(a)
The temperature and relative humidity of air when it leaves the heating section.
(a)
Answer to Problem 75P
The temperature and relative humidity of air when it leaves the heating section is
Explanation of Solution
Express initial partial pressure.
Here, partial pressure at state 2 is
Express initial partial pressure.
Here, initial pressure is
Express initial specific volume.
Here, universal gas constant of air is
Express initial specific humidity.
The amount or quantity of air moisture will remain constant while flowing through heating section,
Here, specific humidity at state 1 and 2 is
Express initial enthalpy.
Here, initial specific enthalpy at saturated vapor is
Express partial pressure at state 3.
Here, relative humidity at state 3 is
Express specific humidity at state 3.
Here, partial pressure at stat3 is
Express enthalpy at state 3.
Here, specific enthalpy saturated vapor at state 3 is
Express the mass flow rate of dry air.
Here, initial volume rate is
Express final specific enthalpy by applying an energy balance on the humidifying section.
Here, the rate of total energy entering the system is
Express temperature leaving the heating section.
Here, temperature at state 2 is
Express relative humidity leaving the heating section.
Here, partial pressure at state 2 is
Conclusion:
Refer Table A-2, “ideal-gas specific heats of various common gases”, and write the gas constant and specific heat at constant pressure of air.
Refer Table A-4, “saturated water-temperature table”, and write the saturation pressure at temperature of
Substitute
Substitute
Substitute
Substitute
Substitute
Refer Table A-4, “saturated water-temperature table”, and write the initial and final specific enthalpy saturated vapor corresponding to temperature of
Substitute
Substitute
Substitute
Substitute
Substitute
Refer Table A-4, “saturated water-temperature table”, and write the specific enthalpy saturation vapor at temperature of
Substitute
Refer Table A-4, “saturated water-temperature table”, and write the specific enthalpy saturation vapor at temperature of
Substitute
Hence, the temperature of air when it leaves the heating section is
Refer Table A-4, “saturated water-temperature table”, and write the saturated vapor at temperature of
Write the formula of interpolation method of two variables.
Here, the variables denote by x and y is temperature and saturated vapor respectively.
Show the saturated vapor corresponding to temperature as in Table (1).
Temperature |
Saturated vapor |
15 | 1.7057 |
19.5 | |
20 | 2.3392 |
Substitute
Substitute
Hence, the relative humidity of air when it leaves the heating section is
(b)
The rate of heat transfer in the heating section.
(b)
Answer to Problem 75P
The rate of heat transfer in the heating section is
Explanation of Solution
Express the rate of heat transfer in the heating section.
Conclusion:
Substitute
Hence, the rate of heat transfer in the heating section is
(c)
The rate at which water is added to the air in the humidifying section.
(c)
Answer to Problem 75P
The rate at which water is added to the air in the humidifying section is
Explanation of Solution
Express the rate at which water is added to the air in the humidifying section.
Conclusion:
Substitute
Hence, the rate at which water is added to the air in the humidifying section is
Want to see more full solutions like this?
Chapter 14 Solutions
Thermodynamics: An Engineering Approach
- Classify internal combustion engines taking various factors into consideration. What is athermodynamic temperature scale or absolute temperature scale? Explain theestablishment of such a scale.arrow_forwardAs the Airstream is cooled, the enthalpy_____ and the wet-bulb temperature____. A. Decrease, decreases B. Increase, decreases C. Decreases, Increases D. Increase, Increasearrow_forwardDEFINE THE INTERNAL ENERGY, ENTHALPY, AND SPECIFIC HEATS OF IDEAL GASES.arrow_forward
- How much much heat must be supplied to water at 180 degrees celcius to make 1 kg of wet steam at 9000 kpa , having a dryness fraction of 80% ? .arrow_forwardTwo hundred kg/hr of air at 28°C and 50% relative humidity is then heated to 50°C, passed through an adiabatic dryer, and discharge at 40°C and 85% relative humidity. The pressure in the reheater is saturated at 100kPa. Rair=287.08J/kg-K. Atmospheric condition is 101kPa. Calculate the following: 1.) The amount of steam to reheat the air; kg/hr2.) The fan capacity, m3/hr3.) The amount of moisture removed in the feed, kg/hr4.) The moisture content in the feed if the product is 500kg/hr with 8% moisture content, kg/hr5.) The amount of feed< kg/hrarrow_forwardAn air-conditioning system operates at a total pressure of 1 atm and consists of a heating section and an evaporative cooler. Air enters the heating section at 15OC and 55 percent relative humidity at a rate of 30 m3 /min, and it leaves the evaporative cooler at 25OC and 45 percent relatively humidity. Determine the TOR.arrow_forward
- What is the heat transfer rate required to condense the water, cool the water vapor, and cool the air?arrow_forward- A room humidifier works as follows: a stream of air with 20% humidity and a dry bulb temperature equal to 20 °C is mixed with a stream of water also at 20 °C until saturation is reached. Then the saturated air stream passes through a heat exchanger where it is heated. Knowing that the flow rate of the air stream entering the humidifier is 100 m3/h and that the heat exchanger supplies 500 kcal/h to heat the saturated air stream, determinea) the minimum mass flow rate of the water stream to saturate the air stream.b) the temperature and humidity percentage of the air stream at the exit of the heat exchanger.arrow_forwardIn the summer, when the air motion is increased body heat loss is also increased. True or false ?arrow_forward
- Which is better for humidifying air, adding steam or water? Justify?arrow_forwardair at a dry ball temperature of 95 degrees Celsius and RH 5% is passed over the cooling coil so that the temperature of the air dry ball becomes 50 degrees Celsius. how much heat is released from the air in the process? = (kj / kg)arrow_forwardIn your own words, answer the following questions: 1. What is the dew-point temperature? 2. How does the air motion in the vicinity of the human body affect human comfort? 3. What is the difference between dry air and atmospheric air? 4. Describe the difference between mass fraction and mole fractionarrow_forward
- Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University PressMechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSONThermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
- Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEYMechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage LearningEngineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY