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US Iceman
12-01-2007, 11:53 PM
Hi guys,

This new forum is being started so we can keep all of the ideas in one location for large industrial systems.

Feel free to ask questions and post comments, or start new threads.

Since this is a sub-forum on optimization I'll start with this....

Keep the discharge pressure as low as possible
Keep the suction pressure as high as possible
Keep screw compressors fully loaded
Use VFD's on fans (condensers and evaporators)
Take the time to learn how you are billed for the electricity you use
Start using recip compressors if you can
Here is one I think Josip will like... Don't make promises you can't keep.:D

The MG Pony
13-01-2007, 01:29 AM
Here is one I think Josip will like... Don't make promises you can't keep

I have a saying: I prommis nothing, other then to try my best to give you the quality you are owd.

Ie I will do every thing in my power to give best quality and efficiency but I prommis nothing ells, this way they are usualy happy and usualy it can be don, when it can, they at least know you did what you could and are not disapointed or left feeling cheated.

US Iceman
13-01-2007, 02:21 AM
I will do every thing in my power to give best quality and efficiency...


I understand what you mean, but you have to be very careful with what you are trying to provide (at least in words).

Doing your best is admirable, and all anyone can ask of you. Saying you provide the best quality and efficiency can be something that comes back to haunt you.

Some shyster will say his is better, and then you are on the defensive. It's a fine line to walk, but I think you understand where I'm coming from.

It's better to do, than to say...;)

Saves a lot of anxious discussions.:cool:

winfred.dela
13-01-2007, 05:15 AM
Can we add: Use Soft Starter for large Electric Motors.

autt
13-01-2007, 03:14 PM
This is my love, I have been doing this from a long time ago.
I thought optimization is very important, but looks like it is seldom applied everywhere.
From my work, a large a/c system can be optimized in reality.
How many people in this forum have ever done optimization calculating? I can put some program code on here for discussing.

Josip
13-01-2007, 10:48 PM
Hi, Autt :)


This is my love, I have been doing this from a long time ago.
I thought optimization is very important, but looks like it is seldom applied everywhere.
From my work, a large a/c system can be optimized in reality.
How many people in this forum have ever done optimization calculating? I can put some program code on here for discussing.

Someone must be the first;). It will be nice to show us some of your works. Thanks.

Best regards, Josip :)

SIGNSTU
17-01-2007, 05:13 PM
This Maybe Somthing Of Intrest. I Work At An Ice Skating Rink In Ny. We Had 2 12 Cyl 125 Hp York Compressors With Brine As The Secondary.we Now Installed 2 6cyl Sabroe 75 Hp Using Ammonia With A Flooded Chiller And Glycol. We Insulated The Floor And Roof (to Stop The Radeant Heat) And Our Electric Bill Went From An Average Of 12000 To An Average Of 4500. The New System Runs Fukky Loaded Then Shuts Down On Temp. Great System But The Sabroe Parts Are Not Cheep!

nh3wizard
17-01-2007, 05:36 PM
Who do you buy your parts from, I have several contacts that sell sabroe parts.

nh3simman
25-03-2007, 06:14 PM
This is also one of my favorite topics.

I don't think real optimization can be achieved after the plant is installed since the effects of the original design decisions are so overriding.

Here is a simple example

What Iceman says about the discharge pressure is quite right. So how do you do this? Make sure that the air cooled condenser is kept clear and that it is clean...

But you can only do so much with this. As Gary pointed out in another thread, "you can add as much condenser area as you want but the sub-cooled liquid can never go below ambient".

If, however, the designer chose to use a water cooled condenser then the discharge pressure would be much lower.:( So you can't really optimize this system without changing the condenser!

What exactly is optimization?

You may want to optimize the flow of chilled water to be supplied underground. In this case, I expect that you would be concerned with low chilled water temperature and chilled water flow and not plant power.

So optimization depends on what you are trying to achieve.

Usually, you would choose a target parameter (for example plant power usage) and you will select all of the variable parameters that you can control to minimize (or maximize) the target parameter.

In an ideal world, you then run some experiments where you can change each variable at will.

In the real world, however, you don't always get this freedom. Even if you identify the chilled water flow as a potential problem, you can't easily increase the flow rate without making system changes.

Satisficing solution

The next best thing is to find a suitable answer. Optimization curves have a convex shape and there will be a band where you can make big changes for small gains. The good old 80/20 rule.

