Waste Heat

Guest

Thanks for your time and knowledge.

I go along with that.

Strictly speaking specific heat of air is in BTU/lb/°F, but result is OK

Cheers........Codey

Here's a question to a question. Why would you exhaust this heat? Can't you re-use it for some energy generation...heating hot water at the least?

Guest

Thanks for response. To shed a little light on the subject. My Blower is actually vaccuming flour from an exterior silo and exhausting in the building. To be more precise it is exhausting in a large room occupied by 4 pasta dryers which alone give off a great deal of heat. This heat finds its way to other parts of the building making it very uncomfortable for production team. I would like to exhaust to exterior of building in summer and to warehouse for heat source in winter. My thinking is sometimes to " outside the box " for my managers, which results in opposition. Thanks to your first response, I can now compare it to our warehouse heaters. This converted to $ may result in favorable response.

Thanks again for your responses!!

The heat is valuable and the first step is to determine if the air flow has entrained flour and moisture. These will need to be considered in any system design..

Many dryer processes have been improved with waste heat recovery systems. The key is to use the heat recovered to reduce energy consumption. In your case, you can reclaim the heat prior to exhausting it outside. The heat can be introduced into replacement air in winter to make up the air loss from the building. In summer or winter the heat can be introduced into the dryers as combusion air, if you have burners, or process air if you have a steam heated dryer.

The main concern is in cleaning the exhaust air so that the system does not create

fouled duct work etc. By removing the heat, any moisture in the flow may combine with any dust or flour in the exhaust and clog the system. If the exhaust flow is cleanable, a well desinged system can last for twenty years paying back with saved

heat energy.

rlphaywards@hotmail.com

I don't have a thermo book with me, but equation is Q=m*h, where Q=heat released (kJ/s), m=mass flow rate of air (kg/s) and h=enthalpy (kJ/kg). You need an Air Table or HVAC Book to find the enthaply of air at your temperature. Convert your cubic feet per hour to kg/s from knowing the density of air at T=157F. Then, your home free. Also, convert your final answer (kJ/s) to BTU/s or BTU/hour. To put it in terms your boss understands, a standard natural gas burner for a home stove is rated in BTUs per hour, something like 5000 BTU/hour. Compare your number to leaving a burner on a stove on for so many hours per day. Your water heater might also have a BTU/hr rating.

Good Luck!

Ha! Ahhhh... Always a Gas Del.

Although I must say, I have learned not to attempt to slurp my Java while reading your posts in fear of it escaping through my nose.

Everyone understands $$$.

Convert your BTUs to dollars saved.

If they can't understand the above, then they are plain thick.

Del you hit the nail square on the head. I use to wonder how people like this got promotions, now I know. The secret is proper placement of lips on derriere.

Have a great one!!

little off topic. so where is the air in this room being displace, is there a return, or is this room open.

Do you have any alternatives. such as what part of the coutry is this, northern?where the heat may hekp or southern

and your comment

so I can compare this to something that my managers will understand.

How do these morons manage, if they can not understand. Get thier chair buffed a$$es in the room,

total heat this air carries will be 11,600x0.24x(157-room temp)BTU.You are diascharging this heat in the area. If you dotn need to hea tthe area, it is predwerred to discharge in to outside .Or else, you could use this eha tfor many purposes.

You need to speak in terms the bean counters, managers, and accountants can understand. And then you need to speak slowly.

Today they get by with dumping the heat in the immediate area of production. As far as they know the equipment still is working and producing a benefit to them. Why should they spend money to fun ductwork, cut a hole in the roof or wall, and expell the heat elsewhere?

Will OSHA or other government regulator come in and fine the company for unsafe practices?

Will a cooler environment for the machine help it be more productive? Will increase productivity pay for the installation of the exhaust?

Will a cooler environment help the workers make fewer mistakes and reduce scrap rates? Will better quality parts pay for the exhaust system?

Have the manager come and watch the machine operate for two or three hours. Perhaps feeling the heat for an extended time frame may convince him it would be a good idea to install the exhaust. Or maybe it could be ducted within the plant for use in a different area.

In short WIIFM! (What's In It For Me!) If I need to spend money, what is the benefit for making the expenditure. A caveman was smart enough to know he needed a hole in his ceiling or wall to let the smoke and excess heat out, so there might be some hope a manager or accountant could figure that out.

Two other notes.......why are you generating all that wasted heat in the first place, when perhaps some better insulation or "closing the windows/doors" would heat the thing you are heating with less fuel/power. Second, another example to provide your managers is that that amount of lost energy (BTUH) is enough to heat two full sized 4 bedroom homes in a Michigan winter. You can figure the cost by using local utility rates for that number of BTUH.

BtuH= 1.08 x scfm x ( T2- T1) see www.isothermics.com

exhausting this volume will create negative draft on building and sepage into building to replace it. design can be made to use this waste heat for other purposes and reduce cooling loads which i assume is your problem.

FLASHLIGHT,

If you contact me at rlphaywards@hotmail.com, I can get you the calculations you need on your waste heat.

Rlphaywards