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The temperature of liquid nitrogen can readily be reduced to its freezing point −210 °C (−346 °F; 63 K) by placing it in a vacuum chamber pumped by a vacuum pump. [2] Liquid nitrogen's efficiency as a coolant is limited by the fact that it boils immediately on contact with a warmer object, enveloping the object in an insulating layer of ...
Temperatures between approximately −78 °C and −17 °C can be maintained by placing coolant into a mixture of ethylene glycol and ethanol, [1] while mixtures of methanol and water span the −128 °C to 0 °C temperature range. [2] [3] Dry ice sublimes at −78 °C, while liquid nitrogen is used for colder baths.
Because the liquid-to-gas expansion ratio of nitrogen is 1:694 at 20 °C, a tremendous amount of force can be generated if liquid nitrogen is rapidly vaporised in an enclosed space. In an incident on January 12, 2006, at Texas A&M University , the pressure-relief devices of a tank of liquid nitrogen were malfunctioning and later sealed.
A Assuming an altitude of 194 metres above mean sea level (the worldwide median altitude of human habitation), an indoor temperature of 23 °C, a dewpoint of 9 °C (40.85% relative humidity), and 760 mmHg sea level–corrected barometric pressure (molar water vapor content = 1.16%).
The effect also applies when the surface is at room temperature but the liquid is cryogenic, allowing liquid nitrogen droplets to harmlessly roll off exposed skin. [8] Conversely, the inverse Leidenfrost effect lets drops of relatively warm liquid levitate on a bath of liquid nitrogen. [9]
So throttling from 200 bar to 1 bar gives a cooling from room temperature to below the freezing point of water. Throttling from 200 bar and an initial temperature of 133 K (point c in fig. 2) to 1 bar results in point d, which is in the two-phase region of nitrogen at a temperature of 77.2 K.
In the second part, the person in the video cracks an egg open into the liquid and the content solidifies very quickly as you can see after it's taken out. WATCH: See how a GoPro handles a torture ...
The working fluid is 3 He, which is circulated by vacuum pumps at room temperature. The 3 He enters the cryostat at a pressure of a few hundred millibar. In the classic dilution refrigerator (known as a wet dilution refrigerator), the 3 He is precooled and purified by liquid nitrogen at 77 K and a 4 He bath at 4.2 K.
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