# How to calculate pressure from steam

• 01SpAcE01
In summary, the hoop stress is the circumferential stress inside the container due to the pressure exerted by the steam.
01SpAcE01
So let's say we have a cylindrical pressure vessel of volume 2.4 x 10^-3 m^3 carrying 2 liters of water heated to 130 degrees Celsius, how would I calculate the circumferential pressure inside the container?

height = 0.24 m

I know the equation would be stress=pressure x radius / thickness. Just never had to calculate the pressure before.

Also, if someone is feeling extra nice, would you mind clrifying this for me please: If steam is created in an environment that has 2 liters of water, but then the element further heats the water to 130 degrees Celsius, then would this create saturated steam or superheated? I always thought superheated, as the vapour must exceed 100 at some point if it is in a sealed environment. I just read something today that confused me somewhat.

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01SpAcE01 said:
So let's say we have a cylindrical pressure vessel of volume 2.4 x 10^-3 m^3 carrying 2 liters of water heated to 130 degrees Celsius, how would I calculate the circumferential pressure inside the container?

height = 0.24 m
Is this a homework problem?

You could say it is. I'm at home and working. Not a student though. Trying to design something and refresh my engineering skills.

Google online steam tables. You can look up the answer there. As long as the volume of the container is bigger than the initial volume of water, it will not influence the answer.

As long as you have both liquid and vapor in the tank, the vapor will be saturated, and you can look up the properties of saturated steam. Is there also air in the container? If yes, it will affect the answer.

I certainly hope that you are not trying this as a home experiment. Boiler explosions are deadly. We do not discuss dangerous topics on PF.

anorlunda said:
Google online steam tables. You can look up the answer there. As long as the volume of the container is bigger than the initial volume of water, it will not influence the answer.

As long as you have both liquid and vapor in the tank, the vapor will be saturated, and you can look up the properties of saturated steam. Is there also air in the container? If yes, it will affect the answer.

I certainly hope that you are not trying this as a home experiment. Boiler explosions are deadly. We do not discuss dangerous topics on PF.

Absolutely not something I would experiment with at home :) I've another year of design and research before I have some prototype to test, but that would be done in a controlled environment and with professionals.

There will be air in the container, then 2 liters will enter, seal, and then heat to 130 degrees.

01SpAcE01 said:
Absolutely not something I would experiment with at home :) I've another year of design and research before I have some prototype to test, but that would be done in a controlled environment and with professionals.

There will be air in the container, then 2 liters will enter, seal, and then heat to 130 degrees.

anorlunda said:
Google online steam tables. You can look up the answer there. As long as the volume of the container is bigger than the initial volume of water, it will not influence the answer.

As long as you have both liquid and vapor in the tank, the vapor will be saturated, and you can look up the properties of saturated steam. Is there also air in the container? If yes, it will affect the answer.

I certainly hope that you are not trying this as a home experiment. Boiler explosions are deadly. We do not discuss dangerous topics on PF.
Would you mind giving me an online link. I'm a bit confused as to what to do...

Also, please tell us your understanding of the term circumferential pressure. Do you really mean "circumferential stress?" If this is what you want, then you also need to know the wall thickness of the tank.

If there is air in the tank to start with, then you need to use the ideal gas law to include its contribution to the total pressure.

Chet

Chestermiller said:
Also, please tell us your understanding of the term circumferential pressure. Do you really mean "circumferential stress?" If this is what you want, then you also need to know the wall thickness of the tank.

If there is air in the tank to start with, then you need to use the ideal gas law to include its contribution to the total pressure.

Chet

The hoop stress is what I mean. Firstly I need to understand the uniform force created by this circumstance I guess. Isn't there some simple calculator online?

I don't mean to sound rude here, but you are asking some questions you could be googling. The equation for hoop stress is pretty straightforward, so I'd just use that...but does an online calculator exist? I don't know: I could Google that for you...

russ_watters said:
I don't mean to sound rude here, but you are asking some questions you could be googling. The equation for hoop stress is pretty straightforward, so I'd just use that...but does an online calculator exist? I don't know: I could Google that for you...

Sorry but you are being a bit rude. I've already stated the hoop stress equation above. Coming at something from a fresh angle can be a bit too broad and makes you unsure what you should be looking at.

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I don't think Russ was being rude. What he was referring to was that there are two separate parts to this problem:
• Determining the final pressure at 130 C
• Determining the hoop stress
Russ was saying that the equation for determining the hoop stress from the pressure is readily available on the internet. Also available on the internet is the equilibrium vapor pressure of water vapor in equilibrium with liquid water at the each temperature. Also, if you assume that the starting pressure of the air is 1 atm, and you assume that the volume of liquid water does not change significantly when the temperature goes to 130 (and some of it vaporizes into the heat space), then you can calculate the new pressure of the air using the ideal gas law. So, you have everything you need to solve your problem.

PF rules are that we don't solve the problem for you. So please start using the info we have provided and show us your progress. If you still can't solve it with the information we have provided, you need to hire a consultant.

Chet

01SpAcE01 said:
I always thought superheated, as the vapour must exceed 100 at some point if it is in a sealed environment. I just read something today that confused me somewhat.

Okay, let's see your work. Equations and calculations. Which is it going to be...

## What is steam pressure?

Steam pressure is the force per unit area exerted by steam. It is typically measured in units of pounds per square inch (psi) or kilopascals (kPa).

## What factors affect steam pressure?

The pressure of steam is affected by the temperature and volume of the steam. As temperature increases, pressure also increases. Additionally, pressure increases when the volume of the steam decreases.

## How do you calculate steam pressure?

To calculate steam pressure, you can use the ideal gas law, which states that pressure is equal to the number of moles of gas multiplied by the gas constant and the temperature, divided by the volume. Alternatively, you can use a steam table to find the pressure at a specific temperature and volume.

## What is the relationship between steam pressure and boiling point?

As steam pressure increases, the boiling point of water also increases. This is because the higher pressure allows for more energy to be stored in the steam, raising its temperature and increasing the boiling point.

## Why is it important to calculate steam pressure?

Calculating steam pressure is important for ensuring the safe and efficient operation of steam-powered systems. It allows engineers and scientists to determine the appropriate pressure levels for various processes and equipment, as well as identify potential issues or hazards related to steam pressure.

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