Tips on getting the most from your wort chiller.

I thought i would post this up to give some ideas on how to make your wort chiller more efficient. The biggest thing is i see people who buy one with the kitchen faucet type of adaptors. This is fine if your house is cool enough so you cold water is..well cold ! In the summer for some there house is in the 80s to high 70s. your water and pipes will be too !

Before you buy a wort chiller check your water temps. You may find water coming out of your hose faucet "witch comes from the ground pipes" will be colder than when it runs into your house. I was for me so i went the hose connector route.

One trick i tested was to put a ball valve on the end of my hose. something i stumbled on rather than knew. I added a ball valve so i could turn the water on at the chiller. this way if i had a leak or spray i was in control right there. What i found out is if you dial back the water flow. You give the water enough time to "soak" the heat before coming out of the chiller. Full blast did not cool as fast. Cooling 4g of wort on 15 min to 65deg.

It was interesting just how fast the wort temp dropped by doing this. Also i did stir the wort while cooling.

"What i found out is if you dial back the water flow. You give the water enough time to "soak" the heat before coming out of the chiller. Full blast did not cool as fast."

Sorry, I think this is false. I believe the opposite to be true.

BronxBrew said:

What i found out is if you dial back the water flow. You give the water enough time to "soak" the heat before coming out of the chiller. Full blast did not cool as fast.

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Have to agree with Pilgarlic. It's certainly not linear, but the higher the volume of water going through your chiller the faster it will chill. You reach a point of really poor efficiency, but it always will be faster the more water you pass through.

The best way to improve the effectiveness of an IC is to continuously stir.

Pilgarlic said:

"What i found out is if you dial back the water flow. You give the water enough time to "soak" the heat before coming out of the chiller. Full blast did not cool as fast."

Sorry, I think this is false. I believe the opposite to be true.

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I do this test every year in my class room. This may not work from a kitchen sink faucet because of displacement. But from a water hose to 3/8 copper tubing "which speeds up flow" it does work. if the water coming out at full blast is luke warm. Compared to dialing it back and its coming out hot. Where is the heat transfer coming out the most ? Im not talking about cutting it off down to a trickle. But enought that the water can absorb the heat and carry it away.

BronxBrew said:

the water coming out at full blast is luke warm. Compared to dialing it back and its coming out hot. Where is the heat transfer coming out the most ? Im not talking about cutting it off down to a trickle. But enought that the water can absorb the heat and carry it away.

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You are transferring heat to a much smaller amount of liquid. If you transfer the same amount of heat to 5G of water and 50G of water, the 5G of water will be much warmer. It doesn't mean that the 5G of water was more efficient in transferring the heat.

What you're not factoring in is the calories removed/volume of water through the chiller. If you could slow it to a drop, it would likely be scalding. But it's removing very little heat from the wort because it's a very low volume. The same holds true at every point in the change in the flow rate. The relationship does not reverse at higher rates of flow. The higher the rate of flow, the greater the temperature differential, the greater the heat exchange.

BronxBrew said:

I do this test every year in my class room.

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(edit: you're teaching this to kids?)


It's not the water that cools the wort. It's the surface area of the copper that the heat is transfered to. The goal is to keep the full length of copper tubing at as close to the tap water temperature as possible.

The temperature of the water coming out the end is only relevant with respect to the volume of that water. One degree of heat removed from your 5 gallon of wort and transferred into 10 ounces of water will produce hotter water than if it was transferred into 10 gallons of water. But it's still just one degree.

Edit to say:
Ideally you'd want the water coming out the end to be almost the same as going in. Efficient use of water, no. Effective, yes.

It doesn't even make common sense that you wouldn't want the water in the chiller to be as cold as possible, which is only possible by increasing water flow.

Simple example:

With 100% heat transfer and the chiller static (not flowing) and filled with 100 degree wort and 50 degree water, both liquids will normalize to 75 degrees over time.

NOW, speed up the water flow, and the wort is continuing to cool downwards, but the 50 degree water is constantly being replaced by more 50 degree water, so it IS NOT normalizing in the direction of the wort tem, so the static wort will chill to 50 degrees over time.

Slowing down the water flow certainly DOES NOT increase the cooling efficiency of the wort chiller.

Flip flop the variables, and you'll see that slowing down the WORT flow certainly DOES increase the cooling efficiency of the wort chiller!

BronxBrew said:

I do this test every year in my class room. This may not work from a kitchen sink faucet because of displacement. But from a water hose to 3/8 copper tubing "which speeds up flow" it does work. if the water coming out at full blast is luke warm. Compared to dialing it back and its coming out hot. Where is the heat transfer coming out the most ? Im not talking about cutting it off down to a trickle. But enought that the water can absorb the heat and carry it away.

