Hello Guest, Welcome to Apnea Board !
As a guest, you are limited to certain areas of the board and there are some features you can't use.
To post a message, you must create a free account using a valid email address.

or Create an Account


New Posts   Today's Posts

Is the ResMed ClimateLine Heated Tubing worth buying?
#11
An interesting problem
Relative Humidity is essentially the percentage of water held in air expressed as a percentage of the maximum amount the air can hold.
Air can hold more or less absolute amount of water depending on temperature and pressure
When you pressurize the air ( blow it through a CPAP at say 9 cm H2O - a simple measure of pressure when small increments are used) it can hold more water. It doesn't decrease the amount of water in the air from the intake - it just increases the air's ability to hold water. This is experienced as a lower relative humidity - the percentage of the water in the air relative to the amount it could hold is decreased and we feel it as drier leading to all the effects we know from un-humidified air.

Similarly with temperature - if we heat air - it can absorb more moisture than cold air. If we cool it, it can hold less, This is why you get dew on the car on cold mornings. So if we simply heated the air without the water tank - it would feel even dryer, which is why the instructions for the humdifier tanks say to never run it without water. I seriously doubt at the temperatures we are talking about it can harm anything, but it will feel like the wind from the Sahara is going up your nose.

Heating a tank of water gives off water vapour into the pressurised air - the goal isn't really to heat the air but force vapour off the water into the air. Warmer air is a side effect, that leads to rain out if the air in the tube cools too much - balancing the vapour forced off the water tank is one way of controlling rain out, but only if doing so gets enough moisture into the air for your comfort - otherwise you need to heat the tube to maintain the air's ability to carry more water up, and then release it once it gets to your nose, assuming some cooling effect from the mask. mind you in winter (or the fridge my wife turns our bedroom into in summer), the warmer air is pleasant.
Conversely Cooling the air will make it feel wetter.

I will go dust off the old text books for the formula - but chilling the pressurized air could also increase its humidity to where it balanced the humidity reduction from increasing its pressure. The question is, how much colder would you need for each cm H2O to balance the pressure effect so the relative humidity remained unchanged from the air in the room. The thermodynamic equations are not trivial but an interesting problem

Really interesting idea -
Post Reply Post Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  HELP BUYING AN ASV MACHINE Johnny Bravo 17 1,313 02-13-2017, 03:04 PM
Last Post: steve823
  Buying online Trickey280 12 386 02-07-2017, 10:20 AM
Last Post: KSMatthew
  Water Changing in H5i Heated Humidifier ppca 6 364 02-06-2017, 02:09 PM
Last Post: PaytonA
  ClimateLine Hose Cover joelrk35 11 365 01-31-2017, 07:04 AM
Last Post: RichardVT
  CPAP Questions before Buying sjishan 10 419 01-09-2017, 10:09 PM
Last Post: trish6hundred
  AirSense 10 Heated Hose Willky 12 589 01-09-2017, 08:19 AM
Last Post: derekroy
  ResMed H5i heated humidifier - broken GrammaBear 7 371 01-08-2017, 10:39 AM
Last Post: GrammaBear

Forum Jump:

New Posts   Today's Posts




About Apnea Board

Apnea Board is an educational web site designed to empower Sleep Apnea patients.

For any more information, please use our contact form.