Process for the transfer of refrigeration

In a process for the transfer of refrigeration from a source of liquid cryogen to a heat load via an intermediary fluid comprising the following steps:

• (a) introducing the liquid cryogen from its source into the tube side of a shell and tube heat exchanger;
• (b) passing the intermediary fluid through the shell side of the shell and tube heat exchanger referred to in step (a);
• and
• (c) passing the intermediary fluid from step (b) to heat exchange means, which is in a heat transfer relationship with the heat load,
• the improvement comprising:
• (i) maintaining the intermediary fluid in a closed loop, a portion of which loop is the shell side of the shell and tube heat exchanger referred to in step (a) and another portion of which loop is a passage in the heat exchange means referred to in step (c);
• and
• (ii) circulating the intermediary fluid through the closed loop
• wherein
• (A) there is provided in the closed loop, in addition to the intermediary fluid, a gas, which is essentially inert to, and essentially insoluble in, the intermediary fluid, said gas being present in such an amount that the pressure in the closed loop can be maintained in the range of about 1 to about 2 atmospheres at the operating temperature thereof;
• (B) the intermediary fluid is a liquid of such viscosity that it is capable of being circulated through the closed loop at the operating temperature and pressure thereof;
• and
• (C) the closed loop has a total volume calculated in accordance with the following formula:
• ##EQU3## B=mass of intermediary fluid in the closed loop C=density of the intermediary fluid at temperature J
• D=density of the intermediary fluid at temperature H
• E=maximum design pressure for the closed loop within the range set forth in paragraph (A) above
• F=vapor pressure of the intermediary fluid at temperature H
• G=desired closed loop pressure at temperature J within the range set forth in paragraph (A) above
• H=maximum intermediary fluid temperature
• J=minimum operating temperature for intermediary fluid
• K=gas constant for vapor of the intermediary fluid, and
• all temperatures and pressures are in absolute units.