Ammonia system

[herman]

Dear friends,

I have to repair an facility that serves the freezing tunnels and storage of frozen products.
In facts the plant is DX ammonia system which doesn't work properly.

So, the frozen product ( -20C room temperature) is works properly when the freezing tunnels is off. The tunnels do not reach freezing temperature, even when frozen deposits are stopped.

So I am thinking about to keep the circuit (DX) for the frozen product store and to mount an separatelly liquid separator pumps and ammonia pumped air coolers for freezing tunnels.


In fact to use the same compressors and evaporating condenser. But after the liquid receiver to split in one DX circuit and another one for ammonia pumped. For return circuit to join again the two circuits before the suction of compressors.

Do you think is it possible something like this?
Will working?

Thanks for your help.

[Segei]

Are you sure that you have DX coils? Usually, people use TEVs and DX coils for high temp. evaporators.
To solve the problem, you should find out the reason of this problem. If evaporators, suction line, compressor capacity are under sized, liquid pump will not help.

[Sandro Baptista]

Herman,

What's the problem of the plant?

[Josip]

Hi, herman

Dear friends,

I have to repair an facility that serves the freezing tunnels and storage of frozen products.
In facts the plant is DX ammonia system which doesn't work properly.

So, the frozen product ( -20C room temperature) is works properly when the freezing tunnels is off. The tunnels do not reach freezing temperature, even when frozen deposits are stopped.

So I am thinking about to keep the circuit (DX) for the frozen product store and to mount an separatelly liquid separator pumps and ammonia pumped air coolers for freezing tunnels.


In fact to use the same compressors and evaporating condenser. But after the liquid receiver to split in one DX circuit and another one for ammonia pumped. For return circuit to join again the two circuits before the suction of compressors.

Do you think is it possible something like this?
Will working?

Thanks for your help.

First I have only a few questions, because something is not clear to me...

A1. How old is your plant? Probably very old..

A2. The problem you described are from the day one or jump out by the time? Probably from day one ....

B. What you can tell us about (please, give us some figures):

1.Capacity of evaporator in cold room/s-freezing storage/s at -20*C
2.Capacity of freezing tunnels
3.Capacity of compressor/s at -40*C/35*C (type and size of electrical motor)

This will put some more light on your plant and hopefully give us chance how to help you.


Best regards, Josip

[herman]

Hi, herman



First I have only a few questions, because something is not clear to me...

A1. How old is your plant? Probably very old..

A2. The problem you described are from the day one or jump out by the time? Probably from day one ....

B. What you can tell us about (please, give us some figures):

1.Capacity of evaporator in cold room/s-freezing storage/s at -20*C
2.Capacity of freezing tunnels
3.Capacity of compressor/s at -40*C/35*C (type and size of electrical motor)

This will put some more light on your plant and hopefully give us chance how to help you.


Best regards, Josip

Hallo,

here are the answers to your questions:

A1. It's a new one plant; 1 year old

A2. The problems apperared from the first day

B 1. 60 kW storing rooms ( -20C)

B2. 65 kW freezing tunnels ( -30C)

B3. I don't know the cooling capacity. The compressors 2 pcs, Mycom 200 VLD H; electric motor 200 kW ( Leroy Sommer PLS 315)

Thank you for your help!

[herman]

Herman,

What's the problem of the plant?

Here is the problems:

So, the frozen product ( -20C room temperature) is works properly when the freezing tunnels is off. The tunnels do not reach freezing temperature, even when frozen deposits are stopped.

So I am thinking about to keep the circuit (DX) for the frozen product store and to mount an separatelly liquid separator pumps and ammonia pumped air coolers for freezing tunnels.

[Sandro Baptista]

Here is the problems:

So, the frozen product ( -20C room temperature) is works properly when the freezing tunnels is off. The tunnels do not reach freezing temperature, even when frozen deposits are stopped.

So I am thinking about to keep the circuit (DX) for the frozen product store and to mount an separatelly liquid separator pumps and ammonia pumped air coolers for freezing tunnels.

