How far water flows in a tilted oven before evaporating?

In summary: That's a lagging insulation, and the kiln will hold 500kg of material at a time. You're looking at around 9000W of energy to dry that material.
  • #1
crclayton
3
0
If I throw 10 gallons/minute of cold water for 4 days into an oven that's 300°C Celcius and 300ft long sloped at an angle of 10°, how far would the water make it down the oven before completely evaporating?

i5Nel.png


Even if you can't solve this directly, I'd love some advice or recommendations of how to approach the problem. I'm an EE student on an internship and this is totally out of my area of expertise.

Thanks in advance.
 
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  • #2
crclayton said:
If I throw 10 gallons/minute of cold water for 4 days into an oven that's 300°C Celcius and 300ft long sloped at an angle of 10°, how far would the water make it down the oven before completely evaporating?

i5Nel.png


Even if you can't solve this directly, I'd love some advice or recommendations of how to approach the problem. I'm an EE student on an internship and this is totally out of my area of expertise.

Thanks in advance.

Welcome to the PF.

Is this a schoolwork problem? If so, it needs to be posted in the Homework Help section of the PF, and you need to show some effort on the solution. What is the context of the question?
 
  • #3
berkeman said:
Welcome to the PF.

Is this a schoolwork problem? If so, it needs to be posted in the Homework Help section of the PF, and you need to show some effort on the solution. What is the context of the question?

Thanks! No, it's not a homework problem, I'm on an internship working at a mill and have been asked to look into this. I've looked into Newton's cooling equation, hoping to get a value for the time it would take water to evaporate like so:

To = 10 degrees (cold water)
Tf = 100 degrees (evaporated water)
Ta = 300 degrees (ambiant temperature of oven)

T(t) = Ta + (To-Ta)e-kt = 100 = 300 - 290e-kt

But I'm having a hard time determining a value for K without a second reference. Any guidance or recommendations for how to solve this would be very welcomed.
 
  • #4
The first thing to do is to focus on the hydrodynamics. What's the diameter of the pipe? If there were no heating, how much of the cross section would be filled? What is the method of heating in the oven?

Chet
 
  • #5
Chestermiller said:
The first thing to do is to focus on the hydrodynamics. What's the diameter of the pipe? If there were no heating, how much of the cross section would be filled? What is the method of heating in the oven?

Chet

It's 10 ft in diameter. As much as how much is pumped in would remain until boiled off. It's heated using natural gas and it's safe to assume that the pipe doesn't get cooled at all by the water and remains 300 degrees.
 
  • #6
crclayton said:
It's 10 ft in diameter. As much as how much is pumped in would remain until boiled off. It's heated using natural gas and it's safe to assume that the pipe doesn't get cooled at all by the water and remains 300 degrees.
The pipe is heated from the outside? What about the air(?) inside the pipe. Where does it enter the pipe and where does it exit? The pressure is at 1 atm?

Chet
 
  • #7
Looks like a cement kiln, and without some information about the burner, you're going to have a tough time figuring out how far down the tube the water might get before being carried back out the top end. Methinks you've been sent for a "left-handed pipe wrench," or "copper fallopian tubes," or some other rookie initiation equivalent.
 
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  • #8
10 gallons of cold water a minute is going to have an incredibly large cooling effect, and this is not a trivial problem. There will be large internal temperature gradients, and the heat flux will be very large. I'm not convinced there's a reasonable analytic way to solve this.
 
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  • #9
cjl said:
the heat flux will be very large
3MW, a small cement kiln.
 
  • #10
Running some numbers here, you're putting in around 0.63 kg/s of water. Assuming the water is at 20C, it'll take 211kW to heat that water up to boiling, and another 1400kW or so to boil it off (it takes a very large amount of energy to vaporize water). Are you still sure that it's safe to assume the pipe doesn't get cooled at all?
 
Last edited:
  • #11
A 300 foot kiln? Thousand tons of material an hour being dried? We'll call it 360, 100 kg/s of presumably light minerals being dried, specific heat about a quarter that of water, another 5 MW on the burner. Residence time in the kiln? Fifteen minutes? Hour? Heat capacity of a "how many" hundred ton steel drum plus how many hundred tons of dried and drying product? Heat losses to atmosphere? Presumably the drum has some sort of lagging/insulation. Bulk materials processing is done in large numbers.
Are you being asked to come up with numbers to shove into process control algorithms to handle a "wet trainload" that comes into the plant?
 

Related to How far water flows in a tilted oven before evaporating?

1. How does the tilt of an oven affect the flow of water?

The tilt of an oven can affect the flow of water by creating a slope for the water to move along. This can cause the water to flow more quickly or slowly depending on the angle of the tilt.

2. Does the type of oven matter in how far water will flow before evaporating?

The type of oven can make a difference in how far water will flow before evaporating. Convection ovens, which use a fan to circulate air, can cause the water to evaporate more quickly due to the increased air flow. However, the tilt of the oven will still play a role in the distance the water travels.

3. Why does water evaporate in an oven?

Water evaporates in an oven due to the heat and air flow. As the oven heats up, the molecules in the water gain energy and begin to move more quickly. This causes them to break free from the surface of the water and become water vapor. The air flow within the oven helps to carry the water vapor away, allowing for more water to evaporate.

4. Is there a maximum distance that water can flow in a tilted oven before evaporating?

There is no specific maximum distance that water can flow in a tilted oven before evaporating, as it will depend on various factors such as the temperature of the oven, tilt angle, and type of oven. However, generally, the steeper the tilt and the higher the temperature, the shorter the distance the water will flow before evaporating.

5. Can the distance water flows in a tilted oven before evaporating be predicted?

The distance water will flow in a tilted oven before evaporating can be predicted to some extent, based on the factors mentioned above. However, there are also other variables such as the amount of water, humidity, and altitude that can affect the evaporation process and make it difficult to accurately predict the distance the water will travel.

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