liquid cooling

[GENERALCOOL]

Hi friends,

We have a cooling system and want to decrease liquid temp. from 90C to 5C.
I know for this type of cooling we should use 2 stages. First decrease temp. via cooling tower to about 40C and then decrease form about 40C to 5C via compressor on evaporator.
Now suppose we need omit cooling tower and want to decrease form 90C to 5C in one stage with compressor.
As you know refrigerant temp. coming back to crankcase and compressor should not be more than about 25C ~ 30C.
But in first hours our liquid at evaporator is 90C and returned refrigerant to compressor is very warm.

By injecting liquid to crankcase can we solve this problem ?

[seanf]

Could you first cool the 90C liquid with another fluid, using a larger amount of this second fluid so that its temperature is lower. Then with this large amount of secondary fluid at a manageable temperature you could cool it with a refrigeration system without the problems of high working temps.
Once the 90C liquid is down to a reasonable temp you could then switch to direct cooling from the refrigeration system.

Why cant you use a cooling tower initially?

[GENERALCOOL]

Could you first cool the 90C liquid with another fluid, using a larger amount of this second fluid so that its temperature is lower. Then with this large amount of secondary fluid at a manageable temperature you could cool it with a refrigeration system without the problems of high working temps.
Once the 90C liquid is down to a reasonable temp you could then switch to direct cooling from the refrigeration system.

Why cant you use a cooling tower initially?

Hi,
Problem is exactly here. We do not need use cooling tower. As I explained above same as your saying, We can use intermediate cooling with colling tower to decrease from 90C to 40~45C then decrease by compressor to 4C.
Now we do not want to use cooling tower, I know this cooling system little is unusual and we must use technic to prevent motor damage.
Just my question is, Is it possible to keep compressor cool via liquid injection to crankcase ?

[seanf]

Sorry, I meant you could cool the 90C liquid with a secondary fluid that then goes to a storage vessel (no cooling tower), the storage vessel could then be cooled with a refrigeration system.


Just my question is, Is it possible to keep compressor cool via liquid injection to crankcase ?

I think you would need to be careful with the design of the whole system. I dont think it would be as simple as bolting on a liquid injection system to the crackcase of a standard system.

If you give more information about the application and what you are planning for the system others may be able to give you more help.

[rize1159]

Please share some more info.
1- What is nature of liquid at 90C. Is it water?
2- What is the process where you are generating 90C?
3- Can you split heating process in steps, if it is heating, or use some partial return?
4- What is return flow rate of 90C liquid?
5- Is it possible to break the flow in primary and secondary circuits?

[GENERALCOOL]

Please share some more info.
1- What is nature of liquid at 90C. Is it water?
2- What is the process where you are generating 90C?
3- Can you split heating process in steps, if it is heating, or use some partial return?
4- What is return flow rate of 90C liquid?
5- Is it possible to break the flow in primary and secondary circuits?

Please do not make it complicated. Very brief and very simple way, we have for example 500 Litr water with 90C temp in a tank and we want to cool it to 4C via compressor.
Who we can protect compressor and prevent burning ?

Thanks.

[NH3LVR]

The questions being asked are very valid.
This needs to have some questions answered in order to advise you.
It cannot be calculated without more information.

Is the process continuous?
If it is batch cooling how long do you have to cool it? For instance you could do it in one hour with a 15-20 Horsepower compressor.

If it is continuous the flow needs to be known.

If you just want to know how to protect the Compressor you have to make sure the Suction Super-heat is within reason. This would require some engineering work on the evaporator design.

You might want to inject liquid into the suction to desuperheat-not the crankcase.

[Glenn Moore]

Hi
Not only have you got possible discharge temperature problems, but also motor overload issues as well. There are many ways to safeguard the compressor/compressors depending which type of compressors you use.
There are many pak controllers that incorporate liquid injection control , or invertor control , or current limitation these can safeguard the compressors or suction limitation
Electronic expansion valves have adjustable MOP settings etc or even crankcase pressure limitation .
It is always easier to select controls to suit the plant , but it is necessary to have full details of the plant requirements before de icing which type of control is suitable as , pull down times may be an issue as most safety requirements would limit the capacity of the plant to prevent overload, burnout failures

[Glide]

Can you incorporate a dry cooler in your project perhaps?

[GENERALCOOL]

The questions being asked are very valid.
This needs to have some questions answered in order to advise you.
It cannot be calculated without more information.

Is the process continuous?
If it is batch cooling how long do you have to cool it? For instance you could do it in one hour with a 15-20 Horsepower compressor.

If it is continuous the flow needs to be known.

If you just want to know how to protect the Compressor you have to make sure the Suction Super-heat is within reason. This would require some engineering work on the evaporator design.

You might want to inject liquid into the suction to desuperheat-not the crankcase.