Click to expand...

You are teaching this in a classroom?

One thing I believe has helped my cooling times a bit is modifying the coil of my chiller to fill my kettle. I staggered the coils, pulling the bottom one right, next one left, etc etc, so that there are fewer pockets in the wort that are far away from the copper. Made my chiller look pretty janky, but I think it trims off a few mins and thus saves some water

Cerevisaphile said:

You are teaching this in a classroom?

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It's really never too early to instill sound brewing sensibilities in our youths.

*Crazy scientific discussion ahead*

Alright, a little science from a power plant mechanic. Heat transfer in a condenser/cooler/wort chiller/etc. is boiled down to the basic following equation:

Q = mc(T2-T1)

Q=overall heat transfer in BTU/time

m= the mass flow rate of your cooling medium in vol/time
c= the specific heat transfer capability of your chilling surface (i.e. the copper surface of the wort chiller in this case)
T2= wort temp (higher temp substance)
T1= water temp (lower temp substance)

The only way to increase the heat transfer capability of your cooler (without structural modification) is to either:

INCREASE the mass flow rate of your cooling medium (not decrease) by turning the water flow up
or
INCREASE the difference in the two temperatures, by using a pre-chiller or some other way of getting colder water inside the chiller.

This can be proven with further explanation if required. Anyone that disputes this fact is temping the laws of thermodynamics, and I would like to hear an arguement against. Discuss.

WharfRat said:

One thing I believe has helped my cooling times a bit is modifying the coil of my chiller to fill my kettle. I staggered the coils, pulling the bottom one right, next one left, etc etc, so that there are fewer pockets in the wort that are far away from the copper. Made my chiller look pretty janky, but I think it trims off a few mins and thus saves some water

Click to expand...

Perfect example of "structural mods", but one of the best ways to increase your cooling efficiency with an IC by maximizing the surface/stratification area you are cooling.

macleod319 said:

*Crazy scientific discussion ahead*

Alright, a little science from a power plant mechanic. Heat transfer in a condenser/cooler/wort chiller/etc. is boiled down to the basic following equation:

Q = mc(T2-T1)

Q=overall heat transfer in BTU/time

m= the mass flow rate of your cooling medium in vol/time
c= the specific heat transfer capability of your chilling surface (i.e. the copper surface of the wort chiller in this case)
T2= wort temp (higher temp substance)
T1= water temp (lower temp substance)

The only way to increase the heat transfer capability of your cooler (without structural modification) is to either:

INCREASE the mass flow rate of your cooling medium (not decrease) by turning the water flow up
or
INCREASE the difference in the two temperatures, by using a pre-chiller or some other way of getting colder water inside the chiller.

This can be proven with further explanation if required. Anyone that disputes this fact is temping the laws of thermodynamics, and I would like to hear an arguement against. Discuss.

Click to expand...

Ok not a thermodynamics expert and my only training with hydraulics is running Fire Pumpers, that said my little brain can see how running the water slower could prove to be more efficient. I’m thinking that the issue could be at the reduction going into the chiller. When running water full blast through a ¾” garden hose into a ½” or even a 3/8" fitting, you’re going to run into a friction problem. Water is incompressible so as it tries to squeeze more volume through a smaller line you will end up losing overall flow, and the friction at the reduction could add heat to the liquid. Also if there are any air bubbles anywhere in the system this will add cavitation, further reducing flow, generating more heat and in the long run leading to damage of the soft copper fittings. I believe this calls for some testing. Try running full bore through the chiller without being in hot wort and check the temp of the outflow over say 5 min, then dialing the flow back and running the temp checks again.

SNIP...

dover157 said:

I believe this calls for some testing. Try running full bore through the chiller without being in hot wort and check the temp of the outflow over say 5 min, then dialing the flow back and running the temp checks again.

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What you're suggesting is running liquid through the wort chiller in air and checking the discharge temp, right? (supposedly) Demonstrating friction losses due to heat?

Macleod, that is exactly what I am thinking. My theory may be way off base but a test is the only way I can think of to prove or disprove it. If I had a chiller I would test it myself but that will have to wait. As for me when I get the setup I plan on running lower volume over longer time to save a little wetter, living in a desert and all it just seems like a wise choice.

My tip is to ditch the immersion and spend the extra bucks on a Plate Chiller

I just recently did this after using an Immersion for a for years...can't believe I didn't do this from the get go considering a plate chiller is only a few more dollars more

Ok, in a different world. When I use to work on race engines we would put a reducer plate instead of the thermostat. You didn't want a thermostat because a closed thermostat caused back pressure on the water pump causing reduced available horsepower. You didn't want to just have full open because the coolant would flow to fast to pick up the heat and to release the heat though the radiator.

