PDA

View Full Version : additional liquid line cooling / below ambiant







knighty
04-05-2015, 02:46 AM
I need to increase the cooling capacity of a blast freezer (we use it as a blast freezer, but it struggles to qualify as a blast freezer)

but there's not much room inside for extra evaporators

and, the freezer is going to be removed within a year and replaced with a new one when some other building work is finished (bigger/more capacity)

right now the room is fitted with a 4hp scroll compressor, and a 5hp recip compressor
room is small, 8feet wide/6feet high/26foot long
there's a false wall along one long side, with a 7inch gap, with fans blowing air through it, to give good air flow around the freezer / across the products

room is set to -22, we empty it every morning, fill it during the day, need meat to be frozen for the next morning... normally in the morning it's down to temperature... but if we have a busy day (put a lot of fresh meat into freezer), the next morning the temp can be as high as -12'C


left over from some other upgrades, we have a few fridge compressors from rooms which were running at 0'C

as a stop gap, until the new freezer is built, can/could we cool the freezer liquid lines below ambient via fridge compressors and heat exchangers ?

ignore efficiency for now, just interested in cooling capacity

I'm worried superheat might be too low, meaning refrigerant could condense inside the compressor and damage it ?
(hope I got the terminology right here)


just after a few opinions before I phone my fridge engineer, and interrupt his day with what could be a totally stupid idea :-o


p.s. I know it's not great... but only other option is to replace the existing systems with larger ones... seams a shame/waste to scrap two reliable systems, spend 10,000 replacing them with bigger systems, only for them to be removed in less than a year

(already have 2x30hp systems for new freezer, but the evaps too big for this freezer)

The Viking
04-05-2015, 07:14 AM
Short answer is: Yes, you could.

And your solution of using sub coolers will not affect the superheat of the suction gas, only the sub cooling of the liquid.

However, unless there is an issue with the system where there isn't enough sub cooled liquid reaching the expansion valves, your solution of sub cooler will not give you any noticeable increase in capacity.

As you probably knows, you are overloading your existing system and only a significant increase in capacity will solve this. (Or indeed, a lowering of the load will also solve the issue)

:cool:

RANGER1
04-05-2015, 09:55 AM
Knighty, Can you post some pictures or draw a sketch to show us exactly how product is stacked & how air flows over it & air coolers.
Can you explain how it is packed normally & when heavily loaded.

Assume you have checked existing plant superheat & running pressures to see if its doing the best it can.

Subcooling definitely helps valve may end up system capacity, but TX valve might end up to big.
It would be a lot of effort for little result.