Need Advice In Setting Up A Chiller
I am not normally involved in HVAC matters. But I need to spec out a basic chiller system which I'll describe below; and I'd tremendously appreciate some inputs on this.
I work in a laboratory and have a new "furnace" (instrument that heats copper up to its melting point). It is a state of the art furnace and well insulated, and will be heating up to 1100 Deg C. in the heated part. The manufacturer of the furnace has an inlet and outlet hose fitting on the rear to run water through for any time it goes over 700 Deg C. The purpose of the water is to keep the electronic controls and so forth cooled down when it is running at its hot temperatures.
They say to run tap water through it at about 1/4 GPM (13.6 GPH, or 1 Liter per minute). That is all the specs they give. Since they say tap water, that means a continuously flow of ambient temp water then down a drain. I can't do that (for water conservation and cost reasons - use a lot of water), so I need to create a closed loop system that will adequately cool the water.
I am figuring on the flow rate they specify, and that water I send in will be around 75 Deg F, and I am presuming the water coming out will be less than boiling. So I am figuring about a 103 Deg F delta temp. So using the those numbers, I came up with around 20,000 BTU/Hr.
I don't need precision cooling, just something low cost that will work. But everything seems to be too big or too small or too expensive.
I'm thinking of getting a 55 Gallon plastic water barrel, a small water pump (like for RV's), filling with store bought distilled water (or maybe even filtered tap water). Running clean garden hoses from the barrel to the furnace.
But I'm still left with the chiller part. I believe with the set up above, the water will heat up fairly quickly. At 13.6 GPH, the water would be burning hot in about 4 hours.
So I'd REALLY appreciate any suggestions on a low cost way to cool the water. It doesn't need to be precise or 100% efficient. It needs to reasonably cool the water that was heated by the furnace and not ice up.
I'm even thinking of buying a drinking fountain remote water chiller. Or, does anyone know of any submersible cooler elements that could be put in the water barrel, or perhaps an inline cooler element to place either in the ambient inlet line, or the hot water outlet line on its way back to the barrel?
I would think that a small cooling tower would be a better option since you are only trying to achieve 75 degrees. RSD sells small cooling towers in small tonnage setups.
Thanks very much for that input. I've already sent them an email to inquire about pricing. I guess it will just depend on pricing. I had not at all thought of that alternative solution.
You could build a small cooling tower by converting a side discharge evaporative cooler (swamp cooler). Use a small external pump and connect the suction side to the bottom of the sump. The pump discharge would connect to the inlet side of your furnace and the outlet side of the furnace would connect to the spray tree on the evap cooler. The evap cooler and external pump would have to be sized properly for the GPM, total head and delta T to match your furnace thingy. If this catches on you could give Marley and BAC a run for their money.
Effort is the 1st step towards failure.
anychance of a ground loop system.
It's hard to stop a Trane. but I have made one helluva living keeping them going.
I'll have to read through that one a couple of times to process it; but I think it sounds like a very good idea. Just to keep the topic interesting, I found some air to liquid heat exchangers from a company called Brazetech. There is a 22 fin unit that I wonder if something like that with some fans attached could work. I'm an engineer, but a "metrology" engineer. So I have to dig to look up the various numbers each step of the way. I will take a detailed look at the post above and see what I might be able to do with that.
SOUTHERN MECH - I'm not sure what you mean by Ground Loop System. I use "ground loop" in the electrical sense; but not sure in the HVAC.
Air to Liquid heat exchanger.
I think you are on the right track with the air to liquid heat exchanger. For one it would be a closed loop system, and you would not have to worry as much about water treatment as with an open system. All you need is a heat exchanger, piping, expansion tank, pump, and some basic controls to cycle it on temperature.
I agree with this. I have seen oil coolers at the mines that look like big radiators with fans that cool the oil feeding the crusher.
Originally Posted by HVACFITTER562
I also think a closed loop heat exchanger would be your best option but it won't be able to drop the water temperature below ambient temperature. Do you really need the water to be cooled down to 75 deg F or would 5 deg above outside ambient temp be o/k?
An evaporative cooler will get the water temp below outside ambient temp, down to a few degrees above the dew point. Since it will be evaporating water you'll be constantly adding water with a water make up valve and you'll need chemicals.
My real bottom line goal is to protect the electronics in the furnace from running too hot. The manufacturer says to use tap water (which means they spec it to be "ambient" water running through the coolant loop on the furnace). So if I am running a closed loop, lets say (for discussion) with no cooling (i.e.: a 55 gallon drum of distilled water, a pump and lines). The water will go in ambient and come out hot. This will gradually continuously heat up my "chilling" water until it is hot water, and eventually steam. So I don't know that it MUST be brought exactly back down to ambient. I think what it needs to do is to stay ahead of the curve. I am thinking of getting one of those air to liquid (or is it liquid to air) heat exchangers. I found some with Brazetek.com that look sort of like car radiators. they are designed to run hot water through and heat the air around them. And they have pretty high BTU ratings, but for the opposite transfer direction. I don't know how to translate that into my direction. I want to run hot water through them, maybe design in some fans (probably a set of blower ("boxer") fans. But I am totally ignorant of how to determine the BTU's involved.
If any of you know any of the math for these heat exchangers, please let me know. If you go to Brazetek.com, click on the finned coil heat exchangers on the right side of the home page, I am looking at the 22 x 22 finned unit. Do you all think something like that (with some added boxer fans - how ever the max number of CFM that I can run through this thing) may be a viable solution? I'd like to figure out what kind of BTU's I might be working with. I THINK I can probably get away with a higher water flow rate. But, with higher flow rate, I transfer more BTU's out of the furnace, and have to increase my cooling BTU's on the water that m uch more.
Thanks so far for all of the great inputs. I'm already coming up with a variety of possible solutions. I kind of like the heat exchanger idea; I just need to figure out if the BTU's will add up. It is kind of like a similar principle to what is being accomplished with a cooling tower (pretty different format, though).
What you need is a "dry cooler". It is a complete package with coil, fans, etc. You can even get them with pump and storage tank. Here is one web site but there are many to choose from.
As far as btu rating, the manufacture of your furnace should be able to tell you how many BTU's their furnace puts out and the dry cooler rep can help you size up the dry cooler.
As far as higher flow rate transferring more BTU's, that's not necessarily true. A higher flow rate will give you a lower delta T and vica verca. Total btu/hr transfer is the product of flow rate (GPM) X delta T X 500. There is an optimal flow rate for best performance though.
Last edited by R123; 09-22-2011 at 11:26 AM.