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RE: Hot - PoolQ - 09-27-2015
The quote is from a granted patent, 2013, which means it could have been in use years before. They invested in the research and patent costs, now I agree that they may have decided to not use this idea and used a heat only element that they do not have a patent on and programmed the software to give the user a choice of low temperature settings even though the machine could never even try and lower the temperature, but I have no idea why they would not just use the invention that they have. Anything is possible.
here is the link to the patent for context http://www.google.com/patents/US6332462
The only way to test this out is to use a dry tank so you don't get evaporative cooling and blow some air with mask fit and see if the temperature drops with a low setting and maybe not even then if the temperature does not activate in mask fit mode.
Any way I now have an electronic temperature device sitting in my empty mask waiting for it to adjust to room temperature.
RE: Hot - surferdude2 - 09-27-2015
I suspect they couldn't meet the specs they claimed in the patent. It claimed to lower the temperature 2 to 4 degrees C. under normal air flow. Many times patents have unrealistic claims so as to cover all bases and discourage competition.
Patona, The air exiting the mask is cooler since it is having its pressure reduced. It is not cooler inside the mask. This is called adiabatic expansion. Conversely, when you compress air, it becomes hotter. That's partially why the air inside the mask is hotter. The other reason is the heat being produced by the various components of the system, motor, circuit board. Some of that motor and circuit board heat gets into the air passing through. The rest of it flows into the ambient air of the bedroom.
Dude
RE: Hot - PoolQ - 09-27-2015
okay test done
room temp 71.3
mask set face down on pillow so only air was escaping from the mask vents
mask covered with a pillow to keep it in place and insulate it from the room air
turned aircurve to mask fit
temp quickly jumped to 75.8 and kept going up
at 77 degrees I change to normal operation of aircurve
temperature continued to rise slowly to 77.6 and then started coming DOWN
when temperature got to 75.1 I shut down the Aircurve
whatever cooling is going on is enough to compensate for the heat generated by the motor and conduction from the surrounding electronics
will it ever get back to room temp, maybe
what happens when my face is attached and I am breathing, don't know
BUT COOLING IS going on
Dude +1 at least, that box is using 50-100 watts of power, mostly motor and motor driver I suspect
RE: Hot - surferdude2 - 09-27-2015
You just illustrated how a direct compression/expansion refrigeration system works!
If you compress air, it is heated by adiabatic compression. Let's say for example the adiabatic compression adds 5° of specific heat to the air. If you started with 70° air, you will now have 75° air. Then as the air flows through the delivery hose, it gives off part of its heat because it heats the hose above room ambient and that means the hose is acting much the same as a condenser coil in a refrigeration system. Let's say the hose dissipates 2° of the added heat from compression so we will now have air that is 73° being delivered to the mask. Now when we release that air back to ambient pressure, the adiabatic process cools the air exactly the same amount as it was initially heated. So now we have the 73° air being cooled by 5° which gives us 68° degree air. That's like the evaporator coil in a compression/expansion refrigeration system. Indeed it is cooler than the air that entered the system initially (only because some heat was dissipated by the hose). And yes, there is some refrigeration taking place but it has nothing to do with the Peltier effect.
Dude
ps. Since the system we are analyzing doesn't have the characteristics of a normal refrigeration system whereby the refrigerant goes through a change of state (liquid to vapor & vice versa) we don't get very dramatic results by squeezing air and then releasing it.
RE: Hot - PoolQ - 09-27-2015
hummm I would think that if that was all that was going on that the mask fit temperature and the run temperature would be about the same. No?
mask fit was still rising when I switched to run, it then kept rising 0.6 more degrees and then it started to slowly fall.
RE: Hot - surferdude2 - 09-27-2015
There is always the matter of residual heat that makes for a lag in observed measurements. The heat created by the mask fit (higher compression) method of operation takes some time to dissipate. Eventually it will get to a balanced condition if you don't change the pressure.
Dude
ps. You may enjoy learning more about thermodynamics. There are several good presentations available. Here's one: https://www.youtube.com/watch?v=GOrWy_yNBvY
RE: Hot - eseedhouse - 09-27-2015
(09-27-2015, 07:38 PM)PaytonA Wrote: Hook up a Mirage Quattro or probably any mask with open vent holes (not the "quiet" versions) to a CPAP running at 20 cm/H2O.
Don the mask in a warm-hot room and start the CPAP up.
Put your hand in front of the vents and tell me that the exhaust air is not cooler than ambient and, by the way, this is at 54 liters per minute
Actually it is not cooler, but it will feel cooler because moving air causes water to evaporate from your skin, cooling it. Same thing as the "wind chill factor" you might hear about on the weather report.
RE: Hot - PaytonA - 09-27-2015
(09-27-2015, 08:57 PM)surferdude2 Wrote: I suspect they couldn't meet the specs they claimed in the patent. It claimed to lower the temperature 2 to 4 degrees C. under normal air flow. Many times patents have unrealistic claims so as to cover all bases and discourage competition.
Patona, The air exiting the mask is cooler since it is having its pressure reduced. It is not cooler inside the mask. This is called adiabatic expansion. Conversely, when you compress air, it becomes hotter. That's partially why the air inside the mask is hotter. The other reason is the heat being produced by the various components of the system, motor, circuit board. Some of that motor and circuit board heat gets into the air passing through. The rest of it flows into the ambient air of the bedroom.
Dude
RE: Hot - PaytonA - 09-29-2015
(09-27-2015, 11:43 PM)eseedhouse Wrote:(09-27-2015, 07:38 PM)PaytonA Wrote: Hook up a Mirage Quattro or probably any mask with open vent holes (not the "quiet" versions) to a CPAP running at 20 cm/H2O.
Don the mask in a warm-hot room and start the CPAP up.
Put your hand in front of the vents and tell me that the exhaust air is not cooler than ambient and, by the way, this is at 54 liters per minute
Actually it is not cooler, but it will feel cooler because moving air causes water to evaporate from your skin, cooling it. Same thing as the "wind chill factor" you might hear about on the weather report.
I think that a little factual evidence is in order. This morning I masked up at my normal bi-level pressures of 20/16. Measured ambient and vent temperatures.
Ambient 73.0 deg. F
Vent air 74.6 deg. F
Eseedhouse wins the cuppa joe.
Best Regards,
PaytonA
RE: Hot - PoolQ - 09-29-2015
I am still not buying all of this, I just don't know how much more time I want to spend on it. Some things I am not sure about
1. adding your exhale breath into a heat source does not seem like it would be helpful
2. this expansion thing, just where is this expansion going on? The face side of the mask is sealed. The humidifier chamber, the hose, and the mask are all at a constant pressure so any expansion is happening at the vent exit and not in the system air path
The only way to tell what is going on short of opening up the machine is to tape a thermos couple on the metal place and run the machine without the humidifier water chamber installed.