supermarket heat reclamation systems

[danny x]

I am looking for information on design, installation, and service of heat reclamation systems for supermarkets.


Any links would be appreciated

Dan

[-frozen-ocean-]

the heat reclaim 3-way valve energizes during reclaim mode diverting discharge gas to a remote mounted air reclaim coil or water heating coil. after the discharge gas passes through the reclaim coil,it returns to the system through a check valve and then to the condenser.the check valve assures no back flow and flooding when heat reclaim cycle is off.during heat reclaim,the heat reclaim coil rejects superheat from the refrigerant vapour and the condenser coil rejects latent latent heat and produces quality liquid for the refrigeration process. hope this helps u out.

[mspanky]

The trick is to have the reclaim operate without condensing the discharge gas before the condensor, especially air coils in cold climates. This is why most reclaims are valved off in my area, other than hot water reclaim.

[icemeister]

The hot water reclaimer are easy to handle because they are primarily desuperheaters. The actual heat available in the superheated refrigerant is roughly 15% of the total heat of rejection of the system......the rest of the available heat is latent, and it amounts to a whole lot of free heat.

Those heat reclaim systems that you see valved off probably didn't work because the system receivers weren't big enough to handle the transient summer/winter charge difference. One of the main reasons split condenser piping became common 20 years ago was to allow the reclaim systems to operate with a smaller total system charge.

It's a good thing to see a 55,000 sq ft store on a windy day in the low teens running all racks on full reclaim heat, condensers at 25% split w/subcooled liquid going to the condenser, 20% in the receiver and no auxiliary heat needed.

[Edited by icemeister on 11-22-2005 at 08:33 PM]

[bryan l]

With heat reclaim systems you need to be cautious of your setup and control.
First of all if its a air reclaim you need to ensure your t-stat is going to be in a area that wont hammer the reclaim valve open and closed rapidly.
Next you need to look at what the interlocking method is and how its connected to the rack so as to ensure the heat reclaim valve is not diverting to the reclaim coil if the fan is not running.
Next is some sort of lockout for the heat reclaim to protect against the instance that its head pressure drops down really low when its cold outside. What happens with a heat reclaim system is the heat reclaim system (water, air, ect)is the first to get the discharge gas from the rack, from the reclaim it then goes to your condenser(s). So when its very cold you effectively have a larger condenser to deal with and you usually drop your head down to a pressure that you will loose all your gas up on the roof and then life sucks as a mechanic. To avert this you need to put in a lockout to prevent the head from say dropping below say 150psi R-507, (depending on the type of rack it could be higher or even lower such as the hybrid racks we use its down to about 130.)

Last but not least is to be ready to shut the coil down at the first sign of liquid logging on the roof or add more gas, (usually allot of it)


Hot water reclaim is another common type and usually involves a pre-heat tank type of setup, your not going to be able to heat city water up to the 130 degree you would get out of a common hot water tank, your mainly heating the water up to somewhere in the 100 degree range.
With a hot water reclaim system you will need a bypass differential valve installed between the reclaim outlet and return. Set it up for 10 to 15psi differential to ensure your not condensing the discharge gas in the reclaim loop.


The rest is all SWAG (Silly wild ass guess, or in some cases scientific wild ass guess)

have fun :)

[mccool]

Found a link to a summary of various refrigeration studies that include heat reclaim and other energy saving ideas, makes for an interesting read. http://www.orni.gov/sci/engineering_science_technology/Annex26/Annex-26-final-report-draft4.pdf

OK not working, try a Google search using "heat reclaim quebec high speed defrost" should be second hit in line. Maybe someone can fix this link :D

[Edited by mccool on 11-23-2005 at 02:01 AM]

[mccool]

Google "Serge Dube heat reclaim" for some insight on his refrig. ideas

[frozensolid]

Properly engineered heat reclaim and reheat systems are a good thing. In Publix you will rarely see them with closed valves. More often the water tank is closed off due to refrigerant leaks. A few stores had hot water reclaim only, and it was hot.

We don’t have cold winters down here, so cold is not a problem. Even on cold days if the system was engineered correctly and maintained correctly it should work. I think a lot of the problems encountered are a lack of knowledge by mechanics on these systems. The bigger problem is cheap store managers who don’t want to pay the mechanics who can make it work.

[bryan l]

Originally posted by frozensolid

We don’t have cold winters down here, so cold is not a problem. Even on cold days if the system was engineered correctly and maintained correctly it should work. I think a lot of the problems encountered are a lack of knowledge by mechanics on these systems. The bigger problem is cheap store managers who don’t want to pay the mechanics who can make it work.


