[darien2009]

Why does liquid nitrogen has power and quality of economically more than CO2 solid (dry ice)?

I mean liquid nitrogen uses to refrigerate better than dry ice, I want to know what is the reasons for that?

[Yggdrasil]

I am not sure but as far as i know CO₂ is reason for global warming and pollution.As a refrigerant dry ice is not use to avoid pollution.

That would be true if dry ice were produced from CO₂ that was made specifically to become dry ice.  In reality, dry ice is produced from waste CO₂ created from other processes (e.g. from the production of ammonia or fermentation reactions).  Because the CO₂ from these reactions would have entered the atmosphere anyway, creating dry ice then letting the CO₂ from the dry ice enter the atmosphere just delays the release of CO₂ into the atmosphere.

Of course, the production of dry ice involves steps that require energy inputs (e.g. refrigeration).  Because those steps require electricity and electricity is generated from fossil fuels primarily, the production of dry ice is not carbon neutral overall.  This fact, however, would also apply to the production of liquid nitrogen.

I'm not sure why liquid nitrogen is more economical than dry ice.  Liquid nitrogen (~-200^oC) is much colder than dry ice (~-80^oC), so perhaps that has something to do with it.

[renge ishyo]

As Yggs alluded to, liquid nitrogen is much colder than dry ice, so it can be much more effective at cooling things down very quickly. For example, it is used when fast freezing food. Nitrogen is also quite abundant and easily available to industry; i.e. 80% of the atmosphere is N₂, so the source isn't a problem and keeps it reasonably cheap.

However, its greater efficiency at heat transfer means that liquid nitrogen is used up somewhat faster than dry ice depending on the use (although waste can be minimized by proper apparatus design, if I just handed you a small chunk of dry ice and a large bottle of liquid N₂ and asked you to keep something cool for me, the smart money is you would burn through the liquid nitrogen supply long before your dry ice was used up). Also, liquid nitrogen is more of a pain to deal with than the solid dry ice just in general. You can easily chop off a chunk of dry ice, wrap it up in paper, and hand it to a customer and let them be on their way, but liquid nitrogen would HAVE to be stored in some sort of special container (such as a thermos) at all times to prevent the liquid from spilling away.