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Peter_1
16-04-2004, 07:43 AM
Need some good advice:
Had a meeting yesterday with an engineering office (EO).
They had prescribed AKV's where I had suggested TEV's.

Their argument was that they could lower the energy bill with at least 15%. That sounded music in the ears of the owner but for me it seemed figures Danfoss themselves gave them.

He said that decreasing one 1°C in condensing pressure can lower the energy bill with 2%. Correct you think?

The argument was that they with the AKV's can lower the condensing pressure significantly and rise suction pressure, without loosing a good liquid injection in the evaporator.

I stated that the biggest advantage should be lowering the condensing pressure but that this can also be done with conventional TEV's if you had selected them to this 'special' working conditions (= low condensing pressure)

He said that my condensing pressure should follow the outside temperature (which is of course correct) but that the injection of the AKV's is constantly adapted to the outside temperature. :confused: :eek:
What he tried to explain - I think - is when the HP decreases due to lower ambient temperatures, the injection pulse should also been longer to remain at the same SH setting.

I argued that if the condensing pressure goes up and down with TEV's, then the sensing element of my TEV will send a signal - in this case a mechanical or pressure signal and not electronic - to my TEV so that a constant superheat will be maintained if Hp decreases whereby TEV injects not enough liquid. Same - perhaps a little bit higher - as with AKV's.

He said that we then needed to go on site (with TEV's) several times a year, each time the outside temperatures should change to adapt the superheat settings of all our TEV's. :confused:
I completely disagreed whit that.

If you look in the manuals of Danfoss (haven't them here not with me), then you can see that TEV's still keeps function properly even with low DP's over it. (but with a lower capacity at lower DP's of course)

My point was - but I can be wrong - that the higher price of AKV's, compared to TEV's will never be repaid by a lower energy bill.
We are talking about a small meat factory with 10 evaporators in the range from 2 kW till 7 kW, total capacity 45 kW.

We also proposed a heat reclaim for water (+/- 1.000 l and additional lowering of condensing pressure) but now they doubt that the costs for this will ever be repaid.
We even proposed a ground coil below the inclined loading docks (we did this already twice) to de-ice them and make so also an additional condenser.

That should have lowered the energy bill.

So, I need some feedback from you guys.
Where am I wrong, where am I right, what different opinions you have, what arguments can be given to justify my idea's? Numbers, tests, testimonials, calculations... anything is welcome because we want this case.

Just found this pdf http://mfnl.xjtu.edu.cn/edu-dk-et/Staff/jmj/Energy_analyses_of_a_supermarket_refrigeration_system.pdf

I doubt if this is a 100% neutral test. It's done in Denmark with Danfoss material, Danish professors,measured with Danfoss material...

Andy
16-04-2004, 09:11 AM
Peter :)
during discussions with one of my competitors, we discussed the merits of akv's. On large supermarkets there is an advantage, you could select your tev's on a low dp, but they would/maybe be inclinded to hunt at higher ambients. For a small job such as this I think the cost will out weigh the benifits. Larger cooler still require the same valve+controller, making the cost more attractive. On the other hand there maybe some grants available to ofsett the cost.
Better fit convensional tev's, with liquid pressure amplification, boosting the lost in dp due to low condensing by use on a small pump on the liquid line.
Kind Regards. Andy. :)

Budokan
17-04-2004, 05:10 PM
Peter,

In my opinion I would agree with the engineering office, the AKV valves would perform better the a mechanical TEV.


Without knowing all the facts it would appear that they are looking for a low energy system via a low condensing pressure. At the moment I cannot find the relevant info but although the Danfoss catalogue supplies performance data for DP as low as 2 bar I am sure they they require at least a 6 bar DP to operate. The only viable option for a low condensing presure system would be a AKV or a balanced port TEV. The only concern with a balanced port TEV ties in with the point raised by the engineering office that if the valve was selected for a low DP in high DP conditions the valve could have poor control, possibly requiring seasonal superheat adjustment.