The items listed by Iceman are good general practice for running plant but they are not optimization.

To do optimization, you need to keep good records, make systematic changes to the plant and monitor the result.

You make a proposition. What if we did... Then you make some changes to see if the proposition is true. Sometimes, you can make predictions by studying existing plant. A good option lately is simulation. With much less cost, you can predict the effect of changing a parameter any parameters.

In this way, you get an idea of what is realistic and know the sensitivity of the parameters. The most sensitive parameter is the one that will give you the best results.

Stoecker simulates a simple vapor compression cycle and shows the relative component sentitivities as:
Compressor = 6.3
Condenser = 1.3
Evaporator = 2.1
So the logic for this example is start looking at the compressor. An improvement here will be 5x more effective than work in the condenser.


I hope we get plenty response in this thread. I think it is a most valuable area of our work. Especially in light of our current world energy crisis.

US Iceman
25-03-2007, 10:38 PM
Wikipedia defines "optimization as the process of modifying a system to make some aspect of "a system" work more efficiently or use less resources."

In some cases efficiency is confused with using less power, as an example. In other circumstances it might be said the area of interest is using less energy, while at a less than optimimum operating condition.

There are many situations where it is possible to lower the total energy costs, but in acheiving this, the system may operate at a less than optimum condition.

Furthermore, this subject finds many different requirements that might define optimization. One of these might be a sufficiently flexible system to operate in any condition that "provides the required cooling capacity at the lowest possible operating cost".

Certainly an existing system will have specific barriers that limit the lowering of energy costs below some perceived minimum.

Some of these limits may be mitigated by recommisioning the existing system to meet the original design intent, or, to meet the current conditions as well as possible.

The items listed in the original post were some suggested areas where optimization can occur during the design stage.

As with any system revision you want to start with the areas that offer the greatest return. Quite simply this the ability to run the discharge pressure at the lowest possible level, without creating other operational problems.

Since the compressors use the most energy, any change to the system that lowers their energy use is a recommended starting point.



... you need to keep good records ... and monitor the result.


This is benchmarking. You need this to verify the optimization paths selected. Benchmarking is the measurement that provides a useful frame of reference for determining a good plan of action.

Benchmarking and optimization go hand in hand just like predictive and preventative maintenance. Neither are mutually exclusive.

Lc_shi
26-03-2007, 02:51 AM
Hi Iceman
You've given a very good topic but also a very difficult area:p
Optimisation should be based what extent we know the system performance at all the possible operation conditions. It's almost impossible ,so we need to make the mathematic model to simulate it and get the "optimaisation" result.
So I think the optimisation is a process along with we're more amd more familiar with the system. It need much test data support. Software is a good help tool but not the decisive. I'd like to say optimisation is base d on good test and good predicting model which must support by big money.
Of coure,"optimaisation" offer much jobs for there're never a perfect system no need improvement, to make a system better is alwayes a part work of HVACR engineer:)

best regards
LC

nh3simman
26-03-2007, 05:49 AM
I'm not a big user of Wikipedia! I must admit that the link that Iceman gave some time back was very informative and did keep me busy for a few hours.


http://en.wikipedia.org/wiki/Refrigeration

Someone once told me he didn't trust Wiki since anyone can edit the info. I don't know but statements like this tend to hang around.

Nothing like a trusted source and one of my favorites has always been Stoecker. His book co-authored with Jones "Refrigeration & Air Conditioning" in 1982 is still relevant today (25 years later).

In terms of optimization, Stoecker "Design of Thermal Systems" makes an interesting point.
There is nothing in the optimization procedure that will jump from one model to another.
He gives the example that no model will automatically change technologies.

Mathematically, optimization is defined in a very concise way by:

y = y(x1, x2, ..., xn) -> optimize
y is the function to optimize
xi are the independant variables
this of course subject to constraints.

If we can't optimize the whole system, then the best alternative is the optimization of sub-systems.

As I think about the subject and read the other replies, it becomes clear to me.

Optimization has to be one of our primary function. As engineers, we are entrusted with the task of benchmarking and optimizing the system. After all, who else has the tools to do this?


[Note on sources of information.
I only recently installed ADSL and got the freedom to explore the Internet like Brian_UK does. I found this site by chance through Google and since then I'm continually drawn back. I don't always agree with what I read but it sure provokes thought. And then there are the links to some amazing sources. Where else would you find a place to talk to 4000 people about your favorite subject?]

