Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Boiler Efficiency Calculation Inquiry

Boiler Efficiency Calculation Inquiry

Boiler Efficiency Calculation Inquiry

Hello experts and professionals,

I want to confirm one thing regarding boiler efficiency calculation method.

My feed water temperature at dearator tank is 95C after which it goes to air preheater before going finally into boiler. The water temperature after air pre heater is 110 C. So while calculation boiler efficiency via direct method, I have to take value of feed water at 95 C or 110 C?

My vote goes for 95 C since it is the heat given to water for heating. The rest temperature is raised via exhaust gases emission which should not be included as it is heat extracted from something which is not produced separately for water.

Please confirm.

Also, if anybody like to help me confirming/clarifying following,

To get natural gas fuel in KJ/KG from BTU/SCF, I am doing following steps

1- Multiplying BTU/SCF with KJ/cubic meter.
2-Dividing this figure by natural gas density (kg/cubic meter) to get finally KJ/KG

A much thanks in advance.

RE: Boiler Efficiency Calculation Inquiry

Here is your problem with your OP. An air pre heater heats up combustion air before the combustion air is captured the burners. What warms up your feed water is the economizer, so research terminology associated with boiler operation before getting involved in determining the efficiency cycles of boiler operation. Study thermodynamics on boiler cycles and you'll get your answers.

RE: Boiler Efficiency Calculation Inquiry

Yeah right its economizer instead of air pre heater but it does not mean I am not aware of boiler operations terminologies.

RE: Boiler Efficiency Calculation Inquiry

To get to kJ/kg from Btu/scf,(use FG lower heating value LHV)
Btu/scf x 379.5 = Btu/lb mole
Btu/lb mole x 1.055 = kJ/lbmole
kJ/lbmole x 2.204 = kJ/kgmole
kJ/kgmole / FG mol wt = kJ/kg

If you are looking for overall eff, use 95degC, the feed temp to the BFW preheater / economiser.

RE: Boiler Efficiency Calculation Inquiry

The boiler cannot count any "running start" it gets from preheating water, air, or fuel. The boiler manufacturer typically states that his boiler will produce X #/hr of steam at Y pressure, based upon conditions like feedwater temp, air temp, at a given blowdown rate, etc

Think of the boiler as the engine in a car. When an economizer is added, that doesn't change the boiler - it's like adding a another higher gear to the transmission in a car. The car will get improved fuel economy, and will go faster, but that modification had nothing to do with the engine. The engine itself remained unchanged.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close