bi-compressor heat pump

[Lc_shi]

a parellel compressor heat pump as:
#Manurop performer parellel compressor
#two parellel evaporator
#two parellel condenser
#two tevs

attached a sketch for your review:
I want to know what your ideas about this kind system:
# both the evaporator and condensers are all plate heat exchanger type
#use one tev for both evaporators(same size)
#condensers(same size) are in parellel
What the better way to design pipes to meet oil return requirement while single compressor is working?

welcome any input:)

best regards
LC

[Lazarus]

Hi Lc shi
Presumably the TEV bulbs are positioned purely diagrammatically at the moment.
As to your question i would suggest a common oil separator with individual solonoid controlled oil returns (probally activated by delta signal). The separator should be mounted in the permanent common disharge line.
You will of course need NRV's in the individual disharge lines (depending on wether the compressor is designed to sit at discharge or suction pressure that is!!)

[frank]

Why 2 evaps and 2 condensers?

When only one compressor is running the TEV won't have any control as you will have high suction superheats (partially filled evaps)

[NoNickName]

Why 2 evaps and 2 condensers?


I'm also wondering.

[al]

Lc shi

York have a similar design but have two seperate circuits which gives very good temperature control, there is really no need for oil seperation if this is going to be a "packaged" unit?

Al

[NoNickName]

Lc shi

York have a similar design but have two seperate circuits which gives very good temperature control, there is really no need for oil seperation if this is going to be a "packaged" unit?

Al

Wow, York has two separate circuits. :D
I think most of the chiller manufacturers have at least two circuits. And most of them manufacturers do not separate oil. Instead, a liquid strainer is installed, to prevent slug to be pumped by the compressor while reverting the cycle.
We heat, defrost and back heating without stopping the compressor(s).

[star882]

Here's a PNG version for those who fear macro viruses, don't want to wait for OpenOffice to load, etc.:
http://i1.tinypic.com/v5ak1x.png
As for the question, the tradtional solution is to use an oil equalizer line.

[NoNickName]

But why should you bother with this layout?

[Lc_shi]

At first,many thanks for all of you.
Two evap and two condenser are required by our customer for special application. It can't be changed.
Both the evaps and conds are equal size and work at almost same condition.
My concerns as follows:
# while single compressor working, one TEV for both evap,certainly superheat is high, I'm not sure if the TEV can work properly from 50% to 100% capacity range
# single compressor working cause refrigerant flow velocity is lower to 1/2 of full load, the oil return from vertical tube may be with problem. I want to use bi-vertical U tube design to solve it.--is it OK?

PS, manuerop perfomer parellel scroll compressor has its special piping sets to keep both compressor from short of oil return situation. What I need to do is connect the discharge and suction as normal compressors. The parellel compressor is 18HP. For your ref:)


thanks and regards
LC:)

[US Iceman]

Hi LC,


# while single compressor working, one TEV for both evap,certainly superheat is high, I'm not sure if the TEV can work properly from 50% to 100% capacity range

A TXV will normally compensate for a 50% reduction in capacity reasonably well. A balanced port valve is my suggestion. I have had much better success with these valves.

One thing I am concerned about is the refrigerant distribution into the two evaporators. Without two TXV's the flow can become unbalanced and dependent on the pipe symmetry for balancing by pressure loss.

If the piping from the TXV to each evaporator is not symmetrical, the pressure losses will be unequal. This could force more refrigerant into one of the evaporators.

When only one evaporator is ON, what is to keep the refrigerant from stacking up in the inactive evaporator?


# single compressor working cause refrigerant flow velocity is lower to 1/2 of full load, the oil return from vertical tube may be with problem. I want to use bi-vertical U tube design to solve it.--is it OK?

If you are describing dual risers for the suction lift and oil return, I agree.

[US Iceman]

star882, can you resize your graphic please. It is much to large for the screen.

Thanks.

[Peter_1]

LC-Shi, why then not use an EEV, it will control teh SH perfect.
I think you can buy them in your country at cheap prices:p
Saginomyia and Fujikoki (Japanese brand I think) are valves we often see here in AC's.

[NoNickName]

LC-Shi, why then not use an EEV, it will control teh SH perfect.
I think you can buy them in your country at cheap prices:p
Saginomyia and Fujikoki (Japanese brand I think) are valves we often see here in AC's.

Siemens polycool also.

[Peter_1]

If the name Siemens is on it, then it certainly cost too much.:D
Heard from it but never saw it in real life.
It's the former Landis&Gyr Staeffa product I suppose.

Indeed,...Carel has it again, no PWM EEV like Danfoss but rela stepper motor control.
It works very fine and it's cheap.

[NoNickName]

It's the former Landis&Gyr Staeffa product I suppose.

It was developed by Siemens in Zug, Switzerland.



