Evaporative Compressor energy Saving

Hi,
We have total of 14 compressors in our 1st phase of the project.Two same kind of room are cooling using these compressors.So one Room using 7 compressors.Out of 7, two are Danfoss MT320-Hw4, 3 are MT160 and Another two are of MT 160-4VM type.Room size is 21Mx14M and height 3M.The Lequid product is cooled down from 45 deg C to 10 Deg C.Every 24 hours 150 Ton of this Lequid(Palm Oil Kernel) produce( means hot Product into the room and cold Out from the room).But Present compressors are running by adjustable timers.Our concern is: How we can save energy in this application? Can we install new Evaporator,Condenser or by any extra take care..Please reply if any other info required.


Thanks & Regards,
Khairul basar

Think I will reply to all three of your posts.
FIRST you have double posted this one.
SECOND in another post you have indicated dismay in your present position and not being able to do what you want. The challenge of saving energy will take some redesign of your current systems both from a mechanical standpoint and from a controls standpoint. This will greatly benefit from using VFDs and PLCs - which are the stuff you said you wanted to do.

I would evaluate using water cooled condensors on your refer compressors. The most immediate and quickest savings will come from reduced head pressure resulting in lowered current.

Then there is using the heat you have obtained. This will take some study and calculations to determine how much heat you can capture from the condensors.

NEXT you need to look where you can dump this heat. Look at how much hot water and steam you use. You can preheat boiler makeup water. You can use the warmed water for office heat.

Do not let the cold water dripping off your evaporators go to waste. You paid good money to condense and make that water cold. Use that for non potable makeup water either for the boiler or your recirc water system - it is basically distilled water. You can use this water in part to cool the refer condensors or use it for a moisture separator on your air compressors.

Lots n lots of calculations.

If you are using a recirc liquid to chill your product then consider some method of staging your compressors (PLC application)
AND if you can get there use VFDs to control the speed.

Use VFDs on your recirc pumps. Throw away bypass or throttle valves and save money on pumping power by controlling pump speed. Remember the affinity laws of centrifugal pumps.

I would love this project. Need another body??

Dan Bentler

The Lequid product is cooled down from 45 deg C to 10 Deg C.Every 24 hours 150 Ton of this Lequid(Palm Oil Kernel) produce( means hot Product into the room and cold Out from the room)

This equates to 4200Kw of heat extracted from this oil in 24 hours

Out of 7, two are Danfoss MT320-Hw4, 3 are MT160 and Another two are of MT 160-4VM type

These compressors I believe equate to 124Kw per hour

Your outside air temperatures are about 38 deg C (100 deg F).
At these temperatures your COP is not going to be high.
If all those compressors ran for 24 hours continuous extracting that heat, your COP is about 1.5, but as you say they run controlled by timers so your COP will be higher.

The info above is only the heat in the oil then there is the cooling of the room to consider.

How many hours do your compressors run during a day.
How well insulated is the room.
Are there places that the outside air temperatures can enter the room.

I have a suspicion that there is not much we can sugest that can improve your situation.

leitmotif said:

I would evaluate using water cooled condensors on your refer compressors. The most immediate and quickest savings will come from reduced head pressure resulting in lowered current.

Click to expand...

I'll second that recomendation. Put simply, it takes less energy to pump a kilogram of water than a kilogram of air (pump-vs-fan efficiency) across a condenser, and the kilogram of water will remove a great deal more heat, meaning that you don't need to move as many kilograms of water as you need to move of air.
- this translates directly to energy savings in fan/pumps and lower energy consumption at the compressor motor as well because of lowered refrigerant pressures at the condenser. Install a cooling tower and use the cooling tower water to condense your refrigerant. Then also use the cooling tower water to do the pre-cooling of your product. A properly sized cooling tower should be able to produce 30C water year round, depending on how humid it is where you are located you may even be able to get 25C water, and if you are in a high altitude deseret like I am you can even get 21C water even with outside temperatures of 40C.

If you have a cooling tower then the initial cooling of your product from 45C down to around 35-30C could be done by heat exchanger with the cooling tower. I don't have enough information about your process to do any calculations, but I would guess that you could see a 20% energy savings right there.

leitmotif said:

I would love this project.

Click to expand...

I agree with Dan again, these kinds of projects are fun.

