Any opinions on choice of antifreeze -- specifically, ethanol versus ethanol (a.k.a. Environol)? My geo contractor routinely uses methanol in preference to propylene glycol, but I get the feeling that he's never given ethanol serious consideration. WaterFurnace's first choice is ethanol (their Environol™ product is ethanol plus some blue dye and corrosion inhibitors). Methanol and ethanol appear to be very similar with respect to pumping pressure drops and Reynolds numbers, but I find WF's argument's in favor of ethanol rather appealing: - non-toxic -- essentially, pumping 50 proof vodka around the loop - slightly higher specific heat than methanol (very slightly) - less corrosive than methanol -- although neither is likely to be a problem Looby
WF gets a lot for their Environol. I can't remember the quote I got at the time, but it was an easy decision. I purchased Methanol from a local fuel/oil supplier for under $5/gal, it comes in 5 gal buckets. In Iowa, they restrict anything other than ethylene glycol if put under 20' in the ground. Methanol was fine for my horizontal loops.
Not a clue. Ethanol should cost no more than gasoline -- especially since there's currently a glut of corn ethanol on the market -- but WF can charge whatever the traffic will bear. I infer from rw1995's response that it's priced at over $5/gal. My system's total volume is only 70-80 gal, so it shouldn't need more than about 20 gal of pure ethanol (Environol 2000). So, no matter what they charge, it's a tiny fraction of the total price tag (to retrofit a 50 year old 2200 sq ft ranch from oil-fired HW/baseboard to geo/hot air). Mine's a 450 ft vertical loop in highly-fissured, water-saturated shale. The static water level is only 8' below the surface, and the driller estimated that it was blowing out 20-25 gpm. All the talk here about "short loops" has me a little worried, but I'm hoping that the subsurface water flow will be a big plus. Looby
Methanol I believe methanol has a lower viscosity and equivalent freeze protection at lower concentrations. The best heat transfer fluid is water itself, so you generally want to minimize the amount of antifreeze added. Combined with the ease of being able to source methanol locally made the decision for me. Keep in mind, methanol is highly flammable. You should never see it in concentrations in a ground loop that this would be an issue though (25%), but when you add it, try not to have a smoke in your mouth
Environol I just had the glycol in my system flushed this past friday and replaced with Environol. It was diluted at 30%. It seems to work better as our 4 ton Envision has not had any "water flow" issues in 4 days and we are keeping the house at 68 degrees. I was "short looped" by my installer to begin with and this was their answer to fix our heating problems. We'll see how well this solutuion holds as colder temps are expected in CT later on this week. I don't know the reason as to why is so expensive, this is just ethanol.
My system was around 100-110 gal. Methanol at 20% by mass will get you to a freeze protection to around 0 deg F. 10% by mass will protect down to 20 deg F. I dumped 20 gal into the system getting me into the 15-20 deg protection. My loop EWT is around 50 at this time. Keep in mind Methanol and Ethanol are very flammable, the flash point on Methanol is 54 deg F. This means at temps above 54, its giving off enough vapor to ignite with an source. I would dilute it down before adding to the flush cart just to be on the safe side. I went 50/50 with water to get the flash point up in the 75-80 deg F range before pumping.
True, but the difference is very minor -- pumping resistance for ethanol is about 2% higher when mixed for 15 F freeze protection (that's 20% V/V for methanol or 25% V/V for ethanol). Reynolds number for methanol is about 10% higher, but that's not a problem in my system -- either one will have an Re above 6000. Flash points are similar (methanol 54F / ethanol 62F) and ethanol actually has a specific heat slightly higher than water. The big differences are toxicity and availability. Undenatured ethanol is tightly regulated by US ATF, and you can't use generic "denatured alcohol" because there's no telling what's used as a denaturing agent. Looby
No, the specific heat of ethanol (pure) ranges from 0.51 at 0 F to 0.55 at 50 F. Units are BTU/lb-F (or cal/gram-C). That's slightly more than half of water's heat capacity.
Sorry, I shoulda been more precise. The heat capacity of 25% v/v ethanol in water is slightly higher than pure water. According to WF's Environol specs, it's about 1.05 BTU/lb-F. That's probably related to the fact that an ethanol/water mixture is "more compact" than either liquid in its pure form, i.e., 1.0 gal water + 1.0 gal ethanol = 1.9 gal total. ... 2 + 2 = 5 (for large values of 2) Looby
You are quite right. I didn't know that about ethanol/water mixtures. What I found was that mixtures containing 1 to 35 mol% ethanol do have a heat capacity higher than that of just water alone. In Perry's Chemical Engineer's Handbook, 8th edition, there is this table, giving specific heat vs. concentration and temperature. Specific heat Mole% 3 C 23 C 41 C 4.16 1.05 1.02 1.02 11.5 1.02 1.03 1.03 37.0 0.805 0.86 0.875 61.0 0.67 0.727 0.748 100.0 0.54 0.577 0.621
Update: Water Furnace's installation manual uses the same brine factor to calculate the heat extraction capacity of either ethanol or methanol -- and both have 3% less capacity than pure water: "Use 500 for pure water, 485 for methanol or Environol™." I had overlooked the fact that heat extraction capacity depends on mass flow rates rather than volumetric flow rates (i.e., pounds/hour rather than gallons/hour), and that pure water is heavier than either antifreeze mixture. So, for a given circ pump, the heat extraction performance of all three should be within 5% -- with the pecking order: water > methanol > ethanol Looby
