PDA

View Full Version : Reefers in HIGH ambient temperature zones (+50 to 55*C) How do this work?







RyanCSI
04-03-2015, 11:59 AM
I have a request from a costumer in UAE (United Arabic Emirates) for a costumized 20 feet standard ISO Reefer container. I have tested a container with a Carrier 69NT40-301 in our climatic test chamber, at 45, 50, 55 and 60 *C.
The result was as follows:
With Carrier unit running, everything worked up to 60*C. When Carrier unit was off, it refused to start after reaching 50*C.
This was because the High Pressure Switch setting was equal to the pressure in the refrigerant at 47-48 *C.
So what do you do in High Ambient Temperature areas?
Remove refrigerant?
Replace HPS?
Use water cooled reefers?
How can I make sure that the reefer starts in temperatures higher than setting of the HPS ?(pressure calculated to temperature)

Rob White
04-03-2015, 01:12 PM
.

What is the refrigerant?

You work to a saturation temp that does not exceed the
maximum operating pressure of the system. If you stay at
a safe level under the limits of the system you can work at
any pressure you want.

It depends on the refrigerant and it's saturation pressure.
you would not wan't to have a pressure higher than the maximum
pressure of the system.

Rob

.

cadwaladr
04-03-2015, 05:24 PM
Carrier transicold fit a water cooled condensor as an option as temperatures in the hold of the ship are high,they also do a co2 unit which may be helpfully as gwp May be a consideration,they have a good website,carrier transicold

RyanCSI
05-03-2015, 09:15 AM
.

What is the refrigerant?

You work to a saturation temp that does not exceed the
maximum operating pressure of the system. If you stay at
a safe level under the limits of the system you can work at
any pressure you want.

It depends on the refrigerant and it's saturation pressure.
you would not wan't to have a pressure higher than the maximum
pressure of the system.

Rob

.

R134a Standard on Carrier 69NT40.
The problem is related to a non-working unit who are exposed to high ambient temperatures. The problem occurs when we try to start the reefer.

RyanCSI
05-03-2015, 09:20 AM
The co2 system is not an option for my costumer. The refrigerated container will be used in desert environment, and only be used in special cases. I will look into Carriers solutions with water cooled condenser. I've worked with Thermo King's Co2 units, but this was not a closed circuit and needed refilling from special depots.

Rob White
06-03-2015, 11:27 AM
.

I don't know a solution to your problem but 134a is only at 14 ish bar at 50 odd degC
and at 60 degC it is at 15ish bar. At 70 degC it is still around 20ish bar so if the system
is pressure rated for it can the hp switch be adjusted to allow a start up?

If it is down to the hp switch setting, adjust the switch, as long as you are under the
safe limits of the system.

I might be totally misunderstanding the complexity of the system but it seems a simple
fix to me, to just adjust the controls to allow the start (within the limits of the system design).

Rob

.

Magoo
06-03-2015, 11:37 PM
Just a suggestion
maximum unload compressor for hot start up, 6 cylinder O6D compressor from memory. To get structure and internal temp to a reasonable condition. You will have to check rupture plugs and reconfigure HP switch and control system, and pressure ratings of receivers etc. definitely will be a special design. Should look at operational limits of condenser fan motors as well