Author Topic: DIY water chiller - reading suggestions?  (Read 3242 times)

mobile_bob

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Re: DIY water chiller - reading suggestions?
« Reply #150 on: September 10, 2021, 02:46:32 PM »
not something you probably would want to do at this point, but...

maybe another water cooled plate exchanger for the condenser? you could heat your hot water? for domestic hot water needs?

it would be interesting to use the heat taken from the slab and put it to use preheating water.

ok, i will retreat to my corner
:)

bob g

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

BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #151 on: September 10, 2021, 04:19:22 PM »
No retreat warranted.   Alas, I have no need for lukewarm water in the summer.  My 800 gallon insulated solar hot water storage tank is maxed out.

There's a reason the HVAC industry just uses air; cost and simplicity, power be damned. 
Speaking of damn the power:
I keep waiting on the battery tech to improve.  If I could run my little 1060 watt slab cooling system late at night and early morning that would be a big help.  But LiFePO4 is still bleeding edge and has some reliability/durability issues to be worked out. Not to mention I'd have to design and build 39 battery regulators and a new BMS for it...and work through the birthing issues of that new hardware design.  People forget that a simple failure of the BMS can wipe out a cell or an entire bank. All it takes is a lightning spike on the power or grounding system.

I'm getting close, just don't know if I'll be able to test the full range of temperatures as I won't get the TXV and fittings until mid week.  I suppose I can restrict the condenser air flow to get the desired "simulated hot day" test liquid line temperature.  I think that might work.








mike90045

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Re: DIY water chiller - reading suggestions?
« Reply #152 on: September 10, 2021, 09:53:19 PM »
....... People forget that a simple failure of the BMS can wipe out a cell or an entire bank. All it takes is a lightning spike on the power or grounding system.........

Some BMS's are so poorly engineered ( if at all ), that they are going to fail, and take out the battery bank with them.

32 coupe

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Re: DIY water chiller - reading suggestions?
« Reply #153 on: September 10, 2021, 10:12:37 PM »

 
Looking at your numbers again I don't think you are that far off.......but

At 80F your numbers look good as far as pressures and temps but the compressor amps
still look hi to me. We usually look for RLA to be 10% or better under that number.  I can't
stress this enough. You will loose some cooling but you said you were getting 13k out of it....
It's a 12k unit......I would look for 11k or so. ....I have always tried to be conservative on the numbers.
Reason being the rise in amps and pressures when the outside air temp goes up.


Your idea of using the evap coil on the condenser side might help. Lowering the condenser coil temp a few degrees will make a significant change in head pressure thus amp draw. Look at all the newer home ac
units. The coils are huge compared to older units. (Yes I know different  gas types, etc..) What I see is that
the higher the s.e.e.r is the larger the coil. Some of the super hi efficiency units have 2 layers of coil in the condenser. There must be something there.

The TXV sounds like the answer.....but be aware that it could be opening a can of worms so to speak.
You could end up going in circles and be no more ahead than you are now.


As always,  take this with a grain of salt..........














« Last Edit: September 11, 2021, 12:59:55 AM by 32 coupe »
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BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #154 on: September 11, 2021, 12:50:19 AM »
LG is running the compressor 6% under max rated power at their appliance (compressor plus 80W fan) power rating of 4.6 amps/230v.  At 4.5A I was running it 8% under rating.   I'm still at the education and experimental stage, Gary.  I'm nowhere near a setup for operating at full range of temperatures.  I wouldn't mind running close to full watts on the compressor for a 103F ambient, if vapor temps were at 60F or less, because I only expect less than 40 hours of run time a year. That's 800 hours in 20 years, well beyond my likely expiration.

Floor cooling is a slow process since you CAN'T throw power, very cold water and BTU's at it.  If the house was 80F (return water 77F) and 60% humidity from being closed up for smoke, you don't want the water below 67F at starting conditions.  So about 10 degrees of cooling is all you can use or you get condensation build up at the pex manifolds in the wall cavities.  As the room temperature goes down, so does the dewpoint, so near 10K BTU is OK, but it is the maximum...assuming house humidity is 60% or less.  [Note to self- put manifolds where you can deal with condensation if you're planning for cooling!]  Again, I'm going to have to do some experimenting to work it all out, but my concept was to keep BTU's near 10K, and not much over, unless I increase the water flow rate, which is also a relatively simple option, and I have the extra 12V circ pump on hand.  If I can't get 4 degrees out of the house with 5 hours of running, I'll increase water flow to raise water temperature and raise the BTUs.

