CR4® - The Engineer's Place for News and Discussion®


Previous in Forum: Insulation Between ID FAN and Chimney   Next in Forum: Water Velocity Calc.
Close
Close
Close
8 comments
Active Contributor

Join Date: Mar 2017
Posts: 12

Boiler Closed System or Open System

03/26/2017 8:03 AM

Is boiler open system or closed system. please clarify

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Mar 2012
Location: Out of your mind! Not in sight!
Posts: 3977
Good Answers: 92
#1

Re: boiler closed system or open system

03/26/2017 8:22 AM

Check the definition of an Open system and see if the boiler fits into it.

__________________
Common Sense Dictates
Register to Reply
Active Contributor

Join Date: Mar 2017
Posts: 12
#3
In reply to #1

Re: boiler closed system or open system

03/26/2017 1:10 PM

I know from definition boiler is closed system but during discussion in other forum expert saying boiler is open system following are his comments

. Heating above saturation temperature , be it superheating or reheating, as is normally done in current superheaters will not cause any increase in pressure since it is an open system, or continuous flow system, not a closed one. In an open system there will be in fact a small reduction in pressure due to frictional losses, some 6 to 10 percent being a more or less adequate figure. Only in a closed system, e.g a cylinder or vessel, heating will be acccompanied by an increase in pressure.

Please guide me

Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26689
Good Answers: 700
#5
In reply to #3

Re: boiler closed system or open system

03/27/2017 3:11 AM

The clue is in the word itself.

Superheating raises the temperature of the fluid above its normal boiling temperature, without changing the pressure. It only happens when the vapour is not in contact with its liquid; were the liquid present, then heating will cause the liquid to boil before the temperature rises.

There is a load of stuff in Wikipedia on the topic, among other places.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26689
Good Answers: 700
#6
In reply to #5

Re: boiler closed system or open system

03/27/2017 4:55 AM
  • Air at ambient pressures and temperatures is superheated, for example, as its normal boiling temperature at ambient pressure is below -194degC. Liquid air does not exist at ambient pressures and temperatures.
  • Steam at ambient pressures and temperatures is not superheated, as the boiling temperature at ambient pressure is 100degC. Steam at 1 barg pressure and 200degC is superheated, as liquid water does not exist at those conditions.
__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Power-User

Join Date: Oct 2009
Location: Central Midwest
Posts: 398
Good Answers: 31
#2

Re: Boiler Closed System or Open System

03/26/2017 10:50 AM

Pradeep,

Excluding leaks, most boiler systems, used in power generation, process chemicals and building/district heating are closed systems.

A long boiler life is important. It is important to keep dissolved oxygen and CO2 out of the system to prevent internal corrosion. Continuous discharge of these dissolved gasses is done by the system deaerator.

The deaerator has a vent that discharges to the atmosphere....

So, with the exception of this vent, these are closed systems ....

__________________
We have met the enemy....and he is us. POGO
Register to Reply
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 19979
Good Answers: 749
#4

Re: Boiler Closed System or Open System

03/26/2017 3:18 PM

It depends on the particular system, which can be either open or closed. Your "expert" is not especially clear.

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Guru

Join Date: Jan 2010
Location: Mineral wells Tx
Posts: 612
Good Answers: 33
#7

Re: Boiler Closed System or Open System

03/27/2017 5:19 AM

An individual boiler can not be considered as a system.

If you mean steam generating boilers for electric plants, it's different.

ASME B31.1 defines two main systems and several sub systems

Also you can check ASME I. Small explanation below

Open system boiler systems are non pressurized and called “Open” because they vent naturally to the atsmosphere. If the boiler is overfired and boils, steam comes out a pipe and is vented. It cannot explode because it can not build pressure. There are many boilers in service that employ this method. The main drawback of these types system is they must be mointered constantly and kept full of water. The water is constantly evaporated off the system and must be replaced or the boiler will eventualy fail from overheating. It will normally make a terrible racket causing you to think there is an 800 lb. gorilla inside that is not happy. If that happens you have a few minutes to save your boiler. There are automated fill systems that will keep your boiler full of water at all times. If you choose an open boiler system, make sure you invest in a good one. If the automated fill system fails it will normaly either flood the boiler room with tap water, or not add water as needed. Always check this system and make sure it is functioning properly.

There is such a thing as an combo open/closed boiler system. This is common when you find the boiler is an open system and the radiant system is closed. Most radiant systems and heat handlers are closed. The way this is accomplished is through a heat exchanger that can be a finplate, or a sidearm exchanger. The open boiler system is its own loop and it circulates that way. BTUs are transferred through a heat exchanger into the closed loop system.

Register to Reply Score 1 for Good Answer
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 2993
Good Answers: 416
#8

Re: Boiler Closed System or Open System

03/27/2017 10:20 AM

Here's the original posting. It's this sentence that is being misinterpreted:

"...Heating above saturation temperature , be it superheating or reheating, as is normally done in current superheaters will not cause any increase in pressure since it is an open system, or continuous flow system, not a closed one..."

The "it" refers to a superheater, not the entire boiler, as explained further "...Only in a closed system, e.g a cylinder or vessel...", which a superheater is not since the working fluid continuously flows through it.

__________________
Curious minds want to know, engineering minds get answers....
Register to Reply Score 1 for Good Answer
Register to Reply 8 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

IdeaSmith (1); MJCronin (1); pradeep4u (1); PWSlack (2); RAMConsult (1); Tornado (1); Whitephone (1)

Previous in Forum: Insulation Between ID FAN and Chimney   Next in Forum: Water Velocity Calc.

Advertisement