Reservoir Water Chiller

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Longhairedcountryboy
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Reservoir Water Chiller

Post by Longhairedcountryboy »

I was working on an unrelated project and it occurred to me that it might be of use to people using recirculating water reservoirs for their condensers.

I picked up an old and dirty dehumidifier for $15 at a thrift store.
Thrift Store Score.jpg
I brought it home and disassembled it.
Stripped.jpg
It cycles on and off according to the humidity level. For my purpose, I need it to cycle according to temp. I found the humidistat.
Humidistat.jpg
And figured out which pins to jump to trick it into thinking it was always humid.
Humidistat Bypass.jpg
I soldered on a jumper to make it think it is in maximum humidity regardless of ambient rh.
Terrible Solder Job Jumper.jpg
(continued ...)
Longhairedcountryboy
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Re: Reservoir Water Chiller

Post by Longhairedcountryboy »

Then I carefully bent the front coil out and away from the unit, making sure to not kink the line.
Bent.jpg
And then carefully bent it down and into a water reservoir.
Reservoir.jpg
Then I cleaned everything up and put it all back together.
Reassembled.jpg


Initial test brought 95F water down to 52F in 20 minutes and 32F in just under 50 minutes.

For my purpose, I will be plugging it into an STC-1000 to set it to the desired temp. I think this would work well for a recirculating reservoir if you can get the coil submerged. You might have to set the unit up on something, or maybe use a plastic tote that is lower to the ground.
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Re: Reservoir Water Chiller

Post by Twisted Brick »

Nice work, Longhairedcountryboy,

Looks to be the perfect tool for keeping a keggle fermenter at the perfect temp in a scorching summer.

Thanks for sharing.
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Longhairedcountryboy
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Re: Reservoir Water Chiller

Post by Longhairedcountryboy »

My thought was for guys that are running dephlegmators off of a recirculating reservoir. You could set the reservoir temp and run your cooling water at a stable temp instead of dealing with a rising temp through the run. Or for people that have small reservoirs that have a hard time getting all the way through a run before the cooling water heats up to the point of having to dial the input heat down. No more ice bottles or dumping and refreshing during a run.

This thing really pulls the heat out and does it better than I had imagined before trying it. I was surprised. The coil ices over when it is first powered up. This is with a small 30 pint a day unit. I bet a 70 pint a day unit could freeze a 55 gallon barrel to solid ice.
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Re: Reservoir Water Chiller

Post by hellbilly007 »

That's a cool idea, lhcb. Pun intended :lol:
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Twisted Brick
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Re: Reservoir Water Chiller

Post by Twisted Brick »

Gotcha. I know on a long spirit run, my 3" pot will heat my 35gal barrel coolant water to 120F, hotter than I want. This unit would work out great to keep it and a dephlegmator reservoir too.
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Re: Reservoir Water Chiller

Post by Yummyrum »

Nice one LHCB .

Never wondered about those dehumidifiers and how they worked .
Cool to see inside one .

Any chance you talk about how they work as designed and how you utilised this .

Have you worked out any numbers like if you put 2kw of heat into a wash , how many kw does the cooler take to maintain coolant equalibrium ? . Guess I’m wondering what is the maximum boiler power ( ball parking ...taking into account loses in a typical setup ) this beast can keep cool without the temp climbing .
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Re: Reservoir Water Chiller

Post by Longhairedcountryboy »

Yummyrum wrote: ...Any chance you talk about how they work as designed and how you utilized this.
A dehumidifier pulls air across a cold coil to cause the moisture to condense out of the air. The dry air then passes through a warm coil and is discharged back into the room. The condensation drains into a collection bucket. That is it in a nutshell.
Yummyrum wrote:Have you worked out any numbers like if you put 2kw of heat into a wash , how many kw does the cooler take to maintain coolant equilibrium ? . Guess I’m wondering what is the maximum boiler power ( ball parking ...taking into account loses in a typical setup ) this beast can keep cool without the temp climbing .
I'm not educated enough to calculate the energy and thermal dynamics of the thing. I could probably figure it out over time with it in use. Ball-parking from observing the test run, I would guess it could knock down around 2K input to the boiler. I was hoping one of the more educated people would chime in. Where is ACFixer at? I'm assuming from his handle that he works on air conditioners? The first part of the dehumidification process is essentially identical to an air conditioner. Still Stirrin seems pretty well versed in thermodynamics. Maybe he could help us out with the numbers?


