Closed loop heat exchanger

[abc1234abc]

I'm trying to design a way to keep a fluid near a given temp. by using a closed system. Not too particular about fluid in loop, could be water or propylene glycol, etc. I just need to use the loop to get the test fluid to a certain temp and keep the flow around 65 psi and 10 gpm so that the test equip functions. I havent had much experience with equipment/design so wondering what you would all recommend for how to do this, such as a tank for the water, fittings, pumps, etc. THANK YOU!!

 

[MintJulep]

You need some equipment and controls.

Please provide some specifics about what you need to do. What is the fluid? What is the fluid's temperature entering the temperatue contolling equipment (how many of you assumed that Drusilla wants to heat the fluid?). What temperature does the fluid need to be at the exit of the controlling equipment? Is the fluid highly acidid, basic or otherwise nasty such that special materials are needed?

Does the fluid change phase at the temperatures in question?

What is avaialble in your facility to add or subtract energy from the fluid stream? Steam? Hot water? Chilled Water? Gas, oil, electricity, liquid nitrogen???

 

[abc1234abc]

sorry, i told you i was new to this. the fluid varies depending on the test. actually i'm supposed to come up with something that can hook up to two devices. one already has a heat exchanger on it. i'm not sure about the other one yet, so i suppose i will just worry about one for now. i just need to be able to hook into the existing heat exchanger (i think) and find a way to recirculate the water/propylene glycol throughout the heat exchanger in a closed loop and it needs to flow at around 10 gpm and 65 psi so i guess i need a pump and a way to close up the system and some controls i think. this is all as an alternative to hooking it up to a hose and then dumping down the drain. then i think for the 2nd system it hooks up to i may need a heat exchanger or something but like i said small steps for now. i think the water needs to be different temps depending on the test and that the heat exchanger/test equip takes care of that but if that doesnt sound right let me know. i think i can get whatever i need for energy supply but for sure we have electricity. the other liquid that im heating also changes but i think theyre mostly fuels - i plan on looking into all of this further but didnt even know what i needed to know!! thanks for putting up with me and i hope this helps to clarify.

 

[MintJulep]

Drusilla,

Please do not take this the wrong way. We want to help.

Step 1 to solving any problem is actually understanding the problem. Right now I don't, and it sounds like you don't either.

So, like you said, small steps. Lets see if we can help formulate the problem:

You have a machine that performs some sort of test on a fluid stream. The machine most likely has a place for the fluid under test to go in, and a place for the fluid under test to exit. Right?

What other connections are on the machine?

Does the instruction manual for the machine give any guidence about what conditions (flow rate, pressure, temperaure) must exist for the fluid under test at the entrance to the machine?

If there are other connections to the machine, does the instruction manual give any guidence to what, and at what conditions the things that connect to the machine must be held to?

Your second post mentions two devices. The first device is a machine that performs some sort of test on a fluid stream. What is the second device?

Your second post implies that something goes down the drain currently. Is the thing that is going down the drain the fluid under test or some other fluid? Does it come out of the machine that performs some sort of test? If so, where does it come from before it enters the machine?

I'm sorry that I can't come up with any other questions from the information provided so far.

 

[abc1234abc]

No, I completely understand that I'm not the best at describing my situation. I truly am very grateful for your assistance and hope that eventually we can come up with something.

Both machines have a fluid, typically a fuel, that flows through the machine at a particular tempurature. Each machine has a different set of conditions. I am waiting for a couple of responses in regards to exactly what type of testing is performed and at what particular conditions. For the first machine, I know the manual states that the fluid (fuel) must be supplied at at least 10 gpm and 65 psi or near that value for the machine to function. The fluid generally runs through some sort of engine component, depending on the test and needs to be kept at or sometimes above a certain temperature. Hopefully tomorrow I will have the answer to that portion. The second machine doesn't have a manual so I am waiting for a response on its requirements. So basically we could stick to the first machine for now.

<<The machine most likely has a place for the fluid under test to go in, and a place for the fluid under test to exit. Right?>> The machine keeps the fuel recirculating through the machine during the test so that part is a closed loop that the heat exchanger keeps at the proper temp.

The problem lies in the heat exchanger loop. They've been feeding it tap water through the intake but it's not a closed loop right now, which is what they want. The water just comes out the exit and is sent to disposal. They're trying to not waste so much by making a system that reuses the water (or another fluid if that would work better) and keeps the water in a tank when not used by the machine. It just needs to be able to be hooked up to both machines eventually, but we can always change the connections on the second machine since it might require several modifications.

Is this making more sense yet?

Thanks again.

 

[MintJulep]

Ok, a few more questions?

Will machine 1 only work if it is connected to machine 2, or do machines 1 and 2 do completely independant things?

If you are feeding machine 1 a fluid at a rate of 10 gpm and nothing comes out, it would seem that the machine would rather quickly fill up. So, it seems likely that the fluid either comes out somewhere, or is burned (you said it is typically a fuel), converted into another form (such as exhaust gas) and comes out somewhere. You can't just keep putting fluid in. Is there an exhaust stack?

Tap water goes in, comes out and gets dumped down the drain. When the water comes out, is it hotter than when it went in? Is is it always hotter, or is it sometimes colder?

 

[abc1234abc]

machine 1 and 2 have nothing to do with each other except that they do similar things...trying to kill two birds with one stone. i am told the cooling fluid needs to be supplied at 10 gpm or greater in order for the heat exchanger to work, not the fuel. the fuel is recirculated through the system which is why it needs to be cooled during ops as it heats up too much. the water exits the system, which is why a closed loop method to control the temp is needed...so basically a pump to circulate and a reservoir, tubes, etc. sorry if i mixed up the 10 gpm previously - i keep getting mixed info. Thanks!

 

[lilliput1]

Maybe you need a process chiller that can be either aircooled or water cooled. See Filtrine for process chillers. The cooling capacity and heat rejection capacity must be matched to what your equipment require. What happens is the heat from your process gets transfered to the chilled water. The chilled water is cooled by the refrigerent. The cooled chilled water is circulated by the chilled water pump back to pick up the heat from your process. The refrigerant evaporates in picking up the heat from the chilled water. The evaporated refrigerant gas is then compressed by the compressor. The refrgerant gas in getting compressed also picks up more heat from the compressor. The hot gas then is condensed to liquid in an air cooled condenser if air cooled or in a water cooled condenser if water cooled. If air cooled the condenser fan blows outdoor air over the air cooled condenser coil. The refrigerant pressure at the condenser is such that it condenses into liquid at around 140°F, giving off heat in condensing. The outdoor air at say 95°F absorbs the heat and is heated up to around 125°F. Thus your process heat plus the heat of compression is rejected to the athmosphere. For water cooled condenser, the compressed refrigerant pressure is such that it condenses, giving of heat at around 100°F. The heat is absorbed by condenser water entering at 85°F (with 7°F approach to 78°F wet bulb) and its temperature goes up to 95°F. The condenser water is sprayed into ambient air drawn in by cooling tower fans. The water evaporates into the air, taking with it about 970 Btu/lb, the heat of vaporization. Thus in either the air cooled or water cooled approch, the process heat plus the heat of compression gets rejected to the athmosphere.