×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Oven Preheat vs. Duct Loss/AHU efficiency

Oven Preheat vs. Duct Loss/AHU efficiency

Oven Preheat vs. Duct Loss/AHU efficiency

(OP)
I am trying to improve the efficiency of a painting facility. Five natural gas fired ovens randomly heat 1,000 to 5,000 cubic feet each of 20ºC to 40ºC (midwest US climate) ambient air initially. Upon process completion, 200ºC to 250ºC oven air is ventilated down to <50ºC whereupon oven doors are opened, the finished product is removed, and oven reloaded for the next cycle. Random product size and volume causes random heat cycle times. Approximately 60,000 cubic feet of hi-temp air is exhausted daily. Approximately 400 feet of well insulated 24 inch duct could interconnect these ovens. I would like to rewrite the PLC program to include overall operation of ductwork baffles, valves, AHU, etc., so that a ventilation cycle of one oven would provide preheat for another. Would real world daily ductwork heat loss and AHU power consumption exceed the cost of heating this amount of air? In other words, is using exhaust for preheat worthwhile and feasible?

RE: Oven Preheat vs. Duct Loss/AHU efficiency

Could some type of pebble bed heat regenerator heat exchanger be used to store the heat?

RE: Oven Preheat vs. Duct Loss/AHU efficiency

(OP)
Butelja;
Thank you for the response. I suppose heat storage might be a future consideration. As oven operators were asked to record time of day at process start, it was discovered that ventilation and heating were simultaneaous several times daily. Simple ducting and air handling between ovens is all that is needed right now IF FEASIBLE. Is moving 60,000 cubic feet of hot air worth the effort?

RE: Oven Preheat vs. Duct Loss/AHU efficiency

The total amount of heat you are talking about (based upon 60,000 cubic feet) is between 375,000 and 400,000 BTU, or 110 to 117 kW*hr.  Look at the cost of the energy saved compared to the cost to implement and decide based upon the economics.

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!


Resources