Cold Storage Unit Selection

[Sheej Sagunan]

Dear Forum,
I feel some body will help me .I m working in Middle east where the ambient goes upto 50 Deg C and falls down to 15 Deg C , Due to the high difference in ambient it is very difficult to size an evapourator(Due to the huge diff in Ref KW because of heavy different in ambient)
I need someons help in sizing

[The MG Pony]

and Size the condencer for the 50+C Ambient then use a VFD type fan to make up for the temp swing.

[old gas bottle]

make sure in your calcs that youinclude the correct insulation, product load,operatives,lighting,any other heat source ie fork trucks etc and very important,doors and how many entry-exits, equipement as above,remote condenser with fan speed control.

[NoNickName]

and Size the condencer for the 50+C Ambient then use a VFD type fan to make up for the temp swing.

Yeah, but in low ambient temp, vfd will slow the compressor down, eventually the evaporator will dry out, superheating will shoot in sky, and compressor will overheat. Apart from that, you can only make use of electronic XV for working on that large range of conditions.
If you are working with a dx evaporator for cooling air directly, than you probably be better install multiple evaporators and multiple circuits, so that each of them will work approx in the same conditions.
In low ambient, switch off one or more of the circuits.

[The MG Pony]

No that cool temp it shuts the fan off using the gas to keep a stable flow and when the ambiant goes to the point pur convection will not work the fan kicks in.

[Sheej Sagunan]

any body can give some idea about evapourator pressure regulator and will it solve this problem

[old gas bottle]

thought it was a DX system, whats all that about a variable speed fan being no good,if it ,s sensing the condensing temperature and running at a speed to maintaine it ,whats the problem ! or have i missunderstood.

[shylockw]

Yeah, but in low ambient temp, vfd will slow the compressor down, eventually the evaporator will dry out, superheating will shoot in sky, and compressor will overheat. Apart from that, you can only make use of electronic XV for working on that large range of conditions.
If you are working with a dx evaporator for cooling air directly, than you probably be better install multiple evaporators and multiple circuits, so that each of them will work approx in the same conditions.
In low ambient, switch off one or more of the circuits.

I agree on the above, Especially required mutil-low hp-compressors on a rack. You can calculate the minmum heat load and max heat load, then select some small evaporators based on partly minmum heat load. When in minmum condition, there will be also a few small evaporators and small hp compressors for running to avoiding frequently on-off.

[Julian]

Hi Seej

You have to select the evaporator for the maxium load during peak conditions otherwise yuor rooms will only work during the night, the trick here is not on the evaporator selection but on compressor selection & suction line sizing to handle the low load conditions. As for the condeser selction old gas bottle is right you just VF drive the fans

Cheers

Julian

[Abe]

This may sound ludicrous.........but how about two systems, one to handle day loads, a smaller one to kick in at dusk.

[zvikard]

Here we do it very simple , A) oversize condensing coil , B) a high pressure presostat without reset ( auto) to kick the condensing fan on , based on pressure , if a bigger system a couple of fans , then only one on by presostat.
All the best , Tzvi.

[ernestlin]

I regard the selection of compressor is also important, the T3 reciprocating compressor is the best choice. The temperature fluctuating in Mid East is tremendous, Using VFD condenser which controled by high pressure/ambient temp. may be better.