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Re: Reservoir Water Chiller

Post by still_stirrin »

Longhairedcountryboy wrote:
Yummyrum wrote:Have you worked out any numbers like if you put 2kw of heat into a wash , how many kw does the cooler take to maintain coolant equilibrium ? . Guess I’m wondering what is the maximum boiler power ( ball parking ...taking into account loses in a typical setup ) this beast can keep cool without the temp climbing .
I'm not educated enough to calculate the energy and thermal dynamics of the thing. I could probably figure it out over time with it in use. Ball-parking from observing the test run, I would guess it could knock down around 2K input to the boiler. I was hoping one of the more educated people would chime in. Where is ACFixer at? I'm assuming from his handle that he works on air conditioners? The first part of the dehumidification process is essentially identical to an air conditioner. Still Stirrin seems pretty well versed in thermodynamics. Maybe he could help us out with the numbers?
Well, this is an interesting discussion. Too bad there isn’t an easy answer. The engineering involved in the “closed system” thermodynamic analysis involves partial differential equations which would make it beyond the understanding of most readers here. So, approximations of the states of the system help our understanding of the mechanics involved.

First, look at the “system boundary” in which is the distillation process is contained: the boundary includes the still and the coolant reservoir. Energy crosses the boundary by way of the electrical input (or heat source fuel, such as propane or natural gas). The immersed electric element is very efficient at heat transfer to the wash such that it is acceptable to assume that all power is converted to heat and very little heat is lost to the surroundings (note- this is not entirely a good asumption because the still house will heat up during the run, especially with a fuel fired heat source).

And similarly, heat is transfered from the dehumidifier evaporator to the ambient air of the still house and that energy crosses the “system boundary” as well. Looking at the system, the power input equals the power output minus any losses due to inefficiency. A little energy is lost in the electrical control circuitry, although it can be nglected. And energy is lost with a fuel fired burner because of the method of heat transfer to the boiler, that is - not all of the fuel burned heats the boiler only as the ambient air is also heated.

A lot of discussion here which likely seems obvious to most and perhaps even redundant to the knowledge base. But let’s “dig deeper” hopefully to understand the limiting factors.

Heat transferred to the wash causes the liquid to change state and that energy is removed in the product condenser. Likewise, the heat is transferred to the water reservoir from the cooling water loop. Now, the addition of the modified dehumidifier pulls heat from the water reservoir via a closed loop refrigeration system. The closed loop uses a refrigerant to transfer the heat from the condenser (cold side) which is immersed in the water reservoir to the evaporator (hot side) which rejects heat to the ambient air and across the system boundary.

The closed loop refrigeration system must be able to transfer energy at the rate equal to or greater than the energy input into the boiler. Factors involved in this refrigeration cycle are the temperatures of the hot side and cold side heat exchangers as well as the mass flow rate of the refrigerant within the closed loop. Heat transfer (energy per unit time) is proportional the temperature differential and the flow rate times the heat transfer coefficient for the refrigerant. Typically, these type of consumer dehumidifiers do not have a large refrigerant flow rate because they don’t need to move a lot of heat, rather just a temperature difference which will allow condensation on the cold side coils and liberate that heat back to the warm, dry air.

So, while the system you’ve built LHCB, will chill the water reservoir to a cold temperature, I question whether it will keep up with the heat input into the boiler. At 2kW input, perhaps it might. Without more information of the dehumidifier design, it would be speculative at best.

