How to determine energy reqirement for storage tank

[egebull]

Hi:

I have 4200 gal capacity storage tank for water. I want to keep water at 60 F and lowest outside temp is -20F. How do I calculate electrical energy requirement?

Thanks,

 

[TBP]

What is the surface area of the tank? Will there be any insulation? Will any colder water ever be added to this tank?

Once you know the BTU/hr heat loss from the tank, at design conditions, you simply need to add that much heat to the tank to maintain it's temp.

 

[desertfox]

hi egebull

You could use the formula:-

Q= m * Cp * (T1-T2)

to work out how much heat you need to heat that capacity of
water.
Then if you do as TBP suggests and work out your heat loss
from the tank for a given time period, you will know how much heat you need to feed back in.
From the heat input requirement for a period of time you can calculate the power of the heat source.

regards

desertfox

 

[JStephen]

NFPA-22 has some charts for sizing heaters for tanks to prevent freezing that may be of help. Seems like I've seen links to more general sources here as well.

 

[egebull]

Thank you all of you. My Tank is 9'-6" OD and height is 8'. I used this formula;

Qlc(heat lost by conduction)= A x k x Delta T/ d 3412 Btu/kW

CALCULATED VALUE= 8.36 kWh- Heat Loss my conduction.

Is this make sense to you guys?

Thanks,

 

[desertfox]

Hi egebull

I think your on the right track your units are not what I would normally see but I recognise 8.36kWh as the power loss.
But remember that that power loss is for a constant temperature difference as the water cools less heat is conducted away through the tank.


regards

desertfox

 

[desertfox]

Hi egebull

Whats your tank thickness and material I need those to check your figures.
If I assume steel tank and a wall thickness of 10mm I get
44kW heat loss from conduction using the formula you quoted.
Note however I get kW not kWh check your units.

regards

desertfox

 

[IRstuff]

What wind speed are you expecting?

The convection coefficient is heavily dependent on air speed. For low speed, the convective heat loss should be around 2 kW, while for high wind, the loss is around 20 kW.

Assuming an emissivity of 1, there should be about 4 kW of radiated power loss

TTFN

FAQ731-376

 

[desertfox]

hi again

On reflection I think the best thing you could do is repeat the heat loss calculation but this time add an insulating
layer to the tank outside.
On the basis of your heat loss provide some type of electical heating either inside the tank or next to the tank outerwall.

regards

desertfox