CW5200.The Specification Relies on Your Naivety
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- Опубликовано: 31 авг 2023
- This piece of equipment has become a recognized necessity for any laser tube over 80 watts and especially if the laser machine is used in a hot environment. There are many videos available that demonstrate how to change away from the factory settings but none that explain how the chiller functions or how “fiddling” with the settings will significantly affect the performance away from the claimed specification.
Very few hobbyists understand the principles of refrigeration and even fewer are aware of the critical parameters that control the efficiency of the water-cooling process. As a consequence, there is much hearsay and many myths about the best settings for a CW5200.
This video digs deep into how the CW5200 is controlled by a programmable thermostat and also explains the science behind refrigeration in a very non-scientific way. Understanding those simple concepts will allow users to make logical decisions about adjusting settings away from factory presets because the factory settings are truly unsuited to cooling a laser tube. 
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Hi Russ... thanks for an awesome video full of useful info... here in South Africa the CW 5200 is necessary in summer where our temps are in the 30's daily... laser heats up way to fast during production with the 3000 which I used to have... I would definitely not set the temps that low as it will crack the tube.... some manufacturers rate either 16 or 18 degrees C as the minimium to prevent thermal shock and cracking the tube... stay safe until the next one.... God bless...
I used to work on electron microscopes that had water cooled lenses. Obviously, when you're looking at individual atoms you want your lenses to be as stable as possible. They all used chillers made by Haskris that are super stable because they have a hot gas bypass loop. It feeds a controlled account of heat from the hot refrigerant into the water bath to make up the difference between cooling capacity and the load (the equivalent of 70w in your example). The only drawback is the compressor runs 24/7. Well that, and the condenser used to be cooled by running tap water through the coil and down the drain. Electron microscopes are crazy expensive to run.
Hi
Thanks for that great "other world" experience where I completely understnd the need for absoloute temperature stability. Although I understood the basic principle of refigeratied cooling, it was not until I started examining the way that the CW5200 worked that I began to learn that reservoir temperature had such a massive effect on the rste of hest extraction. It's obvious when you break the problem down but who has ever done this? Hence the laser community is has always been sold a seriously over powered cooling system. There are myths about power and water temperature that I will tackle in another video. My own simple trials in hot summer months with just a simple tank reservoir allowed me to run at 45C for an extended period with little loss of power. I will do a more detailed examination of this issue because I am convinced that temperature stability , rather than absolute temperature, is the most important factor to stabilizing power output.
Best wishes
Russ
I am cooling my laser tube with a water dispenser, for around 3 years now. It goes very well, with a temperature digital controller, for the compressor. 250 wats. cost $75.
Another great video. And I certainly learned a bunch.
Very nice tutorial about my 5200 chiller Russ, thanks a lot! I didnt know I could turn off intelligent control, now I will! Also, since I am lazy, my solution to this fluctuation problem would be just to add a "capacitor" to the system, in a form of additional water tank before it enters the laser tube, this will just smooth temperature fluctuations, quick and dirty. Or is there something I am missing? What do you think? I am aware that it wont fix the pump overflow, but it should fix the temperature flux.
Hi Vlad
Yes. additional volume of cooling water will buffer the changes but it cannnot be an "open" reservoir if you wish to use the same pump. The normal "fix" for this issue is to make a simple copper coil from 10mm copper pipie from a DIY store and pump the chiller water through it. Drop the coil into a seperate buffer reservoir and use a submesable pond punmp to supply water to the tube. However. running at a low temperature may achieve the stability you require without any of the fuss. I have chaecked a friends 160 watt tube and with just 2.5L/min flow, the temperature difference is 2C. This is equivalant to 350 watts of heating effect and can easily be stsbilized by running at a low temperature.
This is not the end of this story because I am in the process of buying a micro chiller that I plan to integrate within the case my machine. This reearch has shown me that the conventional CW5000/5200 approach to chilling is something that works but is unneccesary overkill
Best wishes
Russ
@SarbarMultimedia 5200 is a total overkill I agree, but thats all the market has to offer and at a reasonable price at the moment. I personally do not have such issues, despite using this same model, but you know I don't engrave a lot of photos on wood either :-) i do engrave on wood sometimes, and have not noticed anything like this and I am in USA also. My outside temperature is often 38C or more, I usually try to run mine at a minimum, so it's set to 27C usually. Dont like the compressor to have to frequently kick in and also dont like it to waste too much electricity either. Everything else is to default. I will definitely get rid of that intelligent control right away, it never made any sense to me for CO2 laser anyways. I constantly had to readjust that.
I have different problem. CW5200 is no so efficient. So I start in morning with 18C and temperature slowly reach 30C... The water tank is too smal and refrigeration unit pretty weak.
