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chilled2005
03-09-2005, 09:13 AM
Hi ive been working on some ref packs and noticed a heat reclaim switch on the front.... can anyone tell me what it does?
thanks

chilly
03-09-2005, 10:11 AM
Usualy heat reclaim switch divers some or all the discharge gas into a paralel condencer in the air handeling unit for the stroe, Hence the hot condencer air is reclaimed to heat the store, Sainsbury's were more sucsesfull at doing this, the safeway system used to cause problems in the winter where we had liquid migration problems.

Some asda stores used the discharge gas to heat water.

If I were you i wouldnt use heat reclaim if you can leave it off, Its hard to balance the gas between the heat reclaim condencer and the roof condencer.

Peter_1
03-09-2005, 12:55 PM
If I were you i wouldnt use heat reclaim if you can leave it off, Its hard to balance the gas between the heat reclaim condencer and the roof condencer.
We did it many times: you only need a SV to open the heat reclaim condensor, a CPR valve from Danfoss t omainatain sufficient HP (some of the discharge is bypassed then automatically to the outside condenser) and an NRV. That's all you need and it always works fine, whatever the temperature may be.

I have a complete different opinion: if you can use the waste heat, then you allways have to use it.

Adding a plate HE between compressor and condensor is the easiest and cheapest way.

We often use heat reclaim in small vending trucks where we make a small coil - connected between condensor and compressor in a water reservoir of +/- 100 l. so that they can wash their hands with warm water which was heated for free.
It also helps reducing the HP in warm weather.

chilly
03-09-2005, 01:35 PM
Your totsly right Peter, If you can get it to work well, then its a good thing, and its free.

Although on a single split system, or small multi split i think it will be much easyier to achieve, On a veru big supermarket pack that is running on minumum charge, in practice ive found the liquid level to be way too sporadic and the heat reclaim has been responsable for the whole system becoming unbalased.

Try it and moniter the system. When it works it is a fantastic achievement, but if your number one goal is to maintain a shop full of cabinates at the right temperature, using the heat reclaim can make the system too tempermental. In my opinion.

Peter_1
03-09-2005, 02:07 PM
We did it at least 10 times on packs installed at Carrefour Belgium and some Delhaize's, packs of +/- 300 kW to 500 kW, positive and negative packs.

Danfoss published around 1980 a small (55 pages), nice book/guideline wit all examples in it of heat recovery systems, domestic water, AHU's, single units, packs,...
I have it here in front of me, covered by an inch of dust.

Hey, thought already on the opportunities which will come in the very, very near future with fuel prices sky-rocketing now?
Heat reclaim, systems for increasing COP, heatpumps in general, ground coupled heatpumps more specific, ...

US Iceman
03-09-2005, 06:05 PM
Energy is not going to get any cheaper. Our gasoline prices are increasing almost daily due to the hurricane down south.

Gas and electricity costs will continue to increase also I think.

In my opinion, any heat recovery we can do, on any refrigeration system we should be looking at.

Heat pumps for industrial processes are beginning to be seriously reviewed.

One of the more common things I find with heat recovery on refrigeration systems is the heat reclaim condenser does not freely drain the liquid refrigerant.

Most of the systems have pressure regulators and solenoid valves, but do not include any provisions for draining the liquid well.

Look at a steam system. A coil has hot steam entering the heat exchanger. The steam condenses into liquid, which heat the airstream or other fluid. If the heat exchanger accumulates liquid (water), the heating process is reduced.

Since a steam system uses steam traps to drain the liquid out of the heat exchanger, the heater continues to produce heat at the desired rate.

Any refrigeration heat reclaim device or coil should be able to drain the liquid out of the coil at the rate the liquid forms.

This is the simplest type of heating system we can use. Turn the steam (or refrigerant) flow ON with a solenoid valve and drain the liquid with a liquid drainer (high-side float valve, modified steam trap, etc.)

Danfoss has a high-side float valve I believe you can look at for this purpose. Some of this may have been described in the book Peter was describing. I have not seen it, but it sounds like a good reference.

Also, look at some steam books for other ideas. A steam system is not much different from a refrigeration system. They use a boiler, we use a compressor.