Family's in town this week, but I'll get to this over the weekend. I'll do two tests, one dry, one in water. Anyone have anything specific they would like to see? I'll document in pics.

Wouldn't this test be as simple as two experiments: 1). Running water fast 2). Running water slowly; in two separate trials with the wort and water temperatures the same (different from one another but the same for each experiment). Then measure the time it takes to disburse heat from boiling to 70deg in both. Seems you could run the test twice or three times to be more scientific, but that would answer the question. Might save us some reading of scientific theorems. My money is still with the folks teaching brew science to a classroom of eager students. Enroll me please...

The science has long ago been settled. It supports the intuitive, that a faster flow rate removes heat faster by creating a greater differential. Details (with all appropriate formulas, if you prefer) in July/August issue of BYO Magazine, Science column by Chris Bible.

Before I waste my time then, is there any way to show those of us w/out a hard copy? Thanks - Jeremey

To repeat all the sane people here...

macleod319 said:

Q = mc(T2-T1)

Q=overall heat transfer in BTU/time

m= the mass flow rate of your cooling medium in vol/time
c= the specific heat transfer capability of your chilling surface (i.e. the copper surface of the wort chiller in this case)
T2= wort temp (higher temp substance)
T1= water temp (lower temp substance)

The only way to increase the heat transfer capability of your cooler (without structural modification) is to either:

INCREASE the mass flow rate of your cooling medium (not decrease) by turning the water flow up
or
INCREASE the difference in the two temperatures, by using a pre-chiller or some other way of getting colder water inside the chiller.

Click to expand...

Perfect.

macleod319 said:

*Crazy scientific discussion ahead*

Alright, a little science from a power plant mechanic. Heat transfer in a condenser/cooler/wort chiller/etc. is boiled down to the basic following equation:

Q = mc(T2-T1)

Q=overall heat transfer in BTU/time

m= the mass flow rate of your cooling medium in vol/time
c= the specific heat transfer capability of your chilling surface (i.e. the copper surface of the wort chiller in this case)
T2= wort temp (higher temp substance)
T1= water temp (lower temp substance)

The only way to increase the heat transfer capability of your cooler (without structural modification) is to either:

INCREASE the mass flow rate of your cooling medium (not decrease) by turning the water flow up
or
INCREASE the difference in the two temperatures, by using a pre-chiller or some other way of getting colder water inside the chiller.

This can be proven with further explanation if required. Anyone that disputes this fact is temping the laws of thermodynamics, and I would like to hear an arguement against. Discuss.

Click to expand...

You're absolutely right that increasing the flow rate will increase heat transfer. However, your use of that particular equation is absolutely wrong. This equation can be used to measure the heat transfer of the water only.

The proper use of the equation's variable is this:

Q = heat transfer rate
m = mass flow rate of water
c = specific heat capacity of the water
T2 = the leaving temperature of the water
T1 = the entering temperature of the water

You can calculate your heat transfer rate if you know all of your variables. In an immersion chiller scenario, increasing mass flow rate will tend to decrease T2. Decreasing mass flow rate will tend to increase T2. However, knowing that still doesn't tell you what conditions will maximize your heat transfer rate. The best way to determine your ideal conditions is by experiment.

Obviously, your calculated heat transfer rate of the water (Q from above) will also be the amount of heat removed from the wort by the water. Again though, the only way to properly calculate the conditions at which the heat transfer rate will be highest is by experiment (or by modeling with FEA/CFD software).

The being said, I intrinsically know that your heat transfer will be at its maximum when the flow rate is at its maximum. For a moment ignoring any knowledge of the water in the chiller, the way in which you'd calculate heat transfer from the chiller to the wort is very complicated (and nearly impossible by hand). But, I can tell you that the heat transfer rate will largely be proportional to two things:

• The surface area of the chiller
• The temperature difference between the chiller and the wort

Since the temperature of the chiller is a gradient throughout the length of the chiller, any method of calculation involves calculus (and a lot of assumptions and Reynolds numbers and Prandtl numbers and blah blah blah). But think of it this way: you want a maximum surface area of the chiller to be as cool as possible. A lower flow rate will cause the latter half of the chiller to become warmer, thereby decreasing the heat transfer from the chiller to the wort. A higher flow rate will keep a larger portion of the chiller at a lower temperature, thereby increasing heat transfer from the chiller to the wort.

Also, efficiency in this context is very wishy-washy term. If your goal of "efficiency" is to decrease water consumption, then there will be an ideal flow rate that balances heat transfer and flow rate. On the other hand, if your goal of "efficiency" is to decrease cooling time, then you want the flow rate to be the maximum possible.

