Condensing System 3

[ChexMix]

Hello,

I'm attempting to come up with the best method to achieve maximum condensation (air dryness).

In the system an exhaust fan will draw in steam (212F) and pass it through a 90 degree pipe (~12-14 inches) before it enters an area where it needs to be cooled for the purpose of removing the maximum amount of humidity.

The steam produced in an hour equals:
337.7 cubic feet
14,495 BTU,
4.24 KWh

The purpose of condensing the vapor back into liquid is to protect the down-stream activated charcoal filter from degradation due to high humidity.

The questions I'm having difficulty answering are as follows:

1) How to match the cooling/dehumidifying efficiency of a system with the optimum amount of air flow (ie choosing the right fan for the right amount of airflow for the system to be the most efficient)

Example: If I am passing 500 cubit feet of air through the system per hour and I want to achieve a certain % humidity where do I go from here?

I've attached the concept drawing

Thanks in advance for your replies

 

[ChexMix]

Concept image

 

[rmw]

You have to know something about your condensing water (or fluid) incoming temperature. Your resultant RH will be a function of approach to your incoming coolant temp.

rmw

 

[ChexMix]

Thanks for the reply. I tried doing a cursory search on the temperatures that evaporator coils can achieve with no luck.

I guess there are multiple ways of backing into the solution for this....

I do know the amount of steam and energy going in....

 

[fegenbush]

ChemMix,

Evaporators can only operate as low as the boiling point of the working fluid within them (at the operating pressure). Check the boiling point of common refrigerants at the desired operating pressure (R-134A, R-22, and Ammonia are common refrigerants).

 

[MintJulep]

R-22 may be common, but if you're in a Kyoto accord signatory country it's no longer an option.

"Maximum dryness" is a pretty fuzzy design goal.

The theoretical limit for the air at the exit of your contraption is 100% RH at the evaporator temperature. So the "coldest" refrigerant is best.

The near saturation of the air leaving the coil pretty much guarantees that you will get condensation inside your charcoal unless you can keep the temperature above the dew point. So if the design goal is to protect the charcoal you're going about it the wrong way.

 

[Compositepro]

Mixing air with the steam and then trying to dry the air does not make sense. Condense the steam before it mixes with air. You don't provide enough detail to give any other suggestions.

Consider that if your blower capacity were 1000 cfm the RH would be low because the steam was so diluted. That solves the moisture problem. Of course, the carbon would not capture anything because every other component in the air would also be diluted.

 

[ChexMix]

Great feedback. The problem is pretty simple

A process creates steam that smells awful. The process creating the steam cannot be pressurized. My attempt here is to try to reduce the smell to a negligible amount.

The activated charcoal filter was my attempt at a solution for the smell. Since their useful lifes are reduced *significantly* by increased water vapor in the air that is passed through I was also trying to create a system to increase the life of the filter.

* "The output of the condenser would probably be 100% RH at the temperature of the evaporator" - Very true and I had not thought of it that way.

Thanks for the replies.

 

[Compositepro]

If your process cannot be pressurized, it must be vented. Do all of your condensing and odor control before venting anything to atmosphere. Seal the process and keep it at either slightly negative pressure, so leaks are inward, or slightly positive so you don't need any blower.