Author Topic: DIY water chiller - reading suggestions?  (Read 3980 times)

BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #60 on: August 23, 2021, 02:12:09 AM »
 I appreciate the reminder, Bronco.  I did plumb it for opposing flow direction, per the heatex mfgr recommendation.  It's all plumbed into the house floor system in the photo shown, I just left out all the other plumbing in that closet! The flare connections Gary recommended made the tubing connections to the heatex easy. 
 



« Last Edit: August 23, 2021, 02:16:52 AM by BruceM »

32 coupe

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Re: DIY water chiller - reading suggestions?
« Reply #61 on: August 24, 2021, 12:45:04 PM »
Bruce,
I would rotate your HX so the unit is vertical with the cap tubes at the bottom.

You MAY need an air bleeder in your water line as well.

Gary

« Last Edit: August 24, 2021, 01:28:26 PM by 32 coupe »
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BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #62 on: August 25, 2021, 05:46:10 PM »
Thanks for the note and the phone call, Gary.  i'll have to revise my refrigerant flow; for others benefit I'll summarize; most water chillers (Gary sees many on boats)  have refrigerant coming in on the bottom, with return off the top, to maximize vapor only return to the  compressor.  The liquid on the bottom is "boiling" into vapor due to the low pressure. 

The air bleed for the water line is also an excellent idea.






BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #63 on: August 25, 2021, 06:40:58 PM »
There is a dense technical manual on AlfaLaval's web site regarding the use of their brazed flate plate exhangers for water chillers. 

https://www.alfalaval.com/globalassets/documents/microsites/heating-and-cooling-hub/technical-reference-manual-refrigeration.pdf

On page 65 of the pdf document (printed page 58);

''3. Flow arrangement.
3.1. The one-pass BPHE.
3.1.1. Evaporator.
♦ The evaporating fluid is normally flows upwards and the
heating media flows downwards.
♦ Downwards evaporation is not impossible but needs a
comparably high channel and low nozzle pressure drop
to distribute the liquid properly.
A high nozzle pressure drop means that the fluid will
have a maldistribution from the first to the last channel.
A low channel pressure drop means that the liquid will
not distribute properly over the channel width.
Downwards evaporation in BPHE has been little studied
and tests should be made before an installation is
made. Expect a fairly large capacity reduction compared
to upwards evaporation.''


This clearly indicates that bottom up flow for the refrigerant in brazed plate exchanger water chillers is the preferred engineering configuration, as Gary noted , and I'll switch to that configuration.   I'm very grateful for his sharing his water chiller system knowledge.  i'm grateful Gary caught this before I charged the system.







BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #64 on: August 26, 2021, 12:02:41 AM »
I got a few things done on the project, but now must wait for the sun to go lower or the clouds to get thicker; it's too damned hot and bright for me to do the copper hookup to the condenser unit.  The heat reflecting off the west facing shop wall makes me think I may have picked a poor location.  I'm going to proceed with it for now. 

I reoriented the brazed plate exchanger/evaporator per Gary's advice.  I finished the window unit case modifications to basically reverse the case, with a solid rear panel and recessed condenser fins with hardware cloth protecting them from curious dogs and goats.  The cover has been modified so that it screws to the chassis, and is a lift off design for service. The former window AC base or chassis has been shortened to allow the case to overhang the condenser coils. I changed the orientation so  that the condenser side is protected from hail.  It now faces north.  I did run the fan with it in this position to see if this might be a problem, and I think it's OK.

Clouds are getting thicker so I'll try to make the last copper connections.

« Last Edit: August 26, 2021, 12:05:34 AM by BruceM »

BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #65 on: August 26, 2021, 03:00:08 PM »
Finished the copper connections but alas, on pressure testing I found that the BSP adapater bushings were leaking at the stainless steel BSP female fittings of the heat exchanger/evaporator. So much for Nylog Blue and Chinese made BSP threads...

I also found the brass 3/8 flare/1/4 NPT male fitting was dented, so I'll be heading to ACE this morning to get a replacement.


Rectorseal Tru Blue is listed for refrigeration and stainless, and ACE carries it, usually. 




BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #66 on: August 27, 2021, 06:54:09 PM »
Thursday, after more fiddling with the fit of the alleged BSP adapter bushings into the female 1/2 BSP thread heat exchanger, I noted that there was little improvement over 1/2 NPT.  No non-setting pipe dope will solve that problem, so I did more research on silicone/RTV compatibility with refrigerants.  I decided to use my old favorite for damaged and old leaky fittings,  Permatex Ultra Grey.  The worst case with RTV is normally swelling, which is a non-problem for pipe thread sealing.

I got it in and tested at 50psi nitrogen a few hours later.  No leaks detected.  Rain and wind encouraged me to wait until Friday to test again at higher pressure.  I did that this morning, first at 100 psi, then 200 psi.  All is well, so far.  I'm evacuating the system now, will let it run for a few hours, then start the R-410a charging.

Gary suggested by phone that I might find it easier to just sit the brazed plate heat exchanger on the floor, on foam.  A very helpful suggestion, and I strapped it upright to a board with a piece of styrofoam board under it.  So hookup was a little easier, as was air burping, this time.

I purged the water line hookups and have confirmed circulation flow at 2 GPM , with the flow sensor I'll be monitoring via some custom electronics to shut down the compressor to avoid freeze damage to the brazed plate exchanger.  High hopes!

Bruce

« Last Edit: August 27, 2021, 07:32:41 PM by BruceM »

32 coupe

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Re: DIY water chiller - reading suggestions?
« Reply #67 on: August 27, 2021, 09:27:47 PM »
Looks good Bruce !

Looking forward to seeing the charge numbers.

......................
Nothing to do with your set up, just another example of what's out there.
I worked on a SubZero drawer freezer today (evap replacement) and noticed
the the evap coil has the cap tube in the top of the coil and the suction right
next to it at the top. So in this case the liguid is sprayed in the top with the tubes
running horizontal so the gas falls down half of the tubes then returns through
the remaining tubes to the top. Interesting setup.

I have replaced many of them through the years and never gave it much thought
untill your "chiller" project popped up.

Just another "way of doing it".




« Last Edit: August 27, 2021, 09:42:09 PM by 32 coupe »
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BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #68 on: August 28, 2021, 01:31:33 AM »
Slowly sneaking up on the charge:
90F Outdoor temp
High Pressure: 390 psi
Suction:            90 psi
Superheat: 40F (Suction at compressor 72F minus Sat. Temp per low side gauge: 32F)

Water cooling differential at 2 GPM: about 6.5-7F  Less than I'd like- goal was 10F.

Got rained out, so will have to continue tomorrow. 





broncodriver99

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Re: DIY water chiller - reading suggestions?
« Reply #69 on: August 28, 2021, 02:21:42 AM »
What were your fluid entering and leaving temps?

What was your liquid line temperature?
« Last Edit: August 28, 2021, 02:24:05 AM by broncodriver99 »

BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #70 on: August 28, 2021, 02:35:46 AM »
Water temperatures 71F in, 64.5F out, at a measured 2 GPM.

The actual temperatures are  likely a few degrees higher, but I used the same digital thermometer probe on each rubber hose, with an foam tape wrap, so the measured delta temperature is accurate.

I'll do better tomorrow at getting calibrated temperatures, and perhaps some house floor temps near one of the manifolds.





32 coupe

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Re: DIY water chiller - reading suggestions?
« Reply #71 on: August 28, 2021, 03:30:57 AM »
I would bet you are within a few ounces of a full charge.

This crowd never ceases to amaze me. A guy with no real experience in
the field with a little research and encouragement can pull off building a
"home brew" chiller system. I don't care what anyone says thats pretty impressive.
There is a lot more there than meets the eye.

I'm just happy I could help the little I did.

Bruce, my hats off to you sir !!

Looking forward to seeing your final numbers.