What you mean with frozen deposits are stopped? When the tunnel is empty what is the lower temperature you can reach?

What's the suction pressure of the comps and its set point. What's happening to the suction pressure when all is working. The cold store share with the tunnels the same compressors, as far I understood, right?

[Magoo]

What are the operating pressures at the compressor? Have the commissioning start up socks been removed from compressor suction strainer?
The mycom 200VLD-H should eat the load, at -35/+35 'C = 250 Kw duty.
Sounds like system loses in pipework maybe something to start with. Liquid overfeed coils are purpose designed, so converstion from DX to flooded is not straight forward.

[IceMan_4000]

SINGLE STAGE SCREW COMPRESSOR : 14.0 MYCOMW 14.0ep
DATE : 05-17-2011
MODEL : N200VL*-H
REFRIGERANT : AMMONIA
RECOMMENDED PORT : H
BOOSTER : False
COMPRESSION RATIO : [-] 14.5

CAPACITY : [kW] 304.4
CAPACITY : [TR] 86.6
ABSORBED POWER : [kW] 181.3

DRIVE SHAFT SPEED : [rpm] 3550
COMPRESSOR SPEED : [rpm] 3550
INDICATOR POSITION : [%] 100
CONDENSING TEMP. : [degC] 35.0
EVAPORATIVE TEMP. : [degC] -35.0
SUCTION SUPERHEAT : [degC] 3.00
LIQUID SUBCOOLING : [degC] 5.00
SUCTION TEMP. : [degC] -32.0
OIL SUPPLY TEMP. : [degC] 50.0
SUCTION PRESS. : [MPaA] 0.093
DISCHARGE PRESS. : [MPaA] 1.35
OIL SUPPLY PRESS. : [MPaA] 1.54
SUCTION PRES. DROP : [MPaA] 0.000
DISCHARGE PRES. DROP : [MPaA] 0.000

SWEPT VOLUME : [m3/h] 1460
LOAD(VOL. FLOW RATE) : [%] 100
DISCHARGE TEMP. : [degC] 85.5
REFRIG. FLOW RATE SUC. : [m3/h] 1260
REFRIG. FLOW RATE DIS. : [m3/h] 127
REFRIG. FLOW RATE SUC. : [kg/h] 1023
REFRIG. FLOW RATE DIS. : [kg/h] 1023
INJECT. OIL FLOW RATE : [L/min] 58.4
LUB. OIL FLOW RATE : [L/min] 54.6
F.SIDE OIL FLOW RATE : [L/min] 9.47
*TOTAL* OIL FLOW RATE : [L/min] 122
OIL HEAT REJECTION : [kW] 122.7
OIL SPEC HT : [J/kgK] 1930
OIL DENSITY : [kg/m3] 880

COP : [-] 1.68

--- SUPER HEAT is NOT counted in refrigeration capacity ---

--- WITH WATER COOLED OIL COOLER ---

--- Refrigeration oil is not soluble with refrigerant (mineral oil) ---
--- When choosing the motor set a safety factor of more than 10% for the brake power ---

plenty of kW's for cooling.

If it was the suction sock the system would be going down on low suction but the liquid would be hotter than suction pressure.

[charlie n]

Low temperature Dx ammonia systems can be a nightmare. Sounds like some commercial ***** engineer was let loose here. Get rid of all of the expansion valves and install a proper pumped ammonia system. Or bring a bed to the plant 'cause that's where you'll be living.

[Josip]

Hi, herman

Hallo,

here are the answers to your questions:

A1. It's a new one plant; 1 year old

A2. The problems apperared from the first day

B 1. 60 kW storing rooms ( -20C)

B2. 65 kW freezing tunnels ( -30C)

B3. I don't know the cooling capacity. The compressors 2 pcs, Mycom 200 VLD H; electric motor 200 kW ( Leroy Sommer PLS 315)

Thank you for your help!

Seems you have enough cooling capacity within compressors - I prefer tunnel evaporating temperature to be -45*C or max -40*C freezing must be very fast to protect the goods (-35*C ET we use for ice cream cold room to keep the room at -26*C - safety margin for handling), but even at evaporating temperature of -45*C your compressor will give more capacity then you actually need....

