Steam generation thermodynamics

In summary, the conversation discusses a cylindrical tank with a volume V, filled with a volume of water and air. The tank is heated using coal combustion and when the gauge reads a certain pressure P, the valve is opened to release steam. The mass flow rate of the steam and the pressure in the tank are questioned, with the assumption that the rate of heating is constant. The conversation also mentions the tank being vacuumed and having a volume Vt, with a valve closed and water added at T1=20C. The water is heated until it reaches T2=120C, and the mass of steam generated and the flow rate when the valve is opened are questioned. The conversation concludes with discussing how to find the amount of vapor generated
  • #1
Ali Ahmad
5
0
a cylindrical tank with volume V
a volume of water is inside the tank and the rest is air
now if coal combustion is releasing heat into the tank Qin
and when the gauge reads a certain pressure "P", the valve is opened which allows steam to exit the boiler
what's the mass flow rate of the steam?
 

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  • #2
Is this a homework problem?
 
  • #3
The mass flow out will depend most strongly on the size of the valve and the outlet pipe. The flow rate will also vary with time.

If that is homework, there is too little information given to solve it.
 
  • #4
anorlunda said:
The mass flow out will depend most strongly on the size of the valve and the outlet pipe. The flow rate will also vary with time.

If that is homework, there is too little information given to solve it.
I think they want him to assume that the rate of heating is constant.
 
  • #5
this is a part of a senior project that I am working on.
you can assume anything to simplify it
assume it's a bachelor's degree level question
 
  • #6
Ali Ahmad said:
this is a part of a senior project that I am working on.
you can assume anything to simplify it
assume it's a bachelor's degree level question
What is your analysis of this so far?
 
  • #7
Ignore the previous question.
now let's say that the tank is vacuumed and has a volume "Vt", and the valve is closed
then a volume "Vw" of water at T1=20C is added to the tank
water is heated using an external heat source (coal combustion) until its temperature reaches T2=120C
what is the mass of steam generated in the tank, and when the valve is opened, what is the flow rate of steam? what is the pressure in the tank?
assume the cross-sectional area of the pipe is "Ap" and ignore heat losses
 
  • #8
Ali Ahmad said:
Ignore the previous question.
now let's say that the tank is vacuumed and has a volume "Vt", and the valve is closed
then a volume "Vw" of water at T1=20C is added to the tank
water is heated using an external heat source (coal combustion) until its temperature reaches T2=120C
what is the mass of steam generated in the tank, and when the valve is opened, what is the flow rate of steam? what is the pressure in the tank?
assume the cross-sectional area of the pipe is "Ap" and ignore heat losses
What are your thoughts on how this would be approached?
 
  • #9
after t seconds, the heat rate is:
Qdot = mw . (cp2 . T2 - cp1 . T1) / t
control volume thermodynamics
Ein - Eout = dE/dt (assuming steady)
Ein = Eout
Qdot = mout . u2 -------eq1
at T2=120C
P2=gauge pressure reading just before opening the valve
then from steam tables, we get u2 and substitute in eq1 to find mout
and how do I find the amount of vapor generated after t seconds?
 
  • #10
Is this what you are asking: I have water in a constant volume tank, and I am supplying heat at a constant rate. When the pressure gets to a certain value, I start removing mass at a rate necessary to hold the pressure at this constant value, while continuing to supply heat?
 
  • #11
yes
 
  • #12
The simplest solution makes use of energy conservation. Can you write expressions for the total energy in and the total energy out?
 
  • #13
Ali Ahmad said:
yes
Are you currently learning about the open system (control volume) version of the first law of thermodynamics?
 

Related to Steam generation thermodynamics

1. What is steam generation thermodynamics?

Steam generation thermodynamics is the study of the principles and laws that govern the conversion of heat energy into steam and its subsequent use in various systems and processes. It involves the analysis of thermodynamic cycles, such as the Rankine cycle, which is commonly used in steam power plants.

2. How is steam generated?

Steam is generated by heating water in a boiler until it reaches its boiling point, which is dependent on the pressure inside the boiler. The heat energy is then transferred to the water, causing it to vaporize and become steam. This steam can then be used to power turbines, engines, or other processes.

3. What are the key components of a steam generation system?

A typical steam generation system includes a boiler, which is used to heat the water and produce steam, a steam turbine, which converts the steam's energy into mechanical energy, and a condenser, which turns the steam back into water. Other important components include pumps, valves, and steam traps.

4. What is the efficiency of a steam generation system?

The efficiency of a steam generation system is the ratio of the energy output (in the form of work) to the energy input (in the form of heat). The maximum theoretical efficiency of a steam power plant is determined by the Carnot cycle and is dependent on the temperature difference between the steam and the surrounding environment. Real-world steam generation systems typically have efficiencies ranging from 30-40%.

5. How is steam used in various industries?

Steam is used in a wide range of industries for various purposes, including power generation, heating and cooling systems, industrial processes, and transportation. It is also used in household appliances such as steam irons and humidifiers. The versatile nature of steam makes it a valuable resource in many different applications.

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