eBay compressor

[Bob Pratl]

When I first tested mine it was 90 deg F inside my garage and after two minutes of running, in filling a 90 CI tank, the head temperature went up to 60 deg C so I added two large blue freezer packs to the 5 gallon cooling tank which brought the head temperature down to 45 deg C. Right now I automatically add the freezer packs to the tank when using the compressor.
Other than the noise, I'm extremely happy with the Yong Heng compressor. Bob

[OleTomCat]

The heat transfer formula is Q=MC*(T1-T2).  Q is the total hear transfer, M is the mass flow rate of the coolant C is the heat transfer coefficient of the medium (1 for pure water), (T1-T2) is the differential temperature across the heat exchanger.

So the object of this is that if you increase the flow the DT(Delta temp) will change for the same heat exchanger.  It is very hard to get more cooling out if the heat exchanger by just changing flow, best way is to make the inlet water colder....

An idea just rattled through my head (with the other 2 BB's in there) as I sit and look at the Tuxing compressor and I recalled someone else posting about getting a higher volume pump for their system.  I know that I've always heard that taking the thermostat out of a car can cause it to overheat due to the water moving through the system too fast and not having enough time to pick up heat from the engine and then shed heat in the radiator.  I've never really bought that idea myself but then again I've never really tested it exhaustively either.  But on these compressors the water definitely circulates across the head very rapidly.  I have my water return line mounted just above the water level in the reservoir so that I can see the flow at all times and it is a fast moving stream.  I wonder if the water is actually having enough time to "pick up heat" from the head?   I wonder if slowing the flow down might allow more heat to be removed?  Just wondering.  I haven't used mine longer than about 3 minutes (to fill a fully empty M10) and usually more like 1 to 1.5 to top off a reservoir).  I've noticed that although the head does get hot the hottest spot is the SS line connecting the upper and lower head sections.

[bandg]

Thanks for that Al but I think it misses my point.  It's not so much the heat exchanger (the "radiator" in this case being whatever water reservoir we are each using") that I am wondering about since we obviously can ice that and get it cold.  It is the amount of time that the water actually stays in contact with the head itself to allow heat to transfer into the water.  I'm really wondering how much heat the water is carrying away from the head since the head is physically small (relatively little contact area with the water) and the water is flowing through it very fast.  I have an infrared thermometer in the shop somewhere but I don't know if it will register water temperature from the surface to allow checking for any temperature rise in the water itself.  My use of this compressor is short enough that it is not a major issue for me.  For those needing longer run times it may be something to consider but other than slowing water flow I don't know how else one could change it.

I think I would try to find a high flow computer cooling fan to mount behind the head of the compressor to further aid cooling if it ever needs to run longer for my use.

I do recall a post noting that an owner of one of these small compressors had contacted the seller with concerns possible overheating and the information I recall being quoted from the seller was that 60C  was not a problem.   Certainly seems like cooler would always be better but maybe the concern threshold is pretty high.  Maybe.

[StevenG]

The heat transfer formula is Q=MC*(T1-T2).  Q is the total hear transfer, M is the mass flow rate of the coolant C is the heat transfer coefficient of the medium (1 for pure water), (T1-T2) is the differential temperature across the heat exchanger.

So the object of this is that if you increase the flow the DT(Delta temp) will change for the same heat exchanger.  It is very hard to get more cooling out if the heat exchanger by just changing flow, best way is to make the inlet water colder....

An idea just rattled through my head (with the other 2 BB's in there) as I sit and look at the Tuxing compressor and I recalled someone else posting about getting a higher volume pump for their system.  I know that I've always heard that taking the thermostat out of a car can cause it to overheat due to the water moving through the system too fast and not having enough time to pick up heat from the engine and then shed heat in the radiator.  I've never really bought that idea myself but then again I've never really tested it exhaustively either.  But on these compressors the water definitely circulates across the head very rapidly.  I have my water return line mounted just above the water level in the reservoir so that I can see the flow at all times and it is a fast moving stream.  I wonder if the water is actually having enough time to "pick up heat" from the head?   I wonder if slowing the flow down might allow more heat to be removed?  Just wondering.  I haven't used mine longer than about 3 minutes (to fill a fully empty M10) and usually more like 1 to 1.5 to top off a reservoir).  I've noticed that although the head does get hot the hottest spot is the SS line connecting the upper and lower head sections.