Sadly I need that 9 or 10K BTUs in the high noon and afternoon  to use my excess PV power.

I may do a wee hours of the morning run on Lister CS power just to see how manifold temperature and floor temperature changes over 4 hours of running, with refrigerant charge adjusted  for 9-10K BTUs.  I  want to see how 10K BTU's performs on house temperatures over the following hours.  My house is a slow moving temperature mass.






32 coupe

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Re: DIY water chiller - reading suggestions?
« Reply #155 on: September 11, 2021, 01:06:12 AM »

Shoot Bruce, you know I don't know anything !

I think you are doing a fine job and am confident you will get it going.

Probably do better if I leave you alone  :laugh:

Metro 6/1 turning a ST 7.5 KW gen head
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mobile_bob

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Re: DIY water chiller - reading suggestions?
« Reply #156 on: September 11, 2021, 03:27:30 PM »
Bruce

just for my own amusement

how do you have the water flow going through the exchanger? 
is it inline or counter flow?

something popped into my noggin last night, (frequently happens about 2am), that is the heat flow in an exchanger often times improves with counter flow.

just curious

thanks
bob g
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BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #157 on: September 11, 2021, 05:12:18 PM »
Hey Bob,
I started with counter flow, but am now running inline, in order to have lower suction side vapor temperatures, which are needed for compressor cooling.  It dd not measurably change water cooling.  My 40 plate BHPE is a bit larger than I needed.

I've been doing some reading on the influence of higher temperatures on air cooling performance.  I didn't realize how huge the COP/EER losses were as outside temperature climbs. 

From this paper with some R410a testing data, page 6:
file:///C:/Users/Bruce/Downloads/A_Comparison_Of_An_R22_And_An_R410A_Air_Conditione.pdf

"If we evaluate the combined data obtained with both compressors, the air-side capacity decreased in a nearly linear manner as the outdoor temperature increased from 27.7 C (82.0 F) to 68.3 C (155.0 F). Over this temperature
range, air-side capacity decreased from 11.8 kW (40345 Btu/h) to 6.7 kW (22699 Btu/h); a decrease of 43.7 %. The COP (EER) also decreased linearly by 80.3 % as it dropped from 5.36(18.3 Btu/Wh) to 1.06 (3.6 Btu/Wh). "


This performance affect of ambient temperature is much, much higher than I expected.  With the ground heating effect, my air inlet is 10F over ambient.  My worst case ambient is 103F.  So a condenser inlet of 113F.  That will give me a COP reduction of 33%, (in my case from 3.5 to 2.35).  This has a huge effect on my BTUs, since I don't have enough head room at the compressor for increasing watts much.  I should have started with a larger compressor, and limited it's BTU's and watts at the evaporator valve.  Then power could climb as temperatures rise to keep the output closer to 10K BTUs.

Evap cooling will buy me 20F in June with single digit humidity in the mid day, so I'd be OK at 103F ambient. I don't like it because of the maintenance with my hard water, but it would be a huge energy leveler/reducer that could make my current condenser unit viable.  One thought that comes to mind is since my run hours per June and July are low, if I could find a descale chemical spray to use that wouldn't wreck the fine aluminum fins, maybe I could just use the fan rim system with my well water.  That's super simple; I just add a tray and float valve, fed by 1/4 drip tube, controlled by a solenoid triggered by ambient air temperature.  I'd just have to blow out the water line in the fall. 

I'll probably have to add a water bypass at the BPHE, also, to allow the TXV suction line bulb to in effect, limit the outgoing water temperature.  This lets the water (and suction vapor) temperature in the BPHE to be lower than the re-combined combined water temperature, by diverting some water directly from inlet to outlet pipes, not going through the BPHE.  I tried to get the 1" Pex crimp tees I needed for this yesterday but ACE didn't have them.

I've read some papers about R290 performing well for higher temperatures, and will follow up on that reading to try and look at their data to see if it's significantly better.  It requires a larger volume capacity compressor compared to R410a; R22 compressors are a better match.

