Re: A Search For A Tiny CPXV
Will you be varying the compressor speed during normal operation?
Or the other way of asking, do you have varying loads?
Re: A Search For A Tiny CPXV
The compressor speed will indeed be varied during operation, that is why I want to use a constant pressure ex valve so that it does not vary the suction pressure too.
The load too will vary slightly as well but not very wildly.
Perhaps I should specify that this is a project to build a personal cooling system, so the compressor speed will be adjusted to match the btu output of one's body at different times, hopefully with very little load from the environment.
I know the military manufactures them but there are no schematics or anything that I could find.
Re: A Search For A Tiny CPXV
I'm not sure why you want to maintain a fixed suction pressure when you state that the load will vary and with a variation on compressor speed.
You could perhaps look into using an evaporator pressure regulator to restrict it.
Read up on document 90- 20 here....
http://sporlanonline.com/literature-...nal-materials/
Re: A Search For A Tiny CPXV
Hmm would it be possible to have only a txv and then automatically control the compressor speed to maintain the suction pressure at a set psi?
So when the heat load comes up the txv will open in turn raising the suction pressure which should then cause the compressor to speed up to bring the suction pressure down thus increasing capicity. Does this sound about right to you?
Re: A Search For A Tiny CPXV
Yes, entirely possible. It is a common form of control.
Re: A Search For A Tiny CPXV
I am still having a hard time finding a thermal ex valve or a constant pressure ex valve that is small enough.
The smallest I could find is parker EF series and it's rated for 1/8th ton, the company also does not think that valve will work either.
Why is it exactly that it won't work, I understand that it will hunt and I know what it means to hunt, but couldn't I stop it from hunting by insulating the evaporator and valve bulb. Or could I even go as far as turning a new valve orifice and needle on a lathe?
Re: A Search For A Tiny CPXV
Re: A Search For A Tiny CPXV
Ive struck another idea; Would it work to mount the bulb of a txv and insulate it so that the temperature fluctuates very little and in turn make the txv into a constant pressure valve? Or I could even remove the charge from the bulb and fill it with compressed argon or some such just so that pressure is maintained on that side of the diaphragm.
The reason I want to use a constant pressure valve is so the compressor speed can be user controlled so the output temperature can be adjusted to what ever temperature the user prefers.
Looking into using an electronic valve leads me to believe it would be too costly and it would consume too much energy, and my system runs off of 12vdc and their valves are rated at 24vac at the lowest.
I have appreciated all your advice so far, thank you.
Re: A Search For A Tiny CPXV
How about a change of thought?
Can you control the water flow at all to allow for the change of load?
Re: A Search For A Tiny CPXV
yes, my water pump is PWM.