134a - Condenser cooling problem in the Gulf

[TheChief]

Gentlemen,

This is my first post and by all means I am no refrigeration expert. I am the Chief engineer on a 72m Superyacht. I have been advised that we may be relocating to the Gulf.
Now here is my problem. Sea water temperatures in the Gulf have been known to reach temperatures of 39 degrees C. We have onboard an indirect expansion chilled water air conditioning system. This comprises of three 176kW Bitzer CSH 75 61 - 60Y compressors. The refrigerant fluid is 134a. The condenser is sea water cooled. The system specifications state that the maximum permissible sea water temperature is 32 degrees. Normal operating pressures are around LP 2 Bar and HP 10 Bar. My concern is that with the higher sea water temperatures my machines will trip on high pressure. I have tried to find a table or calculation to work out the boiling temperature of 134a at 10bar but I have had no success.
Does anyone have any suggestions? Perhaps a gas change or is there a good and efficient way to regulate the HP?

Like I said I am no expert so all opinions and advice is much appreciated.

[install monkey]

bigger condensers, increase flow rate of sea water, dont run ur compressors at full load, last resort surely a 72 mtr yacht has windows
http://www.csgnetwork.com/r134apresstempconv.html

[monkey spanners]

39C shouldn't be a problem in itself. The problem will be if the system is not designed or set to cope with it. Agree with what IM said above, also I have seen inverter driven compressors that slow down when they near the hp tripping pressure effectively limiting the heat rejection to what the condenser can cope with. A marine refrigeration engineer would be the best person to advise.

[TheChief]

Thanks for the advice guys. I have also seen systems with VSD's controlling the compressors. I am looking for the cheapest way around the problem unfortunately so that might not be an option.
What is the condensing temperature of 134a at 10Bar or how do I go around working that out?
Bigger or additional condensers could be an option.
I will also have the same issue with my refrigeration system that is running on R507.

There are plenty of windows but they are all bolted shut

[install monkey]

click on the blue bit on my previous comment- hyperlink to a 134a pressure/temp chart

[TheChief]

ahh didnt see that. I love a good tit. Thanks for that. Looks like my press temp range will be ok as long as I can provide enough cooling capacity

[moideen]

The average temperature od gulf region at peak summer is 35c.in this temp you can run your system up to 45c condensing temperature(157 psig/10.8 bar).

[Tesla]

If you do have a problem when you get there you can take out some of the gas to reduce the head pressure until water temps cool then put the gas back in. When I first went to Brisbane on very hot days this is what was done to prevent units from tripping out and it seemed to work well. Just a temporary measure and not good on the mechanical gear of course.

[Mohammed Nofal]

the corresponding condensing temperature for 10 bar is 43 C which means the entering water temperature must be around 35 .. when you use a water with 39C the pressure increase, you can't change the temperature of sea water so you need a bigger condenser to get a suitable value of condensing pressure