Thanks Magoo
got it, I can understand that (had to re-read a few times though)
R's chillerman
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Hi MF.
very good and very clever, as in direct injection sub-cooling, a bit of a hand grenade with a loose pin though. But then again with stable loads would be very manageable in hindsight.
What happened with Mr T and Pete etc., after last conversation, good or hopeless.
magoo
Hi again MF.
out of interest, are you using split circuit PHEs or other HXs.
magoo
O.k. Mad. At the risk of a crash and burn probablity, there is another thought i have. Can there be a free energy effect,( minus mechanical losses) where one could use discharge pressure, or more likely liquid, while compressor is running to power a small turbine. My thought is.. the slave turbine in the suction line can increase suction pressure to compressor at the added benefit of reducing evaporator pressure, thus increasing evaporator efficiency? Seals will be a problem and so will driveshaft configuration. Increased pressure to compressor gives better efficiency on the low temp applications. So.. what do you say? Has this been debated before?.. Mike,( not the one sipping beverages on the beach :p).
There is no crash or burn on this thread, (not on my watch)
The discharge pressure has to be produced by power, (how ever some have looked at using ejectors to produce higher than motive pressures, but this is beyond my what I know)
using liquid soley as a driver (very little benefit) this watt a low wattage pump can pump L/S versurs head.
using the liquid then expanding through a turbine may work (energy purpose only), very similar to gary's attachment.
A lot of work has been done on efficiency and using ejectors, but I "believe" using the widget method is original and somewhat more practical (I not attepting to get 100% better performance 100% of the time)
good thoughts.
Even though you have a concept you still need to prove possible performance. I have my method, which may be right or wrong, but I am wanting others appraoch to see if it could be a goer.
If you split the flows as follows:
1. Vapour only (your 'flash gas') at m'fg;
2. Liquid only at m'l...
3. m'r = m'l + m'fg (total flow before split)
... then, if we know the pressure of each stream, we can locate the individual state points as follows:
1. Vapour - assume saturated vapour - located on right of bell;
2. Liquid - assume saturated liquid - located on left of bell.
If the fluids are mixed, then the mixture properties are constructed based on 'x', the vapour percentage in the mixture.
If the vapour is transported away, then only m'l goes towards the evaporator. The net refrigeration effect (assuming fully saturated liquid) is:
Q'evap = m'l*hfg
Where :
Q'evap = evaporator capacity [W]
m'l = liquid mass flowrate [kg/s]
hfg = latent heat of vapouraziation [J/kg]
So, the real amount of duty [W] managed by the evaporator will depend on how much liquid is actually going to it.
See that this thread was very busy during the night and noticed also it has been filled up to nearly 5 pages.Will make some time this evening to read was said.
Sir, the beach is not for me but the sailboat is;) and of course, so is the beverage sipping.
MF, Without a lot of pondering, I would think the venturi part of the widget will need to be on the suction line as the "motive force" would best come from higher velocity gas from the evap. There needs to be a certain differential to make the venturi work, typically 5:1 to 10:1 and there is an increased head loss incurring when the "motive force" or the straight line flow is restricted to create the suction through the branch.
(one could use discharge pressure, or more likely liquid, while compressor is running to power a small turbine. My thought is.. the slave turbine in the suction line can increase suction pressure to compressor at the added benefit of reducing evaporator pressure, thus increasing evaporator efficiency? Seals will be a problem and so will driveshaft configuration. Increased pressure to compressor gives better efficiency on the low temp applications. So.. what do you say? Has this been debated before?.. Mike)
There are very low wattage circulators that are magnetically coupled so the seal issue is not a problem. Of course, they are typically in the range of 1-3L/m LIQUID flow and have head values of around 1-2m. I don't know if this helps with mikes pondering. Messed up the quotes above.
It is not really a venturi,( I think), more like an air mover "condell" (or maybe not).
There is difference in the pressure.
This where true expertise in this field is required. ( and it aint me!)
Also you already have flow regime in the suction line (verses a dead head/static flow on say a normal venturi)
If you look on your copeland compressor program, pick R404a, pick a low evap temp and mid range cond temp, check duty,( note pressures) now just up the evap temp a bit and see what the new duty is, check the pressure difference. (you will be suprised) maybe
Yeh, missed the velocity factor during my pondering :(.
I'm not an expert in venturi effect, but I have 2 concerns about this widget.
1. To create venturi, we need significant pressure difference between pressure in this vessel and suction pressure. This pressure difference will not be significant.
2. In verturi, main flow will suck secondary flow. As far as I know, main flow should be significantly greater than secondary flow. For example 10:1. Assume that flash gas is 20% of total gas flow. 80% of gas create by net refrigeration effect. It means that that 1 part of main flow will suck 4 parts of secondary flow. This will not happen.
A thought:
1. Replace TXV with small rotational device;
2. Liquid flashes across rotational device (RD1) to desired LP;
3. Rotational device (RD1) drives a rotational device (RD2) placed in suction line.
4. RD2 'stuffs' flow into compressor.
I tend to agree with this assessment. In the Denco configuration, the full flow of the system is harnessed to provide the motive force. As i understand it, the Carter configuration attempts to use a small fraction of the flow for it's motive force... or possibly I misunderstand the workings of the Carter Widget. I'm thinking a flow diagram might be helpful.
