Wasted Energy From Refrigerated Display Cases

[SgtRock]

Greetings EEVBees:

--Please see below, and article from Inside Science about possible energy saving designs for open style refrigerated cases.

http://www.insidescience.org/?q=content/curtailing-open-grocery-refrigerators-energy-loss/685

--In some ways open cases seem stupid, but in the case of cooled fresh and thawed, meats, poultry and fish, they seem to be pretty much unavoidable, given the extremely close and prolonged scrutiny, the inevitable crowds of people give the most important, and expensive items on their shopping lists.

--I live in Florida, and in the Summer, heat is always on our minds. In North Dakota or Alaska, wasted heat from refrigerator units is not as big of a problem. In Florida and in other hot locations, dumping refrigerator waste heat into air conditioned spaces seems wasteful, but at this time seem to be unavoidable from a practical standpoint. One thought I had was if  refrigerator units were located against outside walls, perhaps waste heat could be dumped to the outside.

--Does anyone know anything about, how this sort of thing is done, and what the state of the art is?

"Noise proves nothing. Often a hen who has merely laid an egg cackles as if she laid an asteroid."
Mark Twain (Samuel Langhorne Clemens ) 1835 1910

Best Regards
Clear Ether

[PeterG]

Here in Australia the heat is pumped outside the building for big supermarket systems.

Regards

[SeanB]

In a big supermarket the refrigerant system will serve many cases in a row, each having it's own valving to allow the refrigerant into the section of evaporator it has. Either way all the vapour is returned via a common suction line, and then is compressed to a hot gas then cooled with ambient air to a hot liquid before going back again. The compressor and condenser coil will be outside and in a well ventilated area ( hopefully, as it costs money to cool and the hotter the outdoor unit the less heat it can pump and the more electricity it uses) mostly at the rear or on a roof. Controls are present to do various things, controlling the temperature of the coil so it will not freeze for a cold case, and controlling defrost cycles on a frozen food case. Both will run on the same circuit in most cases, and the controller will generally be set to either slow down the compressor at low load or switch some of the paralleled compressors off on bigger systems. Generally there are either curtains or removable doors that are placed on the case at night after restocking to reduce heat loss, this is the simplest and biggest saving. As well keeping them from drafts helps a lot.

On smaller cases there is nothing external, the unit has everything inside, and simply pumps the waste heat out of the top or back of the unit ( where it will not be objectionable to the customers) with much simpler controls. The big units can have as many as 100 cases controlled by a single controller, with the defrosts being staggered to reduce the load, and automatically controlling both the doors, fans and the lighting to reduce energy demand.

If you are in the UHK and shop at Tesco, they amongst others are busy changing over to CO2 refrigerant systems, and are having a few issues with the very high pressures that you have to run a supercritical CO2 system at, having had a few faults that disable the entire system for days until it is rebuilt.

[caroper]

having had a few faults that disable the entire system for days until it is rebuilt.

That must be costing them a fortune. If the Cold Chain of the product is disrupted for even a few minuets the sell by date is invalid and the Product must be withdrawn from sale.
If you daisy chain the fridges and they all go down, that is a lot of stock to write off.

[SeanB]

Yes, and they have been working on it......................

Local stores are still lucky in that they can use reliable refrigerants that are non toxic, non flammable and work at sane pressures.