This tends to address the erratic problems with liquid management.

The other item to review is the required pressure. Heating comes from the condensation of the refrigerant. The phase change is where most of the heat energy is. This does not have too much to do with pressure.

Heat recovery is a double edged problem. First, how much heat energy do we need, and second, what temperature is required?

botrous
03-09-2005, 06:26 PM
Well as i heard today on the news the petrol prices are increasing in a dramatic way , well that's at least one thing to make the big companies do their jobs in energy economical and efficient designs .
I hoped that this happens in other conditions , not based on the suffering of people from a hurrican and not based on the increase of petrol prices but based on the human intelligence to save this planet , but it seems that money controls everything even human brains ,nations and goverments . . . .
Maybe and maybe US citizens can force their goverment to sign the international agreements of the greenhouse effect and of the polluting gases that are increasing the earth tempreture resulting in such desasters like the one america is facing today.

Praying for all the suffering people.

chilly
03-09-2005, 06:40 PM
Whenever heat reclaim can be done without compramising the system eficiency its got to be good, Daikin have just introduced a wonderfull system designed for the domestic market, the controles to maintain balance is quite indepth but the end result works very well. This is got to be good all round.

Peter_1
03-09-2005, 09:26 PM
In my opinion, any heat recovery we can do, on any refrigeration system we should be looking at

I totaly agree with you on that point.


Danfoss has a high-side float valve I believe you can look at for this purpose. Some of this may have been described in the book Peter was describing. I have not seen it, but it sounds like a good reference.
If I find some time, I will scan, it for those interested.


I hoped that this happens in other conditions , not based on the suffering of people from a hurrican and not based on the increase of petrol prices but based on the human intelligence to save this planet , but it seems that money controls everything even human brains ,nations and goverments . . . .

I couldn't explain it better Botrous but as you said, in this world, it's only money and oil that counts.

But we as Refrigeration technicians can help saving the environment and making big savings without expensive and fancy tricks.
But we must try to convince our clients.

Chilly, where can we find some more information about the new Daikin system?

botrous
03-09-2005, 09:55 PM
But we must try to convince our clients.


Hi Peter
Hopefully we try but unfortunably the majority of them aren't brain controlled or remote controlled , they are money controlled :mad:

US Iceman
04-09-2005, 01:24 AM
Heat reclaim and energy savings can be hard to sell to a client. However, I think we can strive to accomplish this during the initial design of any new system.


Hopefully we try but unfortunately the majority of them aren't brain controlled or remote controlled , they are money controlled.

The majority of clients do not understand refrigeration. They know their requirements for food processing or cold storage for example. They know how do this very well if they are successful. Refrigeration is something they have to pay for, and unfortunately they may think any increase in cost is unnecessary.:(

On the other hand, there is something we can do. Peter said it best,


But we as Refrigeration technicians can help saving the environment and making big savings without expensive and fancy tricks.
But we must try to convince our clients.

It is my belief that we can design refrigeration systems to use the minimum amount of energy, if we re-think how we design systems. The majority of refrigeration designs are still based on old technology and methods.

Take head pressure controls as an example. These are required because of the dependence on the minimum liquid supply pressure for the expansion valves. If we use EEV's or balanced port TXV's this is a good beginning. With these we can float the discharge pressure in the winter time (big savings!:D ).

Copeland has a new compressor that has been out for some time: Delta Reed valve. This is designed for low condensing temperature operation. The older Discus compressors have a factory minimum limit of ~21C (70F) condensing temperature.

I have ran some of the original Discus compressors down to ~7C (45F) condensing on R-12 and R-502 systems with the balanced port Sporlan TXV's.:eek: This worked quite well.

Supermarkets: If we can provide better dehumidification in the stores, the display cases do not have to perform the humidification of the store air. More or improved dehumidification in the store reduces the refrigeration system load (less equipment & less run-time).

Why not use a 2-stage compression system in a supermarket?:confused: We have to get creative when selling these projects.

Electric defrost?? Is this really cheaper than hot gas defrost. Compare the electricians cost difference. The owner needs to be convinced to look at the big picture. Not your costs versus your competitors.

