almost forgot,it has taken me a while to finish them other than pressure testing and final polishing which i do after to hose is connected.but here is the cleaned up evaperators.
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almost forgot,it has taken me a while to finish them other than pressure testing and final polishing which i do after to hose is connected.but here is the cleaned up evaperators.
ooh copper goodness!! i love those blocks! when is the true test coming up?
Bowman,
You do good work my man.
baker18
well soon i hope.i need to finish some friends stuff first.Quote:
Originally posted by Pimpsho
ooh copper goodness!! i love those blocks! when is the true test coming up?
ok i have been getting one evap ready for testing for pressure.:D
i saw a few days ago someone wondered if bakers blocks could handle high pressure of a cascade.well i knew they would ,working with real high pressure stuff for a living i knew these little evap would work fine.
but when i assembled the block to my pressure rig,that connects with flare fitting,i got a bubble leak at the fitting.this leak accured at just over 200psi and was just a bubble every second or 2.
now thes would go unnoticeable by most since a normal system you would think would go that high,but at rest with a hot compressor that was just turned off,can and will exceed these sometimes in the evaperator.
now i knew i had properly tighten the fitting but i checked again,tight.
i remove them and checked the sealing surface,thats was fine.hooked up again and leak at simerlar pressure again.
now i normally do use a sealant on them but i was just doing a test and didnt worry about it since it was only a small test.i removed it again and this time used my sealant.
and now it is holding at close to 450psi and no leak.this is why i use this sealant.under extreeme contitions it works great.and this is how it sould look properly used.and when you remove the fitting there will be no contamiation to the inside tube.
but here is how it looks prperly used.just barly covering the face of the flare.
i do not like leaks and if i have to use a flare i will use this way to seal it.
ok this pic shows the extreeme pressure i put bakers block under.shown in my sink which i summerge all my pressure tests to see bubbles.it is handling 450psi just fine...
i will let it set overnight and then i can use it being sure it if perfectly sealed.
Bowman,
I really like the look of that new block, but do you think it can transfer enough heat to the 'Baker' section? The out casing looks a little thin and the fins only touch a small portion of the top of the casing.
If Baker's block was recessed through the casing onto the fins, it might transfer a bit more heat.
well you cannt see by the picture,and i didnt think about taking a pic of the bottom of bakers block.Quote:
Originally posted by Nico
Bowman,
I really like the look of that new block, but do you think it can transfer enough heat to the 'Baker' section? The out casing looks a little thin and the fins only touch a small portion of the top of the casing.
If Baker's block was recessed through the casing onto the fins, it might transfer a bit more heat.
i used the lath at work to mill flat the bottom and turned a lip into the bottom so the top and bottom seat into one another.the bottom is flat sitting on the fins almost.proberly brased to them.the silverflow i use will pull to any gap.
but i am using the block to give the refrigerant more time in the block thats all.
when i was brasing it ,i was supprised how well the heat moved to the top as i didnt apply much heat to the top,just the bottom and side.the heat moved pretty well.as this is normally a good way to tell when you try and brase them.
but testing it the only real way.and i proberly will test it on one of my units before the cascade see's it....i like to test test test.
but then again it pays off.:D
well my man i have great made evaperators from you to work with.so the rest is easy.......:DQuote:
Originally posted by baker18
Bowman,
You do good work my man.
baker18
Those new blocks look like a work of art. Nice job baker :toast:
Keep up the good work Bowman :thumbsup:
well forgot to tell,i had to brake down and get me a new vacuum pump.man i hated that......money.
but my old one wasnt pulling a good enough vacuum for me anymore and i know the cascade will require i low micron rating to acieve a good dry system.:D
looked at a bunch and got another robinair,it will pull a 20 micron rating..that should work,didnt need as large of one but for the price i got a 6cfm.it was as cheap as the smaller ones.and i have had good luck with robinair before....stick with what you have faith in i always say.
guys you dont need but a small one 1.5cfm will be fine for these small systems,but for me 6cfm will help me on some large systems when i nned it.
