Electric Air Heater Sizing for Tunnel

[gopher6]

I'm working on a tunneling project and trying to determine if we have rented an adequate size heater to raise the air temperature in the work area from 20 degrees F to 50 degrees F. The work area is an open top, vertical shaft bored through rock - 63 feet diameter by 250 feet deep. We have a 150KW electric heater, with a maximum airflow of 7020 cfm. Any guideance is much appreciated.

 

[IRstuff]

But, what's the temperature of the surrounding earth? Your shaft is a gigantic chimney, so that might need to be considered. How are you going to distribute the heated air?

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[racookpe1978]

Also, how much other eqpt is releasing energy into that chimney base? What kinds of energy?

Compressed air (if the air compressor is working at the top of the shaft, and the air is released down low at the working surface, will cool the air in the tunnel bottom as it expands (often using in mining to bring "new" air into the tunnel mouth). Other machinery will release energy at the working surface. Water will cool it, unless you it a hot spring. Massive amounts of concrete will heat it for a little bit, then will end up at the rock temperature after a few days.


How much fresh air are you blowing down there for safety and to clear dust out?

 

[MintJulep]

No, it won't be even close.

 

[trashcanman]

You are essentially trying to heat up an infinite amount of air with that big "chimney". If you are trying to provide comfort heat for the workers, use infrared heaters. They are made for this purpose, to provide heat where there is vast or infinite outside air (car garage, loading docks, aircraft hangars). There are "spot" heaters you can use, directing the rays at a work site and are portable. Visit Reznor, or Spaceray companies.

 

[racookpe1978]

That far own it should be about 62 deg F all year, right? (You're not getting any real "volcanic" heating until several hundred more feet, and the large opening will vent out what very little does occur.)

How many lights and other electrical loads do you have? (Each will heat a little, but IR heat is definitely the best idea I've heard) How much OSHA-safety ventilation do you need and where?

 

[willard3]

Hire qan Engineer who does HVAC and read forum policies which begin as follows:

>>>>>>>>These fora should not be used to bypass your own in-depth research on the issues that affect you, nor is it intended to be a substitute for appropriate professional assistance within your field or geographical region.

 

[chicopee]

With a high amount of make up air that you have in this tunnel, you may want to consider propane gas fired salamanders whereby the discharge (mix of products of combustion and fresher)can be directed toward the work areas. Don't use kerosene or diesel fuel to fire these salamanders due to noxious gases. We have used these on bridge construction projects and wide open equipment maintenance structures with no ill effects. You will need an abundance of fresh air with such heating units.

 

[chicopee]

One more thing, these salamanders are used for spot and not area heating.