Dear Dan Bentler,
your judge is right & control portion is obviously me who is doing.
We have total of 14 compressors in our 1st phase of the project.Two same kind of room are cooling using these compressors.So one Room using 7 compressors.Out of 7, two are Danfoss MT320-Hw4, 3 are MT160 and Another two are of MT 160-4VM type.Room size is 21Mx14M and height 3M.The Lequid product is cooled down from 45 deg C to 10 Deg C.Every 24 hours 150 Ton
of this Lequid(Palm Oil Kernel) produce( means hot Product into the room and cold Out from the room).But Present compressors are running by adjustable timers.Our concern is: How we can save energy in this application? Can we install new Evaporator,Condenser or by any extra
take care..Please reply if any other info required.

dear gil47 , thanks.your answers are given here.
adding few information.
1.******t Temperature Min 28-Max 34 deg C, Average 31 deg C.(Country-Malaysia).
2.Timer settings:40 minutes OFF and then 4 hours ON,approx. 20 Hours ON and 4 Hours OFF in 24 hours(a day) for all the compressures.But not all are starting /stopping at the same time.There is a secuence.
3.I have measured Power the each compressureS taking are follwing:
compressure 1=21kw/440VAC/34A/50Hz
compressure 2=21kw/440VAC/34A/50Hz
compressure 3=27.6kw/440VAC/37A/50Hz
compressure 4=23.4kw/440VAC/23.4A/50Hz
compressure 5=37.7kw/440VAC/37A/50Hz
ABOVE EACH ONE(1-4) ARE USING 4 SAME SIZED(120W APROX)-CONDENSING FAN FOR CONDENSER.
compressure 6=18.5kw/440VAC/21A/50Hz
compressure 7=18.5kw/440VAC/21A/50Hz
ABOVE EACH ONE(6&7) ARE USING 3 SAME SIZED(120W APROX)-CONDENSING FAN FOR CONDENSER.ALL CONDENSERS ARE OUTSIDE THE BUILDING.
fOR STARTING THESE ABOVE ALL COMPRESSURES AUTO-TRANSFORMERS ARE USED.
BLOWER-1(EVAPORATION) FOR COMPRESSURE-1,2&3 FOR LINE-1 FOR THE SAME
ROOM=18.5kw/440VAC/21A/50Hz
BLOWER-2(EVAPORATION) FOR COMPRESSURE-4&5 FOR LINE-2 FOR THE SAME
ROOM=18.5kw/440VAC/21A/50Hz
and(440VAC 3 phase giving)V12=438VAc,V23=435,V31=432 aprox for all.
4.The room is well insulated but there is some workers(average 4 person always) working for taking out the cold-freezed/solidified (oil became solid after cooling) from the room through the gate.When they enter/exit the room some outside air obviouly enter the room.

dear aleric,
5.PRESENT SYSTEM AIR-COOLED CONDENSER.SO I THINK IF WE CHANGE ALL THESE AIR COOLED SYSTEM TO WATER COOLED CONDENSING SYSTEM THE COST WILL BE VERY HIGH.and much more work to do!

leitmotif said:

Use VFDs on your recirc pumps. Throw away bypass or throttle valves and save money on pumping power by controlling pump speed. Remember the affinity laws of centrifugal pumps.

Click to expand...

hmm.. interesting.. good ideas guys.. but pardon me for asking... "what is the affinity law of centrifugal pumps"?

affinity of pump

danieluy said:

hmm.. interesting.. good ideas guys.. but pardon me for asking... "what is the affinity law of centrifugal pumps"?

Click to expand...

follow this for affinity-
http://www.engineeringtoolbox.com/affinity-laws-d_408.html

Think of your refer compressors as heat pumps -- ie they pump heat from where you do NOT want it (palm oil) to where you can tolerate it (outside air).

150 ton of anything chilled by 35C is a whole bunch of heat. At present all you do with this heat is throw it away. Now you know how much heat you produce (heat source). Next think of other things that have to be heated that you can dump this heat into (heat sink).

Now consider what you have to heat
1. Palm oil you are heating to roughly 113 F. How are you heating it now?? You could use the hot water produced by water cooling your condensors to heat it to say around 85 to 90 F.
2. Water for your process - do you use warm water? What is temp of cold water entering plant? Again use your refer condensors to heat it at least partially.
3. Hot water used for washdown what is that temp - how much do you use?

Instead of using a whole bunch of compressors to chill the palm oil in only 4 hours use a smaller compressor to make 150 ton of ice in about 20 to 24 hours. Then use ice chilled water to cool palm oil.

As I said lots of thinking, measurements, calculations.
Absolutely no argument water cooling compressors is more costly BUT only once. If you are doing this plant in stages you could water cool the new yet to be installed equipment. After a while and as they break install water cooled condensors on your existing compressors. Better yet build up a couple spares on skids so all you have to do is pull the old one slide in the new one hook up electrical, freon and water lines and you are in business. Rebuild the one you took out for use as future replacement.

Dan Bentler

recycling room air

leitmotif said:

Think of your refer compressors as heat pumps -- ie they pump heat from where you do NOT want it (palm oil) to where you can tolerate it (outside air).

150 ton of anything chilled by 35C is a whole bunch of heat. At present all you do with this heat is throw it away. Now you know how much heat you produce (heat source). Next think of other things that have to be heated that you can dump this heat into (heat sink).

Now consider what you have to heat
1. Palm oil you are heating to roughly 113 F. How are you heating it now?? You could use the hot water produced by water cooling your condensors to heat it to say around 85 to 90 F.
2. Water for your process - do you use warm water? What is temp of cold water entering plant? Again use your refer condensors to heat it at least partially.
3. Hot water used for washdown what is that temp - how much do you use?

