Glycol reservoir size

[beervoid]

Dear scientists,

I've come across a glycol chiller thats rated at 4000btu. 3/8hp.
The glycol reservoir holds approx 13L / 3.43 gallons.
This seems a bit small as other glycol chillers on the market are roughly 38L / 10 gallons (ssbrewtech) but a 1hp 5000btu penguin is 3 gallons.
Wondering if this can be problematic and what would the main issues with this.
I'm planning to use it to control 4x1bbl jacketed tanks.
Should the reservoir ideally be bigger?
Input very much appreciated.

 

[Silver_Is_Money]

BTUH = GPM x Fahrenheit-Delta-T x Pounds Per Gallon of Circulating Solution x 60 min/Hr x Specific Heat Capacity relative to Water.

At 40% Propylene Glycol and 60% Water the Specific Heat ratio is 0.895/1 = 0.895

At 40% Propylene Glycol the density is 1.034, so the pounds per gallon = ~8.64

The method you must use to determine Delta-T is to have F. temperature gauges at the inlet and outlet sides of your combined barrels.

BTUH = BTU's per hour

Lets say your circulator (I.E., Pump) is measured (or throttled) to sustain 1 GPM flow across your system.

4,000 BTUH = 1 x Delta-T x 8.64 x 60 x 0.895

4,000 BTUH = 464 x Delta-T

Delta-T ~= 8.6 degrees F.

If (given these criteria) you measure a rise in the Propylene Glycol solution temperature of 8.6 degrees F. across your barrels, then you have verified that your chiller is indeed delivering 4,000 BTUH of cooling.

Edit: Corrected "drop" to read "rise" within the line directly above.

 

[Silver_Is_Money]

If it is delivering less than 4,000 BTUH, then throttle down the GPM's of circulating flow until it does equal 4000 BTUH.

Then throttle it back a bit more and you will be able to ascertain if it has a bit more than 4,000 BTUH cooling capacity. But OTOH, if no degree of GPM throttling results in 4,000 BTUH cooling, then the unit is not capable of delivering 4,000 BTUH of cooling.

 

[Silver_Is_Money]

A de-Facto standard HVAC equation for hot water heating system installers (systems such as a hot water boiler and cast iron radiators or hot water baseboards or in-floor radiant) is:

BTUH = GPM flow x Delta-T across the "users" x 500
(where users = radiators or baseboards, etc...)

But notice that Water weighs ~8.33 Lbs. per Gallon, and 8.33 Lbs./Gal x 60 minutes/hour = 499.8

They are merely simplifying the equation via condensing 2 constants. And they further simplify by ignoring that at different temperatures water exhibits differing Lbs./gallon, such that rather than being a constant, it is a variable.

 

[Silver_Is_Money]

The glycol reservoir is merely a buffering tank. It's purpose is to buffer the returning solution temperature so as to not wear out the componentry of the circulator.

Note that in any fully closed loop "system" a pump is never called a pump, but rather it is properly referred to as a circulator.