mushroom growing

[nh3simman]

I was asked to comment on an installation at a mushroom farm.

The system was a real mess of badly installed parts, home made fan coils, undersized liquid receiver and much more.

The client said that he has lost 2 compressors and by the looks of things, the will be more to come.

I started of nitpicking about every detail but then I thought, the actual design is WRONG!

There are 10 growing rooms, each with a fan-coil unit. Refrigerant control is by the Danfoss AKV-15 electronic expansion valve.

From what I can tell, the Danfoss Adap-Kool control is ideal for steady load refrigeration rooms.

But the growing cycle in a mushroom farm has dramatic load changes and I'm not sure how a solenoid type valve responds.

Could this be the reason that 2 compressors have failed? Liquid slugging back when the farmer changes the growing cycle.

Personally, I would have used a chiller with a primary/secondary circuit.

Is there a better way to control big load changes with direct refrigeration?

[Renato RR]

Can you specify whic compressors and how is plat designed?How many evaporators?How many compressors?

Renato

[NoNickName]

The adap-kool valve has a very big drawback and flawed design (sorry, Andy, your mileage is different here). By intermittently spraying liquid refrigerant into the evaporator, sometimes spray is returned to the compressor, or (for s&t evaporators) the inner liquid distributor fails by liquid hits.

Attached a photo how it shall look like. When hit by liquid, the welded pierced plate would eventually fall off.

[US Iceman]

...the inner liquid distributor fails by liquid hits.

I have heard a similar comment from welded PHE manufacturers also. Apparently they have seen repeated failures from this.

Is there a better way to control big load changes with direct refrigeration?

Using a liquid overfeed system with a low-pressure receiver sufficiently large enough to provide adequate separation.

It seems as if this application you are describing experiences the same load changes as large VAV air conditioning systems using DX evaporators. Those are absolutely horrible to work on. And yes, the end result is the same as you mentioned... wrecked compressors.

[NoNickName]

I would recommend a chilled water system, or better yet, a four pipe system, with a chiller having heat recovery, so that heating, cooling and dehumidification (if necessary) can take place and be modulated. It may be possible to save money by using relatively high temperature water system in pipes running under the mushroom beds.

[nh3simman]

Can you specify whic compressors and how is plat designed?How many evaporators?How many compressors?

Renato

10 growing rooms, 1evap coil per room
all feeding back to common suction
suction split to 3 Copeland recips

[nh3simman]

I would recommend a chilled water system, or better yet, a four pipe system, with a chiller having heat recovery, so that heating, cooling and dehumidification (if necessary) can take place and be modulated. It may be possible to save money by using relatively high temperature water system in pipes running under the mushroom beds.

This is exactly my thinking.

The chiller system gives a nice capacity buffer in a storage tank and allows mixing to modulate the supply water temperature.

In the current DX system, the low suction causes loss of moisture by condensation and they expect the room to maintain a fixed 85% rh!