If the main concern is the extra cost for the AKV valves/controls if you selcted the correct controls package i.e. not Danfoss you may find that the AKV valves are a viable option.

Peter_1
17-04-2004, 05:45 PM
Peter,

...it would appear that they are looking for a low energy system via a low condensing pressure. ....supplies performance data for DP as low as 2 bar ....

Isn't realistic: at -10°C evaporating will say condensing at 3°C. How is this possible without a compound compressor?
Let's face it, a DP of 5 is an absolute minimum in a common supermarket.


The only viable option for a low condensing pressure system would be a AKV or a balanced port TEV. The only concern with a balanced port TEV ties in with the point raised by the engineering office that if the valve was selected for a low DP in high DP conditions the valve could have poor control, possibly requiring seasonal superheat adjustment.


Let's say we will evaporate at -10°C or 3,4 bar (50 psi) and we take a mean outside temperature of 10°C (mostly during the day 15 and 30°C in summer) but I'm not optimistic, this means condensing at 20°C or 10 bar (150 psi) for 10 K. This is a DP of 7 bar.

Let's take a TEX2 - orifice 3, for a needed capacity of 6 kW. A 4 should be too big, therefore we should work on a DP of 2. A 3 needs 6 DP.

The previous 7 bar DP gives us 6,2 kW. Suppose it becomes colder, let's say freezing, condensing at 10°C -->4 DP gives 5,1 kW and it becomes warmer let's say 30°C or condensing at 17 bar gives a DP of +/-13 so 7,2 kW. Valve will perhaps hunt a little bit (but that's what an AKV is also doing but with a smaller frequency) As far as I can remember, hunting is dangerous to damage the compressor but when it hunts, you're sure that the evaporator is sometimes overfilled with a change of insufficient superheat.
IF it will hunt.


If the main concern is the extra cost for the AKV valves/controls if you selected the correct controls package i.e. not Danfoss you may find that the AKV valves are a viable option.

Main concern is not the cost, on the contrary. If I can sell them like asked by the engineering office, I earn more.

But 1st, the client is someone who did already a lot for me, believed in me when I started in the refr business long time ago, and still believes in me and I don't want that he pays for something which will - in my opinion - never pay back the investment. I'm thinking by myself: 'If it should be for me, should I do this?'

2nd i hate it to install things in which I don't believe 100%. I don't say that AKV's are not a good product but they have to be used in the right applications. If someone can convince me with good arguments, then I go for it. But till know, I haven't got any.

And besides that, I believe more in the stepper controller EV then in PWM ones. We had a thread around this some time ago but there were almost no replies.

Budokan
17-04-2004, 06:12 PM
Peter,

Most low energy systems are sold on the idea that when the climate allows they can operate with condensing temperatures that track the ambient. In your example you use an example of a system with a 7 bar DP which would still have enough design capacity if the DP dropped to 4 bar. This sounds fine in theory however how well would the pack run in these conditions because the TEV's would struggle to operate as required.

One point that would be useful to clarify is what is the required minimum supplied liquid pressure required for a TEV to operate correctly.

Peter_1
17-04-2004, 07:00 PM
Peter,
In your example you use an example of a system with a 7 bar DP which would still have enough design capacity if the DP dropped to 4 bar. This sounds fine in theory however how well would the pack run in these conditions because the TEV's would struggle to operate as required.

Why should the pack run worser due to this? See lower


One point that would be useful to clarify is what is the required minimum supplied liquid pressure required for a TEV to operate correctly.
2DP (!!) according to Danfoss manual.

Just thinking on the following: what if we subcool the liquid mechanically?

But I believe in the technique of Hy-Save (See Marc has joined) together with TEV's, more then I believe in the AKV's.
In fact, with an AKV, you even can't use a Hy-Save or it's almost useless. Is this correct?

Budokan
17-04-2004, 08:34 PM
Peter,

I think the only point we disagree on relates to the performance of TEV with a low DP.

If you have a system with a low side pressure of 2 bar and a DP of 4 bar using R22 as an example getting liquid to the valve is at best difficult. Danfoss may detail perfromance data for a DP as low as 2 bar however my personal opinion is that this is based on non-realistic theory.