Cold storage: Design the shipping docks to do the dehumidification before the moist ambient air gets into the low temperature storage space. (similar discussion above on supermarket dehumidification)

Heat Recovery: We are discussing this in this thread.

We need to consider how the systems work in cold weather, not only during the hot weather. Part load operation is a big consideration when using screw compressors.

We can develop or use "smarter" control systems. Defrost by time of day and fixed duration?:mad: Why??

Measure the liquid solenoid On time and adjust the defrost to the amount of time the evaporator is cooling.

Use ECM motors in display cases for supermarkets. We can use variable frequency drives on larger evaporators in cold storage. Less energy input = energy savings times 2 (lower motor heat in the space reduces the refrigeration capacity required & less fan motor power input).

I think we can do this... We have to get creative and quit doing things the way we used to. No gimmicks, no experiments. Just good old engineering and common sense used for long term decisions.

What do you guys think?:cool:

botrous
04-09-2005, 04:57 AM
I sure agree with you and with Peter , anything to save the planet :)

Peter_1
04-09-2005, 11:42 AM
Us Iceman, we're completely on the same line.

You said "The owner needs to be convinced to look at the big picture. Not your costs versus your competitors"
Well.... I will translate and modify this quote a little bit in Dutch and put it in every offer/quote I make in the future.

Worth reading some of these links:
http://www.energy.ca.gov/reports/2004-04-23_500-04-013.PDF

From a university in The Netherlands (in English, don't worry) http://www.mep.tno.nl/wie_we_zijn_eng/organisatie/expertisegebieden/koudetechniek_warmtep/PDF/Review_calprogr.pdf

http://images.freepatentsonline.com/us6216481.pdf

http://images.freepatentsonline.com/us4193781.pdf

http://images.freepatentsonline.com/us5673567.pdf

http://images.freepatentsonline.com/us6167715.pdf

botrous
04-09-2005, 08:18 PM
Nice idea Peter to put such quote in your offers , it's the 1000 miles journey starting from here .

Best regards

dallan
04-09-2005, 09:57 PM
Icemans suggestion to use inverter drives on evaporator fans seems appears good. Has anyone seen this done, a relatively straight forward idea that i and all of the designers I know have overlooked.

botrous
04-09-2005, 11:33 PM
Hi Dallan how are you ?
Yes we used inverter drives in the airport and the results were great , we minimized the energy consumption in a good scale ... there we used all the technology to minimize the bill , well because the customer was the goverment and they wanted all the system to be energy efficient and to preserve the environnement , also we used vsds for air handling units , pumps etc . . .
I used the heat from the power generators to preheat the water entering the steam generator in a silk factory and that lowered the bill about 10 to 15% .
We can always use our engineering skills to make efficient systems and designs , but what we most need is to convince the clients , that what they are paying for it more now , they will be rewarded for it in low bills in the future , some of them just don't care and prefare the conventional systems , some of them don't want to pay more for the moment and after the system installation they will be calling you to try to lower the bill , someothers are mature enough to know that this is the futur we are talking about and accepts .
Regulations and laws are the most needed to force clients to use efficient systems.
Best regards

US Iceman
04-09-2005, 11:50 PM
Hi Dallan,

I have done several of these. Everything has worked well to date.

The use of an inverters on large evaporators should be carefully reviewed. Electrical issues are one thing (harmonics, controls, etc.).

Don't mount the drives in the cool spaces. The load from the heat sinks on the inverters is picked by the refrigeration system.

Fan motors in cold air applications can have higher power input than the same motor size in ambient air. The colder air increases the air density and increases the power input requirements. Watch this when selecting the inverter.:eek:

The other area that requires some investigation is the application of inverters to refrigeration coils.

First big issue: Be very careful applying these to direct expansion coils. Control systems can be made to operate in milliseconds. Refrigeration systems work much better if their response time is slow (like a turtle!!).

Anything that can change the system pressures quickly should be slowed down. Very slow. Same applies to evaporative condenser fan motors.