Indeed,...Carel has it again, no PWM EEV like Danfoss but rela stepper motor control.
It works very fine and it's cheap.

And it sucks. Carel interfaces their EEV with their software, but the hardware has a cycle time which is too slow for catching up without hunting. On the other hand, the first models of Adapkool by Danfoss were solenoid valves with PWM, and the repeated liquid hits into the evaporators were causing breaking-ups of the liquid distributors inside the tube bundles.

[Peter_1]

I have other positive experiences. In fact, only positive ones. And I think I can say I have some experience in different domains.

Very, very strange, almost unbelievable.

The more and more I read your posts regarding Carel, the more I think your vision is influenced by other factors, commercial, price,...
They're never founded.

In fact, it's not my problem.

Anyway, different visions exists and there need to be different visions. You have yours, I have mine.

Who's distributing Montair in BE?

[NoNickName]

We are dealing with Delta engineering and Amatech Diffusion. In case we can do business together, I'll install and setup a ****ty Carel controller for you. In fact, it will not then be my problem. :)

[NoNickName]

Oh, in order to stay on topic: in the schematic of LC, at least two liquid solenoids are missing, or would anybody trust the gas-tightness of a uniflow TEV?
And the bulbs are on the wrong side of their respective evaporative devices

[Lc_shi]

Oh yeah
The bulbs positions are wrong:(
You mean the liquid solenoid valve is a must. We've not used it in our heat pump product. Is there any concerns for it?
EEV is also a good idea. Worthy of thinking it over

rgds
LC:)

[NoNickName]

I think solenoids must be at least 2. How do you make sure otherways that liquid does not cross the TEV the other way around?
EEV will shut down, but the TEV will not necessarily...

[Peter_1]

Oh, in order to stay on topic: in the schematic of LC, at least two liquid solenoids are missing, or would anybody trust the gas-tightness of a uniflow TEV?


We don't fit SV's, never saw this before.
It's not wrong but it's not necesarry.
And and additional item that can cause faults.

[NoNickName]

So Peter, what TEV are you using in order to make sure liquid will not flow in the other direction?

[Renato RR]

the main concern is the unbalance of two evaporator loading which will cause the mass flow different. The inlet and outlet pressure must be equal, so the evap superheat is out of control that may one low loading evap make the Tev close. It's not a good idea but help you do brain exercise-

rgds
LC:-)
Your answer to 1 Tev 2 evaporators thread started by mee.So you are going by my steps IC SHI.

Renato

[US Iceman]

...repeated liquid hits into the evaporators were causing breaking-ups of the liquid distributors inside the tube bundles

I have heard of this from one manufacturer also.

Apparently the problem is due to the liquid hammer created by the pressure pulses of the valve opening and closing quickly.

I still think each evaporator needs a separate TXV.

[NoNickName]

Yes, Iceman, that's it. Danfoss denied responsibilities, charging the evaporators manufacturers of poor quality product. Incredibly, Danfoss retired the Adapkool shortly after.

[US Iceman]

...charging the evaporators manufacturers of poor quality product

I don't think it was a quality issue at all. It is a phenomena of dealing with strange fluid mechanics that no one thought of.

The basic idea of the valve was OK, but as it turned out the valve caused the failure of the distributor.

I doubt the evaporator manufacturer was to blame...


Incredibly, Danfoss retired the Adapkool shortly after

Kind of completes the story, heh?

[Andy]

Yes, Iceman, that's it. Danfoss denied responsibilities, charging the evaporators manufacturers of poor quality product. Incredibly, Danfoss retired the Adapkool shortly after.
Adapkool is still alive and strong, we use it every day, installing it in our high quality installations. Energy savings are in the region of 33%, at least 25% higher than any other controller or electroniv valve I have used.

Kind Regards.Andy:)

P.S ice in the inside of the tubes will damage the coils in such a manner;)

[NoNickName]

I referred to the first version of Adapkool with on/off regulation. No savings at all, and responsible for liquid bursts into compressors.
I would not consider as serious any chiller with Danfoss EEV.

[Andy]

I would not consider as serious any chiller with Danfoss EEV.

Please explain as I have just retro fitted two flooded R22 chillers with AKV,s with no ploblems, it's all in the setting up, please don't dismiss AKV's they are very effective in any application I have seen, but you do need to fit the S1 pressure transducer type, NOT the probe type.

Kind Regards. Andy

[NoNickName]

The problem is not the probe. But, if you feel ok with Adapkool, fine for me. But I would personally never buy it. I used Adapkool and rejected. I go with Polycool by Siemens and it suits me better than Danfoss.

[Lc_shi]

Hi Sirs
Question need advice:

# is it feasible to use T joint for distribute to parellel condenser ?
#is it feasible to use distributor after TEV for parellel evaporator?
#how to size suction riser tube

attached a sketch for ref

best regards
LC