Do you know the flow rate?

Water in my area is very cheap, running it down the drain assuming it was only a couple hundred gallons would be fine where I live. I just want to make sure that the flow rate is low enough before I do that.

[bandg]

I haven't tried to measure flow rate-I have the stock pump that came with the Tuxing compressor and as noted my use times are short so heat has not been a major concern for me.  I would suggest trying something like Water Wetter and recirculating the cooling water to maintain that chemical-it is supposedly designed to increase heat transfer from metal into water.  When the pump is running there is a very brisk return flow into the reservoir and I believe it may simply be too fast to allow heat to transfer from compressor head to water.  I may be totally wrong on the mechanism here so try your own research.  The next time I fill anything with the compressor I am going to stick my finger into the return flow and see if it is "hot"  in relation to the reservoir water (using a thermometer would certainly be most accurate for this).   If it isn't noticeably higher in temperature than the reservoir water then it could not be removing any heat.  I may try to restrict water flow to see if more heat could be removed but I suppose this could damage the pump long term.  I still suspect that an external fan blowing directly on the head may be the most effective way to keep temperatures as low as possible on these small compressors but I could be totally wrong.

[OleTomCat]

The heat exchanger i was referring to is the head of the compressor, not the water tank, the heat transfer rate of it is fixed by it's size and composition, pushing the water through the head faster or slower isn't going to change the overall amount of heat removed, there are two things that help.

1.) Colder injection water, this will draw more heat from the head since colder water in makes for a larger DT between the water and the head, there is a point where this gets dangerous when you get it to cold and you run the risk of embrittlement, I don't think this is much of a concern since the water would probably freeze before that.

2.) Improve the heat transfer coefficient of your coolant, I think you suggested it above.

Thanks for that Al but I think it misses my point.  It's not so much the heat exchanger (the "radiator" in this case being whatever water reservoir we are each using") that I am wondering about since we obviously can ice that and get it cold.  It is the amount of time that the water actually stays in contact with the head itself to allow heat to transfer into the water.  I'm really wondering how much heat the water is carrying away from the head since the head is physically small (relatively little contact area with the water) and the water is flowing through it very fast.  I have an infrared thermometer in the shop somewhere but I don't know if it will register water temperature from the surface to allow checking for any temperature rise in the water itself.  My use of this compressor is short enough that it is not a major issue for me.  For those needing longer run times it may be something to consider but other than slowing water flow I don't know how else one could change it.

[bandg]

I believe that for any given temperature in the reservoir there should be an ideal flow rate for coolant to maximize heat removal from the head.  Think of the water flowing but VERY slowly.  Would the water not heat up rapidly and therefore allow the head temperature to increase?  The opposite condition would be the coolant flowing very fast and having insufficient time for heat to flow from head to water again allowing the head temperature to increase.  I can't see the heat transfer being instantaneous-it takes time. 

[Sprungout]

You could get an inline pond pump flow valve, splice it in and see if the compressor temps drop. Easy to play with the flow rate then.

[Buldawg76]

The heat exchanger i was referring to is the head of the compressor, not the water tank, the heat transfer rate of it is fixed by it's size and composition, pushing the water through the head faster or slower isn't going to change the overall amount of heat removed, there are two things that help.

1.) Colder injection water, this will draw more heat from the head since colder water in makes for a larger DT between the water and the head, there is a point where this gets dangerous when you get it to cold and you run the risk of embrittlement, I don't think this is much of a concern since the water would probably freeze before that.

2.) Improve the heat transfer coefficient of your coolant, I think you suggested it above.

Thanks for that Al but I think it misses my point.  It's not so much the heat exchanger (the "radiator" in this case being whatever water reservoir we are each using") that I am wondering about since we obviously can ice that and get it cold.  It is the amount of time that the water actually stays in contact with the head itself to allow heat to transfer into the water.  I'm really wondering how much heat the water is carrying away from the head since the head is physically small (relatively little contact area with the water) and the water is flowing through it very fast.  I have an infrared thermometer in the shop somewhere but I don't know if it will register water temperature from the surface to allow checking for any temperature rise in the water itself.  My use of this compressor is short enough that it is not a major issue for me.  For those needing longer run times it may be something to consider but other than slowing water flow I don't know how else one could change it.