Vacuum pumps are sensitive to oil cleanliness and oil level. You might want to try a few oil changes on that old pump to see if it can be brought back to top condition.
yep you are right.if you followed the oem specs it says change the oil in the pump after every pull down ...i think thats what i remember,but hey i dont know anyone who does.Quote:
Originally posted by Gary Lloyd
Vacuum pumps are sensitive to oil cleanliness and oil level. You might want to try a few oil changes on that old pump to see if it can be brought back to top condition.
what brand do you like gary,i meant to get a old mans oppinion before i ordered mine,but i forgot.
by the way,the old man thing..well i have learned most what i know from old men, who since i paid attention to them when they were talking,told me lots of tricks...funny how if you keep you mouth shut and listen to the older guys how much you can learn..
but then again it seams most young guys try to tell the old men how to do it anymore.
but then again what is old,and what is young.depends on the person i guess...i feal like i am getting old...but not as old as you gary...LOL
by the way...thanks old man.:D
I like the J/B pumps, but Robinair would be my second choice.
Old people know more about being young than young people know about being old. :D
I learned that from my mom, who can still kick my butt. It's all relative... LOL
well you know i almost when with a J/B...but didnt feal like changing brands...and the J/B's only pull to 25 microns the new Robinairs pull down to 20 microns and the yellowjacket has one that pulls to 15 micron.Quote:
Originally posted by Gary Lloyd
I like the J/B pumps, but Robinair would be my second choice.
but i have never used a yellow jacket..wasnt sure about that without knowing someone who had one.
Regarding the finned evap -
I'm not being disrespectful or anything but isn't the second level maze a waste of time?
Since there there's 3 seperate pieces of copper to the cooling section of the block (base/fins, fin cover, maze level) it would create a signifigant thermal interface between them, hence minimal amounts of heat being transfered to the maze level from the fins. Even the use of rather pure silve solder would create a large thermal resistance between the pieces.
e.g fins -> silver thermal junction -> fin cover -> silver thermal junction -> maze level
You would lose alot of freon cooling the block rather than the processor.
Could the left over liquid coming out of the evap could be better used for subcooling?
well good question..:DQuote:
Originally posted by fr0st
Regarding the finned evap -
I'm not being disrespectful or anything but isn't the second level maze a waste of time?
Since there there's 3 seperate pieces of copper to the cooling section of the block (base/fins, fin cover, maze level) it would create a signifigant thermal interface between them, hence minimal amounts of heat being transfered to the maze level from the fins. Even the use of rather pure silve solder would create a large thermal resistance between the pieces.
e.g fins -> silver thermal junction -> fin cover -> silver thermal junction -> maze level
You would lose alot of freon cooling the block rather than the processor.
Could the left over liquid coming out of the evap could be better used for subcooling?
but i have found over the many i have built it dosnt work like the text book says.the more mass helps alot in a evap block i have found,even just adding mass without passages can help on a small evaperator .but the cooling of the block itself doesnt take away any from the cooling of the cpu.actally it helps.
once the evaperator is dropped to a opperating temp it doesnt draw anymore from the system because it should be fully insulated.
i can give you a example of one of my tests.one of my systems can start without the compressor running and then start up the compressor and catch up and cool the cpu.this is only possable because of the mass of the evaperator.i can also shut down the compressor and run for 1 minute before the temp rises above 0 c
so mass makes a big differance.yea it looks like it would hurt.but if i hadnt made all these variations i wouldnt know for sure.
the upper block of bakers is there for another reason rater than just to cool,but i can assure you it will be full of refriegerant,there is no doubt it will have freon well past the evaperator.proberly all the way to my manifold,if i get it how i want it...:D
You have to watch out to not add to much mass. Take your everyday standard heatsink for example. A thinner base will heat up quicker but, a thinner base will also transfer heat to the fins at a faster rate.Quote:
Originally posted by bowman1964
well good question..:D
but i have found over the many i have built it dosnt work like the text book says.the more mass helps alot in a evap block i have found,even just adding mass without passages can help on a small evaperator .but the cooling of the block itself doesnt take away any from the cooling of the cpu.actally it helps.