As for the Hy-Save system it appears rather gimmicky, however in theory it would have the same benefits using AKV valves?

With regards to energy efficiency in the real world if consultants could specify packs correctly there would be more saving to be made there.

Prof Sporlan
17-04-2004, 09:46 PM
If the Prof may, the fundamental advantage of an EEV over that of a TEV is that the TEV has a gradient, which is to say that for the valve to stroke further open, the operating superheat it controls must rise. Conversely, for the TEV to move to a more closed position, the operating superheat it controls must decrease. As a result, the average operating superheat control with a TEV will vary with load and pressure drop across the valve.

With an EEV, particularly one wth a step motor actuator, you have no valve gradient. The valve will control a fixed average operating superheat, as long as the valve as the proper capacity for the application.

The problem with the EEV is the controls and sensors add to the cost of the valve. So one must weigh the added costs to the improved control. On large capacity chillers, the EEV wins. On small capacity a/c and refrigeration equipment, the added cost can be difficult to justify. On supermarket equipment, it depends on what you are trying to do. If one is looking to improve remote diagnostics, perhaps... If one simply wants better superheat control... Hmmmmmm.... :(

If the Prof is correct, the Danfoss AKV is a solenoid valve controlling refrigerant flow via pulse width modulation. An EEV with a step motor makes for a better EEV design, though the motor does add considerable cost to the valve.

Budokan
17-04-2004, 10:03 PM
frank,

My understanding of hysave is that it was specified by a couple of US supermarket groups (around 6 years ago?) on the basis of it's energy saving claims but has since been dropped (gimmick expired?) in favour of better packs with better controls, floating suction pressure etc.

It reminds me of the Savawatt plugs that a lot of the Supermakets started fitting to their integral cabinets a few years ago, lots of nice graphs showing possible yearly savings but in the end no-one cared they just started buying better integrals instead.

While I am sure hysave has some good features for some applications, it is not going to revolutionize anything. All it really offers is the ability to float condensing pressure with a bit of discharge de-superheating thrown in.

Budokan
17-04-2004, 10:04 PM
Prof,

I have not really seen much about the Sporlan EEV, what control systems can it be used with?

Peter_1
18-04-2004, 09:55 AM
Marc,
What is NRE? The rest was understandable. You are a walking encyclopedia.

Budokan, .
I agree that most engineering offices are office guys who never stood in the field. For example: we had to make a year ago a quote for some big cold rooms (5 of 600 x 450 x 300 ft) and also two big freezers on -22°C and now it comes....all with DAIKIN chillers, preferable with DAIKIN air handling units and glycol coils in the freezers (they even forgot that they needed to be defrosted) I wrote a letter to them and also to the owner that I never before saw such a stupid description and they are not competent to do this kind of work. 3 contractors did the same and we were then the only who were allowed to make a serious offer... without the engineering office.

We lost finally the bid.


The Hy Save system
You can draw this easily in a logP diagram and see for yourself the benefits. It's in fat a very simple invention but it works, even if I never will install one, I believe in the concept.


Having the same benefits as an AKV?
No, this statement i not correct. It's not a Hy-Save or an AKV or an Hy-save against an AKV.
You only have the so praised benefits with an AKV IF and only IF you reduce also the HP as low as possible. (volumetric efficiency of the compressor increases)
So it's Hy-save and TEV against AKV. (Am I correct Marc?)


When I was at Copeland two weeks ago, I mentioned this (Hy-Save) to an R&D engineer. He said that the power input for the Hy-Save pump will be the same as the power gain at the compressor side.
I disagreed with him but couldn't explain it on that moment.
Perhaps you can help me further Marc.

How to control it?
You can control an EEV with a standard RMS board (is provided on board as far as I can remember), a PLC or I should say that a simple Logo of Siemens can do this also (never tried it, perhaps this could be a good graduate project for a Refr Tech) It's a basic stepper motor which can easy be controlled. Only finding the controlling algorithm can be a little bit difficult.


