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 08-07-15, 04:58 AM   #1
TechShop
FNG
 
Join Date: Jul 2015
Location: Washington
Posts: 67
Thanks: 6
Thanked 18 Times in 12 Posts
Default 2 Heat Exchangers - Overkill?

To begin, I have a new Carrier model 50YDS049NCD311.
That's a re-badged Climatemaster 4 ton indoor split GSHP.

My project involves converting this system into a hydronic heat pump. The way I intend to do this is to build an enclosure on top of the existing unit which will house the following components:

1) 4-ton TXV (Sporlan CBBIZE-4-GA)
2) Filter Dryer (Sporlan Catch-All)
3) Sight Glass (Sporlan See-All)
4) 4-ton or larger heat exchanger(s)
5) circulation pump (will feed a water storage tank)


This week I came into a pair (two) of these TurboTec BTSSN-48 coaxial heat exchangers (see attached performance graphs).

Is there any downside to running two of these 4-ton rated heat exchangers in parallel?

Do I stand to gain much in efficiency or should I just run a single HX and save the other for a future project / shelf-spare?

Thanks. As I get going on this I'll start posting up some photos, etc of my project.


TechShop is offline   Reply With Quote
Old 08-07-15, 06:17 AM   #2
stevehull
Steve Hull
 
Join Date: Dec 2012
Location: hilly, tree covered Arcadia, OK USA
Posts: 829
Thanks: 241
Thanked 164 Times in 122 Posts
Default

Looks like a great project. Putting the two coaxial Hxs in parallel cuts the heat exchanger resistance in half. Good thing as a lot of the total system resistance is in those helical/spiral exchangers. Allows use of a smaller pump and less cost to run it.

Would get double the amount of BTUs from the incoming water stream.

Water tank?


Steve
__________________
consulting on geothermal heating/cooling & rational energy use since 1990
stevehull is offline   Reply With Quote
Old 08-07-15, 04:38 PM   #3
TechShop
FNG
 
Join Date: Jul 2015
Location: Washington
Posts: 67
Thanks: 6
Thanked 18 Times in 12 Posts
Default

Quote:
Originally Posted by stevehull View Post
Looks like a great project. Putting the two coaxial Hxs in parallel cuts the heat exchanger resistance in half. Good thing as a lot of the total system resistance is in those helical/spiral exchangers. Allows use of a smaller pump and less cost to run it.

Would get double the amount of BTUs from the incoming water stream.

Water tank?


Steve
Thanks, I was thinking the same things: less head-loss in the water circuit and double the wetted surface area in the HX = more efficiency.

Since you asked about the water tank... I plan to use a standard electric water heater tank with a few temp sensors. It will store the heated (or chilled) water produced by GSHP through these 4-ton HX.

From your post, I think I may have miscommunicated my setup in my original post...

The heat pump I have is a GSHP already. It has a pair of 2-ton Koax brand HX inside in parallel. These HX take the ground loop water and couple it to the refrigerant. This GSHP is only one half of the split system. It was designed for use with a fan coil unit in a forced-air sytem inside the home.

My building is set up for hydronic heating and cooling with radiant concrete floors and large radiators for chilled-water. So I want to use these 4-ton TurboTec HX to turn this split system GSHP into a packaged hydronic (water to water) GSHP. Hopefully that makes more sense.
TechShop is offline   Reply With Quote
Old 09-10-15, 07:48 AM   #4
Daox
Administrator
 
Daox's Avatar
 
Join Date: Aug 2008
Location: Germantown, WI
Posts: 5,441
Thanks: 1,096
Thanked 361 Times in 294 Posts
Default

Did you ever try this in an actual application TechShop?
__________________
Current project -
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
&
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Daox is offline   Reply With Quote
Old 09-10-15, 10:31 AM   #5
TechShop
FNG
 
Join Date: Jul 2015
Location: Washington
Posts: 67
Thanks: 6
Thanked 18 Times in 12 Posts
Default

