kzimmer0817 said:
I apologize ahead of time for shooting from the hip, but I read this thread because I was interested in trying to work out something to do with a glycol chiller quite a while back. I ended up purchasing a small chest freezer instead. Nevertheless, Chugmaster's original question interests me. I also have a question about Kyle93's calculations based upon the specs for a particular pump.
Prior to finally giving in to purchasing the chest freezer and Ranco controller, I was interested in someone's suggestion to place the carboys into a tub filled with cold glycol - that the direct contact of the glycol on the carboy wall (or even water) would be much more efficient than trying to cool the ambient air inside a fermentation chamber.
1. It would be interesting if one could engineer a DIY jacket that would seal against the outside wall of Chugmaster's tank such that the outside wall of the tank provided one wall of the jacket. There would be connections for in/out of the glycol. I would think that the resistance thru this jacket would be much less than that thru 100 ft of 1/4" copper tubing.
2. Regarding the "head" rating on the pump, something just occured to me: if a pump has a head of 10 ft, doesn't that mean that the pump is capable of pumping a column of water up 10 ft and dumping it into a bowl? But . . . if that tube that contains that column of water simply goes up "almost" 10 ft, then this closed system tubing goes back down to the pump, doesn't this change things? Harkening back to college physics days: if you loop a rope thru an overhead pulley and down to a 100 lb load, you have to provide a 100 lb pull on the rope to raise the load (assuming a frictionless system). If you hang a 100 lb weight on the other end of the rope, it shouldn't take any force at all to move the weights up and down. Of course, in the real world, you have to apply some force to overcome the friction in the system.
IOW, if your entire tubing circuit is closed (both ends of the tubing are submersed well into the open glycol bath in the freezer where it's being chilled) a pump rated at 10 head should be able to pump to a much higher level than its rating. I guess the siphoning effect of the downhill leg of the circuit takes the load off the pump.
Am I understanding this correctly, or is there something I'm missing?
3. Another idea: instead of circulating thru 100 ft of 1/4" tubing, would it be more efficient to have a much larger tube go from the pump to the tank where it serves as a manifold to split into 4 or 5 parallel coils of 25 ft each which then rejoin into the larger tube to return to wherever the glycol is being chilled then back to the pump? The electrical comparison might be comparing resisters connected in parallel instead of in series.
I apologize for jumping onto this thread, but I wondered if any of this would help the OP with his solution.
Thanks,
Keith
Keith,
I think this is a great thread with some truly great questions. Here is my opinion on the items you brought up.
1. Yes you are correct if you were to use 1/4". Ideally 3/8 copper tubing or larger would be best to compensate for the pressure drop. I am not sure I understand what you are saying with the jacket idea though. Right now my setup would be similar to the OP's. Except mine is stainless and their's is plastic. If you were to take a slice of my wall it would look like this. Stainless steel, 1/4" copper tubing, 1.5" thick Armaflex insulation.
2. Found this as a great example from another website.
Head - Defined
Head is a measure of fluid energy. It is used to describe the Specific Energy of a pump.
Specific Energy is defined as energy per unit of mass. For example, if we lift up a one-pound object by three feet, we say we have three foot-pounds of energy. It doesn’t matter whether it's a pound of lead or a pound of feathers; we still have 3 foot-pounds.
This is why head doesn’t change with the type of liquid being pumped. Whether pumping water, alcohol, or oil, a pump’s head rating is unaffected.
Sometimes Head is described as the resistance that a pump must overcome. While this may describe what’s going on while pumping, it is not technically correct.
Head vs Pressure
Pressure is not Head. Pressure is a force applied to an Area. For example, PSI refers to Pounds per Square Inch. The “Square Inch” part is the big difference between Head and Pressure. With Head, there is no Area in the calculation.
Types of Head
There are four types of head; Static Head, Friction Head, Pressure Head, and Velocity Head.
Static Head – Applies only to open systems, such as a waterfall in a manmade pond. It is the difference, in feet, between two water levels. So if the pump is at the bottom of our pond with a waterfall, then the Static Head is measured from the top of the pond water to the top of the waterfall (yes, the TOP of the pond water, not the bottom where the pump is sitting.) A pump's head rating is usually the maximum Static Head the pump can overcome.
In What we are dealing with to move chilled water, the Static Head should be zero assuming you are not using a bucket and the loop is completely a true closed loop.
Friction Head – Also called Pressure Drop. It is the resistance to flow. When a pump pumps liquid through a component, that component creates a resistance to the flow of liquid. Typical components are tubing, radiators, fittings, and waterblocks. This resistance to flow is usually expressed in feet of head.
Ideally with the 100' of 1/4" we are talking about this is where most of the pressure comes into play.
Pressure Head – Refers to the different pressure levels between two vessels. For example, if a pump must pump rainwater (collected in an open tank) to a second tank that is closed and slightly pressurized, then in addition to Static and Friction Head, the pump must also overcome the pressure being exerted on the water in the tank. Exist in open systems only.
This would apply if you had a freezer with a bucket of glycol (slightly pressurized) ie the top is shut and the pump is moving a fluid.
Velocity Head – Refers to the energy required to accelerate the fluid. Exist in open systems only.
This information was edited a bit to apply it to our application. But was found here :
http://www.overclockers.com/forums/showthread.php?t=488081
If you have a system that is closed you are correct that the pump will not have to work as hard. Theoretically, the pump is only moving the fluid and head could be negated to an extent..obviously we are not in a Perfect world.
3. This could also work as long as you can over come the pressure. Theoretically, the same pressure is present whether you have a manifold or a single straight system when you one back to the suction side of the pump. Just like an electrical the fluid will take the least resistance path. By adding a manifold and more fittings, technically we are increasing more pressure for the pump to overcome based on fluid dynamics. I am not saying it wouldn't be better I am merely saying that more calculations would have to be calculated to confirm the correct size for the pump.
Kyle