So what your saying is that YOU can come up here and make our heat reclaim systems work even when its -15f to -40f?

because if you can then pack your bags and I will personally pick you up at the airport.

[frozensolid]

If it is properly engineered for those temps I can. But your on your own, I don't have the time. :)

[Edited by frozensolid on 11-25-2005 at 07:42 AM]

[danny x]

Originally posted by icemeister
The hot water reclaimer are easy to handle because they are primarily desuperheaters. The actual heat available in the superheated refrigerant is roughly 15% of the total heat of rejection of the system......the rest of the available heat is latent, and it amounts to a whole lot of free heat.

Those heat reclaim systems that you see valved off probably didn't work because the system receivers weren't big enough to handle the transient summer/winter charge difference. One of the main reasons split condenser piping became common 20 years ago was to allow the reclaim systems to operate with a smaller total system charge.

It's a good thing to see a 55,000 sq ft store on a windy day in the low teens running all racks on full reclaim heat, condensers at 25% split w/subcooled liquid going to the condenser, 20% in the receiver and no auxiliary heat needed.

[Edited by icemeister on 11-22-2005 at 08:33 PM]

Lets assume it is an air mounted reclaim coil, how can the receiver be checked for proper size and capacity to function normally in summer or winter? Or in simpler terms, how do I know my receiver is sized properly? How do I determine what size it needs to be?

Dan

[icemeister]

In order to size a receiver to allow for operation throughout the range of seasons you have to estimate the system's transient summer/winter charge and select a receiver size that will allow for that.

If you have a typical air cooled rack system with a reclaim coil in a central air handler that's piped in series with the condenser through a 3-way valve, look at what components of that system and the interconnecting piping runs and consider which of those will be full of liquid during the winter, then those with only vapor during the summer season.

During summer operation on a design day, the reclaim is off with all liquid returned to the receiver via the pumpout line and the main condenser is fully loaded. There's your baseline condition.

Now at the other extreme, a cold winter design day, you should assume that the main condenser is now fully flooded, the piping between the reclaim coil and the condenser is full of liquid and the reclaim coil is now doing 100% of the condensing load from the system.

To arrive at some numbers, you need to know the normal operating charge of the main condenser and its fully flooded charge. (You can usually get this info from the condenser manufacturer's literature or you can calculate it based on internal coil volume.) If you're splitting the main condenser,account for that now. If you also assume that the reclaim coil may be partially flooded during cold weather operation you need to know its internal volume and calculate that charge, say 25% or so. The total you get is the amount of refrigerant the receiver must be able to accommodate, max to min.

Now, I don't know anyone who charges a system 100% receiver level so pick a number you're comfortable with, say 80%. Then what is the minimum level you want to see.....How about 20%? That's a 60% difference. It's telling you that the transient charge you just calculated should equal 60% of the rated receiver capacity. I believe this is where many systems with reclaim get messed up because they use the full rated capacity for the transient charge and end up way too short.

[pecmsg]

Originally posted by danny x
I am looking for information on design, installation, and service of heat reclamation systems for supermarkets.


Any links would be appreciated

Dan



Danny

I did a Google search under Supermarket Refrigeration and got a load of info.

http://www.google.com/search?hl=en&ie=ISO-8859-1&q=Supermarket+Refrigeration&btnG=Google+Search

http://www.ornl.gov/~webworks/cppr/y2003/rpt/117000.pdf#search=%22Supermarket%20Refrigeration%2 2



I’m still on dial up so it takes to long. Check it out your self. Have Fun.

[danny x]

Ok, so we have calculated internal volume of the condenser coil, and or the manufacture says its X amount for a fully flooded condition. In this case it is not a spilt condenser and the fans are cycled off.

Now I am not fully aware of the difference between having the reclaim coil fully flooded or partially flooded(or does it matter), and in this case which is a more desirable condition? Either way, we can take this amount and then add it to X from the condenser.

These two variables are all I need to determine system receiver size? What about allowances for piping runs and such?

“I believe this is where many systems with reclaim get messed up because they use the full rated capacity for the transient charge and end up way too short.”

I read the last sentence a few times but I fail to understand it correctly. I assume you mean they don’t figure the transient charge (in this case the sixty percent)?

Dan

[icemeister]

Originally posted by danny x
Ok, so we have calculated internal volume of the condenser coil, and or the manufacture says its X amount for a fully flooded condition. In this case it is not a spilt condenser and the fans are cycled off.

Now I am not fully aware of the difference between having the reclaim coil fully flooded or partially flooded(or does it matter), and in this case which is a more desirable condition? Either way, we can take this amount and then add it to X from the condenser.

