EcoRenovator  

Go Back   EcoRenovator > Improvements > Geothermal & Heat Pumps
Advanced Search
 


Blog Register 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 03-09-18, 03:10 PM   #1
HugoW
Lurking Renovator
 
Join Date: Mar 2018
Location: the Netherlands
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Default Propane expansion valve temperatures?

Hi,

as I am planning to make my own heat pump and I like to be in control of what I do, I am looking into the way the Expansion valve is controlled. I think I have figured out how to make an Arduino controlled valve, but I need to know values to test it. Looking at a convensional valve and the placement in the system:



I can see the capillary bulb or sensor 'steers' the throughput of the valve, based on the temperature between the outlet of the evaporator and the inlet of the pump / compressor. Is there a standard value / value range for specific refrigerants, and if so, which is it for propane / R290?

Thanks,

Hugo

HugoW is offline   Reply With Quote
Old 03-12-18, 10:46 PM   #2
jeff5may
Supreme EcoRenovator
 
Join Date: Jan 2010
Location: elizabethtown, ky, USA
Posts: 2,394
Thanks: 410
Thanked 604 Times in 506 Posts
Send a message via Yahoo to jeff5may
Default

Yes there is. R290 is a pure substance, so it exhibits a single boiling point/dew point at any given pressure. Many refrigerants are a blend, and exhibit glide.

Ok, pictures speak louder than words.



jeff5may is offline   Reply With Quote
Old 04-02-18, 10:38 AM   #3
Zwerius
Helper EcoRenovator
 
Zwerius's Avatar
 
Join Date: Aug 2014
Location: The Netherlands
Posts: 63
Thanks: 12
Thanked 26 Times in 14 Posts
Default

Quote:
Originally Posted by jeff5may View Post
Yes there is. R290 is a pure substance, so it exhibits a single boiling point/dew point at any given pressure. Many refrigerants are a blend, and exhibit glide.

Ok, pictures speak louder than words.

.....
Should the pressure/temperature at the exit of the evaporator not be depending on the ambient (outside) temperature?
Zwerius is offline   Reply With Quote
Old 04-05-18, 06:58 AM   #4
HugoW
Lurking Renovator
 
Join Date: Mar 2018
Location: the Netherlands
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Default

I don't think so. The medium should still be in gas state after the evaporator. With the mechanical valve, the sensing bulb is the same temperature as the medium line at that point, its mechanically joined. If the medium in the line is still a liquid after the evaporator, it will also be a liquid in the sensing bulb. With the medium in the sensing bulb giving less counter pressure to the valve spring, less medium will pass through the valve and this is how the system steers itself. My system will need both a temp and pressure sensor in that position and look up the values in a table.

Hugo
HugoW is offline   Reply With Quote
Old 04-06-18, 07:24 PM   #5
jeff5may
Supreme EcoRenovator
 
Join Date: Jan 2010
Location: elizabethtown, ky, USA
Posts: 2,394
Thanks: 410
Thanked 604 Times in 506 Posts
Send a message via Yahoo to jeff5may
Default

You two are both correct.

Hugo says that only gaseous refrigerant should be leaving the evaporator. This is a hard rule. The metering device should never allow liquid refrigerant to find its way to the compressor. Liquid slugging is a leading cause of compressor burnout.

Zwerius said that the evaporator will follow outdoor temperature. To evaporate, the low side pressure must be low enough to allow the refrigerant to exist as a gas. What that means practically is the boiling point of the refrigerant has to be colder than the heat exchanger temperature. In an air hx, the boiling point must be a dozen or more degrees below the outdoor temperature, to insure at least a few degrees of superheat in the leaving refrigerant. In a water hx, the boiling point can be closer to the entering water temperature, because water has a lot more heat capacity than air.

Last edited by jeff5may; 04-07-18 at 05:13 PM.. Reason: Soelling and grammer
jeff5may is offline   Reply With Quote
Old 04-06-18, 07:57 PM   #6
HugoW
Lurking Renovator
 
Join Date: Mar 2018
Location: the Netherlands
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Comes natural to us Dutch folks �� I am currently working on a prototype pump with two plate exchangers, one with coolant on the cold side running through a radiator type 'heater' block, the other one with water heating up a 200 liter oil drum. If it all works I will burry a long hose in the back yard to reheat the coolant and the hot part I am still considering some options.

Hugo

HugoW is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 11:41 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design