US Iceman
26-03-2007, 03:49 PM
If we can't optimize the whole system, then the best alternative is the optimization of sub-systems.


Through one, the other becomes possible.

I tend to see people get their knickers tied in a knot over finding the best point of operation and saying the system is optmized.

It is my opinion the optimization occurs by having the sub-systems designed such that no barriers are artificially created by the design for any operating condition.

Traditionally, the sub-systems are the weakest link and generate the overall system dependencies that force the energy use.

For example, take the liquid feed method that might be chosen.

A high pressure liquid feed to a TXV sets the minimum discharge pressure of the system. The discharge pressure must be maintained at some artificial lower limit to achieve the rated capacity of the TXV. So, we use head pressure controls. This in turn fixes the compressor energy use, as the amps have a greater dependency on discharge pressure.

If you can develop a method of liquid delivery to the evaporators that removes this barrier, the overall system operation has been optimized to achieve higher savings during periods of lower ambients.

Once the design is flexible to allow operation in any condition (or any ambient) with minimum energy input the control system provides the ability to sustain the goals achieved in the design.

nh3simman
01-04-2007, 12:54 PM
Iceman has given me much to think about here.

We all know that optimization of big industrial plant is necessary. Problem is, many of us would not know where to start in optimizing a big system.

Since first reading this thread, I have done some background reading and find that all of the tools of optimization are highly mathematical.

What we end up doing is making random changes based on value judgement. Hopefully these changes lead to improvements or in the least, a better understanding of our plant.

I don't always advocate software but in this case it has distinct benefits. If you have a simulation of your plant, then you can make changes and plot the improvement. In this way, achieve a sort of manual optimization.

Does anyone know of actual optimization programs that were developed for refrigeration plant?

Sergei
02-04-2007, 04:39 PM
I don't know any software for refrigeration plant optimization. Usually, every refrigeration plant is unique and it is very expensive to create universal software. I've done my own research in optimization of refrigeration plants. Based on this research I can find optimum set points and operating strategies for every industrial refrigeration plant. Tuning up of existing refrigeration plant is the best first step to optimization.

nh3simman
02-04-2007, 05:16 PM
Tuning up of existing refrigeration plant

Hi Sergei, What do you mean by "turning up"?

US Iceman
02-04-2007, 06:39 PM
Based on this research I can find optimum set points and operating strategies for every industrial refrigeration plant. Tuning up of existing refrigeration plant is the best first step to optimization.


I agree with both parts of this.

If you understand the system components & sub-systems and know what to expect, a simple recommissioning project (tuning) will take care of most of the bigger problems.

These "relatively easy" areas can be considered low-hanging fruit as they are the easiest to modify and get almost instant results. This helps to build the confidence of management that energy conservation works.

You need this before you tackle capital intensive projects.

lana
02-04-2007, 06:54 PM
Hi everybody,

Just wanted to add something.

Optimization means getting the best cooling effect for the least power consumption. ( I think :p :p ).

First the equipment must be selected properly. And the important one is the compressor which consumes the major part of the energy.
Secondly the system must be balanced and find the balance point i.e. the operating point at design condition.
Thirdly the part load operation - in low load - must be considered and studied.
At this stage any deviation from design can be spotted and corrected. Also you can change the equipment for better efficiency.
This can be done with good Balancing programme.
Fourth : When the system is installed and commissioned then proper maintenance and service would insure the design conditions are met.

Actually My brother and I developed two computer programmes (our M.Sc. thesis) which balances the system - one for recips and one for screws-. What the programme does is very complicated and long for telling it here. They work very accurately (if the inputs are correct) and we check them with real systems and they are OK :p :cool:

Just to add something to your brain storm.
Cheers:)

nh3simman
02-04-2007, 07:05 PM
...developed two computer programmes (our M.Sc. thesis) which balances the system - one for recips and one for screws-. What the programme does is very complicated and long for telling it here. They work very accurately (if the inputs are correct) and we check them with real systems and they are OK.. :eek::eek::eek:

Hey lana, You can't throw out a teaser like that and leave us hanging. I have been playing with systems like this since 1985 and would love to hear more.

US Iceman
02-04-2007, 07:30 PM
Optimization means getting the best cooling effect for the least power consumption. ( I think :p :p ).


