marine refrigeration (Yacht)

[marincarl]

May I present you with a bundle of strange
situations, as this marine installation is quite
remote of a refengineers dream, but resulting of
being merely forced to get and keep things going
to prevent spoiling of the food under way. The
refrigeration installation consists of a double
door domestic freezer-fridge which, despite shaken
about violently in a seaway performes best. in the
galley there are 2 Foster fridges and 1 freezer
press-fitted next to each other into a niche, no
clearance anywhere, the condensing units are
mounted on the bottom, air circulation is enhanced
by additional fans. The galley was unbearably hot,
much of the heat came from the ref-units,
performance was mediocre. I added water cooled
coils to the condensing circuits, the only
circulating water in the vicinity was the chilled
feedwater for the airhandler of the electronics -
battery room next door. I hacked a hole into the
fire retarding wall and stuck 3 water tubes
through it, 2 for circulation and 1 as drain for
the fridge units, using the condensate drain from
the air handler. Previously it was meant to
evaporate, in practice it spilled with every
movement of the ship, causing a mess on the galley
floor, which has no drain. Using the chilled water
on the galley fridges enhanced their performance
tremendously, the galley is a lot cooler, flow has
to be pinched however, not to get too cold (less
than 15°C) as the pressure difference accross and
refrigerant flow through the TEV's drop. The
normal temperature of the chilled AC water is at
9°C, fluctuates however frequently to 16°C, by
playing I found an acceptable adjustment. The air
cooled condensers I left in the circuit althogh
this can lead to re evaporation of some of the
refrigerant in the condensing unit, but so, even
with the AC failing, there is no imminent urgency.
To some of you this might look as a foul
compromise, but short of a mayor redesign little
can be done to improve it - can you prove me
wrong? Greetings from Tahiti, French Polynesia,
marincarl

[The MG Pony]

May I suggest you look into purchasing a Johnson's V46 series head modulated valves as this will further improve the efficiency of you condensers! and keep a steadier head pressure.

I would plumb it so you can take water cooled via the haul and circulate that though your condensers, this way you do not over burden the A/C.

Use a water to water exchanger using sea water to cool the fresh water/glycol in the system and circulate that for the refrigeration systems, this will avoid the annoyance of plugging and fowling of the head modulating valves and condensers.

[marincarl]

Hi MG Pony, thank you for replying on the tahitian story, and for the ideas with head modulating valves, as there are 3 units each unit would have to get its own valve installed, the second part with a heat exchanger is difficult to set up, under the galley are guest cabins, it would take a lot of persuading to lead sea water tubes through them, a circulating pump would be required as there is nothing close by, drain could be thru the AC condensate drain of the converter room, the galley is on the second deck in a fire retardent enclosure as is the converter room next door, hacking through the floor would require a class survey to take place, thats why i am pretty much limited to existing installations, using a heat exchanger from the circulating chilled AC water to the refrigeration circle would require an additional pump... i like cargo ships, if its needed and you can explain why there is usually the go-ahead right there, on a yacht one needs to worry about appearance, class and the mood of the owners: 'it works, what do you want now (again)??' I still like to discuss things though...
Thanx again for your nice reply, greetings from the south seas, marincarl

[The MG Pony]

Welcome to the board, Even with out using sea water you can still use the A/C water with the valves and that would greatly improve the system.

You can save money on said valves on ebay, and this will greatly reduce the water used as it modulates it better.

http://cgi.ebay.ca/NEW-JOHNSON-CONTR...QQcmdZViewItem

[marincarl]

Tnx MG Pony, i'm already trying to source at least 1 head modulating valve for the freezer, i'm reluctant to use E-bay though, as I would have to use my own means to pay, and, will I ever get it back? The AC is a fairly stable and chunky device with 4 120 ton chiller units (replaced recently) which can take the additional burden without a scream. we are about to leave Tahiti for the Fijis, greetings from the south seas, marincarl