Capillary tube size, refrigerant, oil

[desA]

^ That is quite a remarkable picture.

Can I ask why you are using so many capillaries, & not a TXV?

[aabbcc]

^ That is quite a remarkable picture.

Can I ask why you are using so many capillaries, & not a TXV?

Because of the :
Efficiency
Cost
Efficiency Again - No Valve can match the cappilary in efficiency.
Rapid balance of the system
No malfunctions , No orifice
Well many more ...

And because I have tried the TXV's without having the same results.
But results for each one of us different ... So for me the capillary is the one.

[desA]

Because of the :
Efficiency
Cost
Efficiency Again - No Valve can match the cappilary in efficiency.
Rapid balance of the system
No malfunctions , No orifice
Well many more ...

Very interesting.

I'm finding the capillary to be very challenging. For small power systems, it's difficult to get a TXV anyway - they are also expensive. It is going to be worth the time & effort to get to understand these fascinating parts of our toolbox.

How do you see the cap tube working for a heat-pump, with the large spread in Tc,sat from cold to hot condition?

[aabbcc]

Very interesting.

I'm finding the capillary to be very challenging. For small power systems, it's difficult to get a TXV anyway - they are also expensive. It is going to be worth the time & effort to get to understand these fascinating parts of our toolbox.

How do you see the cap tube working for a heat-pump, with the large spread in Tc,sat from cold to hot condition?

I have never tried to work capilary on a heat pump.
However my opinion is the target with the Cap is to make the LOW PRESSURE decreases as possible even in 40C work conditions. As mentioned before the Tcsaturation and/or superheats, subcooling and all the book of thermodynamics can be manipulated else way. As mentioned in previous posts for R22 and R404A this can be done with Presure switches to control the fan. Also the use of more capilaries instead of one, the quantity of refrigerant, a receiver , fan rpm, fan pitch, Diam of fan, condensing unit and many more...

What I am thinking now is that the Cap on a heat pump might and should work different since the system advantages from the HOT PLATE - not the cold.

So the more HP in the Hot plate (that in standard systems is the cold plate) the more of the benefit...
So we are talking for a smaller condenser and bigger in length capillary... Then wll need some more fluid in it, but will change the thermodynamics once more...
So you need a small receiver in order to store the excess of the refrigerant fluid.. Receiver can be a small filter of let say 60gram as the excess of refrigerant should only be a +25gr ~ 50gr.

I refer ,as have in mind an older htread of yours, to the system have in your lab and the rest of the members gave a fantastic analysis and manipulation of DANFOSS programs...

The noise you were listening it is because the system needed those 25~50 grams... BUT in a warmer weather you would have a problem... BUT WHO CARES as in warm weather the HEAT PUMP will be out of work...

Again sorry for my LONG TEXT..
I have tried NOT to enter in any formulas or calculation because I would make it with my Greek letter formulas and then we would LOST TO TRANSLATION and more important BECAUSE I STRONGLY believ that formulas CANNOT PREDICT CAPILLARIES...

[desA]

I have never tried to work capilary on a heat pump.
However my opinion is the target with the Cap is to make the LOW PRESSURE decreases as possible even in 40C work conditions.

With a heat-pump, there is advantage in allowing the LP rise in a controlled way. If the LP s dropped, then compressor pressure-ratio will be stretched, resulting in high compressor discharge temperatures. There is a limit as to how high the discharge temp should be allowed to climb.

As mentioned before the Tcsaturation and/or superheats, subcooling and all the book of thermodynamics can be manipulated else way. As mentioned in previous posts for R22 and R404A this can be done with Presure switches to control the fan.

For a heat pump, the equivalent of your LP manipulation techniques, would be at HP - by adjusting condenser performance eg. speed up water flow.

Also the use of more capilaries instead of one, the quantity of refrigerant, a receiver , fan rpm, fan pitch, Diam of fan, condensing unit and many more...

Can you perhaps tell us more on your ideas here?

What I am thinking now is that the Cap on a heat pump might and should work different since the system advantages from the HOT PLATE - not the cold.

So the more HP in the Hot plate (that in standard systems is the cold plate) the more of the benefit... So we are talking for a smaller condenser and bigger in length capillary...

Yes, the HP side needs to be worked with - but, don't raise the Tc,sat, as this will lower system COP. The condenser heat-transfer efficiency needs to be adjusted.

Then wll need some more fluid in it, but will change the thermodynamics once more...

I'm interested in this comment & why you need more fluid. Is this because of increased cap tube length?

So you need a small receiver in order to store the excess of the refrigerant fluid.. Receiver can be a small filter of let say 60gram as the excess of refrigerant should only be a +25gr ~ 50gr.

I refer ,as have in mind an older htread of yours, to the system have in your lab and the rest of the members gave a fantastic analysis and manipulation of DANFOSS programs...

The lab system has an inline filter-drier, as well as a small suction strainer, before the cap tube.

The noise you were listening it is because the system needed those 25~50 grams... BUT in a warmer weather you would have a problem...

So, you feel that the noise was because the system was short of refrigerant? Can you perhaps explain this further?

[aabbcc]

I do not think this will lead to any logical conclusions. But will try...

With a heat-pump, there is advantage in allowing the LP rise in a controlled way. If the LP s dropped, then compressor pressure-ratio will be stretched, resulting in high compressor discharge temperatures. There is a limit as to how high the discharge temp should be allowed to climb.

• That was the general idea. The start of my thinking ending in the next sentenses that in a heat pump things should work else way...

For a heat pump, the equivalent of your LP manipulation techniques, would be at HP - by adjusting condenser performance eg. speed up water flow.

Can you perhaps tell us more on your ideas here?


Yes, the HP side needs to be worked with - but, don't raise the Tc,sat, as this will lower system COP. The condenser heat-transfer efficiency needs to be adjusted.

I assume you are talking for the COP ratio of ref capacity and compressor consumption.
The HP will not increase dramatically and will definetely not infect the compressors consumption , but with the longer Length will increase the HP and (Boyle/Marriot) increasing Pressure = increasing Temp..

I'm interested in this comment & why you need more fluid. Is this because of increased cap tube length?

• Because of the Length and the Working Temp is below (assume) 10C... The fluid has shrink.

The lab system has an inline filter-drier, as well as a small suction strainer, before the cap tube.



So, you feel that the noise was because the system was short of refrigerant? Can you perhaps explain this further?

As mentioned I assume the Heat pump is working below 10C. The ref is shrinking. Perhaps Cap has been adjusted to work above 10C...
With a small receiver there is the possibility to have the adequate amount in cold days. Over thermodynamics you/we have to calculate again and again with different ambient conditions and different amount of charges...