Carters Widget Revealed (Just Facts - Nothing Else)

[Gary]

I'm wondering if there is sufficient liquid pressure to feed the evap coil?

[mad fridgie]

I'm wondering if there is sufficient liquid pressure to feed the evap coil?

This had to be considered, when designing the rigg, I chose a large EEV!
I am able to control the superheat right down to 1.5 bar difference, then the evap does become starved.
How ever heat transfer co-efficients may be effected. (how ever I did attempt to simulate this during standard tests)
Thanks again gary for your thoughts

[chillerman2006]

In looking at the diagram, it occurs to me that there could be substantial heat transfer (by conduction) between the two flow streams, within the ejector. The motive flow stream being near or at saturation, there could be condensation before the slit inlet followed by rapid flashing at the slit outlet. This could cause turbulence, which is the enemy of coanda effect. A solution might be to increase superheat in one or both flow streams.

I would heat the top of the separator. It would seem preferable to increase the superheat of the motive flow and then balance this against lower evap superheat, resulting in optimum compressor inlet superheat.

Intersting is it not.
gary you have sort of hit an issue on its head, when dealing with gas/liquids at saturation, it is very difficult to determine if for example that the vapour is just that, and not a vapour with a small trace of liquid in it.
On the two purchased units, with motive force is introduced on the circumference, yes larger surface area, and I do not think your suggestion should be discounted. (even though during some of the test , heat was added to the motive line to ensure liquid was not present) If we used a liquid line to motive heat exchanger then we slightly reduce the flash gas being produced. (the energy remains neutral in the system), if we use an external force, then we are adding energy to the system, without benefiting the system directly.
The one I built was more like an industrial TVR, single nozzle in the centre of the body, very little heat exchange would be possible. (these tend to be used for higher compression, but less suction flow) The hand build one I just guessed. (did seem OK until i tried to make it better) These things really do need science behind them, not just for perfection (ideal refrig conditions) but to understand what happens when we move away from ideal, which we all know is the absolute reality with small to meadium systems.
Thanks gary for your thoughts, always valued.

combining your thoughts here gents, is it possible to run the discharge pipe & seperator outlet through a small heat exchanger, ensuring the motive force is just vapour & maybe then allowing for a lower superheat evap outlet ???

[Gary]

combining your thoughts here gents, is it possible to run the discharge pipe & seperator outlet through a small heat exchanger, ensuring the motive force is just vapour & maybe then allowing for a lower superheat evap outlet ???

Hmmm... you have pumped heat from the low side to the high side. Now you want to transfer that heat back to the low side... to be pumped again. Doesn't sound very efficient.

[chillerman2006]

Hmmm... you have pumped heat from the low side to the high side. Now you want to transfer that heat back to the low side... to be pumped again. Doesn't sound very efficient.

Hi Gary

liquid injection agreed, but the minimal discharge superheat required prior to condensor to ensure no liquid to fwidget, surely makes sense, the problem I have is I can not get my head around the quasistatic process required to fathom equilibrium, best left to the real brains of the industry, as not many will, unless you can do us the honour of explaining the process in detail with all your calcs,

R's CM

[Gary]

Calcs? You are confusing me with someone who does math.

[chillerman2006]

Ok, mate we shall have to hope Chef, DesA or Peter_1 does us the honour of explaining it one day & you can add that to the other 99.9999% of the industry you already have tucked away, thanks anyway mate

[Tesla]

Hi mf
Just thinking outside the square - is it possible to calculate roughly when it is not working? with graph gradients or measurements verses time. Say on start up it could be that the sweet spot is not found till after x seconds and then check for additional times. There may be some common parameter values at start up which equal definite failure of experiment. You could be looking at a resonant response for success.

[mad fridgie]

All tests were completed on a 20 min cycle, with only one change per made at any single time.
So about 12 tests a day.
Plus short term tests when a major change is made. (some times you can see when things are just wrong)
As with any refrig system, time is taken to reach equilibrium, even though this section was ignored for the performance results, it was all ways monitored.

Good thoughts

Tesla

CM; your point also has merit, but as Gary says we are introducing extra energy, what you should of considered is using the liquid line (how ever this has its own issues "less flash gas"

Individual parts can be made to work with satisfaction, but refrigeration is not a group of parts, it is a system!

[chillerman2006]

Post removed - as again have miss-understood...not a designer...just mr nuts & bolts !