DaBit
18-06-2002, 03:03 PM
Well, as some of you still remember, I am busy developing a liquid chiller which cools a water/methanol mixture, which in turn cools various parts of my PC. More information can be found in my previous topics, but I will summarize the most important data here:
- Refrigerant: R134a
- Compressor: Danfoss NL11F
- Evaporator: coaxial heat exchanger
- Qmax=200W @ -20 °C
- Qnom=150W @ -20 °C
- Coolant used: 30/70 vol.% methanol/water mixture.
- Coolant flow: 600-1000L/hour, netto.
Currently I am using capillary expansion which is not very suitable for this application due to the large variations in system load. Superheat at the compressor inlet varies between 5K at low load conditions, going up to 22K at high load conditions. The average liquid temperature is about -12 °C.
Progress since my previous topic is not so much. I had troubles with the methanol leaking around seals, which I solved (a PVC hose<->metal junction is an ideal methanol filter, which passes methanol and keeps water inside). I also finished most of the system elektronics, and I did some minor adjustments to the coolant loop. Also, the CPU, chipset and RAM is cooled now, which allows me to run at about 2GHz CPU speed (using a 1533MHz processor). No condensation or ice forming takes place anymore on the elektronics since all elektronics are mounted into a airtight box which is equipped with silicagel to get the moisture out of the air. This works very well, even better than expected.
For the liquid chiller itself: it has not yet changed, but the current setup runs flawless. I am still trying to find parts to upgrade it.
The person who used to be able to obtain parts for me seems to be dead. He does not react on E-mail or phonecalls.
The crucial parts I still need are:
- dryer with 1/4" ODF solder connections.
- receiver.
- starting relay and capacitor to use the NL11F as HST compressor.
I can build the receiver and starting relay myself, so that's not crucial. The filer/dryer is more critical since I have not yet been able to find a company which is willing to sell me one.
One part I have been able to obtain is a Danfoss TEV type TEN2, a solder->flare adapter for 1/4" ODF, and a orifice size 00. This TEV+adapter has an external pressure equalisation port (1/4" line), 1/4" liquid line connection, and a 1/2" connection to the evaporator.
Now, orifice 00 is not the smallest orifice available for this valve (that's orifice 0X). It has a rated capacity of about 700 Watts @ -20 °C (this from my memory since I do not have datasheets ready over here. The actual number might differ) when mounted in a TN2/TEN2 valve. I know I am better off using a 0X size orifice which has a rated capacity of about 300W @ -20 °C, but things are just the way they are.
Questions:
- Is it safe to mount this TEV+orifice in the mentioned system, or is it a ticket to a lot of trouble? I read that TEV's can work flawless down to 30% of their rated capacity. 30% of 700W is still a lot more than the load I am applying.
- What will actually happen when the orifice is too large? I understand that a thing called 'valve hunting' starts to happen. I understand that this is the rapidly opening and closing of the valve due to control loop instabilities. But what is the effect in practice?
- Does anyone of you know an address of a company in The Netherlands which is willing to sell me at least a simple dryer with 1/4" solder connections? Please keep in mind that I do not posess the required (STEK) license.
(Due to the extreme heat here at work my English might be even worse than normal. My excuses for that.)
- Refrigerant: R134a
- Compressor: Danfoss NL11F
- Evaporator: coaxial heat exchanger
- Qmax=200W @ -20 °C
- Qnom=150W @ -20 °C
- Coolant used: 30/70 vol.% methanol/water mixture.
- Coolant flow: 600-1000L/hour, netto.
Currently I am using capillary expansion which is not very suitable for this application due to the large variations in system load. Superheat at the compressor inlet varies between 5K at low load conditions, going up to 22K at high load conditions. The average liquid temperature is about -12 °C.
Progress since my previous topic is not so much. I had troubles with the methanol leaking around seals, which I solved (a PVC hose<->metal junction is an ideal methanol filter, which passes methanol and keeps water inside). I also finished most of the system elektronics, and I did some minor adjustments to the coolant loop. Also, the CPU, chipset and RAM is cooled now, which allows me to run at about 2GHz CPU speed (using a 1533MHz processor). No condensation or ice forming takes place anymore on the elektronics since all elektronics are mounted into a airtight box which is equipped with silicagel to get the moisture out of the air. This works very well, even better than expected.
For the liquid chiller itself: it has not yet changed, but the current setup runs flawless. I am still trying to find parts to upgrade it.
The person who used to be able to obtain parts for me seems to be dead. He does not react on E-mail or phonecalls.
The crucial parts I still need are:
- dryer with 1/4" ODF solder connections.
- receiver.
- starting relay and capacitor to use the NL11F as HST compressor.
I can build the receiver and starting relay myself, so that's not crucial. The filer/dryer is more critical since I have not yet been able to find a company which is willing to sell me one.
One part I have been able to obtain is a Danfoss TEV type TEN2, a solder->flare adapter for 1/4" ODF, and a orifice size 00. This TEV+adapter has an external pressure equalisation port (1/4" line), 1/4" liquid line connection, and a 1/2" connection to the evaporator.
Now, orifice 00 is not the smallest orifice available for this valve (that's orifice 0X). It has a rated capacity of about 700 Watts @ -20 °C (this from my memory since I do not have datasheets ready over here. The actual number might differ) when mounted in a TN2/TEN2 valve. I know I am better off using a 0X size orifice which has a rated capacity of about 300W @ -20 °C, but things are just the way they are.
Questions:
- Is it safe to mount this TEV+orifice in the mentioned system, or is it a ticket to a lot of trouble? I read that TEV's can work flawless down to 30% of their rated capacity. 30% of 700W is still a lot more than the load I am applying.
- What will actually happen when the orifice is too large? I understand that a thing called 'valve hunting' starts to happen. I understand that this is the rapidly opening and closing of the valve due to control loop instabilities. But what is the effect in practice?
- Does anyone of you know an address of a company in The Netherlands which is willing to sell me at least a simple dryer with 1/4" solder connections? Please keep in mind that I do not posess the required (STEK) license.
(Due to the extreme heat here at work my English might be even worse than normal. My excuses for that.)