Instead of using a whole bunch of compressors to chill the palm oil in only 4 hours use a smaller compressor to make 150 ton of ice in about 20 to 24 hours. Then use ice chilled water to cool palm oil.

As I said lots of thinking, measurements, calculations.
Absolutely no argument water cooling compressors is more costly BUT only once. If you are doing this plant in stages you could water cool the new yet to be installed equipment. After a while and as they break install water cooled condensors on your existing compressors. Better yet build up a couple spares on skids so all you have to do is pull the old one slide in the new one hook up electrical, freon and water lines and you are in business. Rebuild the one you took out for use as future replacement.

Dan Bentler

Click to expand...

I think I missed something.The room air is recycling though Evaporator blower-1 and blower-2.Means two separte air-duct line are there.One hot duct line is for taking hot air by Blowers to blow through the Evaporator coil and other cold duct line is for carrying/sending cold air into the room.So actually the heat is carrying by Vapor refrigerant and Throughing out the heat at condenser unit to the outside air.So no saving of this much of heat can be implemented at the moment unless few factory workers put their cloths by hanging them just few feets ahead of condensor to dry it.

If we use one more condensing unit for same compressor will it decrease compressor load by anyway?

Apel said:

follow this for affinity-
http://www.engineeringtoolbox.com/affinity-laws-d_408.html

Click to expand...

Thanks! Apel!

The Lequid product is cooled down from 45 deg C to 10 Deg C.Every 24 hours 150 Ton of this Lequid(Palm Oil Kernel) produce( means hot Product into the room and cold Out from the room)

This equates to 4200Kw of heat extracted from this oil in 24 hours

Click to expand...

Dear Gil47,

dont mind but can you tell me how you equated this to Kw.

thanks

So IF 4200 Kw is correct at the Seattle City Light (Seattle Washington USA) rate of 7 cents you are throwing away
294 US dollars per day. Now if that is inconsequential to your company all well and good. Please have them cut me a check for 2700 US dollars monthly - I need some help to retire in style.


One BTU = 1 deg Farenheight change in one pound of water
One Kw = 3412 BTU

So rounding off 4 K Kw x 4 K BTU = 16 million BTU
Thought you had a bunch of heat in that palm oil

So with that amount of heat you can heat
200,000 gallon of water 10 degrees
40,000 50 degrees
OR 300,000 pounds of palm oil 24 degrees (assuming specific heat value of water - gross assumption I know)

Dan Bentler

Apel said:

I think I missed something.The room air is recycling though Evaporator blower-1 and blower-2.Means two separte air-duct line are there.One hot duct line is for taking hot air by Blowers to blow through the Evaporator coil and other cold duct line is for carrying/sending cold air into the room.So actually the heat is carrying by Vapor refrigerant and Throughing out the heat at condenser unit to the outside air.

So no saving of this much of heat can be implemented at the moment unless few factory workers put their cloths by hanging them just few feets ahead of condensor to dry it.

If we use one more condensing unit for same compressor will it decrease compressor load by anyway?

Click to expand...

Heck you could have the whole town dry their laundry on your condensors. Hmmm maybe you have something there no retrofits, charge them a little to dry their clothes and you may be able to get a significant cost savings from the income.

Think I would still go with water cooled condensors though. You would throw out the freon to air heat exchanger currently in use for your condensors and put in freon to water condensor. Lowered water temp will result in lower heat pressure thus lower amps. Saves on power, burnt out relays etc etc.
Dan Bentler

Apel said:

Dear Gil47,

dont mind but can you tell me how you equated this to Kw.

thanks

Click to expand...

I was unable to replicate the answer of 4200 KW I gave in my first post, but this is how I went about making my calculations this time, and what I though I had used last time.

I used the metric formula of, the amount of energy required to raise 1 gram of water 1 deg C = calories, then divided the calories by 860,000 calories to equal KW

So 150,ton = 150,000,000 grams
Raised by 35 deg C = 5,250,000,000 calories
Divided by 860,000 calories to = KW of 6104 KW
Your compressors total 168 KW running for 20 hours a day = 3360 KW
6104 KW divided by 3360 is a COP of about 1.82

Now I know this is a water calculation, but using Palm oil as the liquid is not going to shift the values by great amounts.
You may be able to refine this calculation by finding exact values to fit in the formula.

Imperial calculation is
150 ton x 2240 = 336,000 lb
Raised by 63 deg F = 21,168,000 BTU's
Divided by 3412 BTU's = KW of 6204 KW
Your compressors total 168 KW running for 20 hours a day = 3360 KW
6204 KW divided by 3360 is a COP of about 1.85

compressor running kwh

find my Khw calculation as per timer settings of the compressors.But it is not matching energy meter reading as per energy meters it should be 36388kwh/month.Is that any key parameter i am missing?