Fast changes in fan speed/pressure can cause problems. For example, you do not want to change the inverter speed quickly as this may cause the TXV to hunt. TXV's have a minimum turndown range. I use 50% as a maximum turndown with balanced port TXV's.

Fast changes can also cause rapid boiling, which can lead to other serious problems (floodback on the suction side).

Big oil separators is another issue that falls into this category (screw compressors). Rapid discharge pressure reductions can cause oil carryover out of the separators.

Make sure the oil separators are large enough (bigger diameter) for low discharge pressure operation.

Flooded or liquid overfeed evaporators seem to be OK. (remember, slow operation is the key)

Inverters on refrigerant pumps is not worth the time. Most refrigerant pumps have flat curves, so the control and or power savings is minimal.

Another good place for an inverter is on reciprocating compressors (open drives) with capacity control (unloading capability).

An inverter on a recip. compressor provides unlimited capacity modulation like a screw compressor slide valve. Except the part load performance is linear through the whole range (unlike a screw with no inverter).

For simple cold storage applications, the annual turndown for energy is about 35% (an estimated number for the evaporators only). When you combine the reduction in heat load (from the motors) in the cold space you also get a reduction in required compressor capacity. Two for one!!

The evaporators in a cold storage application typically account for about 40% of the total connected motor power in the refrigeration system. Any changes to this area generate significant benefits.

Almost any refrigeration system can be designed to use about 40% less energy than most of the current designs I have seen. In some cases more.

This can be done without gimmicks, gadgets, or a lot of control valves.:D

I have included a set of curves to show the relationship for part load performance with inverters for evaporative condenser. A similar behavior is seen for evaporators.

The largest gains are seen in the area from 60Hz to 35 HZ. For 50Hz power supplies the curves need to be re-worked. These are based on 60HZ operation.

Some tips for review. Review everything and take nothing for granted!

A well performing project sells better than one that has had problems.

Hope this helps you.

Best Regards,
US Iceman

Peter_1
05-09-2005, 09:27 AM
BE aso carefully on DX evaporators when you reduce the speed of the fans that the capacity of the evaporator will reduce also and that the TEV can start huting because it's goin out of his regulating range.

Some applications we did in the past:
In a flower cooler, you need as low as possible airflow.
So we installed a VFD on the fans which reduces proportionally the speed of the fans as set temperature is reached. As soon all the flowers were at storage conditions, the fans remained at a very low speed only to remove the heat load through the walls and the aspiration heat of the flowers. It was very quit inside this room:D
We used a chiller that moment but it could even had been EEV's on DX evaporators.

A second application we used several times (we're making one right now) is a vending truck in a counter.
In the counter, we install fans like you find in computers (80 x 80 x 30 mm)
The fans are controlled direct by a Dixell thermostat who controls direct a Dixell speed regulator XV105D.
The control curve can be preset via the Dixell regulator.
And it's a cheap solution.
Dixell is the same founder as Eliwell

Steve Wright
06-09-2005, 11:09 PM
Heat Reclain is great, some things to watch out for; if gas defrost you must have some method to maintain head press in defrost, some relaim valves dont have an off cycle bleed port if it does not then a NO Solenoid valve in series with a cap tube will drain the refrigerant out of reclaim coil during off cycle Sporlan has a good depiction of this, a flush timer that energizes the reclaim valve every 12 hour is a good idea to flush oil that may have accumulated in the coil during prolonged non use periods.

A note regarding Peter_1's coments. Peter you are obiously a very smart man however I think you missed the mark about the government not helping our own here in the US and that may be because of the news. First the US government can only interviem at the request of the state, that took several days. Second the National Guard is under the govenors(state government) control not the presidents. Third when he was allowed to the president acted swiftly and desicivly, most places could not be acessed.

I do appreciate even though I do not completly agree with you. Thing are not as they may appear.

kend
05-05-2008, 05:32 PM
Peter - 1, Did you ever scan the 55 page Danfoss booklet. I could use a copy. I have used residential desuperheaters in series with air cooled HP condensers. Using switching and liquid drian valves is something new to me. I am having trouble convensing the design engineers to use heat recalim and have promised the owner that the system can work.

Thanks, kend
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