Gary


« Last Edit: August 28, 2021, 04:41:06 AM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

mobile_bob

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Re: DIY water chiller - reading suggestions?
« Reply #72 on: August 28, 2021, 03:36:21 AM »
can you throttle down the flow rate a bit?
maybe run a test at 1.5 gal/min?

as a guy that isn't conversant with the finer points of refrigeration...

i would ask how much cold is being returned to the system from the heat exchanger
in other words, is it near what is expected from the system in its original application?

just spitballin,

if the return temperature of the evaporator was for instance 45 deg F in the airconditioner as designed
and in the new application it is say 40 deg F, then i would think i am not getting all the cold that is available.

realizing that it isn't cold you are making but rather heat that is being removed, it is just easier for some of us to think of it the other way.

by slowing the flow, maybe you are able to reject more of the heat of the slab water to the heat exchanger?

something to think about, and  maybe it might have application here.

years ago, the big cam cummins 855cu/in ntc 400 had 2.5" radiator top and bottom hoses, and a water pump that moved a lot of water.

then the big cam 2 or 3 came out and it used a reverse low flow system, with 1" upper and lower hoses, and dramatically reduced flow from the new pump design... the water moved slower so it could use smaller hoses and it did a better job or rejecting the heat of the same 400hp engine in the same class 8 truck with a 80k lb gvw.  none of us thought it would work, but it did.

changing from the way things had been done to a system that used 1" hoses and a tstat the size of a silver dollar was nothing short of amazing.

so i am wondering, maybe slow the flow rate down, giving the water time to shed its heat to the system?

thoughts?

bob g
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

32 coupe

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Re: DIY water chiller - reading suggestions?
« Reply #73 on: August 28, 2021, 05:49:38 AM »

Bob,
 I'm sure Bruce knows slowing the flow will remove more heat but at this point I believe it is still just
a little low on refrigerant. Good  thinking though.

The head pressure is close to the upper limit in my opinion but the low side pressure is just
a little low.

I do know Bruce is reading the amps on the compressor while charging so with that and
pressure/temp readings he should be able to get the charge spot on. Then if the TD across
the "chiller core" is still too low that would be the time to think about slowing the water flow.

Unfortunately because it's a home brew project there are no "factory specs". It's a guessing
game as far as the numbers go. (to an extent....the refrigerant properties and compressor
amp ratings are known)

I could be wrong on all of this......maybe the suction pressure SHOULD be lower . But I still
think geting the suction pressure up a little without driving up the head pressure up much
more would be the palce to start. Bruce could always remove a little freon if the water temp
numbers start to rise.

We will see........


I hope Russell chimes in on this because I believe he is more technically knowledgeable than I am.

Gary







Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #74 on: August 28, 2021, 06:50:52 AM »
The help and encouragement has been a huge boost for me. Good to see you chiming in, Bob.

My water cooling/power consumption target is 12000 BTU which calculates to a bit over 10F degrees of water cooling at 2GPM.  Slowing the flow in this sort of closed loop system would help if a lower target water temperature was needed, but otherwise, no help with actual BTUs of cooling delivered.  The water temps I'm getting are OK at 2 GPM.  I don't want to go below 58F water, or I may get condensation at the PEX manifolds.  Another reason to not just through lots of BTUs at this system.

The suction temp at the compressor was 72F, I'll have to measure it at the heat exchanger.  If it's about 10 degrees colder there (as normal for remote compressor/condenser setup), it's very close to the outgoing water temp...so the exhanger is doing as it should, but I'd like a few more BTUs. 

I'll see what water chilling performance I can get tomorrow. My pressures are a little low for R410a, and my superheat is quite high, both pointing to needed a bit more refrigerant needed, though superheat targets may not be the same for a water chiller.  Still, I hope it may give me some performance improvement. 

Normal use is with an air evaporator, with a colder return, thus lower superheat value. The water exhanger throws a wrench in the normal values-  I haven't been able to find a good tech reference for that part of the design, so I am just going to measure the delta water temperature as I add a bit of refrigerant, watching pressures and monitoring amperes.

The capillary tube adjustment for the brazed flat plate exchanger/evaporator  is another performance impacting issue I don't understand well enough to do, yet.

I will  take a liquid  line temperature tomorrow.  I didn't today because it's not needed for superheat calculation and supercooling isn't recommended for capillary tube systems.


I'm hoping for sunny and hot tomorrow!