I can be wrong, but the Sporlan EEV's are more for the OEM market.
If they could make a simple controller, and do the same huge publicity as Danfoss is doing, then you should sell them.

Why you see a lot of AKV's
It's always the same, those who make the most publicity will sell their systems. Look to Danfoss here in Europe, there is not a month going by where we haven't receive via post something new from Danfoss.
They visit very intensive engineering offices, pays them trips to the factory, provide their books , software, documentation, leaflets...

You can earn points to win teak furnitures when you buy the AKV stuff, win bikes, trips to Denmark (only when buying AKV - AKC related stuff)
You even earn points for free lessons for your techs in their Brussels office.

The company I worked with some years ago, won in 1 year 5 sets of a teak garden set.
They all do this to push their products in the market and once it's introduced, then you will install it further because you learned to work with it.

No one else is doing this.

Prof Sporlan
18-04-2004, 04:32 PM
Prof,

I have not really seen much about the Sporlan EEV, what control systems can it be used with?
Sporlan offers a number of valves with step motor actuators. See following link: http://www.sporlan.com/etcs.shtm

Andy
19-04-2004, 08:01 AM
Marc :)
LPA is a great concept :) the only down side I can see it that people fit it, but don't fully understand it, install it incorrectly and don't commission it properly, then condeme it because it doen't work properly :o
It's hard to make anything fool proof :( maybe Hysave should have been a bit more selective in the US about who they allowed to fit their systems :rolleyes:
Kind Regards. Andy :)

Peter_1
20-04-2004, 05:53 AM
In many respects, those who understand and work confidently and inventively with hy|save pumps are the intellectual creme de la creme of the refrigeration technicians arena.

No MArc, it seems to be the ammonia guys who are the créme de la créme :) :p

Mark C
20-04-2004, 04:25 PM
Funny, funny boys.....

...and you call this an "Industrial Refrigeration" forum??

Andy
20-04-2004, 09:19 PM
No MArc, it seems to be the ammonia guys who are the créme de la créme :) :p
Well at least we are agreed on something :D
just kidding. Nh3 is just another refrigerant, but a very good refrigerant if correctly applied. When quoting work I quote what ever refrigerant is competitive on the size of job I an working on, often R404a up to 200kW, but much above that NH3 is the most cost effective.
Kind Regards. Andy. :D

Mark C
20-04-2004, 09:40 PM
No, No, NO!!! You guys.... :D Here is an acceptable facility that warrants the use of the term, "Industrial Refrigeration"!

Low stage.... http://www.mboxcommunity.com/public/DSC00004a.jpg

High Stage.... http://www.mboxcommunity.com/public/DSC00002a.jpg

To me, "Industrial" means open compressors, not semi-hermetics. ...Something with a little horsepower! (Or kW to you metrics...)

In all fairness, I am being a bit myrth-filled here, and I meant this in jest. However, I am curious as to the actual definition of of "Industrial Refrigeration" as used here in this forum and in Europe. If you say "Industrial Refrigeration" here in North America, you typically are speaking of an ammonia system. "*****" (all the HFC, HCFC, etc.) systems just are not considered "industrial" in nature here. Can someone give me the scoop on what is "Industrial"?

Mark
21-04-2004, 05:33 PM
Great looking plant mark :)

Mark C
21-04-2004, 07:02 PM
Great looking plant mark :)

It's not mine.... :D It is one of my clients' in the past and jus the first photos I ran across on my computer.

Andy
21-04-2004, 08:42 PM
Mark :)
nice plant, Frick screws and maybe York recips, at a guess.
Must take a look and see what central plants I have on my computer and post one ;)
Kind Regards. Andy

Andy
21-04-2004, 09:11 PM
Marc :)
never worked on Fricks, but I have worked on some of what I would call small Grams, which were Fricks made under licence, last one I worked on was a GSF147.
Howdens will do that condensing thing also, and quite often do during cold starts :eek: , doesn't do any real harm, but it can be a bit disconcerting which that old discharge doesn't warm for a few minutes :o
Kind Regards. Andy.

