meck,

Capillary tubes are a fixed orifice junction between the condensor and the evaporator, but they are not a valve. Valves can be adjusted; capillary tubes cannot be adjusted. Consumer refrigeration systems (for homes) use capillary tubes for expense. Commercial systems (for restaurants and other big sites) might use a TEV (thermal expansion valve). In a large setup, the efficiency of a TEV might pay for the extra initial expense in a short time.

superart,

I have always heard HVAC pronounced like H-Vac ('H' as in the letter then Vac as in vacuum).

I really stress the HVAC certification because of the legal liability. I cannot promote what could be an illegal action. The legal landscape today makes me err towards caution. However there is another reason. In theory, you could probable build a system from the description that I gave in the article. But, an HVAC certification gives you practical experience in charging a system correctly. For instance, you can charge a system by watching the amperage draw on the compressor, or by watching the superheat temperature, or by a number of different methods. I also think that there is paperwork to fill out for certain operations like using R-12.

I am not HVAC certified, unfortunately. Last I checked, the easiest way to find out is from your local repair shop. The refrigerator manufacturers are uninterested in dealing with individuals, for the most part. Alternatively, you might contact the Air Conditioning and Refrigeration Institute (ARI). Most HVAC certs are issued as part of 18-month or longer trade schools, but there might be alternatives in your area. You just need to check.

I just updated the entire article with a list of changes Brian pointed out! just spelling and such.

Wow! That was fast, Joe! One important thing to note... in spite of my nitpicking, I was unable to find any technical flaws. For the sheer amount of territory covered, Joe, pHaestus and Brad all produced remarkably error free overviews. Kudos! They really do know what they are talking about.

Yeah that's exactly what I did, I was pointing out stuff as I read. I mention that at the top of my post :D

Your coverage is more than adequate, its the coverage on the "intro/primer" page that is confused.

As for later grammar/spelling errors, I'll confess that as I realized how long the article was a switched from reading to skimming. Time constraints yknow :D

Hey, I'm just trying to help by making things as clear as possible.

I guess I failed to express what I meant clearly. Is closer to ambient better? If it's closer to ambient, then conversely that means that the flow rate is lower and the water exiting the block is at higher temp. This means that the water goes thru a greater temp rise in the block. Averaging the temp in the block, it will be the same as if the flow rate had been faster, and thus the temperatures on the "hot" and "cold" side of the loop been closer. So how is it better when rad output is closer to ambient?

If it makes no difference then however you do it, it is still right...
There is nothing half-assed about putting the pump anywhere in the loop. What would be half-assed would be getting a weak pump.

That said, I agree with what pH has to say about small cases. If it doesn't increase the difficulty of putting the system together, go ahead and put the pump wherever you want. However, if trying to put the components in a specific order gives you some technical problems, keep in mind that the effect it has is virtually negligible, so there is no need to lose any sleep over it.




You've addressed all the more subjective issues I raised, but how about the more technical ones?

In any case yes I did like the article, what I'm trying to do is just try to help to improve it by voicing my views for discussion. Please don't take this as me trying to attack your work, I am not!

Hey Marco,

Don't get me wrong I am not bent about your questions at all! I like them actually, as they are adding some parity to the article.


As for the whole "pump placement" deal. To me it comes down to this:

Your pump DOES add heat. it may be a very small amount, but you cant deny that the pump transfers some heat to the coolant. Now in a optimum situation, where would you want the coolant to go next? right to the thing that you are trying to cool? or to a heat exchanger to remove that heat before it goes to the thing you want to cool?

Logic would dictate that you would want the lowest temp coolant to go to the object you are cooling, so you should have a heat exchanger right before that object to remove any heat that the system as absorbed in its loop before that.

Also some pumps DO generate a good deal of heat. The Hydrothruster is a good example, as well as a few of the other high end pumps. I did a test a few months ago on my Hydrothruster and at full bore with no fan on the radiator running in a loop with no CPU the water heated up to around 100F in 30 min and would have gone higher, with a small fan on the radiator it dropped 10 DegF to 90F with an ambient temp if 73F. With a 120mm fan the coolant remained at around ambient or a degree or so above.

