Designing Glycol Chiller System for Microbewery

A friend of mine owns a microbrewery, and is frustrated with his chiller system. It's a compact unit with a complete refrigeration system, a condenser and evaporator / heat exchanger, a tank and a circulating pump. It's noisy and generates a lot of heat, and runs steadily controlling temps on his fermenters and chilling wort. The problem is that it has almost no storage capacity, nor does it take advantage of cold outside air. Most of the year outdoor temps here drop near or below freezing. A condenser in cold air is far more efficient than one in room temp, thus using far less energy. My proposed system uses a small insulated room outside the main brewery, set up to draw in outside air when it's cold outside, and the chiller unit is essentially outside under a roof in a shaded area. The system will contain a large storage tank (200 gallon), and an ordinary household well pressure tank. A submersible pump will sit in the 200 gallon tank, and maintain 60 pounds or so pressure in the pressure tank and lines, which will be insulated. A pressure switch.... an ordinary well type pressure switch will cycle the submersible pump, a $300 well submersible pump from Home Depot. A thermostat in the large storage tank will operate the chiller. Two main lines, a pressure line from the pressure tank, carrying cold glycol, and a return line back to the storage tank, carrying warm glycol. Each fermenter will have a PID controller and thermocouple operating a solenoid valve to feed it glycol as needed. As an afterthought, a return loop from the pressure to the return should recycle the glycol to the storage tank to keep the glycol in the pressure tank and lines cold when none is being used. This would run from a PID controller sensing line temp.

 

Hi there,

You might want to consider the first in, last out configuration as recommended by the ProRefrigeration guys.

I set up my extreme garage brewery with a cheaper model from rapidswholesale.com factory modified with 1/2" inlet/outlets, 3/4hp and 110V/20A, 6100 BTU unit. I am able to chill 2 1bbl ferm and 2 2bbl ferm vessels using the first-in, last-out method easily. My chiller doesn't break a sweat and allows me to use the remaining BTUs to do a second stage heat exchange when I finish brewing a new batch. Mind you, this set up is in Mesa, AZ where my garage easily hits temperatures of 110F ambient. I can still crash a 2bbl tank from 68 to 35F in less than 5 hours with this glycol system.

Basically my heat exchange has two stages for a single pass from 210F down to 68F. First stage uses city water for 210F to 90F the the second using 28F glycol that drops it from 90 to 65F easily.

Hope this helps.

 

This setup is for jacketed 15 barrel fermenters. I'm not sure what first in last out means in this case. The idea here is that cold glycol runs in pipes just like water in your home, with a constant pressure. The valves on each fermenter open as needed to maintain temp in that fermenter, allowing the glycol to pass through it's jacket and out the drain line back to the storage tank which is maintained at a specific temperature by the separate chiller loop. It's intended to make efficient use of the existing chiller, which is located where the condenser is outdoors where the temps often drop far below freezing . By having the condenser outdoors, the energy costs are greatly reduced. Optimally the evaporator would be submerged in the storage tank, and the evaporator would be outdoors.

I'd love to see the details of your system.........I'm having trouble visualizing it.

H.W.

 

The folks at Prochiller.com have a helpful guide to installing their chillers. (pdf file linked below)


Here is how they describe first in - last out piping design:

www.prochiller.com/files/AllAboutGlycol.pdf

 

Reading through the original post again, I'm not sure what you're hoping to gain from that much storage capacity. Some storage capacity will help to reduce rapid cycling of the refrigeration unit. But it will also require a larger storage vessel with more surface area to insulate against heat gain.

For comparison, the ChilStar system from Pro Refrigeration that I've worked on has a reservoir capacity of 20 gallons.


Make sure you adjust to a high enough glycol percentage to protect against freezing. With equipment moving outdoors you have a new variable to contend with - ambient temp.

 

The large capacity is intended to take advantage of ambient temperature. What's not shown or mentioned is an outdoor radiator which captures nighttime temps which during most of the year are easily cold enough to do the job by itself.

H.W.

 

Gotcha, now I understand where you're going with the 200 gallon tank. I'm not sure it will help though, can you describe what you're thinking for set points and what the ambient temps are?

 

Make sure the chiller is intended for use outdoors and can handle low ambient temps or you end up killing the compressor if it doesn't have a crankcase heater or head pressure controls. 60 psi might be too high for the fermenter jackets as most are designed to handle 15 psi working pressure. Pid's are overkill and simple on/off stats like a johnson A419 are better suited for fermenter control to keep your cycle count reasonable throughout the day. The submersible well pump isn't really intended for continuous operation and is normally an external pump that is made to run the glycol around the loop continuously. Times of no demand from the fermenters is handled by a bypass valve between supply and return mains that keeps the circ pump from deadheading due to no flow through the fermenters.

 

All those issues are addressed. First of all the chiller will have a thermostatic crankcase heater.......... that's a no brainer. Personally I would like to separate things and have the condensor outdoors and the unit indoors.

60 PSI is not an issue....... that's line pressure, not jacket pressure. There is an inlet and an outlet, There is no way to build pressure in the fermenter jacket which has an outlet to a drain line with NO Pressure. It's like feeding water into a garden hose that has an open end. The supply may be 60 psi, but the pressure in the hose is virtually nil.......just enough to push the water through.

Note that the submersible pump is feeding a pressure tank so it can cycle. However I know from experience that a submersible will run for many years without cycling. They are perfectly capable of long term continuous operation.

H.W.

 

Maybe so, but having direct personal experience with the chineese junk from HD/Lowes for well pumps, I don't think you're going to have much luck with longevity. Also, submersible pumps are designed to run at a certain depth/head pressure.

I don't see a need for a pressure storage tank, and when the valves are open the pressure will likely drop off to zero/negligible causing the pump to run non-stop. It's not going to cycle. You don't list the pipe diameters or flow requirements, but most deep well submersible pumps are designed to move anywhere from 5-10 GPM, which isn't going to be enough flow through the jackets to carry the BTUs you need to move.

Unless you are planning a radiator/pump/fan assembly to circulate and cool the storage tank, that mass of cooling liquid isn't going to change temperature much. 200 gallons of coolant is a large mass that retains an incredible amount of heat. Just relying on radiant/convection cooling through the walls of the tank isn't going to work.