Andy
22-04-2004, 08:21 AM
Marc :)
I would say screws with oil pumps running above discharge press would have a greater tendancy to over cool during the inital cold start. The oil flow is rated to cool at full capacity with a warm oil tank. Start the plant with a low slide position, less of this cold oil is needed, but the fixed oriface plate or the hand reg controlling the feed to the rotors knows nothing about this :)
Halls screws are a different problem, they require more cooling/injection at low slide capacity position. On R404a no injection is required at full load on a medium evaporation system, but some is required at part load.
Kind Regards. Andy.

Peter_1
22-04-2004, 09:34 AM
Mark :)
nice plant, Frick screws and maybe York recips, at a guess.
Must take a look and see what central plants I have on my computer and post one ;)
Kind Regards. Andy

I guess Hasegawa for the pistons.

Mark C
22-04-2004, 12:56 PM
These are FES packages, and I do believe that these are the FES "HE" series of screws that FES foisted upon our industry a little over ten years ago. Mercifully, we don't see many of them anymore.... :rolleyes: There are far better machines to use now.

The Recips are Vilters. XL-450 if I am not mistaken. A very old and reliable machine. they are only there to maintain a high Hot Gas "temperature" during low ambient conditions. (And to forestall on/off operation of the larger screws at inefficient slide valve settings.)

Yes, my father quit York as the head of Field Engineering in the late-sixties over that god-awful "R" machine. What was York thinking when they applied internal water jackets and external manifolds for ammonia gas flow? They are a dying breed now as most have been cracked in the odd freeze. Hasagawa have never been more than a poor imitation of the Mycom line.

In this facility, and actually throughout most of the USA, it is the design philosophy to limit the motor size of the compressors to about 500 BHP. Sometimes we can use a bit higher, but it is rarely done. This is because the power grid is the same for all electrical distribution. Despite various starter methods, the inrush current is held to ensure that the others in the grid don't get flashing lights or spikes when we start! It is often the rare thing to see a truly high voltage system operating monsterous screws that are larger than our trucks. These are very fun to work upon, as they are really not your average setup here.

I do believe the basic physics of the equation demand an amount of oil cooling to maintain compressor temperatures to ensure long life of the screw. (or have you boys over there figured some method around this?) One method or another must be used. Oil flooding works just fine for this sytem. However, the discharge is still superheated to a great degree, so I fail to rise to the bait.

Marc, I'd be happy to lead you around on your day or week. I teach boys like you regularly in my classes. :) It is true I specialize in ammonia refrigeration, and prefer not to sully myself on the other stuff. However, I think that both you and I would learn something from our chosen interaction, at least that your tallywhacker is indeed slightly larger... (That is if you could keep on subject and actually accomplish something.)

Mark
22-04-2004, 01:54 PM
peter next time anything AKV related put in the humble supermarket forum :rolleyes: .just kidding

:D :D Regards Mark

Mark C
22-04-2004, 07:54 PM
Once again, Marc seems to be unable to answer any question.

Guys, what makes it "Industrial Refrigeration" over there in Europe?

Andy
22-04-2004, 09:43 PM
Guys, what makes it "Industrial Refrigeration" over there in Europe?
I would say Industrial Refrigeration is refrigeration on an Industrial site used for industries purpose. By that I exclude the canteen fridge :D
The company I work for covers the complete range from small ice rinks to large pumped R717 and R744 plants.
Mark check out our web site

www.star-ref.co.uk

Beauty is in the eye of the beholder. I tend to like R744 cascades and LPR plant closely followed by pumped Nh3.
Others like differnt things :eek:

Me I stick to what I know ;)

Kind Regards. Andy :)

Mark C
23-04-2004, 12:48 AM
Well, Andy.... "Industrial" to me is more equipment oriented. Racks with semi-open compressors.... "*****" refrigerants in copper tubing.... Air Cooled condensers.... These are what we term "Heavy Commercial".