This shows that the pump CAN put a good amount of heat in the coolant, if you have something that is pre heating the coolant before the core wouldn’t you want to have that coolant cooled off more before it hit the core?

You can do what you want and in some cases its easier to not do it that way... I just see it as a main aspect to consider when designing a system. To some people the "reasonable" amount of heat that the pump may introduce to a system is not an issue, and too much work to worry about. But to me the systems overall design is by far one of the issues I look at the most when planning it around a case.

As for the radiator ambient temp deal. Isn't the output of the radiator always better if its at ambient or as cool as possible? Yes i know keeping a higher flow rate through the block will give an overall more "averaged" heat up cycle to the coolant, there will be a very small temp increase through the WB, and a very small temp drop through the radiator at a higher flow. But in reality having a radiator output ambient temp coolant to the core is a best case scenario. It all depends on how you tune your system for the right flow rate for the components you are using.

I loved the article. It covers the most of the basics and is really well written.
But what is this talk about "heat soak point".
There is NO such thing. The increase in heat is linear when a constant amount of energy is added. Untill it changes phase of course. But i guess the CPU will fry before the copper/alu melts.

the part about watercooling was very helpful. but i'm a little worried. i just ordered the innovatek water cooling kit recommended by http://www.overclockers.com/articles545/ and its my first journey into watercooling. you say i need the res to be the highest point, but on the kit the res connects directly to the pump. do i need figure out a way to mount the whole assembly in the top of the case? i understand i could add another res/bleed point, but i don't really consider that an option since i already payed $225 for this kit and it comes with a real nice res as it is.

also, about the water, antifreeze, and water wetter. you say theres no reason to put antifreeze in, and you recommend water wetter. but in one of your older articles you recommended purple ice. and in the review of the kit at overclockers.com he says "Note that any design using dissimilar metals requires that the cooling fluid contain anti-corrosives; anti-freeze is a good additive - a solution of water with perhaps 10-15% antifreeze is fine."

should i use water wetter or purple ice, and should i combine it with a little antifreeze or not?

tia

The reservoir can be at the bottom of the case, its an air trap that should be at the top.

a Pump/rese combo should always be at the bottom of a case (the pump should be the lowest point in the system, something I forgot to talk about I guess)

Hope that helps, your setup will work just fine. and I would use water wetter and not antifreeze.

y is this...

thanks for the quick response. but uh... i'm sure your familiar with the kit, the rese is the air trap for this system. are u suggesting i add yet another component to this already overpriced system?

sorry if i'm missing something obvious here :shrug:

Airtraps do not need to be expensive. Want to see mine? Yes, I'm upgrading, but this one was built, and time is limited, after all.

http://brian.procooling.com/images/pepsi_airtrap.jpg

That one cost about $2.05, including the expense of the brass barbed fittings.

my example of an air trap was a "best case" type deal. You CAN use other stuff, like a Pump/Rese on the bottom of the case and get similar results just not as instant. ( may take a day or so for all the air to get out of the system and such).

Joe

If it's a submersible pump in the res it doesn't need to be at the bottom. As long as there stays water in the res keeping the pump submerged it should pump fine. Issues arise if you have it right at the top, and air pools and gets sucked into the pump.

It's with inline pumps that trying to keep the pump at the bottom helps, because air has the bad tendency of ending up in the impeller, killing its efficiency. I saw a system here with an eheim pump put in with the intake underneath and the output at a side The pump was about at midheight in the loop, and I was asking myself, how the hell did that guy keep the air(edit:air not water!) out?

In any case here is a solution I was pondering for inline users. This is particularly relevant to me with a bong, that can suck air on a weekly basis. Manual priming of the pump can be complicated, as air can pool in countless places in long bong lines. So I was thinking of putting a small cheap submersible pump in the res, and turning it on only when the system needs priming. Guess this does not really apply to closed-loop resless systems though.