I believe it was me that suggested the flow rate could be possibly to fast to transfer the heat to the coolant properly in theses compressors. I am basing that off my 45 years experience as a master certified auto technician. In my experience with cars that use a bypass coolant system that is incorporated into the thermostat housing itself where the thermostat serves two purposes removing the thermostat completely will cause the car to run hot and eventually overheat. The cause is that when the engine is cold the thermostat is closed so the bypass allows for coolant to flow within the engine block itself to prevent hot spots until the thermoset open and blocks the coolant flow inside the block only and allows the coolant in the radiator to enter the engine to maintain the proper temp. By removing the thermostat completely the coolant will not be forced out thru the radiator but rather still just circulate in the block only thereby slowly getting hotter and hotter till it overheats. So in this type system you would only remove the center of the thermoset by cutting the two raised arches that hold the top of the moveable part of the thermostat so it creates a restriction to the flow and causes the coolant to have to flow thru the radiator as well.

In a system that has a separate bypass system it is not an issue since the thermostat only controls the flow thru the radiator itself and not the engine block. In this type system the entire thermostat can be removed without any issues of overheating. Either way it is a definite that the coolant in an engine has to be constantly circulating in the block in order to prevent hot spots and the subsequent damage that would occur if it was stagnant until the thermostat opened.

With that being said I agree that the best way to determine if the coolant used in these compressors is flowing to fast is to monitor the coolants output temp with a thermometer in the output flow as well as the resevior to see if there is in fact a significant difference in the temp of the reservoir coolant and the output temp. That will provide a good estimate of how much neat is being removed from the compressors cylinder as the coolant flows thru the system. That would allow you to have a basis for adding a restriction in the output flow and to monitor it to adjust it for the optimal heat transfer versus flow rate.

If/when I get my compressor that is what I will be doing to provide the optimum heat transfer rate thereby keeping the compressor as cool as possible at all times. If using an infrared thermometer to read heat of objects be aware that any shiny surface is not going to provide as accurate of a reading as a matte finish will due to the reflective nature of shiny surfaces. It's best to focus on a dull dark surface as compared to a bright shiny surface. I don't believe it will be able to read the temp of the actual coolant since it does not reflect the same as a solid object but have never tried either so could be wrong on that account.

Mike

[shultz]

I don't have a lot of run time on my compressor so take this for what its worth...

My compressor was hitting close to 60c at the end of 20'ish minutes of run. I was using ice cold water at start up and changed it before I made another run.

I think the water is moving to FAST thru the head to get really good heat transfer. Some transfer is taking place, the water is warmer at the discharge than intake even after 20 minutes of run. Still, this tell me maybe more heat can be absorbed during that 20 minutes by reducing flow.
The included pump is pushing about 105GPH. I'm going to try an 80 GPH and see if I get better cooling. The pump is only $8, no biggie if it don't work better...

When I ran my compressor, I had a small, box fan blowing front to back. I'm sure this helped. However, next run, I'm using a fan I forgot I had. This fan is 120mm square and nearly 2" thick!, 120vac. It sounds like a freaking JET engine! boy does it move some air, I'd say 250-300 CFM, maybe more. it was used for cooling large enclosures filled with electronics. This fan will concentrate a blast of air directly across the cooling fin part of the head and push it all the way thru the motor housing.

I plan to try the fan first, then the pump. Then both. this should tell me which combo makes the bigger difference. Sadly, none of this will happen until I get my high side filter....

[Jman2311]

I can assure you.  Decreasing flow rate will NOT keep your compressor cooler.  Oldtomcat has it on the money.  Colder intake water will make colder head temperatures.  Flow rate wont mean much of anything on these compressors.

[bandg]

Jeremy, I don't know with absolute certainty which of us is right but I am smart enough to know that I can be wrong and would hope you are as well.   If not, so be it and you can assure away but  I don't do absolutes well when they are simply someones opinion.  The very simple bottom line seems to be that heat does not move from the head to the water by magic-it is a physical flow and certainly would require time and the time rate would seem to relate to coolant flow velocity.  If you disagree, feel free to do some experiments to define the issue.