I have a good relationship with Thinklaser, the company that supplied one of my laser machines and who lent me the CW5200 to experiment with. They have lots of CW5200 experience and they have encountered sevral problems with many of the units
A) They were uundergassed by as least 50% ie the cooling capacity was much lower than specified
B) The Gass specification was and illegal for at least Europe and USA.
The unit you see me using is one that has been fully regassed with the correct legal refigerant.
You have seen that when operating with the correct voloume of refigerant (legal or illegal) the unit is a beast when sert to run at 25 to 30C. The fact that you temperature rises means your refrigerant is low and you are getting insufucient cooling. As you can see from my tests, a 70 watt tube creates 280 watts of heating, If you are not suppling at least -280watts of negative heating (cooling) then you temperature will rise. I suspect that any auto airconditiononing regasser will be able to fix your problem.
Yes ,at 6 litres, the tank is pretty small and IF your refrigerator was working properly it would be swinging by 4 or 5deg C. The bigger the reservoir the slower the temprature changes will occur.
Best wishes
Russ
I don't know if the is true but I heard you want as close to zero temperature swing as possible because otherwise the tube expands and contracts, which changes the distance between the mirrors that needs to be a multiple of the wavelength for maximum power. I haven't done the sums to see if it is practical to keep the distance constant to within microns.
This isn't the case. The mirrors are not multiples of wavelength. The lasing process is what creates coherent light of the same wavelength and phase. When a photon passes by an excited gas molecule, it emits a photon of identical wavelength, phase, and direction. The mirrors just keep enough photons bouncing back and forth to trigger the emissions
@@dannymiller2123 Yes the tube lases regardless but I think the power output peaks when it is a hole number of wavelengths because it resonates optically.
Russ looks into temperature effects in a subsequent video, it turns out that temperature impacts the beam profile, especially on lower-grade tubes. (The critical parameter apparently being the curvature of the mirrors, rather than distance between them.)
Centrifugal pumps use less energy at lower flowrates than open flow so in theory you will be adding less energy when you choked the flow. It is also non linear and at an educated guesstimate a cheap pump like this is likely running at circa 60-70% efficient at your 4 l/min flow. Compared to the Laser heat generated it will be fairly minor and can be ignored unless you want to get really nerdy (no chance of that of course) 😂 **For others no flow is a really bad thing that energy used boils the water in the shell and melts plastic and seals.
I don't use a CW2500 but I have two CW3000 s and another machine with a plastic reservoir and pond pump . Duriing really cold spells in winter months (rare here iin the uk) I leave the pumps running and find they keep the temperatures at 4 or 5C because of the typical 60 watts of energy going ointo the water.. If the
outlet is unrestructed the little centrifugal rotor runs at full speed and delivers the rated pump flow. If you stall the flow the motor does not stop. inbstead there is a fixed captivated volume that remains in the "water wheel" but there is fluid shear (and may be cavitation) happening all round the edges of the water wheel which is where the motoer energy ( only slghtly reduced in speed) is converting its energy to heat.This is witnessed by the long slow temperature climb cycles when I removed the 70 watt input and it was just the pump circulating water. This is totally in accord with the Law of Conservation of Energy. Looked at in simple terms, the 70 watts of of laser energy is created by 280 watts of heating energy . There are other electrical energy inputs at the HV power supply to create the ionization so you can see that the laser tube efficiency is probably about 20%. As you rightly mention. the heating from threpump is a negligible proportion of this heating overall effect but to be clear, was not included in this study because I was measuring just the temperature change across the tube.
Thanks for the great info.
Russ
An interesting topic to think about. A centrifugal pump in the “stalled” state draws less power for the motor because it isn’t doing as much work in moving a mass of water against a pressure gradient. However, as Russ points out there’s more turbulence and shear happening inside the pump body, which will be absorbing energy from the motor, leading to greater heating in that part of the system than otherwise.
When the pump is working properly and circulating water, the motor will in fact be putting out more power (higher current drain from the AC supply), which leads me to wonder where that energy is going? It must be being converted to heat and dissipated somewhere.
I completely trust Russ’s careful measurements and wasn’t paying close enough attention to details at this level during the video, but as long as the water is moving in the same loop, simply with flow restricted in one case but not the other, I’d expect the overall system temperature to increase slightly more rapidly in the full-flow case vs restricted-flow. (OTOH, if the water is traveling a shorter loop in the restricted-flow case, then it very well could warm more quickly because it’ll have less area over which to dissipate the heat.) I expect any difference would be very small relative to the thermal resistance of the system as a whole though.
(Really great work by Russ as always; he does a fantastic job of cutting through myths and getting to what’s actually going on. Sometimes there’s some reason behind the myths (just not what people thought it was), other times they’re complete fantasy. Hard data gives the answers and lets us understand the reasons behind them 👍😁)