Yep in some ways you are right, it comes down to Centrifugal pumps CANT suck water, they can only push water. Using that logic you can do what ever you want as long as your pump isn't trying to pull water up from a pool below.

I'm not disputing that pumps can produce a good deal of heat. The thing is that the heat from the pump does not only heat up the water between it and the heat exchanger!

In a system, heat adding components are the waterblocks and the pumps. Heat loss components are radiators and the lines themselves. Now, the heat loss components are passive, meaning that they don't move heat by doing work like a peltier does, they remove heat by optimizing conditions for convection.

What does all this mean? This means the system must reach a temperature where the heat is lost at the exact same rate as it is gained.

Why is this? This is because the rate of heat gain is constant, but the rate of heat loss is proportionate to the temperature difference between the heat transfer medium and the ambient. That means the hotter the water the faster it will lose heat, given ambient temperatures stay constant.

Now, returning to our problem, what happens is that the pump's added heat requires water in the entire loop to heat up, in order for the rate of heat loss to be able to match the rate of heat gain.

So in summary, if the pump raises the temperature of all the water in the system by an equal amount, what difference does where the pump itself is make?

For a radiator to output air at or near ambient temp, either the quantitiy of heat that it is removing is extremely small, or the flow rate through it is extremely slow. I don't think we even need to address the former case :D. In the latter case, the water may enter the waterblock at the lowest temperature. But what temperature does it leave at? The slower the water flows, the more heat each unit of water will have to absorb in its flow through the waterblock. So it may enter somewhat cooler, but if it exits substantially hotter, it means that it will be hotter in some parts of the block, and in these parts the heat removal rate will be lower. On the average, in theory, the results should be about the same.

However, all this does not take into account some factors. Maybe we could discuss them a bit. One factor is the water in over core issue. One could presume that this would work well with lower flow rates where water comes in cooler, but we also know that it will be heated more intensely for longer. What happens as it heats up?

Another factor is the change in properties of the thermal barrier due to increased turbulence at higher flows. So is any gain acheived by "cooler" water entering over the core greater than the loss incurred by the turbulence due to loss in speed?

I think I found that stash Joe ;)
 

:eek:

* screams and runs from the thread * :evilaugh:

No, thats' wrong, thay can suck water just fine, they just can't suck air very well, and won't self prime.

*rushes out to shed to perform an expriment*

My spare 2500L/H Centrifugal pump (once primed) can easily suck water up 2 metres of 1/2'' tubing and spit out a decent stream.

Of course you wouldn't want to mount a pump like that in a mission critical suitation, since it only has to hickup and the water column will fall and the pump will be left trying to pump air in vain.

I've done that with my pumps. of course they won't suck air up. I filled my sink up with water, turn the pump on in it, with a 2m long hose to the inlet of it. Just lifted the pump out of the water, and it did suck the water up, and pump it out the outlet.

Believe what you want, but you will cut your flow WAY down, and ANY... ANY little disrpution in the coolant flow and the entire thing stops pumping water where it should. A sealed closed loop system is a bit different, but an open rese below the pump is pretty much about worst case scenario.

I prefer to NOT run something that is just relying on water tension to do. ( I mean in some way its just a fancy siphon then.) Which if you think about it.. water wetter could make that even harder to do when it breaks up the surface tension of the water.

Read the the packaging for the pump in there it says pretty clearly, that the pumps are NOT designed to suck but only to push coolant.

Also the higher end the pump teh easier time it would have "sucking water" as it would be able to overcome the gravitational forces that are pulling the water back down. a lower end pump may not dig it at all if there is much resistance on the output side of the pump. Just cause it can be done doesnt mean its the right way to run something.

For all intents and purposes they CANT suck water on their own. (needs to have a water stream established Then raised above the water surface ( prime it)).