Absolutely. Cheers and applause to you.:D

This is the bottom line for our efforts.

Now I'm going to be bold....:eek:

Can I get a copy of your thesis? Please.;)

Sergei
02-04-2007, 10:04 PM
Hi Sergei, What do you mean by "turning up"?
Tuning up is improving set points and operating strategies. Set points are condensing pressure, suction pressure, frequency of defrosting and etc. These settings should be changed from time to time. Operating strategies are compressors' sequence and condensers' sequence.
Lana have mentioned about design conditions. Unfortunately, no system operates at design conditions - they merely cross them at times.

nh3simman
03-04-2007, 03:41 AM
Tuning up is improving set points and operating strategies. Set points are condensing pressure, suction pressure, frequency of defrosting and etc. These settings should be changed from time to time. Operating strategies are compressors' sequence and condensers' sequence.
Lana have mentioned about design conditions. Unfortunately, no system operates at design conditions - they merely cross them at times.


How's that. I'm getting so good that I can introduce spelling mistakes into your words. Of course, its tuning. Just my fingures getting ahead of me.

...The serious part...

But you make it sound so easy. Just drop the condensing pressure and you get better performance.

Let's just look at that one. I reject heat at the condenser to ambient. But I, unfortunately, am not able to control ambient. And, I can't just increase the area of my condenser. So, I do the only thing available. Increase the flow rate...

Great, the head pressure drops and I have succeeded in making the plant better. Optimal? I don't know because I have no clue of where the optimum lies.

But here is a kicker for you. What if the pumping power was greater that the gain in performance? Then I'm actually making the whole system worse!!

lana
03-04-2007, 09:12 AM
Hi everybody,
Actually I don't get it?:confused: Am I being ridiculed or what?:confused:
I just told you my opinion and my 6 months of intense, tiring and interesting work.
Our works are available in UCL (University College London) in M.Sc. Refrigeration and Air-Conditioning department.
The programmes are modified after graduation and they are put for sale here but nobody knows anything about balancing here :D :D :mad: :mad:
Anyway, I hope that I am not being ridiculed here.:(
Cheers

Sergei
03-04-2007, 02:52 PM
How's that. I'm getting so good that I can introduce spelling mistakes into your words. Of course, its tuning. Just my fingures getting ahead of me.

...The serious part...

But you make it sound so easy. Just drop the condensing pressure and you get better performance.

Let's just look at that one. I reject heat at the condenser to ambient. But I, unfortunately, am not able to control ambient. And, I can't just increase the area of my condenser. So, I do the only thing available. Increase the flow rate...

Great, the head pressure drops and I have succeeded in making the plant better. Optimal? I don't know because I have no clue of where the optimum lies.

But here is a kicker for you. What if the pumping power was greater that the gain in performance? Then I'm actually making the whole system worse!!
For industrial refrigeration plant with evaporative condensers head pressure should be controlled by wet bulb approach(temperature difference between condensing temperature and wet bulb temperature).
Example. Refrigeration plant: compressor power - 5000 HP, condenser power(pumps and fans) - 500 HP. This is production facility. Full production during weekdays. Weekends only 500 HP compressors to keep temperature in cold storage. Head pressure was set to 120 psig(8 bars). Wet bulb temperature on weekends is 70F. 500HP of condenser power are running but only 125 psig head pressure have reached. Total power use for weekends operation is 1000 HP(500 HP compressors and 500 HP condensers). We installed PLC with wet bulb feature and set it to 15F. Head pressure will go to 150 psig (85F=70F + 15F). Compressor power will increase to 550 HP, but condenser power will decrease to 50 HP. Total power consumption will be 550 HP + 50 Hp = 600 HP. Our savings is 400 HP.
Idea of wet bulb approach fearture is to balance capacities of compressors and compressors to keep total power use at minimum level.

US Iceman
03-04-2007, 03:14 PM
I'm going to reply to these posts separately.



Anyway, I hope that I am not being ridiculed here.:(


I certainly don't think so. This discussion hinges on what people define as optimization. In your earlier post I can't fault any thing you said and in fact agreed with you.

I think one of the problem areas with this discussion is the various approaches people see and use.

Computer programs if they have been validated by field performance observations would be a great tool to use. I have seen several examples that were very impressive.