Hope that you have suction pipe size min of DN 150mm/6" i.e. common suction pipe for parallel work of cold storage room and tunnel ...

One more question ... can you reach freezing temperature when your tunnel is empty or 25% i.e. 50% full?

Something must be wrong with DX system for freezing tunnel ... I agree with charlie n to revamp that one to pump system ....



Best regards, Josip

[Magoo]

Hi Iceman_ 4000.
I quoted duty at 50 Hz. Do not know what power supply is in Romania

[Sandro Baptista]

Hi Iceman_ 4000.
I quoted duty at 50 Hz. Do not know what power supply is in Romania

If you see the speed motor he considered 3.550 rpm (60 Hz)

[Josip]

Hi, IceMan_4000

SINGLE STAGE SCREW COMPRESSOR : 14.0 MYCOMW 14.0ep
DATE : 05-17-2011
MODEL : N200VL*-H
REFRIGERANT : AMMONIA
RECOMMENDED PORT : H
BOOSTER : False
COMPRESSION RATIO : [-] 14.5

CAPACITY : [kW] 304.4
CAPACITY : [TR] 86.6
ABSORBED POWER : [kW] 181.3

DRIVE SHAFT SPEED : [rpm] 3550
COMPRESSOR SPEED : [rpm] 3550
INDICATOR POSITION : [%] 100
CONDENSING TEMP. : [degC] 35.0
EVAPORATIVE TEMP. : [degC] -35.0
SUCTION SUPERHEAT : [degC] 3.00
LIQUID SUBCOOLING : [degC] 5.00
SUCTION TEMP. : [degC] -32.0
OIL SUPPLY TEMP. : [degC] 50.0
SUCTION PRESS. : [MPaA] 0.093
DISCHARGE PRESS. : [MPaA] 1.35
OIL SUPPLY PRESS. : [MPaA] 1.54
SUCTION PRES. DROP : [MPaA] 0.000
DISCHARGE PRES. DROP : [MPaA] 0.000



--- SUPER HEAT is NOT counted in refrigeration capacity ---

--- WITH WATER COOLED OIL COOLER ---

--- Refrigeration oil is not soluble with refrigerant (mineral oil) ---
--- When choosing the motor set a safety factor of more than 10% for the brake power ---

plenty of kW's for cooling.

If it was the suction sock the system would be going down on low suction but the liquid would be hotter than suction pressure.

In Romania they use 50 Hz i.e. capacity is 20% lower, but still enough around 240kW....

Best regards, Josip

[IceMan_4000]

Ops sorry guys totally missed the 50hz

Thanks for the correction Josip

SINGLE STAGE SCREW COMPRESSOR : 2011 MYCOMW 2011ep
DATE : 05-18-2011
MODEL : N200VL*-H
REFRIGERANT : AMMONIA
RECOMMENDED PORT : H
BOOSTER : False
COMPRESSION RATIO : [-] 14.5

CAPACITY : [kW] 243.5
CAPACITY : [TR] 69.2
ABSORBED POWER : [kW] 159.6

DRIVE SHAFT SPEED : [rpm] 2950
COMPRESSOR SPEED : [rpm] 2950
INDICATOR POSITION : [%] 100
CONDENSING TEMP. : [degC] 35.0
EVAPORATIVE TEMP. : [degC] -35.0
SUCTION SUPERHEAT : [degC] 0.00
LIQUID SUBCOOLING : [degC] 5.00
SUCTION TEMP. : [degC] -35.0
OIL SUPPLY TEMP. : [degC] 50.0
SUCTION PRESS. : [MPaA] 0.093
DISCHARGE PRESS. : [MPaA] 1.35
OIL SUPPLY PRESS. : [MPaA] 1.55
SUCTION PRES. DROP : [MPaA] 0.000
DISCHARGE PRES. DROP : [MPaA] 0.000

