Increasing Heat Transfer Area

[ruzfactor]

I have tried with low flow rate. The heat transfer is much less. My air is coming out from a compressed air cylinder. Could you please explain why the heater is not able to heat the air? could it be because of heat loss through the walls?

 

[Unrest]

I have tried with low flow rate. The heat transfer is much less. My air is coming out from a compressed air cylinder. Could you please explain why the heater is not able to heat the air? could it be because of heat loss through the walls?

Which heat transfer is much less? Heat flux into the reactor? Does that matter if it heats more slowly? Did you see the air temperature (or heater temperature) increase with a low flow rate?

I'd really like some idea of the flow rate to quantify it. However it's hard to imagine anything else besides loss through the walls.

 

[ruzfactor]

Heat transfer is much less in case of low flow rate. I need the reactor to be heated within a shorter period. But it all failed. A new design is the only solution I guess. Is the heat capacity of damp air higher than the dry air? How can I prove (theoretically) that damp air could improve heat transfer? Need some help on that.

 

[ruzfactor]

Is there any effect on temperature, when a flow experience sudden enlargement?

 

[Unrest]

It's a pity you can't know the mass flow rate. With that and your existing measurements you can confidently estimate the losses and predict what wattage heater is required.

I probably know no more than you about using wet air. My guess is it would have a higher heat capacity, but I don't think that's important, just using a higher flow rate should do the same job.

I really think you should work out what went wrong with this design before trying something fancy. Otherwise the fancy thing will fail too. You can probably do it just by replacing the heating element if you have some data to make predictions with.

Is there a reason you don't have the heater wound around the reactor? Why transfer it so far through air? And why is the air flowing?

When gas expands it cools. That will be happening to the gas coming out of the tank. It could easily be below 0C, but probably not enough to make a difference to the overall design.