Jennifer,
I want to be sure you have looked carefully at John's calculations for time required to heat the milk using a 1750W heating unit (e.g., a 120v band heater):
(21,600 BTU (required) / 5,972 BTU/hr) x .50 = 7.2 hr to heat 26 gal. 100 deg.Keep in mind that there is no way around the physics here -- no matter what you do, it takes a certain amount of BTU's to heat a certain quantity of milk in a certain span of time. You may not need 100 degrees of temperature rise, depending on whether you are coming straight from the goat ... but even if you only need 50 degrees of temperature rise, you are pushing your 4 hour window.
Separating the 26 gallons into, say, three 8.6 gallon batches is not the answer. That will let you heat each batch more quickly ... but by the time you have heated all three, one after another, plus the time to hold each batch at heat for 30 minutes, and the time to transfer each batch to and from the heating pot, you have actually taken
more time that you would heating it all at once. Likewise, heating the milk as it flows through a tube is not the answer -- once again, you can heat the quart or so of milk that is in the tube relatively quickly ... but by the time you have heated all 26 gallons, you are back to your BTU equation.
Of course, if you heat each batch
simultaneously with its
own band heater--i.e., using three band heaters at the same time--you can speed things up enough to meet your target. But now you are facing a different issue of physics, or at least of conventional residential wiring: you
cannot plug all three band heaters into the same 120v circuit without blowing a fuse. Most household 120v circuits are wired for 15 amps max, though it is possible to have one wired for 20 amps. 120v X 15 amps = 1800W. Thus, each band heater will use the entire amperage for a given circuit--not for a given
plug or
outlet, but for every plug/outlet on the entire circuit. It is highly unlikely that your garage has three separate circuits wired to three separate outlets; if you have as many as three outlets in the garage, they are almost certainly all wired to the same circuit. In fact, it is quite possible that the outlet(s) in your garage are part of the same circuit as the lights in the garage, and/or any outside outlets (got any Christmas lights plugged in?), or so on. In other words, you may not have enough amperage available to run even one band heater at 1750W on the existing garage outlet(s).
All of this assumes that your garage is wired up conventionally--that no one has, for example, wired up a 240v circuit in your garage. If that is the case, or if you are in a position to have one wired up, the equation changes drastically, though you will still need to check the amperage available. If only a 20 amp circuit, you'd have 3600W available ... but then again, 240v circuits can be wired for as much as 50 amps, which would give you 12,000W to play with.
I hear the concern for not applying so much heat that you scorch the milk ... but the fact remains that you
have to apply a certain amount of heat to raise the temperature of that much liquid in a certain span of time. So, apply less heat to multiple smaller batches, or apply more heat to one big batch, but spread it over a greater surface area and/or keep the milk moving so that it doesn't scorch. I don't believe there is any other way around this!