Quote:
Originally Posted by Daox View Post
Did you ever try this in an actual application TechShop?
I have brazed and pressure tested the heat pump but have not tested the system yet. I will be doing that over the next few weeks. Here's a thread with some details and photos of the system and the pump itself:

http://ecorenovator.org/forum/geothe...onversion.html
TechShop is offline   Reply With Quote
The Following User Says Thank You to TechShop For This Useful Post:
Daox (09-10-15)
Old 09-10-15, 12:39 PM   #6
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 703 Times in 526 Posts
Default

Quote:
Originally Posted by stevehull View Post
Would get double the amount of BTUs from the incoming water stream.
If this were true, then having 4 HXs in parallel would give you 4x the BTUs, and having 8 HXs in parallel would give you 8x the BTUs, etc. and eventually your BTU output would exceed the available heat energy.

Will not happen, violates the laws of physics.

When you run 2 HXs in parallel, you are reducing your resistance only because you are reducing the velocity of fluid flow through each HX.

Reducing the velocity reduces the BTU output.

You will have an increase in efficiency but nothing like 2X.

Sincerely,

-AC_Hacker
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Old 09-10-15, 03:12 PM   #7
TechShop
FNG
 
Join Date: Jul 2015
Location: Washington
Posts: 67
Thanks: 6
Thanked 18 Times in 12 Posts
Default

Quote:
Originally Posted by AC_Hacker View Post
...

Reducing the velocity reduces the BTU output.

You will have an increase in efficiency but nothing like 2X.

Sincerely,

-AC_Hacker

This is absolutely true. You cannot transfer more heat than what is available. What I am hoping for, at best, is a small increase in HX efficiency.

If I am moving 10 GPM of water through one heat exchanger, installing two will cut the flow down to about 5 GPM per heat exchanger (not accounting for head-loss). The water will be exposed longer (due to 1/2 the velocity) and thus it will reach a slightly higher temperature. As the water becomes hot, the heat will not be absorbed from the refrigerant as quickly because HX depends on a substantial Delta-T.

In a perfect world, double the surface area per given quantity of water combined with water moving at a lower velocity means that the Delta-T in the system should be slightly less than a single HX. That combined with the fact that the same quantity of water is flowing with less head-loss may net a tiny increase in system efficiency.

I will not have a control for this experiment, I have never run this system with a single heat exchanger and most likely never will. That means ultimately any data I collect will be meaningless in terms of comparison of 1 vs 2 heat exchangers.

I started this thread to see if anyone had any good input on why NOT to build the system this way.

The only negative aspect I could come up with on my own was fouling. If the water velocity is too low to create turbulent flow in the HX, it could cause excess fouling. I decided that since this is the heated side of a closed loop system, I shouldn't have any major fouling issues provided that I use clean distilled water and the proper anti-freeze / coolant mix. Furthermore, I have selected a pump that should maintain flow through each HX that is well within the manufacturer's design envelope.
TechShop is offline   Reply With Quote
Old 09-10-15, 07:56 PM   #8
jeff5may
Supreme EcoRenovator
 
Join Date: Jan 2010
Location: elizabethtown, ky, USA
Posts: 2,348
Thanks: 367
Thanked 591 Times in 494 Posts
Send a message via Yahoo to jeff5may
Default

I believe even if you only ran one of those turbotec units, the unit would have a greater COP versus running an air handler. By running two, you should extract even more btu's per watt of compressor power. If the turbotecs are too effective, you may not develop enough head pressure unless you choke the indoor water flow. That's what trials are for.
jeff5may is offline   Reply With Quote
Old 09-10-15, 11:23 PM   #9
TechShop
FNG
 
Join Date: Jul 2015
Location: Washington
Posts: 67
Thanks: 6
Thanked 18 Times in 12 Posts
Default

Quote:
Originally Posted by jeff5may View Post
I believe even if you only ran one of those turbotec units, the unit would have a greater COP versus running an air handler. By running two, you should extract even more btu's per watt of compressor power. If the turbotecs are too effective, you may not develop enough head pressure unless you choke the indoor water flow. That's what trials are for.
That's my expectation... I will be running the system with some PLCs, so I will be doing lots of trials to tune it for good efficiency.

TechShop 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 02:00 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design