But, using a secondary refrigeration system to maintain the water reservoir at, or near a controlled temperature would seem to be an innovative way to stabilize the condensing heat exchanger’s performance and help regulate the distillation processes. This type of system is quite effectively used in commercial breweries to maintain the fermentation temperatures in glycol chilled fermenters. But the key feature is the adequate design of the refrigeration cycle to transfer the heat from the recirculating coolant fluid.

So, I apologize to the wordy reply and the omission of long, boring differential equations associated with the thermodynamics involved. But perhaps I have given you a perspective of the mechanics involved with the closed loop system.
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Re: Reservoir Water Chiller

Post by Bombo80 »

Hey countryboy ......

Just wondering how well this setup is working for you.

I just happen to have an old dehumidifier taking up space in the basement. I might try and convert it the way you did.

My current cooling setup is a 13 gallon garbage can with a pond pump, pumping the water into the condenser. Coming out of the condenser it goes through my wort chiller, which is in a 5 gallon bucket with submerged in water, to pre-cool the water before going back into the 13 gallon reservoir. I change the water as needed, or add ice. I have a small counter top ice maker. It kicks out a tray of ice every 7 minutes or so. But all that maneuvering of water is a PITA.

It works OK for a short spirit run, but on a stripping run it gets warm pretty fast. I would like to keep the reservoir water temp about 85°. Just my personal preference.

So, Please let us know how well this is working for you. :clap:
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Re: Reservoir Water Chiller

Post by zach »

Longhairedcountryboy wrote:
I'm not educated enough to calculate the energy and thermal dynamics of the thing. I could probably figure it out over time with it in use. Ball-parking from observing the test run, I would guess it could knock down around 2K input to the boiler. I was hoping one of the more educated people would chime in.

In your test you cooled 5 gallons from 95 F to 52 F in 30 minutes. The cooling capacity required to accomplish this is; 5 gallons x( 8.34 lb/gallon) x (95-52) F x (1 Btu/F lb )/( 0.5 hours) = 4,336 btu/hr. ( The specific heat of water is 1 btu per pound per degree F)

To convert 1 kW = 3413 btu/ hr so the capacity of the dehumidifier operating as a chiller was 1.27 kw.

This unit could likely keep up with 1.5 or 2 kw of boiler input depending on the heat losses of the boiler and column to atmosphere.

The capacity of a refrigeration system increases as the pressure and temperature in the evaporator rises. If you operated the unit with a water reservoir temperature of 80 F, the unit would likely have 25% more capacity. But then the condenser could be undersized and it may eventually cause the compressor thermal overloads to cut out.
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Re: Reservoir Water Chiller

Post by Shyner »

What's the latest on this project. I am working with an unit that was a customer return. It's a floor model AC/Fan/Dehumidifier. The only thing I can find wrong with it is it vibrates due to a section of teeth missing on the plastic squirrel cage throwing it out of balance.

It's a vertically set machine, and the cold coil is on top and easily bent to fit into water reservoir. I disabled the motor that ran the 2 squirrel cages, then started it up. The top colling coil instantly froze and got super cold.

I'm sure I'll have to find a way to mount a fan for the bottom heat exchanger/condenser (radiator looking thing) to keep it from over heating.

I need to figure out how the 2 thermostats mounted to the top Cold condenser work. One is in the fins, one is at the side where the loop end coils pass thru the fins.

Good news is it gets super cold. Bad news is I dont know if its gonna work to cool my worm for a 10 gallon run.