There is also another way of doing this, but it relies on a great deal of experience to understand how the various balances occur. And just as importantly, knowing what to do and for the correct reason.

Either are valid, but tend to be used by people from a specific background. It does not make one method right or the other method wrong.

They are simply two different methods to use.

US Iceman
03-04-2007, 03:35 PM
Lana have mentioned about design conditions. Unfortunately, no system operates at design conditions - they merely cross them at times.


True, but if you think of the various operating modes as design conditions then you are also able to design the system for better performance and efficiency.

As the operating conditions change, the balance points cross different boundaries. This is were we want the energy reduction to be stable and minimized.

The final step is using a control system with the capabilities you are expressing to sustain the overall flexible operation in these different modes.

The various modes would be:

Full load
Part-load
Summer
Winter
The first two deal with cooling requirements and providing the right mix of equipment (or control of specific equipment) to produce the cooling required at any one point in time in an efficient manner.

The last two modes deal with weather. The system has to operate in all of these conditions, so it should be able to take advantage of lower wet bulb temperatures.

The operation of the refrigeration system with any combination of the above modes with various capacity requirements is what we are trying to accomplish with optimization.

So, in effect I agree with you also.

As lana said,



Optimization means getting the best cooling effect for the least power consumption.


This is what we are trying to accomplish as our overall goal.

I think we are all talking about the same thing here, but just using different methods of saying how we do it.

US Iceman
03-04-2007, 04:00 PM
So, I do the only thing available. Increase the flow rate...


Nope. You control what you can, when you can.

You are thinking in terms of water-cooled condensers which are seldom if ever used anymore.

If the wet bulb temperature is high, you can't do anything about that except to run all of the condenser fans at full speed or shed load.

If you can't shed any load, then you just have to run through this period. However when the weather does change, this is when we want the system to react to those changes to use the minimum energy input to produce the required cooling effect.

This is the same message from lana, Sergei, and myself. You even hinted at in the following:



What if the pumping power was greater that the gain in performance? Then I'm actually making the whole system worse!!


We are all saying the same message.

nh3simman
03-04-2007, 04:31 PM
This is clearly a complicated subject. Which makes it all the more difficult to discuss in writing. It would be great to be able to discuss this subject with you guys face to face.

In general, I think that we all agree with the logic. I think that it is possible, in principle, to have an optimal system. I am just not totally convinced that there is a way to know when you have it.

Water cooled, air cooled, evap-cond cooled, it doesn't matter, it's just an example. What I was trying to illustrate is, there is a limit to what you can do. And, even when you do take some action, how do you know that you have a more optimal system.

US Iceman
03-04-2007, 05:07 PM
Hi,

Yes this is a very complicated topic. I started with the hand's on area and learned that. After understanding what transpires with the changes, it is a little easier to understand what the "code" should look like.



And, even when you do take some action, how do you know that you have a more optimal system.


Some of it is done over a period of time using trend analysis. Sometimes you take your best guess for a set point and see what happens. Not very scientific, but the guesses are usually based on science.;)

Some of these you can find the initial set point by using the component performance balances in a spreadsheet.

There are a lot of relatively easy things to do to get started. The old adage of; "keep the discharge pressure low and the suction pressure high" is a starting point.

Both have certain limits that cannot be exceeded, but what we are trying to find out is how to manipulate the system to our advantage.

I'm going to be gone for several days, so I'll catch up with you guys on my return.

Till then, take care.

lana
03-04-2007, 06:46 PM
Hi USIceman and NH3simman,

USIceman you are really a moderator ;) .
I love working with people who have knowledge, experience, patience and important of all willing to share.:cool:

As USIceman said, we are all talking about the same thing here but with different approach.
I think System Optimization is like Democracy:eek: . Everyone likes it but with different approach. Maybe it is not a good example but I said it anyway:D .

I have read a lot of research paper about optimization. Everyone looks to the picture from different point of view.
When you read one about the gpm for water cooled condenser then you think, that’s it; we found the way.
You read another one about condensing temperature then ……
In my opinion there is not any "the best way" or ' the most optimized system". Each system is designed and operates for specific reason.
Sometimes the energy consumption must be sacrificed for other more important reason.
Sometimes, operating cost must be sacrificed for ….

Unfortunately, it is an ongoing dilemma.