SWEPT VOLUME : [m3/h] 1210
LOAD(VOL. FLOW RATE) : [%] 100
DISCHARGE TEMP. : [degC] 82.4
REFRIG. FLOW RATE SUC. : [m3/h] 994
REFRIG. FLOW RATE DIS. : [m3/h] 96.4
REFRIG. FLOW RATE SUC. : [kg/h] 816.8
REFRIG. FLOW RATE DIS. : [kg/h] 816.8
INJECT. OIL FLOW RATE : [L/min] 58.4
LUB. OIL FLOW RATE : [L/min] 54.6
F.SIDE OIL FLOW RATE : [L/min] 9.48
*TOTAL* OIL FLOW RATE : [L/min] 123
OIL HEAT REJECTION : [kW] 112.3
OIL SPEC HT : [J/kgK] 1930
OIL DENSITY : [kg/m3] 880

COP : [-] 1.53

--- SUPER HEAT is NOT counted in refrigeration capacity ---

--- WITH WATER COOLED OIL COOLER ---

--- Refrigeration oil is not soluble with refrigerant (mineral oil) ---
--- When choosing the motor set a safety factor of more than 10% for the brake power ---

[IceMan_4000]

-45 capacity

SINGLE STAGE SCREW COMPRESSOR : 2011 MYCOMW 2011ep
DATE : 05-18-2011
MODEL : N200VL*-H
REFRIGERANT : AMMONIA
RECOMMENDED PORT : H
BOOSTER : False
COMPRESSION RATIO : [-] 24.8

CAPACITY : [kW] 136.5
CAPACITY : [TR] 38.8
ABSORBED POWER : [kW] 140.4

DRIVE SHAFT SPEED : [rpm] 2950
COMPRESSOR SPEED : [rpm] 2950
INDICATOR POSITION : [%] 100
CONDENSING TEMP. : [degC] 35.0
EVAPORATIVE TEMP. : [degC] -45.0
SUCTION SUPERHEAT : [degC] 0.00
LIQUID SUBCOOLING : [degC] 5.00
SUCTION TEMP. : [degC] -45.0
OIL SUPPLY TEMP. : [degC] 50.0
SUCTION PRESS. : [MPaA] 0.054
DISCHARGE PRESS. : [MPaA] 1.35
OIL SUPPLY PRESS. : [MPaA] 1.55
SUCTION PRES. DROP : [MPaA] 0.000
DISCHARGE PRES. DROP : [MPaA] 0.000

SWEPT VOLUME : [m3/h] 1210
LOAD(VOL. FLOW RATE) : [%] 100
DISCHARGE TEMP. : [degC] 81.6
REFRIG. FLOW RATE SUC. : [m3/h] 933
REFRIG. FLOW RATE DIS. : [m3/h] 54.7
REFRIG. FLOW RATE SUC. : [kg/h] 464.6
REFRIG. FLOW RATE DIS. : [kg/h] 464.6
INJECT. OIL FLOW RATE : [L/min] 60.2
LUB. OIL FLOW RATE : [L/min] 55.1
F.SIDE OIL FLOW RATE : [L/min] 9.58
*TOTAL* OIL FLOW RATE : [L/min] 125
OIL HEAT REJECTION : [kW] 111.7
OIL SPEC HT : [J/kgK] 1930
OIL DENSITY : [kg/m3] 880

COP : [-] 0.972

--- SUPER HEAT is NOT counted in refrigeration capacity ---

--- WITH WATER COOLED OIL COOLER ---

--- Refrigeration oil is not soluble with refrigerant (mineral oil) ---
--- When choosing the motor set a safety factor of more than 10% for the brake power ---

[FRIDGE]

looks like compressor has enough capacity!

DX??

you should go flooded evaps, pumped recirculation with low pressure receiver. Pipe work length will have an effect on DX refrig. pumped recirc with low pressure receiver will over come this.

[TXiceman]

DX is basically a NO-NO for anything below about 10 degF for ammonia. There is too may problems associated with proper circuiting and and feeding the coil circuits. To be quiet blunt, anyone that would install a DX ammonia freezer like you described has to be a total idiot.

You can probably redo the feed headers on the coils and add a gravity or liquid recirculation system and make the coils work.