More research required, while I wait on the TXV.






mobile_bob

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Re: DIY water chiller - reading suggestions?
« Reply #158 on: September 11, 2021, 05:41:24 PM »
Bruce

all i can say is wow, what a job you have done with this project, i for one have learned a lot from  your efforts.

another thing comes to mind when you mention the heat soaking of the ground around your unit being ~10deg higher than the ambient air.  i can get my head around that as my temperatures are quite high on the ground as the compressor/condenser unit is on the south side of my house and the house is a light tan color, a lot of reflected heat down onto the ground.

what i am thinking of doing is building a cooling tower out of cedar siding planks, a simple affair maybe 4 ft square and maybe 6-8ft tall, with a drip water system as you describe to trickle down the cedar siding slats. 

how effective that might be at lowering the temperature that the A/C unit has to operate in, because of my location in east central kansas and higher humidity levels i am not sure. however i think it would still drop the air temperatures substantially given the elevated air temperatures.

i also have a well so i don't have to use city water, however the limestone strata that all the well water around here comes through has a high mineral content... so like you i don't want to spray that water on the aluminum fins either.  and i am sure that after a summer of dribbling down over the cedar slats of a cooling tower they would have a good start at being petrified. Not that it would affect the function, the look would be less attractive, but who cares its in the back of the house and no one but me would see it.

i don't know whether something like this would be of use in your application? maybe?

perhaps some of the professional cooling guys can chime in with their thoughts

bob g
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BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #159 on: September 11, 2021, 06:42:52 PM »
Most articles I find are for larger systems, but the acknowledge the mineral problem with direct water misting on the condenser.  They instead opt for indirect water cooling, so that only vapor enters the condenser.  Your scheme is indirect.  If you had misters located in the condenser area but avoid any water droplets getting directly to the condenser fins, that would do it. 

I've had swamp coolers with pan, pump and aspen pads; they work reliably since there are no misters to clog.  Not easy to fabricate from scratch.  I'd like just one panel from a good sized unit! 


BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #160 on: September 12, 2021, 01:24:49 AM »
I tried just spraying water on the ground to see if that would help with the ground heat effect.  No, it didn't make any change at the condenser unit air inlets.  So it seems a true evap cooler design is needed.
 
Oh, how I wish I'd started with a 15000BTU, 1500W 230V unit.
 
I'll probably proceed with adding my leftover evaporator to the condenser,  adding an evaporative precooler using the greenhouse type cooler panels, and adding an insulated chimney with a hat on the air inlet to get it up above the ground heat effect.  It's all simple mechanical stuff. I may raise it up to improve serviceability for the precooler.

I found an article on BuiditSolar that some might find interesting.
https://www.builditsolar.com/Projects/Cooling/ACEvapCool/ac%20pRECOOLING%20G1-1.pdf

His A/C wasn't cooling enough on very hot days, so he added a precooler. Since he used the greenhouse panels I expect not much water makes it to the coils.  I'll separate mine further.  He got very good results.






mobile_bob

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Re: DIY water chiller - reading suggestions?
« Reply #161 on: September 12, 2021, 04:26:19 AM »
Bruce

thanks for the link!

yes i agree he got some very encouraging results!

bob g
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BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #162 on: September 12, 2021, 05:51:43 AM »
Remember that low humidity is key to good results with evaporative cooling.  When humidity rises to 33% (as in the predawn June hours here), your're lucky to get 8F of cooling.  June days here are single digit humidity, so 20F of cooling is common.  I experimented with a water chilling tower, and with evaporative/night sky cooling trickling water down roof panels at night before undertaking this  more conventional water chilling via refrigeration project.  My pre-dawn, prime cooling hours had too much humidity and any clouds (or wildfire smoke) wreck the night sky cooling effect.




BruceM

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Re: DIY water chiller - reading suggestions?
« Reply #163 on: September 13, 2021, 03:21:23 AM »
I've been looking for a condenser fin/tube unit  to add to my setup, to reduce my condenser approach from 15F to half that. I've got to do a whole new housing  for evaporative cooling so I might as well upgrade the condenser.   New aftermarket automotive condensers are affordable and readily available but I wonder about running them in a R410a system since they weren't designed for the higher pressures.  Any thoughts?  Also, for plumbing, any suggestions on series versus parallel? 

I'll be running a 10K BTU test for about 4 hours tomorrow morning, 6:30 to 10:30 on Lister power.  I opened up all afternoon to warm up the house a few degrees and the slab will have all night to soak in that heat and stabilize at something like my actual June use conditions.  FIngers crossed; my delta T is low (10F) and so is my flow rate of 2 GPM. 

32 coupe

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Re: DIY water chiller - reading suggestions?
« Reply #164 on: September 13, 2021, 05:16:53 AM »

I think all the car condensers are aluminum.......and they run much lower pressures.

I would series the additional coil. If you put one behind the other, with the existing fan I
would pipe to the aft coil first then to the one next to the fan. In the top out the bottom, then
again in the top out the bottom.

I think I read, or perhaps you told me, your access valve was directly off the compressor.  Your
access valve should be after the condenser. I have read that there is a 10 to 15 psi difference
between those two spots.




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 !"