01-29-13, 06:31 PM | #1 |
Supreme EcoRenovator
|
Suction line heat exchanger
Ok, so the window AC unit I turned into a heat pump is doing such an awesome job that I have decided to build another, similar unit. The first unit and this unit will have similarly sized heat exchange coils, only this one will be based off a 9k btu compressor vs a 15k btu in the first. So in theory, I should be able to squeeze more COP out of this one. which leads me to this thread...
While researching propane-based refrigeration cycles, I kept coming upon mentions of using suction-line heat exchangers (SLHX). The research and application papers I read said that considerable performance and efficiency gains could and/or should be had by using them in the refrigeration cycles of propane-based setups. Somewhere along the line I decided that I would try one in action and see if it would help. Before I do, though, I need to become more familiar with them and gain some insight and confidence. I have a ton of questions about these gadgets. The main idea behind these things is that they take waste heat from the liquid line and warm the cold suction line with it. This is supposed to subcool the liquid line (a good thing?) and superheat the vapor line (another good thing?) while increasing suction pressure (i know this is good.) and mass flow (definitely good.). This sounds like some sort of free lunch to me. I will be running a TXV on this new unit (harvested from the first unit), so it alone should net me some performance vs. the cap tube running in it now. Keeping this in mind, will the txv work with or against the hx? Should I put the sensor bulb on the evap or compressor side of the slhx? Would it make much difference? Next come the plumbing questions. Should I extend the liquid line or the suction line? Vertical or horizontal orientation? How big is too big? I know I will probably learn more than I accomplish from this endeavor... that's kind of the point. I hope somebody can help clear up the muddy water a little before I jump in. jeff |
01-30-13, 07:14 PM | #2 | |
Supreme EcoRenovator
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,004
Thanks: 303
Thanked 723 Times in 534 Posts
|
Quote:
I think I may have seen such a device in a photo of a Heat Pump that Piwoslaw posted a long time ago. I'm pretty sure BradC has some information on what you're trying to do... maybe Vlad, too. Also, it's not clear from your description if you plan to separate your compressor function from your condenser/fan function, but I think it will make your life a lot more comfortable if you do. There's a reason they call air conditioners "window shakers". I really think that they're best left outside, bolted to a concrete pad. Best, -AC
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker... |
|
01-31-13, 12:22 AM | #3 |
Super Moderator
Join Date: May 2009
Location: Warsaw, Poland
Posts: 961
Thanks: 188
Thanked 110 Times in 86 Posts
|
__________________
Ecorenovation - the bottomless piggy bank that tries to tame the energy hog. Last edited by Piwoslaw; 01-31-13 at 01:47 PM.. |
The Following 2 Users Say Thank You to Piwoslaw For This Useful Post: |
01-31-13, 04:41 AM | #4 |
Supreme EcoRenovator
|
|
The Following User Says Thank You to jeff5may For This Useful Post: | buffalobillpatrick (09-23-14) |
01-31-13, 09:18 AM | #5 |
Apprentice EcoRenovator
Join Date: Dec 2010
Location: Western Australia
Posts: 148
Thanks: 1
Thanked 48 Times in 34 Posts
|
I have lots of theory SLHX, but no experience at all. Therefore I'm watching eagerly!
|
01-31-13, 10:19 AM | #6 |
Supreme EcoRenovator
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,004
Thanks: 303
Thanked 723 Times in 534 Posts
|
Piwoslaw,
It would be useful to English-only readers if you edited in to your diagram post what all the labels are. Best, -AC
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker... |
01-31-13, 01:49 PM | #7 | |
Super Moderator
Join Date: May 2009
Location: Warsaw, Poland
Posts: 961
Thanks: 188
Thanked 110 Times in 86 Posts
|
Quote:
Changed it. Sorry about that.
__________________
Ecorenovation - the bottomless piggy bank that tries to tame the energy hog. |
|
The Following User Says Thank You to Piwoslaw For This Useful Post: | AC_Hacker (01-31-13) |
01-31-13, 11:33 PM | #8 |
Supreme EcoRenovator
|
Piwoslaw,
Yes, the part labeled "w". I had written a descriptive post, but the site ate it when I tried to post it. |
02-01-13, 06:02 AM | #9 |
Master EcoRenovator
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
|
I use them all the time, in 2 ways. The simplest is as the diagram shows and could be fine provided you do not wish to have a reversing system to do cooling as well (or defrost, but there are other ways of doing that). The second one is to get a suction accumulator with a pancake HX inside it. The added benefit of this system is to take up the extra refrigerant when in reverse mode so the pot doesn't get flooded.
The pic I showed on the other thread shows my HP with both types on it. The main reason I am using it is that it will extend the operating range down another 5-8C Last edited by Mikesolar; 02-01-13 at 06:10 AM.. |
02-01-13, 10:16 AM | #10 |
Supreme EcoRenovator
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,004
Thanks: 303
Thanked 723 Times in 534 Posts
|
So what is your rationale for using the size that you chose to use?
Did you just eyeball it, or was there some design criterion that you used. -AC
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker... |
|
|