Any news as to how yours worked out would be fantastic
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Re: Reservoir Water Chiller

Post by Stonecutter »

still_stirrin wrote: Tue Mar 12, 2019 7:53 am
Longhairedcountryboy wrote:
Yummyrum wrote:Have you worked out any numbers like if you put 2kw of heat into a wash , how many kw does the cooler take to maintain coolant equilibrium ? . Guess I’m wondering what is the maximum boiler power ( ball parking ...taking into account loses in a typical setup ) this beast can keep cool without the temp climbing .
I'm not educated enough to calculate the energy and thermal dynamics of the thing. I could probably figure it out over time with it in use. Ball-parking from observing the test run, I would guess it could knock down around 2K input to the boiler. I was hoping one of the more educated people would chime in. Where is ACFixer at? I'm assuming from his handle that he works on air conditioners? The first part of the dehumidification process is essentially identical to an air conditioner. Still Stirrin seems pretty well versed in thermodynamics. Maybe he could help us out with the numbers?
Well, this is an interesting discussion. Too bad there isn’t an easy answer. The engineering involved in the “closed system” thermodynamic analysis involves partial differential equations which would make it beyond the understanding of most readers here. So, approximations of the states of the system help our understanding of the mechanics involved.

First, look at the “system boundary” in which is the distillation process is contained: the boundary includes the still and the coolant reservoir. Energy crosses the boundary by way of the electrical input (or heat source fuel, such as propane or natural gas). The immersed electric element is very efficient at heat transfer to the wash such that it is acceptable to assume that all power is converted to heat and very little heat is lost to the surroundings (note- this is not entirely a good asumption because the still house will heat up during the run, especially with a fuel fired heat source).

And similarly, heat is transfered from the dehumidifier evaporator to the ambient air of the still house and that energy crosses the “system boundary” as well. Looking at the system, the power input equals the power output minus any losses due to inefficiency. A little energy is lost in the electrical control circuitry, although it can be nglected. And energy is lost with a fuel fired burner because of the method of heat transfer to the boiler, that is - not all of the fuel burned heats the boiler only as the ambient air is also heated.

A lot of discussion here which likely seems obvious to most and perhaps even redundant to the knowledge base. But let’s “dig deeper” hopefully to understand the limiting factors.

Heat transferred to the wash causes the liquid to change state and that energy is removed in the product condenser. Likewise, the heat is transferred to the water reservoir from the cooling water loop. Now, the addition of the modified dehumidifier pulls heat from the water reservoir via a closed loop refrigeration system. The closed loop uses a refrigerant to transfer the heat from the condenser (cold side) which is immersed in the water reservoir to the evaporator (hot side) which rejects heat to the ambient air and across the system boundary.

The closed loop refrigeration system must be able to transfer energy at the rate equal to or greater than the energy input into the boiler. Factors involved in this refrigeration cycle are the temperatures of the hot side and cold side heat exchangers as well as the mass flow rate of the refrigerant within the closed loop. Heat transfer (energy per unit time) is proportional the temperature differential and the flow rate times the heat transfer coefficient for the refrigerant. Typically, these type of consumer dehumidifiers do not have a large refrigerant flow rate because they don’t need to move a lot of heat, rather just a temperature difference which will allow condensation on the cold side coils and liberate that heat back to the warm, dry air.

So, while the system you’ve built LHCB, will chill the water reservoir to a cold temperature, I question whether it will keep up with the heat input into the boiler. At 2kW input, perhaps it might. Without more information of the dehumidifier design, it would be speculative at best.

But, using a secondary refrigeration system to maintain the water reservoir at, or near a controlled temperature would seem to be an innovative way to stabilize the condensing heat exchanger’s performance and help regulate the distillation processes. This type of system is quite effectively used in commercial breweries to maintain the fermentation temperatures in glycol chilled fermenters. But the key feature is the adequate design of the refrigeration cycle to transfer the heat from the recirculating coolant fluid.

So, I apologize to the wordy reply and the omission of long, boring differential equations associated with the thermodynamics involved. But perhaps I have given you a perspective of the mechanics involved with the closed loop system.
ss
That being said..... has anyone found a commercially available glycole chiller that can stand up to a 15-20 gallon flute run? I’ve been looking at the chillers available on the beer brewing sites but I’m not sure they’d last up against such intense thermal inputs. Even with supplemental cooling.
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