air distribution in island

[tralex]

Hello anybody
I have some trouble with low temperature island.
I use for testing that island test packs.
Maximum test pack's temperature should be -15 C,
but I have -11 C.

In my opinion refrigeration system (R404A) work not bad
evaporating pressure 1,6 bar
condensing pressure 15 bar
temperature inlet air -27 C
temperature outlet air -19 C

but cooling air is whing the island.

How I can improve air distribution in that island?

Thanks for any advice.

[Renato RR]

Install air curtain.

Renato

[Peter_1]

Try to visualise with smoke what the air is doing in the freezer. That works in most cases.
You're pulling warm air in it or your airspeed is to high or bad directed.

[US Iceman]

It has been some time since I have worked on these cases, but it may be possible the material placed in the case is slightly too high.

I believe there is a level slightly below the air discharge grilles that is the maximum point to place product. In the picture it appears the material is directly under the discharge grill.

As Peter suggested, you should use some smoke to check the air flow patterns. Not only the case, but the ambient air as well.

[Peter_1]

USIceman, the products are indeed stacked too high, you're right.

[tralex]

Thank you guys for answers.
Renato, I have air curtain in island, do you mean extra air curtain?

Really at the bottom of island temperature is -22 C,
but owner want load maximum products in the island.
May be somebody knows how much below air discharge grilles products is disposing in other islands?

It's difficult for me to describe air movement
so I make movie You can click on the following link to download:

http://www.megaupload.com/?d=S8I5K26U

I want seize when air distribution will better.

Thanks for any advice.

[Peter_1]

At least 10 cm under the grilles. Are you making tehse cabinets yourselves? Otherwise, most islands have a max load line.

Perhaps I see it not that well but in your last movie (0004) is the air extracting grille the honeycumb grille?
If so, this is wrong, this should be the pulsion side.

[willie]

check your air supply velocity ,rule of thumb was around 120 -130 fpm .wide island cases need at least -29 air supply to give case temp of -26 ,back pressure seems to be little to high ,what size are your tx valves is unit sized correctly is case from major manufacturor or is it a self design

[US Iceman]

but owner want load maximum products in the island.

Sometimes the owners cannot have everything they want.

I agree with Peter, the top of the product should be stacked no higher than the dimension he provided (from the air discharge).

If the product is stacked into the air curtain, the airflow is disturbed. This can cause the cold air to entrain warmer ambient air also.

Another possibility is a potential for external air currents disrupting the cold air flow on top of the display case.

A third cause might also be a higher than normal ambient air (wet bulb or dry bulb temperatures). These cases are designed to be operated in an air conditioned space.

If the space temperature is higher than the design factors the display case will also have problems achieving the desired temperatures.

If all of this is OK, then you need to check the refrigeration system as willie suggests.