Hope this sub-forum can shed a little bit of sun shine on this important topic.
BUT try not to get too much sun shine; we have ozone depletion:cool: :eek: :D .
Cheers

nh3simman
04-04-2007, 03:49 AM
Unfortunately, it is an ongoing dilemma.


Hi lana,
I agree. It's like arguing about unit systems.

I would still like to see some proof that the actual plant can be optimized.

Sergei talked earlier about tuning but refigeration plant does not have a single operating point. It finds a balance point for any given set of conditions.

You can tune an analog radio to give an optimal signal because the outcome depends on your settting.

lana
04-04-2007, 09:10 AM
Hi NH3simman,

I was thinking about this yesterday. What I would like to talk here is this :

Optimization is a relative world:rolleyes: :rolleyes: . The system is optimized relative to what? Assume that a system is working now, and then someone wants to optimize it.
SO he makes some adjustments then Hay, there is better cooling and less power consumption.
NOW he claims that
"I optimized the system". YES he did, BUT the system is optimized relative to the pervious situation.
I think there is NO absolute optimization. Whatever I do to a system, someone can do better or at least differently.
Think about it and let us know.
Cheers:)

nh3simman
04-04-2007, 10:34 AM
Hi NH3simman,

I was thinking about this yesterday. What I would like to talk here is this :

Optimization is a relative world:rolleyes: :rolleyes: . The system is optimized relative to what? Assume that a system is working now, and then someone wants to optimize it.
SO he makes some adjustments then Hay, there is better cooling and less power consumption.
NOW he claims that YES he did, BUT the system is optimized relative to the pervious situation.
I think there is NO absolute optimization. Whatever I do to a system, someone can do better or at least differently.
Think about it and let us know.
Cheers:)


This is exactly my thoughts about the optimization of complex systems.

Sergei
05-04-2007, 12:03 AM
Hi NH3simman,

I was thinking about this yesterday. What I would like to talk here is this :

Optimization is a relative world:rolleyes: :rolleyes: . The system is optimized relative to what? Assume that a system is working now, and then someone wants to optimize it.
SO he makes some adjustments then Hay, there is better cooling and less power consumption.
NOW he claims that YES he did, BUT the system is optimized relative to the previous situation.
I think there is NO absolute optimization. Whatever I do to a system, someone can do better or at least differently.
Think about it and let us know.
Cheers:)
Certainly, optimization is complicated, but we can do it step by step. For example, condensing pressure control. Certain pressure control or wet bulb approach control. I've showed that wet bulb approach is better. What is the optimum wet bulb approach? My research have shown that optimum wet bulb approach can vary from 8F to 30F for different plants and at different outside conditions. For the plant in my previous example, optimum wet bulb approach is 15F. It means that it better than 14F or 16F. This is optimum for this plant and for this outside conditions(wet bulb temperature 70F). This optimum will be different for another plant and for different outside condition, but this is optimum(the best).
Criteria of this optimization is efficiency of refrigeration plant(minimum power use per unit of refrigeration).
You can read this attachment.

Dan
05-04-2007, 03:28 AM
Stoecker simulates a simple vapor compression cycle and shows the relative component sentitivities as:
Compressor = 6.3
Condenser = 1.3
Evaporator = 2.1

I have Stoeker's book, and missed or failed to remember that bit of thought. I wonder how he arrived at that. If you look at all the recent efficieny gains in A/C and refrigeration, most emphasis has been on improving evaporator and condenser performance. Compressor performance is being improved by add-on's such as digital and variable speed or capacity adjustments. Each of these are also available with evaporator and condenser blowers. Sensitivities may be something entirely different from what we can do to improve performance the most. Thanks for bringing that up, nh3simman

nh3simman
05-04-2007, 03:54 AM
Criteria of this optimization is efficiency of refrigeration plant(minimum power use per unit of refrigeration).
You can read this attachment.

Thanks Sergei, I will take some time to read it.

US Iceman
06-04-2007, 03:22 AM
Sergei talked earlier about tuning but refrigeration plant does not have a single operating point. It finds a balance point for any given set of conditions.


That's true. I think the different balance points are what Sergei was referring to.

Let me add a different twist to this discussion.

Let's say we all agree there is only one optimal balance point at any one operating condition. This is the point where the system uses the minimum amount of input energy to produce the desired cooling effect for control of the temperatures at that operating condition.

