Fundamentals

[suny]

I have got a project to fabricate a blast freezer to pull down the temperature of ice cream 1,200 liters from -2 deg C to -20 deg C in 4 hours, and with following: Te -40 deg C, Tc +40 deg C,Room Temperature is maintained at -30 deg C, Total Refrigeration Load 21.5 Kw/Hr. The supplier of equipment has advised me to install a R 404a, 2 stage compressor with a sub cooler. I am not much familiar about 2 stage & sub coolers. Therefore if any member could give an advice on how the compressor works & the functions of sub cooler is much appreciated.

[Sandro Baptista]

You can go to BITZER web site at www.bitzer.de and see the documentation of the S4 and S6 series piston compressor with or without subcooler.

[towd crank]

A bit of fundemental stuff
kW/hr is a nonsense unit. A kW is already a energy or heat flow rate being 1kJ / sec, a Joule being a measurement of an amount of heat or energy.
I we were working in British units, a joule would be the same type of unit as a BTU, and a kW and similar to a BTU/h.
A kW/h would be the same as a BTU/h/h.

As to your design problem and compound or two stage systems - my advice is if you dont know about them stay away from two stage systems or get someone who does know to do it for you - they can be very complicated to design and cause BIG headaches if you get it wrong!

[nando]

you can buy the unit ready to use, installed with subcooler and stage
we have many from this working without any problems, Bitzers
the liquidline will be -5°C around, you have to use a expansionvalve lower

[Magoo]

Icecream is a scary product to blast freeze, mainly because it is usually half air/ ice cream mix. With what is called overrun factor/percentage. If not blasted quick enough the mix settles and air separates out and containers are half full, or half empty. Four hours seems to be too long, more like two hours with high air flow and air at -35'C max lower the better.
Example:A system I work on is retention time 125 minutes, infeed temp -4'C, 30Kw fan power, 3500 litres, 1800Kgs per hour, outfeed product core temp. -20'C, transferred to hardening freezer to get -23'C storage temp.

[suny]

Thanks nando & Magoo for your advice

[D.D.KORANNE]

I CAN HELP YOU SELECT A TWO-SAGE COMPRESSOR WITH IN BUILT SUB-COOLER AS A COMPLETELY ACKAGED AND INTEGRATED COMPRESSOR PACKAGE .

PLS SEND ME A PM ddk0123@gmail.com