Horizontal - & Virtical Plate Freezers

[Polisie]

Hi.

I’m new to this forum and recently started to work at a company which does only refrigeration and coming from an HVAC side this is really specialised.

I have started to make an Excel selection program for horizontal- and vertical plate freezers. The documentation I have is old and it’s from APV and Jackstone freezers.

I got as far as selecting the product, standard plate sizes, calculating stations required, calculating the product freezing times with the freezing weight and the to calculate the refrigeration capacity.

Now I need to calculate the pump circulations and the “standard plate freezer internal volume including the headers for the refrigerant”. Is there any documentation or specification that shows on how to design or do the calculations?

[Polisie]

Thank you to the guy helping out. You know who you are.

[Magoo]

Hello, Me again.
each manufacture has their own method of developing their plates, whether horo or vertical, how they arrange the galleries and distribution has been developed by calculation intially and then proven trials they are not likely to publish the facts and details, mainly to protect their design. But will stipulate the supply rate in litres at a given supply temp., Short of carving a plate up and checking everything, we will never know. About the only thing that can be checked is the supply orifice size which generally is screwed into the supply port of each plate.
Plates in general these days are extruded aluminium sections square externally and are welded together top and bottom stressed heat treated and them machined flat top and bottom. So they have a given mass of aluminium and a heat transfer factor at given delta T temps. I beleive that vertical plates are galleried differently from horizontal.
Just as a comment if design is supply liquid at -38'C aim for -40'C as a cover your ass factor, nothing wrong with over designing at all. Belts and braces as the saying goes.

magoo

[TCL-Eng]

Hello, just one important thing. recirculations have to be as much as possible, but usually 3 or 4 are enough. the gain over 4 is very small.
regarding the flow, only look for enthalpy variation of the refrigerant when evaporating and look how many kilos you need to move per hour to obtain the capacity. remember to consider recirculation factor. the rest is a matter of unit conversion.
the galleries on the plates only affect to the liquid receiver size and the pressure losses, but as magoo says, the orifice is usually calculated by the manufacturer and supplied assembled. don't care about that. 20 to 25 w.m.c. should be enough for the pump.
finally, can I ask why you decided to use Apv or jackstone sizes?

[Sandro Baptista]

Have in account the pressure head loss due to the friction on the pipe line, valves, etc...but also due to the hydrostatic penalty when the vapour have to carry up the liquid, especially when working with low evaporating temperatures (around -40ºC). I always count with 2K more or less.

Also I think many recirculations can have a negative effect on the the final phase of the freezing, when only small heat transfer rate occurs. The liquid has difficult to be drained from the plates and the evaporating temperature ups.

[Polisie]

I only have the AVP and Jackstone size that my boss gave me so I am using the as a baseline.

[TCL-Eng]

Sandro, you are right, but it is very difficult to include those things into a "plate freezer" calculation sheet. In most cases (unless the pipe circuit is meandering or the pipe to the liquid separator is too high), you can consider 20 or 25 w.m.c. Of course, when the project is completely defined, the TDH of the pump must be carefully calculated, but for a first estimation, it should be ok. In most cases, the pump you require will be the same.

Regarding the liquid drain at the end of the cycle, I agree with you, but this is because 90 % of the manufacturers of the plate freezers use the same collector design. At least, this is my point of view.

In VPF, designing the connection to the circuit properly, you can use the gas to speed up the liquid (it is not a Venturi, but the effect is similar) and reduce the problems at the end of the cycle. Of course, those problems means higher pressure drop at the plate freezer outlet and larger freezing times.

In HPF it is more difficult because of the vertical direction of the collector, but there are also systems to use the gas to speed up the liquid.