Energy Consumption Question (boiler)

[Stormxtc]

Hi everyone,

I have a question about energy required to heat an insulated building (completely empty) using two 50 HP diesel boilers.

The building is a mushroom farm with no internal loads, and insulation on walls and roof. Steam is directly introduced into the space with temperature of 17degC. The aim is to raise the temp to 68degC and hold for 24 hours.

Ambient temp is 22degC and heat loss is 5.9kW.

How much energy (total in kJ/s or kW) is required to carry out the above process and how much diesel would be consumed?

If anyone can help or point me in right direction I would be very thankful.

Thanks,

Storm

 

[quark]

The hard part is to assess the heat load and I presume you did it with respect to 68⁰C internal temperature.

Once you provide the initial heat up then you require only 5.9 kW heat energy.

If you want to heat up the a volume of xcu.ft with in one hour to raise to a temperature of 68⁰C, then you require heat energy of

[1.08 x x x (154.4-62.6)]/60 = 1.6524xbtu/hr.

(154.4-62.6) is the temperature difference in degrees F.

Some conversion factors

1 boiler hp = 33479 btu/hr
1 kW = 3414 btu/hr
specific heat of diesel is 41800 kJ/kg


Eng-Tips.com : Solving your problems before you get them.

 

[MintJulep]

Quark's formula works if all of the energy goes towards heating the air, and only the air.

In reality your building is not perfectly insulated, so some heat is lost to the outdoors.

Is the building really completely empty? No tables? No pots full of dirt and mushrooms?

If there is stuff, you need to know it's mass and specific heat.

 

[Stormxtc]

Yes, the building for the moment is completely empty (absolutely nothing inside - highly conceptual at this stage). However, the next step probably will be assessing the energy required with trays of compost and other furniture inside.

How would this effect the energy consumption and how can I calculate it?

Thank you both for the advice.

 

[quark]

Just add the heat loss to the startup load. If you know the mass of material inside the area and their specific heats then you can calculate the heat load by mxCpxdT.

Just be cautious with steam spraying. There may be possible chances of condensation. If you let us know the total volume of the building then you can get some better answers.

Regards,


Eng-Tips.com : Solving your problems before you get them.