has a volume of 600 cm³. It is inflated with CO₂ to a pressure of 80 psi at 20C. How many grams of CO₂ are contained in the tire?

49.2 g

When 0.5 g of a liquid is completely evaporated and collected in a 1 liter manometer, the pressure is 0.25 atmospheres and the temperature is 27C. Assuming ideal behaviour, determine the molecular weight. The gas constant is R=0.0821 atm/moleK.

0.895 cu. m.

A 0.064 kg octane vapor (MW = 114) is mixed 0.91 kg of air (MW = 29.0) in the manifold is 86.1 kPa, and the temperature is 290 K. Assume octane behaves ideally, what is the total volume of this mixture?

1.197 kg/m3

Determine the sp.heat weight of air at 760 mmHg absolute and 22C?

371.56

How long could a 2000 hp motor be operated on the heat energy liberated by 1 mi.³ of ocean of water when the temperature of the water is lowered by 1degC and if all these heat were converted to mechanical energy?

0.23 BTU/lbR

Given that molar C_p of CO₂ is 8.92 BTU (lb.moleR) and molar C_p of N₂ is 6.95 BTU/(lbmoleR), the calculated C_p per pound of mixture containing 25% vol. CO₂ and 75% vol. N₂ is:

3.15

A mixture at 14.7 psia and 68F that is 30% weight CO₂ (m wt=44) and 7% wt. N₂ (m wt=28) has a partial pressure of CO₂ in psia that is nearest to:

162R

Normal boiling point of liquid oxygen is 90K. What is its temp in R?

+5 BTU/lb

Shaft work of -15 BTU/lb and heat transfer of -10 BTU/lb change enthalpy of a system by:

+6.7

A non-flow (closed) closed system contains 1lb of an ideal gas (C_p = 0.24, C_v = 0.17). The gas temperature is increased by 10F while 5 BTU of work are done by the gas. What is heat transfer in BTU?

49

55,000 gallons of water passes through a heat exchanger and absorbs 28,000,000 BTU’s. The exit temperature is 110F. The entrance water temperature in F is nearest to:

5150 ft-lb

Work of polytropic (n=1.21) compression of air ( C_p/C_v = 1.40) in a system moving boundary from P₁ = 15 psia V₁ = 1.0 ft³ to P₂ = 150 psia V2 = 0.15 ft³.

mC_v (T₂ - T₁) + P_a(V₂ - V₁)

A cylinder fitted with a weightless, frictionless piston contains m pounds of air at temperature T₁ volume V₁, and ambient pressure P_a. Heat is added until the air in the cylinder has a temperature T₂, a volume V₂, and ambient pressure P_a. The specific heat of air at constant volume is C_p, the specific heat of air at constant volume is C_v. The heat transferred during the process is:

12.8 BTU/lb

A high velocity flow gas at 800 ft/sec possesses kinetic energy nearest to which of the following?

0.32 ft³

Isentropic compression of 1 ft³ of air (C_p/C_v = 1.40), at 20 psia to 100 psia gives a final volume of:

609kj/kg

Find the work possess for a helium gas at 20C.

Ethane

Two kilogram of gas is confined in a 1m^3 tank 200kpa and 88degC. What type of gas is in the tank?

333.42 KJ/kg

Find the enthalpy of the helium if its internal energy is 200KJ/Kg.

9.47

Compute the mass of a 2m^3 propane at 280 kpa and 40degC.

9.46kg

Find the mass of 10 quartz of water.

1.24 lbs

Find the mass of carbon dioxide having a pressure of 20 psia at 200F with 10ft^3 volume.

1,647.29 kj/kg

Find the heat needed to raise the temperature of water from 80^C to 100^C with 60% quality. Consider an atmospheric pressure of 101.325 kpa. Use the approximate enthalpy formula of liquid.

471 Btu/lb

Find the enthalpy of water 212F and 14.7 psi dryness for factor is 30% use the approximate enthalpy formula of liquid.

115.55 deg C

What is the approximate value of temperature if water having enthalpy of 208 Btu/lb?

416.33K

Convert 750R to K.

0

Air is compressed  adiabatically from 30degC to 100degC. If mass of air being compressed is 5kg. Find the change of entropy?

0

Two kilogram of air in a rigid tank changes its temperature from 32degC to 150degC. Find the work done during the process.

0.0122 mole

An ideal gas at 0.80 atmosphere and 87degC occupies 0.450 liter. How many moles are there is the sample? (R=0.0821 liter-atm/mole-K).