Gary.
I agree that Denco configuration has greater pressure difference. However, volume of main flow is not greater than volume of secondary flow, because main flow has mixture of liquid and vapor and secondary flow has only vapor. I'm not sure that Denco configuration will work either.
By definition, the secondary flow is going to be a fraction of primary flow... the difference will come from flashing in the separator. The question is not will it work, but rather how well will it work?
It is unlikely to be a venturi (as you know it) I have left this part open to what it actually is, Basically it is a Thermal Vapour Compresssor (TVR) or some form Condell effect mover. (these devices use less mass flow for the motive force as the driver).
Your are not really sucking, as this applies a stastic flow, as we know we have flow through the suction.
The first question has to be does it have the potential to work, and how to we prove what the results would be in a perfect world.
Secondly if the question is yes then what piece of equipment is required to achieve the results.
I have formulated my own calculations, and have built a test rigg(s) to test. Thats does not mean my method is correct, nor the parts chosen for the test rigg are even close to what is required.
Morning MF
does it make a difference with suction flow, where the flash gas ends up ?
(Suction line or direct into compressor)
Attachment 7132
A very basic drawing of the widget configuration
MF
I think you have with your drawing & the posts (unless I am missing something)
Your controlling condensor pressure
Your removing flash gas, improving mass to txv, improving evap efficiency
Your increasing suction pressure
Overall refrigeration efficiency has to go up ??? Surely
Now I can see it - I can not see any pitfalls (anyone agree ????)
R's chillerman
It is some what more complicated in the theory, how ever I do not want show how may calculations have been achieved. I do not need some to check that i can add my apples calculation, when in fact what i should calculatting is bananas, in other words my method of determining efficiency/performance may well be flawed, and I do not want to influence, others thought patterns on what the result maybe.
The practical objective is to reduce the compressor displacment, increase COP.
The pic is just a snapshot in time at a steady condition!
Practically and what is required to prove performance is a the system moving to reach a steady state.
The compressor inlet pressure will only increase when the process is underway, so to start with it will run similar to a normal system, as we start to recompressor, the compressor mass flow will increase, which inturn makes more flash gas in the vessel, which gives greater levels of recompression and so on until equalbrium is reached.
ok am no genius am just a fix it tech perhaps you need to look at yr problem from different angle instead of fitting it to existing system as a drop in part to inrease efficency design a whole system around yr widget and then when you have it working 100percent go back and adjust yr design for drop in fitting :) basically taking an idea and making it better is that to easy ? or do i need a good kick and to shut up ? lol
just hit me looks a little like an nrc enviro pack design low pressure reciever that was higer than case tev so gravity fed valve
The drawing show the liquid/vapor seperation in the vessel.
100% in liquid (35C sat)
Reduce pressure (0C sat)
Liquid leaving 69% (0Csat)
Vapour leaving 31% (0C sat)
This would remain a constant as long as the incoming liquid remained constant.
How ever the actual total mass flow SHOULD increase over time (as the process fires up).
PS figures care of old faithful Coolpack!
Certainly no good kick required, it is opinion that we are after, right or wrong does not matter, I would hope that most on here are not here to belittle those who are making an effort. and what you are saying does make sense.
The fact is that you would need to design or redesign the system when fitting the widget, more to do with how the TEV is sized and how the evap coil is confirgured (but that well down the path of proving it works or not)
I do not want to be BS artist, so we have to compare the performance of a system with a widget and without.
The problem is i can not get it working, with any form of repeatability (sometimes very good, sometimes very very bad)
And i am unable (due to lack of funds) to find the right information to solve the issue.
cheers for your input
Mad
G,day C.M. Have not been on long this morning, (as you already know;)), so i'm catching up on reading. Got the telescope out to see if Mike "Canada" is there ready to put a sock in my mouth again. Check top of page 2 :D..Mike.
but the rigs he has are conventional systems ? with widget added ? am talking about complet system design to give him flow required at optimum velocitys :) from my limited perspective if the condensor is over sized slightly with a flow regulator after it and the reciever is used as a surge vessel to back liquid up instead of a conventional reciever which flow passes through liquid will be constant vapour will be constant condenser will act as a semi reciever the rest is standard ish :)
Long story short!
First rigg, just modified an existing rigg nothing to special, to see if there was potential, had possible results.
(also some flawed testing) because part of the design is to consider what happens if there is a failure with the widget (cause and effect)
Built purpose rigg, with 100% isolation and by-pass of each and every component. So it can be run as 100% conventional or 100% with widget and all steps im-between
can control load (flow and temp), pressure, Superheat, sub cooling, and condensing flow rates.
Basically we are measuring for results cooling capacity, power draw and heat rejected, whilst measuring the parts of the refrigeration system to ensure that we keep with component specifications.
The TVR could be wrong (venturi type device) more than one size and the wrong type, the vessel could be wrong, asumed peak performance may be wrong.