Huh? You're shuckin' us, what?
09-27-2015, 11:19 AM
(This post was last modified: 09-27-2015, 01:06 PM by justMongo.)
(09-26-2015, 08:27 PM)surferdude2 Wrote: Huh? You're shuckin' us, what?
I find no reference to it.
A Peltier cooler generally requires a fan to get rid of heat.
(09-26-2015, 07:31 PM)surferdude2 Wrote: Alas, the P coolers are quite large when you get up to the capacity required for a Delta T. of around 10° with a volume exceeding 50 L. per Min.
I have a micro fridge for insulin that uses a 45 Watt Peltier cooler. It can reach 32 degrees F below ambient. The Peltier junction, heat sink and fan are reasonable in size. Where I think it would fall short is: It only has to cool about 250 cubic inches of stationary air Volume. The thermal load of cooling a moving volume of air (my mask intentional leak rate is about 50 LPM at pressure) would certainly limit cooling below ambient to a small number.
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09-27-2015, 02:37 PM
(This post was last modified: 09-27-2015, 02:39 PM by PoolQ.)
There is no way that the CPAP unit could ever cool or heat 50L/m. Like has been said there is no heat spreader on either side of the element.
Water itself has a huge heat capacity and that is where the heat goes, so no heat spreader required. It is a small volume of water and does not need to be warmed up by much or very fast.
Will the unit ever be able to take 80 degree room air and cool it any noticeable amount-not a chance.
most of us leave our CPAP plugged in when we don't use it. This consumes "some" power that is converted to heat which stays mostly in the CPAP machine and will warm the air in the humidifier chamber. The temperature element can compensate for this and will limit that first inrush of warmer than room temperature air we can feel when we first turn the unit on.
It can usually, but not always keep us from breathing air above room temperature. Think of standard use. Water in the tank (lots of mass) and our typical flow rate (not close to 50L/m, for me anyway) with the exhale time to recover. This is a comfort thing and not a "the food is going to spoil" thing (micro fridge), if it makes us feel better before we fall asleep, it's probably good, most people as far as I know that use humidity use heated water anyway.
When we use it to heat the water, then it has it easy. What happens to a Peltier element when you don't take away the cold from the cold side-it swamps out and both sides get hot. When heating water that is not a problem.
As for no reference, well they don't reference anything that they use-Microprocessor, memory, motor specs, processor speed, not a single thing. Humidity is "spec'd" as +1-5 or whatever, not relative humidity.
Do I think that it's a Peltier , yep I do. Have I taken it apart, nope. I could tape a thermocouple on the base plate, but haven't yet.
Oh and Peltier's are quite thin without heat spreaders and fans attached. A 60W one is 4mm thick (0.167") and there is no way they are pumping 60W into it.
"including a Peltier element having a hot side and a cold side, the heat exchanger being inserted into the air stream of the fan, said heat exchanger cooling the air stream supplied by the fan to a temperature 2-4 degrees Celcius below ambient temperature before it is supplied to a nose mask"
US 6332462 B1
2013, Resmed R&D Germany
Typical power consumption: 53W (57VA)
Peak power consumption: 104W (108VA)
I would suggest that there is an airflow used to remove heat from inside that plastic case and over at least a small heat spreader for the thermal unit.
For those who think that air comes out of the CPAP system at the same temp that it goes in, try this.
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 for a Quattro Mirage.
At least this is my experience.