Capillary tube size, refrigerant, oil

[desA]

All this grunting & groaning...

DesA
Grunt;, if we look at the end result, net cooiling or indirectly net heating (cooling plus motor), if you have enough mass flow (compressor grunt), then diresed results can be acheved, nothing to do with efficiency.

Ok, so basically with enough compressor over-size, the job can get done, no matter the efficiency. True, but getting harder to justify in these days of price & energy pressures.

What is ideal sizeing for cap, firstly one that always protects comp, low mid or high, I would look at the combination that gives the best results over a process, even though performance may be poor a some point of the process.
Acc does allow for a an over charge

Fair-enough - I'd agree with that viewpoint. What I had in mind is developing a set of simple design rules which target a cap to work at a representative cycle nominal point. This would allow pretty much a one-shot selection process & save a lot of cut-&-try. If the essential process remains consistent & the evap/compressor/cond selection/design philosophy remains consistent, then there is no reason for such a nominal selection procedure to not have a reasonably high accuracy.

aabbcc, only done alittle work in fractional comp hp range, where TEV valves are not available, so here caps are good.

You are correct. Also, the cost of a TXV may not be justified in these applications.

in commercial range never came across a system that we could protect, i presume you are taking systems with very low loads, where valves minimum are higher than the low load, you are using the cap as a flooded system. critical charge.

What do you mean when you say 'protect'? SH control, liquid floodback?

[desA]

Well My silly receiver...

Madfridgie...
I am talking for capacities of 1/8Hp up tp 7Hp...
Being honest I have a project for more than 7Hp and honestly I am not sure if will work... Then eventually we will turn to TXV's ...

Else could say in the 80% of the worlds ref systems LOL....

Very nice sketch. Thanks for that.

How are you going to get the oil to move out of there, though?

[desA]

And something that have just remember. desA another practical way to help you more fill a cap system with fluid is the sight glass to be installed in suction line... Between the evaporator and the silly accumulator I draw ... (LOL)

I know is common to put the sight glass in the HP line... But try it and see. Just My 2cents

That is an interesting idea. The sightglass will tell us a tremendous amount about what is really going on in the suction line.

Very good point.

[desA]

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...

A good point. The noise level certainly rises in cold weather.