(Edited for clarity)

Also, sorry if that came across as condescending in any way.

When I was in grad school, I would often substitute for a professor and teach a Heat Transfer course for mechanical engineering students (it was my specialty, hence my passion for it). I can tell you that the equation above (there's a name for it but it escapes me) is very often misapplied even by 3rd-and-4th year engineering students. It's extremely useful but only applies to very specific applications.

Since we're so used to it, the concept of an immersion chiller in hot wort seems really simple. But trying to characterize with equations is extremely complicated. First, everything is changing...

• The temperature of the water increases as it goes through the length of the chiller
• The temperature of the wort changes by height due to stratification
• Of course the temperature of both the wort and water change over time as you remove heat

On top of that, we're assuming that the liquid is stagnant when in reality most of either stir or full-on whirlpool! On top of that, the brewpot is transferring heat to/from the ambient air. And so on and so on.

if high flow always cools better why do we need flow restrictors in the thermostat housing on our circle track car and drag boat? wide open flow they over heat, 50% flow restriction and they don't. the water absorbing heat isn't a myth

amandabab said:

if high flow always cools better why do we need flow restrictors in the thermostat housing on our circle track car and drag boat? wide open flow they over heat, 50% flow restriction and they don't. the water absorbing heat isn't a myth

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Because the system and end goal is different in those cases (and more complicated). You've essentially got two different heat exchangers - your radiator and your engine. The engine is actively generating heat that must be removed and the cylinder walls need to maintain a certain temperature. The radiator in your car uses air to transfer heat from the recirculating water. The water has to get down to a certain temperature in order to effectively cool the engine. If you run it through your radiator too quickly you'll end up with a leaving water temperature that is too high to do that. There are two big differences here: You're recirculating the cooling water in your car and your engine is actively generating heat.

A radiator needs a certain lag time of the water to transfer enough heat. It's much more comparable to a plate or counterflow chiller than an immersion chiller.

Beyond all that, the main issue with overheating is not the heat transfer rate but rather the fact that the recirculating water is reaching its boiling point!

JeffersonJ said:

Because the system and end goal is different in those cases (and more complicated). You've essentially got two different heat exchangers - your radiator and your engine. The engine is actively generating heat that must be removed and the cylinder walls need to maintain a certain temperature. The radiator in your car uses air to reduce the transfer heat from the recirculating water. The water has to get down to a certain temperature in order to effectively cool the engine. If you run it through your radiator too quickly you'll end up with a leaving water temperature that is too high to do that. There are two big differences here: You're recirculating the cooling water in your car and your engine is actively generating heat.

A radiator needs a certain lag time of the water to transfer enough heat. It's much more comparable to a plate chiller than an immersion chiller.

Beyond all that, the main issue with overheating is not the heat transfer rate but rather the fact that the recirculating water is reaching its boiling point!

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I'll give you the radiator in the circle track car. the boat is 100% draw and dump.

amandabab said:

I'll give you the radiator in the circle track car. the boat is 100% draw and dump.

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I'm not entirely sure how most boat engines reject heat. Do they actually run seawater (or freshwater) through/around the engine? Or is there a recirculating loop and then seawater cools that loop with a heat exchanger?

If I had to guess I would say it's the latter, but I could be wrong. In that case it's essentially the same situation as a car radiator.

amandabab said:

if high flow always cools better why do we need flow restrictors in the thermostat housing on our circle track car and drag boat? wide open flow they over heat, 50% flow restriction and they don't. the water absorbing heat isn't a myth

Click to expand...

Internal combustion engines operate at max efficiency in a certain temperature range. A thermostat isn't put into a car to increase the heat transfer efficiency, its actually the opposite. It only cools when the engine is above its optimum temperature range, it then shuts itself off when the engine is too cool. The same could be said for the restrictor in your water passage. Although I have never heard of them I would assume that it has been calibrated to restrict the cooling efficiency to keep the engine temps up.

BronxBrew said:

I do this test every year in my class room.

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I hope you don't also teach your students that you can make faster ice cubes if you start with hot water.

[that myth is my biggest pet peeve ever.]

Thanks JeffersonJ, I knew I wasn't using that example (specific heat transfer) 100% correctly, but it was the only one my brain could come up with at the time to possibly demonstrate the point I was trying to make.

I am trying to remember the practical calc's we used when comparing overall heat transfer in condensers (when you know the surface area, surface area, and flow characetristics, along with the enthalpy of the steam and cooling water). That would show you *without structural mods* (like I said in my first post) that using an immersion chiller with a fixed volume blah blah blah.

I'm going to go beat another dead horse. Yeast starters, anyone?