30 replies to this topic

[Andrei]

Imtinan,

I give up, it is outrageous in my opinion to use liquid nitrogen to cool a pathetic air compressor.
You have to ask yourself what are the goals of your endeavor, and what are your means. Is it your goal to cool the water? Or your goal is to make your compressor to work better? Try to think outside of the box.
Than you have to ask yourself why it is required the cooling. It was always required? If not, what was changed and why. If there was a change try to reverse it first, and only after that think at something new.
Was the compressor designed properly in the first place? If not, what were the mistakes?
Put all the identified alternatives on the table and put some numbers for each one of them. Don't look only at the money spent for additional equipment that eventually have to be added, look also at the additional operating costs.
I cannot believe that liquid nitrogen cooling will be the cheapest solution after a deep analysis.

[AndrewWest]

Did anyone ever make sense of this? It turns out that many power plants will begin to use oxygen for oxy-fuel combustion and as a by-product of air separation, they will have plenty of Nitrogen (78% of air). Power plants also consume a lot of water - nearly 50% of the water consumed in the US. We are now facing water shortages. Is there any way to use Nitrogen instead of our rivers, lakes and streams?

I am reminded that Nitrogen from its liquid state to gas expands +500 times. If this happens during some type of cooling process, can't we capture that energy, also?

[Technical Bard]

One probably would have to look at a multi-stage cooling system such that you never cool water with a cryogenic fluid - too much risk of ice formation. This would be very capital intensive and probably unattractive. The problem with trying to capture energy from the volume change in boiling nitrogen is that it take energy to make it boil. The enthalpy balance is the wrong way around.

[AndrewWest]

If the liguid nitrogen was in tubes submersed in the water and it expanded because of the water surrounding it, wouldn't it cool the water and at the same time create some pressure. Assume the Nitrogen is free or surplus.

[Art Montemayor]

Andrew:

In the interest of conserving our environment and fighting to keep it that way, it is in our interest to speak and write with authoritative knowledge of the subject at hand.

It has been almost 4 years ago and our OP has not responded or returned to the query. Nevertheless, to emphasize that our concern is the environment, I will address your comments / questions:

Did anyone ever make sense of this?
As the thread reveals, no one has made any sense of this to date – neither in this Forum or in Eng-Tips.

It turns out that many power plants will begin to use oxygen for oxy-fuel combustion and as a by-product of air separation, they will have plenty of Nitrogen.
That has yet to occur. Even if they did commence to produce oxygen to increase their combustion efficiency, they would have little or no reason to produce the captive oxygen production in the liquid state. It was – and still is – far easier (and more economical) to produce oxygen in the gaseous state. If you are consuming the oxygen in a steady state (as power plants would), it makes more sense to produce the captive oxygen in the gaseous state.

Power plants also consume a lot of water - nearly 50% of the water consumed in the US.
I seriously challenge this assertion. Power Plants DO NOT consume water. They consume fuel and oxygen in the combustion air; they also use water as a cooling medium – but they don’t consume it. They use it as a heat sink. They may circulate the cooling water through a cooling tower and suffer a vaporization loss, but that doesn’t amount to anything near 50% of what is consumed in the US.

Is there any way to use Nitrogen instead of our rivers, lakes and streams?
How would you use the nitrogen? As a cryogen liquid or gas? You would have to pay for all the electrical power it takes to convert it into a cryogen for cooling – and I don’t think any consumer is prepared or anxious to pay for that markup in price.

Nitrogen from its liquid state to gas expands +500 times can't we capture that energy, also?
By “expands”, I presume you mean vaporizes. If you were to try to capture the expansion energy, you would have to invest capital monies. The return on the investment has never been there in prior nitrogen vaporizers.

Assume the Nitrogen is free or surplus.
Nothing – absolutely nothing – in life is “free” --- especially cryogenic nitrogen. It is expensive to produce, expensive to handle, expensive to transport, and expensive to buy. I know. I have produced a lot of both liquid and gaseous nitrogen.

[AndrewWest]

Come on you guys. Help.