OK.
Process is not continuous. We want to make a for example 500 Litrs of water cool. Decrease temp. from 90C to 5C during for example 1 hours.

Are there any difference between injection liquid to suction pipe or crankcase for de-superheating ?

Sincerely yours.

[GENERALCOOL]

Can you incorporate a dry cooler in your project perhaps?

Hi,
They need to decrease temp. via compressor.

[GENERALCOOL]

Hi
Not only have you got possible discharge temperature problems, but also motor overload issues as well. There are many ways to safeguard the compressor/compressors depending which type of compressors you use.
There are many pak controllers that incorporate liquid injection control , or invertor control , or current limitation these can safeguard the compressors or suction limitation
Electronic expansion valves have adjustable MOP settings etc or even crankcase pressure limitation .
It is always easier to select controls to suit the plant , but it is necessary to have full details of the plant requirements before de icing which type of control is suitable as , pull down times may be an issue as most safety requirements would limit the capacity of the plant to prevent overload, burnout failures

As your saying I think we must use :
MOP expansion valve
Crankcase pressure regulator
Liquid injection to suction/crankcase

I think we must use all of protections above for prevent motor damage.

[frank]

What refrigerant are you using in your system

[Grizzly]

Why is General cool posting a direct link to his company website?
If I see this again I will close the thread.
Please use the forum without direct or indirect advertisment.
Grizzly

[Tayters]

Might be that Generalcool can't access the rules to check.
I tried and the link doesn't work so for the time being I'm pulling a fast one too. 藍

Cheers,
Andy.

[GENERALCOOL]

Why is General cool posting a direct link to his company website?
If I see this again I will close the thread.
Please use the forum without direct or indirect advertisment.
Grizzly

It was my signature and i deleted it.

[GENERALCOOL]

What refrigerant are you using in your system

I use R22 refrigerant

[RANGER1]

If water was cheaper than electricity consider new water each batch!

[Brian_UK]

Why is General cool posting a direct link to his company website?
If I see this again I will close the thread.
Please use the forum without direct or indirect advertisment.
Grizzly
If his website is to believed then he could answer his own questions. ��

[frank]

From the Danfoss HeatEx programme. it looks like it can be done with a single BPHE and a superheat of 5K

[monkey spanners]

Just done something similar for a 500 litre batch pasteuriser for milk, we used an ice builder and pumped the chilled water round the milk vessel to cool it.

[GENERALCOOL]

From the Danfoss HeatEx programme. it looks like it can be done with a single BPHE and a superheat of 5K

Thanks, I saw inside data

[mbc]

Hi
Before temperature,pressure is more important to work your system in safe conditions
You can use KVL (Crankase pressure regulator) and
For large capacity you should use PM with pilot valve.
Also you should have a MOP expansion valve
Also it better you use pump down system when you want to turn it off.

[GENERALCOOL]

Hi
Before temperature,pressure is more important to work your system in safe conditions
You can use KVL (Crankase pressure regulator) and
For large capacity you should use PM with pilot valve.
Also you should have a MOP expansion valve
Also it better you use pump down system when you want to turn it off.

Hi, Yes as you said KVL + MOP expansion valve both of them help to protect compressor from overloading. But i thing they help compressor but cooling time will increase by using them.

[sterl]

Devices mentioned keep your compressor (or compressor plus motor) within its operating envelope. Go outside the envelope for any extended period and bad things happen. Adding crankcase cooling via refrigerant injection will decrease suction temperature but increases suction pressure and reduce evaporator mass flow which reduces cooling rate. To understand if the effect is worthwhile and predict whether it can be done at all we would have to have specific understanding of the operating enveloope for the machine and the factors that determine it for the specific Compressor, Motor, refrigerant and lubricant, at the least....

Meanwhile you have a mountain of available pressure difference: So what if you doubled up condenser and ran a (big...) heat exchanger in thermosyphon to the condenser(s) until your batch of water got to (say) 40-deg; then finished the trip with the compression equipment.

[ramesh]

YES ur thought is good u can go for this.

[Aik]

Hi friends,

By injecting liquid to crankcase can we solve this problem ?

In general case - YES!

You may decrease high temperature by several paths: liquid injection to crancase, addition heat exchanger/evaporator as Frank recomended and others. But you have to know that you need decrease suction temperature before or in suction chamber of compressor. There is a problem wiht burnout of windings due to insufficient motor cooling, and another part is high discharge temperature which influences the formation of acid from oil.

[knighty]

I think everyone missed a trick... just alter the flow of the 90'C liquid?

one pump circulating through the heat exchanger - small loop


second pump/mixer mixes the 90'C liquid in, slowly so temperature of the small loop above is maintained

[ramesh]

If you want to cool 90C to 5C then you need best chiller machine to cool your liquid.