once the evaperator is dropped to a opperating temp it doesnt draw anymore from the system because it should be fully insulated.
i can give you a example of one of my tests.one of my systems can start without the compressor running and then start up the compressor and catch up and cool the cpu.this is only possable because of the mass of the evaperator.i can also shut down the compressor and run for 1 minute before the temp rises above 0 c
so mass makes a big differance.yea it looks like it would hurt.but if i hadnt made all these variations i wouldnt know for sure.
the upper block of bakers is there for another reason rater than just to cool,but i can assure you it will be full of refriegerant,there is no doubt it will have freon well past the evaperator.proberly all the way to my manifold,if i get it how i want it...:D
It like holding a spoon in a hot drink... its not hot at first but if you leave it and come back and try to stir it again your not gonna be happy. Use a bigger spoon and it takes longer, but it will stay hot for longer aswell.
Likewise can be said for our evaps aswell, a large base will take time to cool down but will stay cool, likewise a thin base will cool quick and heat up quick. It's more a matter of preference I think.
My last point is to watch the length of your fins. Cooling the top of a large fin will be less effective than cooling the bottom of a small one. All related to mass, large fins will take longer to cool down and blah blah blah...
It all come down to how fast you want to reach the equilibrium. In computers I personly tihnk it would be best to have a smaller block and have it heat up at post/boot rather than getting into windows and start to bench only to find it's crapped itself.
I think you should be more concentrating on how to transfer heat to the freon rather than mass... theres alot more than surface area affecting the preformance. Surface texturing, heat transfer enhancement surfaces to name a few.
what we need is someone with a degree in thermodynamics :rolleyes:
Copper, even though it is a good conductor of heat, also does offer some resistance to the transfer of heat. Say in the case of determining latent infiltration (transmission) of heat through walls (such as those of walk-in coolers/freezers for instance). This characteristic of heat transmission is expressed in terms of btuh per square (foot) of surface area (K).Quote:
Originally posted by bowman1964
[B]... more mass helps alot in an evap block, I have found. Even adding mass without passages can help on a small evaporator...
This value (K) is derived from both the thermal conductivity of the material (U), the thermal resistance (R) of the material relative to the thickness of the material, and the TD (temperature diffence) on each side of the material (I don't particularly know the mathematical formula). The K-factor (of even copper) is proportional to the thickness of the material between the (evaporating refrigerant) and the medium being cooled. The thinner the heat transmission material (copper), the less resistance of the material to the desireable heat transfer. that is why (air) coils are constructed of the thinnest possible copper tubing appropriate for the job.
Quote:
...so mass makes a big difference. Yea, it looks like it would hurt...
The rate of heat transmission is determined by the area of contact of the heat transfer surfaces that are in direct contact with each other (the processor's package and the block - obviously limited by the dimension of the package), and the TD between the two surfaces. the temperature of the contact surface of the block is detemined by the temperature of the evaporating refrigerant inside the block, and the heat transmission of the copper (K). Thicker copper (more mass) in those areas that are not directly in contact with the load (processor) would actually serve to insulate the system from undesireable loads (ambient air for instance). But incorporating more mass (thicker copper) at the point of contact with the load would serve to further insulate the load from the evaporating refrigerant.
Mind you, that in typical refrigeration applications, we can change the heat transfer surface area (in the case of cooling air) in order to change the TD. In cold storage refrigeration we manipulate this purposefully, in order to acheive certain desirable enviromental characteristics of the cooled air for different applicaitons, or somethimes even make the surface area of the evaporator smaller for the sake of economy - we don't have to buy as much copper. But in the proceesor cooling applications, we are limited by the fact that we cannot change the contact area with the package. :( . therefore, we are limited to either increasing the TD (lower evaporating temperature), and/or increasing the K-factor of the block (heat transmission rate).
