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Conduction Cooling for Closed Cycle Refrigerator Using Liquid Nitrogen

IP.com Disclosure Number: IPCOM000086161D
Original Publication Date: 1976-Jul-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

DiLonardo, V: AUTHOR [+2]

Abstract

Publication reference [1] describes a closed-cycle liquid nitrogen refrigeration system for low-temperature computer operation. In that system, cold fingers or fins attached to a refrigerator head are used to reliquify nitrogen gas. Computer elements immersed in the liquid nitrogen are a constant source of heat which vaporizes the liquid nitrogen coolant. Reliquification on the cold fingers requires a large surface area on which the gas molecules can condense into liquid. The cited publication indicated that the surface area of the cold fingers can be increased by the use of wires or fins. The recondensing technique is illustrated in Fig. 1A. Experiments using a closed-cycle refrigeration system indicate, however, that recondensing is probably not the most effective means of removing heat from the liquid.

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Conduction Cooling for Closed Cycle Refrigerator Using Liquid Nitrogen

Publication reference [1] describes a closed-cycle liquid nitrogen refrigeration system for low-temperature computer operation. In that system, cold fingers or fins attached to a refrigerator head are used to reliquify nitrogen gas. Computer elements immersed in the liquid nitrogen are a constant source of heat which vaporizes the liquid nitrogen coolant. Reliquification on the cold fingers requires a large surface area on which the gas molecules can condense into liquid. The cited publication indicated that the surface area of the cold fingers can be increased by the use of wires or fins. The recondensing technique is illustrated in Fig. 1A. Experiments using a closed-cycle refrigeration system indicate, however, that recondensing is probably not the most effective means of removing heat from the liquid.

A superior technique utilizing conduction cooling is shown in Fig. 1B. Here the cold finger is placed directly in the liquid. A problem associated with this configuration is that the head of the refrigerator is typically operated at 30 to 40 K, which is well below the solidification temperature for nitrogen of about 60 K. Thus solid nitrogen may form on the refrigerator head. In fact, the liquid nitrogen may completely solidify. As solidification occurs, the heat removal capability of the refrigerator is seriously reduced.

A solution to the heat removal problem described above is illustrated in Fig. 1C. Here, as in Fig. 1A and 1B, a container 1 is provided including a refrigerator head 2. Container 1 contains nitrogen gas 3, and liquid nitrogen 4 in which the computer elements 5 are immersed. Electrical signals are provided to the computer elements via wires 6.

In Fig. 1A, refrigerator head 1 includes recondensing fins 7 that do not intersect the liquid surface. Fig. 1B shows the solidification of nitrogen 8 that can occur when the refrigerator head is immersed directly in the liquid 4. In Fig. 1C, a high-thermal conduction fin...