[kzz1kaw]

When I first got my compressor I to was concerned about the head temperature. I added ice packs to the water and it did not make a difference. The conclusion I came to Is the high temperature is normal to run it the way it is. And so I did. No problem so far😎

[shultz]

I can assure you.  Decreasing flow rate will NOT keep your compressor cooler.  Oldtomcat has it on the money.  Colder intake water will make colder head temperatures.  Flow rate wont mean much of anything on these compressors.

You may very well be right. Still, for $8 it's worth a shot. No down side from trying unless your careless and let the compressor get to hot...I'm not that guy

[bandg]

I remember reading a post from a purchaser of one of these small compressors (may have been Tuxing but I don't recall) who contacted the seller about concerns over high temps and was told that 60C was not a problem for the compressor.  For what it's worth.  I've seen 54C to 55C indicated after a 3 minute fill with spit on the SS line sizzling.  I will definitely be adding a cooling fan for my peace of mind.  Hope everyone's compressors work well.

[shultz]

Ken,

It's probably in this thread somewhere... anyway, what the max temp you've seen and how long did the compressor run to hit it?

My compressor temp gauge hit 60c when I stopped it for a cool down after 20'ish minutes of run. Not sure how much hotter it would have got OR if it would have stabilized at 60c for a time. The water supply was still cool, but, I didn't take a temp reading. The water coming out was very warm, but, not hot IMHO, again no temp reading. The finned portion of the head hit 65c according to my IR temp gun. The case was like 37c.

Maybe it will run just fine with these temps, I just didn't get a warm fuzzy feeling in regards to longevity running this hot.... I'd rather do several,shorter runs than let it run for to long at what I feel are high temps.

Trouble is, I don't really know WHAT is too hot! I've read you should stop at 60c and change the water, another post was 70c during summer months...

[Bizill]

I don't think slowing the flow rate will help any.  Think of a car running at idle and then think what happens when the engine revs higher.  The flow rate increases if the water pump is driven proportionately to engine rpm.  Usually you don't see them trying to slow the flow.

I think we're all overthinking this.  Just add ice.  Period.

[bandg]

Overthinking it?  Isn't that half the fun.  I'll still disagree with you just for kicks and I can give you a specific example.   I drive a large International chassis RV type unit a couple of times a week.  As temperature goes up you hear the fan clutch kick in and temperature drops.  You aren't revving the engine to increase water flow but moving more air to cool the water in the radiator.  The automotive accessory drive system is designed to move adequate water at idle for cooling but air is another matter.  You're comparing apples to oranges.  But I'll also agree with you, add some ice and fill your tank or gun and go shoot.  If it quits working I'm sure we will try something else.

[kzz1kaw]

Ken,

It's probably in this thread somewhere... anyway, what the max temp you've seen and how long did the compressor run to hit it?

My compressor temp gauge hit 60c when I stopped it for a cool down after 20'ish minutes of run. Not sure how much hotter it would have got OR if it would have stabilized at 60c for a time. The water supply was still cool, but, I didn't take a temp reading. The water coming out was very warm, but, not hot IMHO, again no temp reading. The finned portion of the head hit 65c according to my IR temp gun. The case was like 37c.

Maybe it will run just fine with these temps, I just didn't get a warm fuzzy feeling in regards to longevity running this hot.... I'd rather do several,shorter runs than let it run for to long at what I feel are high temps.

Trouble is, I don't really know WHAT is too hot! I've read you should stop at 60c and change the water, another post was 70c during summer months...

Run time approximately 20 minutes topping off a cf 88 cf tank temps 64 to 67 c running the pump in a bucket of water. Filling my guns anywhere from high 40s to mid 50s. I accepted the fact that the compressor must be designed to run hot each to there own.

[kzz1kaw]

Come to think about it, I have a two stage5 hp compressor twin 60 gallon tanks in my pole barn that get hot if I use a da sander while doing auto body repair and that compressor is not water cooled and has a finned cylinder heads with no overheating problems so maybe this applies to these little compressors?