@ Captain Ted
I didn't know that method but with a little search i found out that it's still used today ! Have a look here :
http://www.imsinc.co/products/brine-freezing/
and here for a nice presentation:
http://www.pfri.uniri.hr/~bknez/REFRIGERATED%20CARGO%20SHIPS.pdf
A big THANK YOU to everybody for the VERY educating comments !!!

@ Nektarios (any info on below appreciated)
I still sailed a reefer vessel which operated with salt and brine as cooling element!!! the Nova Galicia, only time I had such system in my seafaring life. was very interesting and to my knowledge it did not involve FREON ,, I wonder a little why that system was abandoned because of the NONE enviromental damaging aspect of not having Freon ?.

@mumbles
Thanks for the info. I know what you mean by "reefers before 1980". I love them too. I have seen and photographed plenty of them in the 80s and early 90s mainly in Piraeus, but they are on negatives so i need to find a good slide scanner to bring them to the digital era...

If you want to see “proper” reefers, look in the “Reefers Built before 1980” Category. There you will find the ones that were known as “the greyhounds of the oceans” and had their superstructures located amidships or three-quarters aft. It was around 1980 that refrigeration equipment engineers like Danfoss devised freezer eqiuipment that could reach the whole length of a large reefer to chill the forward holds from an aft-located fridge control room. The advantages of the all-aft design were, of course, that mechanical power losses from, and the weight of, a long prop-shaft were saved and the space hitherto taken up by the shaft tunnel could be translated into cargo carrying space. Unfortunately it made reefers look pretty well like any other ship, rather than the outstanding beauties they once were. Such is progress.

Thanks for your comments guys. Reefers are my favourite !!!

They don't make reefers like this anymore.
Excellent photo Nektarios.

I remember as a kid, at the dentist which overlooked Barry Docks, I was having my teeth pulled & after the anaesthetic gas, I was sat in the waiting room looking out the window at a medley of assorted funnels/deck gear. Banana boats as my old man used to call them. It kind of stuck in my mind - I can see them now !!

I sailed ships like that between 2000 and 2004 all builded in the early 80,s to the mid nineties. Very nice seas ships. the cabins and such are not so nice, rather spartan inventories

She looks the business - raised holds too & proper deck gear (it's the way I was brought up!)