With that said, it would be wholly appropriate to apply a "*****" refrigerant with steel piping and evaporative condensers and fully open compressors. I have built such and worked on them. The ice plants I have put in with two 50 BHP compressors using "*****" would be considered "industrial" by you, but are not considered thus here.

There is a definite line here in the USA between what is "Industrial" and what is "Commercial". By your definition, the little systems I do for the tree seedling nurseries are considered "industrial" even though they are 20 BHP and ***** 22 and copper tubing constructed because they are a cold storage, tree seedling production facility in an industrial occupation building. No?

Andy
23-04-2004, 09:49 AM
By your definition, the little systems I do for the tree seedling nurseries are considered "industrial" even though they are 20 BHP and ***** 22 and copper tubing constructed because they are a cold storage, tree seedling production facility in an industrial occupation building. No?
That indeed is the true :) industrial to me is much along the lines you talk about. But it can be anything refrigeration wise that is used in an industrial setting.
Just because it is industrial doesn't mean it can't be small :) or inefficient, such as semi packs on an incorrect application.
Kind Regards. Andy :)

Mark C
23-04-2004, 12:41 PM
Andy, Thanks! It is indeed interesting that the type of refrigeration system, or "classification" as "industrial", is predicated upon the perceived use of the system and not the actual system itself. ...Most interesting!

I would say here that the systems in the home are classed as two different ways: "residential" and "appliance". Then we have the large AC for buildings which is classed as (interestingly enough) "Large AC/Commercial" despite some of them being extremely large which they could be the equivalent to an industrial system in fact. "Commercial" which includes supermarkets, markets, and retail/office AC. Then there is "Heavy Commercial" which is the little systems used in production of ice, small food production, walk in coolers, and rack systems in large markets.

Aside from the specialties like air driers, labs, etc, that leaves industrial.... Here in the USA, "Industrial" is almost solely the domain of Ammonia systems, which recirculated liquid is of primary import. 95% of that classification is ammonia, with about 5% made up of systems using other refrigerants where needed by the occupancy or process, or by the fear of ammonia and the perception it is dangerous.

Andy
23-04-2004, 02:18 PM
[QUOTE=Mark C
even though they are 20 BHP and ***** 22 and copper tubing constructed QUOTE]
Mark in the UK and generally R22 can not be used in any thing new much bigger than a small split. :confused:
Now don'y get me wrong R22 is quite a nice gas, but is also quite harmfull to the ozone layer. :( Would it not be better to use an HFC.
As a matter of interest what is your phase out dates for HCFC'S.
Kind Regards. Andy :)

Mark C
23-04-2004, 09:06 PM
[QUOTE=Mark C
even though they are 20 BHP and ***** 22 and copper tubing constructed QUOTE]
Mark in the UK and generally R22 can not be used in any thing new much bigger than a small split. :confused:
Now don'y get me wrong R22 is quite a nice gas, but is also quite harmfull to the ozone layer. :( Would it not be better to use an HFC.
As a matter of interest what is your phase out dates for HCFC'S.
Kind Regards. Andy :)

Actually, that was a facility I put in in 1993. I have not mucked about with any R22 since 1999, except to fix my AC and my neighbor's.

I believe the beginning of the phase out is 2010, with production halting in 2020, per the original regulation of the Montreal Protocol. (And it is NOT all that harmful to the ozone layer. Ever hear of it being found up there?)

Peter_1
23-04-2004, 09:51 PM
It's not because it's not found up there that it isn't or wasn't there.
It can has decomposed to other elements.

How then must an autocascade which can reach -120°C or a cascade, able to cool till -110°C be classified?

And don't make illusions, industrial has nothing to do with the degree of difficulty of the job/process/machine. Sometimes a simple ice making machine can drive you crazy.

Peter.

Peter_1
23-04-2004, 09:52 PM
peter next time anything AKV related put in the humble supermarket forum :rolleyes: .just kidding

:D :D Regards Mark

Seems a better idea but sometimes, threads divert sometimes to such a unforeseen ways that one thread can be posted in different forums.

