Cold Room

[Chris- Africa]

Currently, I am working on refrigeration and do study’s at the same time to expand my knowledge. The more I know, the better service I can give to my clients.

Could you assist me on the following questions please?

How do I know what size compressor and coil do I have to use on different sizes cold rooms or freezer rooms? For example: My client asked me he wanted a freezer room, length 10m, width 6m, height 2.4m. This size is just an example.

How do I know what size of liquid line and suction do I have to use on the above mentioned?

How do I know at what settings do I set my LP / HP switch to on the above mentioned?

What is the purpose of the solenoid on the liquid line? I assume it’s to cut off the gas, and then build up the pressure to the LP /HP switch, which is switching off the compressor. Is there any other reason for the solenoid? For example: Is the cold room switched off by the thermostat and do you still need the solenoid? If yes, why?

I would really appreciate it if somebody can help me out with the correct info.

Thanking you in advance for your time and help.

Regards,
Chris van der Walt
South Africa
E-Mail: cc.vanderwalt@gmail.com

[ref717]

Hi bro. Vanderwalt, if you're into ammonia refrigeration design and installation I strongly suggest that you should have your own Refrigeration handbook, codes and standards. The IIAR ammonia ref. piping handbook, ASHRAE handbook and ASME std. B31.5 would really help you in expanding your knowledge.;)

As basics, to be able to know the compressor or condenser equipment size, you should first compute your Net refrigeration capacity for a specific room or system(Total room heat loads + Product load). From this, you can also properly select the size of your evaporator cooler.

The liquid line solenoid valve is typical in all evaporator valve stations. This solenoid valve closes when your rm. temp reaches its required temp. as called by the rm. thermostat or temp. sensor. It will open as the temp. inside the rm. rises again. Nowadays, evaporator valve stations are also controlled by a PLC or SCADA system packaged with the whole ref. system.

I hope I gave you an idea. Good luck in your career.

[nike123]

Could you assist me on the following questions please?

http://www.refrigeration-engineer.com/forums/showthread.php?t=19701


How do I know what size compressor and coil do I have to use on different sizes cold rooms or freezer rooms? For example: My client asked me he wanted a freezer room, length 10m, width 6m, height 2.4m. This size is just an example.
Size of room doesn't mean anything without rest of required data for proper heat load calculation.
http://www.refrigeration-engineer.com/forums/showthread.php?t=24673



How do I know what size of liquid line and suction do I have to use on the above mentioned?You need to know required mass flow of refrigerant for required cooling capacity, than you could dimension pipes in that way that total pressure loss in them is satisfactory and at same time speed of refrigerant is OK for oil circulation.
Buy some ASHRAE books.


How do I know at what settings do I set my LP / HP switch to on the above mentioned?

That depend on what is HP and LP pressure-stat is used for. If it is used as compressor protection than HP/LP is set in way that compressor does not operate outside of his operation limits.
If LP is used as PUMP-DOWN control than it is set according to working pressures/temperatures.
http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/01/PF000G102_chapter_03.pdf


What is the purpose of the solenoid on the liquid line? I assume it’s to cut off the gas, and then build up the pressure to the LP /HP switch, which is switching off the compressor. Is there any other reason for the solenoid? For example: Is the cold room switched off by the thermostat and do you still need the solenoid? If yes, why?Purpose of solenoid is to cut refrigerant flow so that compressor suck all refrigerant after valve and when pressure is at level set by pump down LP switch compressor stop with operation. That way is ensured that at next start up of compressor there is no liquid at compressor suction. Thermostat operate solenoid valve and LP switch then switch OFF compressor. When temperature differential is passed, thermostats open, pressure rise and LP switch starts compressor.

Research on Google with PUMP-DOWN keyword.

[Chris- Africa]

Thanks for all the info!!!!!!!!!!!