Calculating btu/energy load of simultaneous fermentations.

[MisterEd]

I am looking for information regarding btus/heat energy generated during a wine fermentation. I have accessed one source and it indicated between 150 and 250 btus per gallon or 25 btus per pound of grapes.

I need to size an air conditioner for a glycol bath that will need to handle as many as three simultaneous fermentations. The fermentations will each be at a different stage depending on actual time of harvest. Volume-wise two fermentations will be in the area of 25 gallons each (white) and the third could appproach 40 gallons (red on skins).

Should I plan on determining an average daily btu rate for each ferment and adding together for a total btu demand? Going with my above data using the high side that would be 22,500 total btus divided by, say, two weeks avg. ferment duration would be around 1600 daily btus generated.

If my approach is not flawed, would a 5000 btu air conditioner seem more than adequate to maintain the whites at 60 dgf and the red at 75? My experience with cold water bath immersion has shown periods during white fermentation, with fairly constant ferment rates, where suddenly fermentation rapidly increases despite attempts to restrain it.

My new system would use internal coils directly in the must as opposed to a water bath.

Any input appreciated,

Mister Ed

 

[sour_grapes]

I'll pay some attention to this later, but please note that one must distinguish between BTUs, and BTU/hour. The first is an amount of energy, the second is a rate of energy change, i.e., a power. I am suspicious that your source of 150-250 BTUs in a gallon is, indeed an energy (BTU), but air conditioners are rated in BTU/hr. Can you share the source of the 150-250 number?

 

[stickman]

The heat generated is around 13kcal for every 100g of sugar fermented, so I get around 468 btu/gal based on 24 brix fermenting completely. For 90 gallons of estimated finished wine there will be released approximately 42,000 BTU's total, but for peak load I would estimate that possibly half of the total heat could be released in 24hrs, therefore rounding up I'd say plan for 1,000 BTU's/hr. The 5,000 BTU/hr AC unit is capable in theory, but additional details need to be determined such as glycol flow rate and fermentation coil surface area.

Often just controlling the room air temperature is enough depending on batch size. When I get up to around 500 lbs of grapes in one vat, and ambient temperature in the garage is in the 80's, that's when some temperature control is needed. In the winter I can lower the temperature of the room to somewhere in the 50's and not need to use other controls.

 

[MisterEd]

I'll pay some attention to this later, but please note that one must distinguish between BTUs, and BTU/hour. The first is an amount of energy, the second is a rate of energy change, i.e., a power. I am suspicious that your source of 150-250 BTUs in a gallon is, indeed an energy (BTU), but air conditioners are rated in BTU/hr. Can you share the source of the 150-250 number?

Foods and Food Production Encyclopedia
By Douglas M. Considine
I was able to glean this from:

https://books.google.com/books?id=x...r pound must during wine fermentation&f=false

 

[MisterEd]

The heat generated is around 13kcal for every 100g of sugar fermented, so I get around 468 btu/gal based on 24 brix fermenting completely. For 90 gallons of estimated finished wine there will be released approximately 42,000 BTU's total, but for peak load I would estimate that possibly half of the total heat could be released in 24hrs, therefore rounding up I'd say plan for 1,000 BTU's/hr. The 5,000 BTU/hr AC unit is capable in theory, but additional details need to be determined such as glycol flow rate and fermentation coil surface area.

Often just controlling the room air temperature is enough depending on batch size. When I get up to around 500 lbs of grapes in one vat, and ambient temperature in the garage is in the 80's, that's when some temperature control is needed. In the winter I can lower the temperature of the room to somewhere in the 50's and not need to use other controls.

My issue is we had an above average temperature September when I started to ferment the nearly 500 lbs of Chambourcin in my detached garage. Even with frequent punch downs and copious air flow across the fermentation barrel the must got too warm for my liking.

I have not sized the stainless coils or circulation pump yet. Is there an optimal flow rate for glycol to achieve max heat transfer?

 

[stickman]

Generally higher flow rates give better heat transfer rates, but realistically a few gallons per minute per vessel is all that is needed. What kind of vessel are you using for fermentation? Most people just freeze jugs of water and submerge in the must during a punch down. Unless your handy and have access to tools and materials, putting together a system can get expensive. Morewine has information that can help you understand some of the considerations and equipment involved.
https://morewinemaking.com/category/temperature-control-1.html

 

[MisterEd]

Generally higher flow rates give better heat transfer rates, but realistically a few gallons per minute per vessel is all that is needed. What kind of vessel are you using for fermentation? Most people just freeze jugs of water and submerge in the must during a punch down. Unless your handy and have access to tools and materials, putting together a system can get expensive. Morewine has information that can help you understand some of the considerations and equipment involved.
https://morewinemaking.com/category/temperature-control-1.html

When purchasing a circ pump is it important to determine if the pump seals or other parts are compatible with glycol solutions?

I am using HDPE plastic barrels for ferment vessels.

I have used water bath w/ ice jugs on my whites with limited success. Never was able to keep it near or at 60 dgf. And then the yeast would sometimes explode in production and the temp would elevate and stay there despite my best efforts to keep the water bath sufficiently cold. My white batches would be 15 - 20 gallons.

I am fairly handy as I have built my home and my support buildings myself and have an electrical/electronics background. So I feel up to the challenge but need to get up to speed on glycol and flow rates. I was reading the more concentrated the glycol solution the less efficient it becomes at heat absorption.

Is an internal coil placed directly in a red wine must going to draw off heat as effectively as in a white juice must? I have my doubts. I do not want to go to a water bath on my reds (400 - 500 pounds) as I would need a container large enough to stick a 55 gallon barrel inside it and then procure a water bath coil big enough to keep the must temp under control. Splitting it up into 2 separate ferments might make more practrical sense.

The whole reason for all this is I want to get away from ice jugs and "up my game" to give me more precise control over my ferment temps. But the devil is in the details. Lol