Peter

Mark C
24-04-2004, 12:59 AM
It's not because it's not found up there that it isn't or wasn't there.
It can has decomposed to other elements.

How then must an autocascade which can reach -120°C or a cascade, able to cool till -110°C be classified?

And don't make illusions, industrial has nothing to do with the degree of difficulty of the job/process/machine. Sometimes a simple ice making machine can drive you crazy.

Peter.

Well, the decomposing elements have not been found there, either. This has all been conjecture and theory, but no "proof" of the culprit being these decomps.

I forgot about cascade systems. They are a specialty in and of themselves. "Super Low Temp Refrigeration" I guess? The lowest temp system I have ever done was -100°F for cold weather testing of farm equipment. Drive it in, and park it. See if it starts in the morning! :p :D

I made no "illusions" of anything. I was stating that in the USA, we seem to classify the system by not only it's use, but the type of construction and refrigerants used determine it. Not simply it's being "industrial" because they make widgets in the facility where it is installed. Most "*****" systems are not considered "industrial".

SNi
06-04-2005, 12:59 PM
Hi

In case of AKV you should be very carefull with the liquid velocity. It must be around 0.6 - 0.8 m./sec. (not more) otherwise AKV can be broken (liquid hammering). Price for the tube in this case will be expensive. But You can adjust MOP which You need, sometimes it`s very important.
Energy in Russia costs almost nothing, but price for AKV + controller is high enough and in this case i try to offer CAREL E2V instead of DANFOSS.

Kevin Yeo
24-07-2005, 11:44 AM
Dear Marc,

In Malaysia climate, ambient temp is ard 35 deg C. Typical cond pressure is 220 psig [42-45 deg C approx]. Condenser capacity is based on net cooling capacity + heat from compressor, rated at 45 deg C condensing temperature. Delta T of 10 deg C for condenser heat transfer.

As I am really a novice for Hysave system, all i can notice from Pressure Enthalpy chart is reduced compression ratio [energy saving, less work for comp] so in another words, reduced discharged & condensing temperature. Is there any change when it comes to condenser selection.? As I know, it needs to maintain a certain Delta T for heat rejection to ambient, right? Thanks for your enlightenment.

wambat
24-07-2005, 10:16 PM
THIS WAS POSTED MAY 2001

Baltimore, MD


Danfoss has conducted a controlled test in a Buffalo, NY, store using Danfoss Smart Case Controller’s and our AKV10 electronic expansion valves (EEVs).

The test consisted of one two-stage and one medium-temperature rack operating 48 evaporators. A contractor field-installed EEVs in parallel with factory-installed thermostatic expan-sion valves. Solenoid valves were also installed to allow switching between the electronic and thermostatic valves.

The valves were alternated every second day to neutralize day-to-day load variations due to shopping, stocking, and cleaning activities. Test data were recorded for four months.

The average daily usage was found to be 703 KWh on thermostatic days and 639.4 on days when the EEVs and Smart Case Controllers were used, for a savings of 9.05%. Savings increased steadily as the weather warmed, from 7.5% in March to 9.9% in June.

Savings from 4.3 to 50.8% were realized from reduced compressor run time, reduced defrost duration, and improved recovery. Average defrost was quicker by 28.7% on one rack and 17.4% on the other. Also, the test revealed higher average suction pres-sures for all three suction groups tested.

It should be noted that the savings generated from EEVs are the result not of the valves, but from the software algorithms within the Smart Case Controllers. Algorithms also determine the stability of the fixture temperatures achieved. Both of these facts were proven by the test results. The entire test’s data collection and test report were audited by the public utility serving the store. Based on the results, a rebate program was established. :)

Peter_1
24-07-2005, 10:36 PM
Danfoss has conducted a controlled test in a Buffalo, NY, store using Danfoss Smart Case Controller’s and our AKV10 electronic expansion valves (EEVs).
....

