| 摘要 |
<p>O In cooling a permanent gas stream 50 (e.g. of nitrogen) at elevated pressure to below its critical temperature (e.g. in a process for the liquefaction of the permanent gas), the stream 50 is heat exchanged with a main stream 52 of working fluid (typically also nitrogen) that has been work-expanded in expansion turbine 70. The refrigeration provided by stream 50 is supplemented by that provided by streams 90, 92 and 94 of work expanded working fluid. The temperatures at which the streams 90, 92 and '94 are introduced into heat exchange relationship with the permanent gas stream are in a defined range extending from 5K above the point at which the rate of change the heat capacity (at constant pressure) of the gas per standared cubic metre increases by about 1% per Kelvin as the gas is cooled to 5K below the point at which the rate of change with temperature of the heat capacity (at constant pressure) of the gas per standard cubic metre is at a maximum.</p> |