Mind you, that if you consider the above:
A "0 degree" TD would indicate that no work is being done.
The greater the TD, the greater amount of work that is being done.
In the case of "more mass" being good, I consider this to be similar to the use of perhaps, dry ice. the dry ice is "stored energy". Mind you, you may say that the "cold" ice has less energy thatn the load, if you think of the actually presence of energy, being heat = energy, cold = lack of energy... but think of it in terms of the sorage of the energy that was required to remove the heat...... okay?
Your properly conceived DX (direct expansion) refrigeration system should be designed to do the work of the highest load that it will be required to satisfy (usually that is the highest load that we anticipate, and if we're lucky, we didn't underestimate it). Spending work for "storage" merely adds an additional load to the system.
PS: I have no degree in thermodyamics, other wise I would know the formula to derive K-factor, by memory, and I wouldn't have such a difficult time explaining my understanding of it.
If you are looking for formulas i may be able to help. This K factor you speak of, k is usually used to define the thermal conductivity of a material expressed as;
rate of heat transfer (eg watts) per thickness of material (eg meters) per temp difference (eg kelvin).
ie 377 W/m.K for copper.
The formula you are looking for is;
Q= kA(T1 - T2) / x
Q= rate of heat transfer
k= Thermal conductivity
A= Area of heat transfer
T1, T2 = Temperatures at surfaces
x = Thickness of material
Thank you Russell_hq. :D
...please consider all my upper case "k's" to be lower case.
You are "Johnny-on-the-spot" :)
But.... Do you know the formula in which "k" is derived for each material?
this formula requires that "U" and "R" be known. "k" is a constant in the formula that you posted, which derives the heat transmission of a particular configuration of material.
????
When I get back to my shop on Monday, I can look it up in my ASHRAE handbook.
see ya'
im not sure what you mean by R. To me this is the universal gas constant R which equals 8.314J/mol.K maybe you are talking about a resistance to heat flow?
Anyway for U taken as the overall heat transfer coefficient then;
Q=U.A.(T1 - T2) and Q=k.A.(T1 - T2) / x
Thus k.A.(T1 - T2)/ x = U.A.(T1 - T2)
Therefore k= U.x
Im not sure how relavent this is though? I was sure that k can be taken as constant for metals, also k is calculated experimentally I dont think that it can be calculated, not for metals anyway.
thermal resistance R can be given simply by x/k and k/x is the transfer coefficient h.
http://www.matweb.com Go here for property data of various materials.
you know, like the "R" value of insulationm (i.e... the Pink Panther.. Dowe corning fiberglass insulation)! Or should that be "r". I dunno! I'm not that well edumucated.
... NO, "k" is not constant for (all) metals. the "k" factor difference between copper and mild steel is near astronomical.. (well, very considerable anyway).
... trust me, the formula to derive "k" exists. I will post it, Monday.
oops , maybe you misinterpreted me. When i say constant, i mean the value doesnt change significantly with respect to temperature and pressure but not constant for all materials.
eg.
Aluminium = 230
Copper = 377
Silver = 412
stainless steel = 16
Bronze = 189
All units W/m.K
r is just the inverse of k. As it makes more sense to represent the thermal resistance of insulation ie bigger values better heat insulation whereas for conduction using k values bigger equals better heat conduction.
So if you take the relationship r = 1/k then as k increases r decreases and as k decreases then r increases as you would imagine. :)
No, I didn't misinterpret you...
your observations regarding "R" and "k" are enlightening. let me get that formula to derive "k", and perhaps that will further open my eyes.
Mind you, the diffence in "k"-factor between copper ("377") and stainless Steel ("16") is what I consider "astonomical" (considerable - i.e. worth consideration).
My understanding, is that the inverse of "R" is "U". "k" is derived from the two values, resistance and conductance, in order to determine rate of transfer (transmission).
But I'll shut up now, because I am at the very realm of my familiarity, at this very point. :) I'll look up the formula, tomorrow (if such formula exists, and I'm not mistaken).
cheers!