nh3 blast freezer.

[balnauld]

I have heard about a frigo freezer that works without surge drum and pumps,and runs off the economizer can anyone tell me how this works,

[Magoo]

Its called LVS ( low volume system ) referring to reduced liquid required in system. No pumps ,no accumulator.
They use high pressure liquid sub-cooled through economiser, and pulse inject into evaporator which gives high velocity agitated flow through evaporator, so suction is dry and does not require an accumulator. The big plus is improved evaporator performance and reduced power consumption at compressor.

[Grizzly]

Very good explanation yet again Maggo!
Thanks Grizzly

[RANGER1]

They do have a small surge drum inside where spiral and evap is though with level switches from what I have seen .

[Segei]

Its called LVS ( low volume system ) referring to reduced liquid required in system. No pumps ,no accumulator.
They use high pressure liquid sub-cooled through economiser, and pulse inject into evaporator which gives high velocity agitated flow through evaporator, so suction is dry and does not require an accumulator. The big plus is improved evaporator performance and reduced power consumption at compressor.

I have a concern about compressor power consumption. Why is it reduced?

[RANGER1]

What symtoms do you see and what type of compessor is it ?

[Magoo]

Sergie . Dry siction, less dense less horse power.
Ranger1 the LVS is basically a cyclone vessel.
Ranger1 the only problem with them is sudden load changes, like idling during lunch breaks and a sudden load change, some saturation occurs, which is covered by a offset suction header before compressor that has a loop pipe through high pressure/warm receiver to flash off any liquid carry-over, also covered by slow compressor loading response. neally always screw compressors, which handled a little saturated suction vapour.

[Magoo]

OK by the way, LVS is a patented design so no drawings available for twenty years, and if they figure me out I am in stumm, so don't ask any more questions. They are brillant to operate.

[Segei]

Sergie . Dry siction, less dense less horse power.
Ranger1 the LVS is basically a cyclone vessel.
Ranger1 the only problem with them is sudden load changes, like idling during lunch breaks and a sudden load change, some saturation occurs, which is covered by a offset suction header before compressor that has a loop pipe through high pressure/warm receiver to flash off any liquid carry-over, also covered by slow compressor loading response. neally always screw compressors, which handled a little saturated suction vapour.

Dry suction will have slightly less resistants than wet one. Almost no difference in density. Wet suction can be larger and will have the same resistance as dry one. I don't see improvement of compressor efficiency,

[mbc]

lets think and find how they did.

[Peter_1]

Is this pdf the one you were referring to?http://rapidshare.com/files/293215241/US5435149.pdf

[sterl]

The little vessel was originally developed to help deliver liquid to highly loaded coils where little headroom was available, so separation distances were challenged....This it does quite well providing liquid temperature at point of delivery remain consistent and load stays high, as Magoo indicates. The separator and liquid entrainment components represents a dynamic arrangement; they rely on flow velocity to achieve the separation and injection. As either flow or flash volume decrease, the separation effect and the injection effect both decrease as well.
Side port subcooling (economizing) will largely provide the consistent liquid temperatures and proportion of flash, but of course the load on a production freezer is dependent on how fast product is going through it. At low flows the vessel starts acting more like a conventional surge drum with limited separation space...Which is to say the edge of flooding.

The circuit operates at both lower coil charge and vessel charge and under design load, no liquid in the return so pipe sizes can be smaller; or existing "wet" pipes, made dry, represents a reduced pressure penalty in the plant mains. They also tend to log up slower than a fixed volume recirc arrangement, so they suit low coils with tall return risers. These advantages are all geometry related, thus site specific.

As to compressor performance: the question is "As compared to what?" Econmizing to a fixed liquid temperature implies a control valve on the side port which has the same effect as any regulator on a suction line, only at low loads any slide valve machine's side port pressure decreases toward main suction pressure so the regulator is eating up more pressure difference. There are practical limits to eliminating the slide valve effect but only real operational load profiles will determine if a VFD on the machine is a better choice than letting it unload volumetrically.

They won't outperform a 2-stage, 2-step flash arrangement though the system is simpler and lower in frist cost and operating charge.

[RANGER1]

Did'nt majonnier carbo coolers have something pretty similar for the last 50 yrs ?

[grant]

flippin can of worms al ??

[Magoo]

Sterl.
You describe the earlier version of, except the sub-cooling is done in low side vessel. Bear in mind no pumps either, sub cool in LP vessel.

PS they were likened to a hand grenade with a loose pin.

Martin

[Magoo]

Sterl.
Despite all the theories about counter flow in evaporators and efficiencies, parallel flow with pump circ., or add agitated turbulent flow, out performs counterflow. Counterflow generally refers to TXV feeds.
martin

[balnauld]

thanks for all your replies I understand it now,but it looks like we are going for a starfrost, price i think.
al

[Magoo]

Hi Balnaud.
well after all that, your client is a tight ##s. Quite normal these days with current economic climate. Starfrost are local and very reputable and support their product. Their spirals are the old rail system, and if well maintained are belts and braces stuff, will last for decades, Frigoscandia developed them many decades ago.

[sterl]

Magoo--
Did I say something about counterflow?

Its still a latent HEX with very little pressure differencea and a high rate of overcirculation...And nominally cooland circulation perp to air circ. Big coils on "lazy" refrigerants just don't have it as an issue unless they're applied very strangely.

[Magoo]

Hi Sterl.
I cannot re-call so dont get your shorts in a bunch.
But the LVS system is brilliant what ever which way.
Martin