The first sentence said everything: 'Danfoss conducted a test with Danfoss controllers' :confused:

I recently wrote an article about 3 absorption machines of 1.4 MW in a rather big hospital.
The existing Westinghouse chillers had to be replaced.

A well known engineering office calculated everything and made a comparison between new chillers and the absorption machines.

They handled condensing temperatures of 57°C and evaporating at -10° for the new chillers. Can you imagine?

They also didn't stated in their calculations of the absorption machine that the hospital had to pay a lot of money for the wasted heat of a huge garbage burner. Waste energy depends on who's side you're standing.

They exaggerated also in the amount that the state should pay in this project.

The final budget was almost double of what was calculated. Try once to do this when you negotiate with a client.

Based on this calculations, they chose of course for the absorption system with all the thinkable options.

Allways be very carefull when you read reports, especially if they were financed by a manufacturer.

Same story for all that huge savings they predict with frequency inverters: it all depends on the application and the working range.

But it's all payed with our money, the society, so who cares.

wambat
24-07-2005, 11:08 PM
The first sentence said everything: 'Danfoss conducted a test with Danfoss controllers' Peter Quote

Well for all I know Danfoss may have done any amount of tests I just happen to read about this one and thought I'd pass it on :confused: In addition the entire test’s data collection and test report were audited by the public utility serving the store. They must be bought off too don’t you think :rolleyes: Also what I found interesting was the fact that they didn.t attribute the energy savings to the valves but to the algorithms :) But be that as it may I believe that EEV are by far the better choice in metering devices then TXV's because the biggest problem with TxV is hysteresis which is the internal friction of any system. In a TEV it takes more force or pressure to deform the diaphragm in the opening direction than in the closing direction. This hysteresis has an effect on the resolution of the TEV, and limits its ability to precisely meter refrigerant over widely changing head pressure and evaporator load conditions. Balanced ported TEV type valves, have a much greater ability to follow load than conventional TEV, but still not to the
extent that EEVs can. :)

homelover
28-07-2005, 07:14 PM
Hi all,
I look at it this way,
The worst thing about electronic valves are the probes that control them, they are usually cheap and fail often, especially the evaporator probe due to ingress of moisture or ice damage, If you lose the evap probe the unit will fail due to the lack of superheat, If you lose the suction probe due to the wide superheat you can flood the pack or compressor with liquid,

The benefit of electronic is only 1 valve ie no solenoid needed,

As for saving energy It sounds good but i'm one for the tradition valve that will work without probes or elctronics.
As I work daily with Electronics and Akvs, most of the problems are with probes failures, There are decent probes out there but due to the high cost no one will buy them.
Stick to the conventional valves,
And you won't spend your days changing probes.

Latte
29-07-2005, 12:33 AM
Hi Guys,

I've got to aggree with homelover, TEV's are just far less hastle.

Most engineers keeps Danfoss TEV's and orrifices on their van, how many people keep AKV10 spares. Also you are not relying on two probes to control it, just one cowboy not putting probe 3 or 4 in the wrong place or loose on the pipes and off it goes.
I do tend to aggree with Danfoss that an AKV is probably cheaper to run, BUT they are only taking into account power usage and not taking into account money spent on call outs when probes fail or downtime going to get AKV spares

YES, i am old and like things the old way but when it comes to TEV's - if it ain't broke don't fix it

Regards

Fatboy

Superheatman
29-07-2005, 10:52 PM
Hi Marc...I am another who is a bit of an ignoramus when it comes to the illustrated system....one of our sites is the national gallery on trafalgar square....recent chief engineer on the site fitted up one of the multiple york chillers there with this system and test bedded it for over a year....they found that the payback for this single install was horrendous...in fact the chief engineer who was a very clever chap by all accounts "moved on" in part due to his recommendations which were unfulfilled by the testbed measurements and metering....as I said I am not used to the system at all but have studied the install on site there out of interest....it has been switched out of circuit to"save money" they tell me...perhaps just a bad install although it looks a very professional job...regards...John.

Calvin Becker
08-01-2006, 02:55 AM
Good work Marc. Long time buddy!