Since the reclaim coil is assumed to be doing 100% of the condensing at worst case conditions I would look at it so as to include a "normal" operating charge for a condenser.....I only picked 25% as a rough estimate of that. It can't be fully flooded because then there wouldn't be any effective condensing surface and it can't be empty or void of liquid because that would mean it's not condensing anything.


These two variables are all I need to determine system receiver size? What about allowances for piping runs and such?

I guess I didn't make that clear in my post. Yes, you have to consider that the piping from the reclaim coil outlet all the way to the main condenser to be full of liquid during the worst case winter condition because we're doing full condensing at the reclaim coil.


“I believe this is where many systems with reclaim get messed up because they use the full rated capacity for the transient charge and end up way too short.”

I read the last sentence a few times but I fail to understand it correctly. I assume you mean they don’t figure the transient charge (in this case the sixty percent)?

No, what I was referring to was that the store engineer will come up with a calculated number for the transient charge of, let's say 350 lbs of R22 and he then picks a receiver like a 14" x 90" that has a capacity of 386 lbs thinking that would be adequate. My example showed that in reality only 60% of that receiver capacity will be available, or about 232 lbs. That system will need some extra gas come January to bring the level up to 15-20% and likely it'll to go down on high head come June.

I hope that answers your questions.

Splitting the main condenser down to 50% or even 25% can often resolve many heat reclaim issues and keep the charge lower. Splitting the reclaim coil as well may help because I've run across some that were oversized. They should be sized for about 50% of the design heat of rejection at a faily high TD like 30ºF.

[oogene]

hey ICE; what do you mean by "splitting the condenser or reclaim coil"? thanks for your insightful anwsers, by the way !!!

[bryan l]

Split is just as it sounds. You split the coil in half. The condenser would have two disc and two liquid headers. With either a Diverting valve or in some new applications actuated ball valves, that valve off the "split" side of the coil. You then pump out the "split" side into the suction header to get all the gas of the roof (or where ever the condenser is). For example in some of the stores I work in we have two stages of split. we can run 100%, 50% and 25%. with a var-speed fan on the remaining full time side of the coil.

One way of limiting your heat reclaim capacity other than splitting it is to use a bypass valve like a A9. This is used on hot water reclaim to prevent condensing in the water tank. No reason why you cant do the same on a Air coil.

[oogene]

I C...so you effectively reduce the condensor by 50% or so or... and make up for it with the reclaimer and utilize the rejected heat with less freon etc. am I close??? THANKS again for even more education for another FlippinNewGuy!!!

[icemeister]

Originally posted by bryan l
Split is just as it sounds. You split the coil in half. The condenser would have two disc and two liquid headers. With either a Diverting valve or in some new applications actuated ball valves, that valve off the "split" side of the coil. You then pump out the "split" side into the suction header to get all the gas of the roof (or where ever the condenser is). For example in some of the stores I work in we have two stages of split. we can run 100%, 50% and 25%. with a var-speed fan on the remaining full time side of the coil.
Good explanation.


One way of limiting your heat reclaim capacity other than splitting it is to use a bypass valve like a A9. This is used on hot water reclaim to prevent condensing in the water tank. No reason why you cant do the same on a Air coil.
The bypass valve that's typically used for bypass of a hot water reclaim tank is the Parker/Refrigerating Specialties A8*L which is a differential pressure regulator. (The A9 series valve is an outlet pressure regulator.) Most often, the flow capacity of the tank is insufficient for the discharge gas flow of a rack at full load so the differential regulator allows the excess flow to be bypass around the tank based on a set pressure drop.

Similarly, I suppose you could use the A8L on an air reclaim coil if the size of the coil would cause excessive pressure drop at higher loads. Good point.

[stanbyyourword]

drawings and pictures guys ;)

[icemeister]

Originally posted by stanbyyourword
drawings and pictures guys ;)
Sporlan Bulletin 30-20 (http://www.sporlan.com/30-20.pdf) Lotsa pictures, diagrams and stuff. ;):D

[stanbyyourword]

hey thanks ice good bulletin ,good drawings for simple guys like me! :) was just wondering if anyone had supermarket pics for airside reclaim.i havent seen this in feild, but know the concept, ie type of air handler and piping etc far from rack? i wouldnt think too far, have seen waterside ones in a few supermarkets, Company I used to work for had some prototype projects at a salami/meat processor drying rooms ,where design would use discharge gas through ahu paralell w evap for reheat where electric is ususally used, we didnt however use 3way valve just pilot operated solenoid teed off from discharge line running to roof, design and application was very successful but the problem that was never worked out was contraction/leak issues at tube sheet of heating coil hot/cold ,on/off so coils never lasted more than a few years regards stan

[stanbyyourword]

come on guys noone has camera phones? ;) regards stan