Therefore, if the operating condition changes (weather, loads, or combination of equipment) the control system and system design should be flexible to allow optimal operation by "using the minimum amount of input energy to produce the desired cooling effect for control of the temperatures at that operating condition."

This requires the development of load profiles to see how the system loads change. From this you can determine the proper mix of different equipment operation for minimal power input. This entails reviewing the part-load performance of different equipment types (screws versus recip.'s as an example) and how all of the components work together in a dynamic situation.

So, to add another term to optimization paths I would add the system needs to be designed not only for optimal operating conditions, it also needs to be designed to be flexible for any potential operating condition it may encounter.

This requires we "design out" all barriers that can limit the potential capability/flexibility of the systems.:cool:

poe_boy
07-04-2007, 01:46 AM
Can I add the use of an infrared scope/camera to check electrical contacts, wires, starters, etc. for potential hotspots.

Dan
07-04-2007, 04:29 AM
Can we add: Use Soft Starter for large Electric Motors.

I have been exposed as a manager speaking to technicians regarding soft starters. We had a middling disasterous startup because either we or the OEM didn't have things set or sized correctly. I would like to hear as simple a description of what "soft start" is and perhaps compare it to "part winding start" and foremost, the technology and devices that provide this.

autt
07-04-2007, 06:19 PM
Optimization is generally the compromise, or lana says relative. To get a more effective system, you often have to cut off some advantages. Criterias are different for different using, every time you have to consider to choose or give up something.

Does every system need a programme? Good news is no necessary. A technology used in aero system is a good clue. For airplane A/C, most influence are managed to transform to a same criteria: Fuel weight. The theory is that every influence finally cause more fuel consumption, so people convert every influence to get total fuel consumption as compensation of each. By this way the system can be optimized to have minimal fuel consumpton with compromise of jet bleed air, ram air consumption and system weight.

For the refrigeration system as industrial product, the best criteria I think can be cost, lifetime cost and weight for most using. This has easy way to achieve without complex calculating, and is reasonable in a economical system.

So we can use one program to optimize most different system to get the one best, or near the best.

How to know if a control or whole system is the optimized/best one, like nh3simman said? I think that is to compare. Whatever thermal, mechanical or electrical optimizing, comparing is needed, some are processed by program, some by engineers.

But usually it is impossible to compare with real products because of cost. Experienced engineers can do it very good, they have real products in brain and compare them with glance.

Also can use program tools to compare. The optimizing program can compare hundreds or thousands of parameter combinations to find the best, remarkably reduce time and cost, problem is that they are not so intelligent to do jobs such as layout system scheme, so engineers need to do most work. After all, programs are just tools, how much efficient depends on how to use them.

nh3simman
24-04-2007, 05:14 PM
I have read some really thought provoking comments on this forum. Probably the most interesting has been in this sub-forum on optimization.

There is an international conference coming up and I have submitted the topic "Optimization of Refrigeration Systems". Many of the ideas are sparked off from this thread and inspired me to do some research on the subject. Thanks for the discussion.

US Iceman
24-04-2007, 07:16 PM
I have a presentation this fall based on the use of benchmarking as a common laguage to explain energy savings to upper management.



Many of the ideas are sparked off from this thread and inspired me to do some research on the subject.


Please cite RE as a reference.:D

TXiceman
24-04-2007, 10:02 PM
A couple of months back we had a presentation at RETA (refrigeration engineers technicians association) dealing with tuning your refrigerations system for optimum performance.

Ken

nh3simman
25-04-2007, 04:22 AM
presentation at RETA (refrigeration engineers technicians association) dealing with tuning your refrigerations system for optimum performance.

Hi TXiceman, Do you know if the RETA presentation is available for download?

nh3simman
25-04-2007, 05:28 AM
I have a presentation this fall

You show good insight in this subject. I would be very interested to read your presentation.


Please cite RE as a reference.

You bet. I notice from my referrer count that some people are taking my suggestion about RE. I have also put a link on my web site.

US Iceman
25-04-2007, 05:38 AM
I have also put a link on my web site.


I think the RE boss will like that. Thanks for doing that.;)

Perhaps we can share presentations after they are completed. I would prefer to wait on sending mine until after this fall though.

No sense in giving everyone a head start on the arguments.:D

nh3simman
25-04-2007, 05:57 AM
Perhaps we can share presentations after they are completed. I would prefer to wait on sending mine until after this fall though.

Good idea. I will post my talk on a free domain.