Very efficient heat exchanger for cryogen free MRI magnet

Patent metadata

Field	Value
Publication number	US-9683759-B2
Application number	US-201214347526-A
Country	US
Kind code	B2
Filing date	Sep 26, 2012
Priority date	Sep 28, 2011
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

A heat exchanger ( 5 ) includes a thermally conductive cylindrical container ( 40 ), at least one thermally conductive tube ( 30 ), a cooling column ( 90 ), and a cryogen coldhead ( 100 ). The cooling column and coldhead condense gaseous helium to liquid helium to maintain a reservoir of liquid helium in the thermally conductive cylindrical container ( 40 ). The at least one thermally conductive tube ( 30 ) coils circumferentially around the container ( 40 ), and extends to at least one superconducting magnet coil heat exchanger ( 20 ), and back. The tube forms a selected loop which holds gaseous helium at pressure up about 104 bar (1500 PSI) or room temperature to about 0.75 bar at cryogenic temperatures.

First claim

Having thus described the preferred embodiments, the invention is now claimed to be:

1. A heat exchanger system comprising:
a first hermetically sealed, passive heat exchanger including:
a thermally conductive cylindrical container containing helium, the thermally conductive cylindrical container being disposed with a longitudinal axis extending horizontally, the cylinder container including an inflow port in a lower portion of one side and an outflow port at an upper portion;
a cooling column disposed higher than and hermetically connected to the thermally conductive cylindrical container outflow port to receive helium gas rising therefrom by thermal gradients and to the inflow port to supply liquid helium by gravity thereto;
a cryogenic coldhead mounted to the cooling column and configured to condense the helium gas in the cooling column into cold liquid helium which falls by gravity to a bottom of the cooling column and flows by gravity to the inflow port of the thermally conductive cylindrical container;
an expansion tank connected with the coldhead and configured to receive the helium gas from the cooling column in the event of a temperature rise and return the helium gas to the cooling column as the helium cools;
wherein the first hermetically sealed, passive heat exchanger is sealed against losing or receiving helium and has no moving parts and operates without external intervention during cooldown, quench, and normal operation;

a second hermetically sealed heat exchanger including:
one thermally conductive tubing coiled circumferentially around and thermally coupled to the thermally conductive cylindrical container such that gaseous helium in the thermally conductive tubing is cooled by the helium in the thermally conductive cylinder container, the thermally conductive tubing extending in a closed, hermetically sealed loop with a superconducting coil heat exchanger disposed lower than the thermally conductive cylindrical such that the gaseous helium sealed in the thermally conductive tubing forms a thermosiphon which circulates the gaseous helium using thermal gradients without moving parts.

2. The heat exchanger system according to claim 1 , wherein the thermally conductive cylindrical container includes:
a baffle plate disposed horizontally in the container to divide the container into a lower portion which receives the liquid helium from the cooling column via the inflow port and an upper portion which supplies the helium as to the cooling column via the outflow port.

3. The heat exchanger system according to claim 1 , wherein the thermally conductive tubing is sealed to retain the gaseous helium at 4.5° K to 295° K at internal pressures up to a least 102 atmospheres.

4. The heat exchanger system according to claim 1 , further including:
a series of thermally conductive disks mounted around an exterior of the thermally conducive cylindrical container wherein a spiral portion of the thermally conductive tubing is supported by and thermally coupled to each disk, such that the tubing is thermally coupled to the thermally conductive cylindrical container via the thermally conductive disks.

5. The heat exchanger system according to claim 1 , wherein the gaseous helium enters a portion of the thermally conductive tubing coiled around the thermally conductive container higher than where the gaseous helium leaves the portion of the thermally conductive tubing wound around the container.

6. The heat exchanger system according to claim 1 further including:
a plurality of thermally conductive plates, each thermally connected to the exterior of the thermally conductive container, extending from the thermally conductive container, and each spaced at intervals along a length of the thermally conductive container, the thermally conductive tubing being coiled around the container in thermal communication with the plates.

7. The heat exchanger system according to claim 1 , further including:
a manifold which connects the cooling to loops to provide pressure balance there between.

8. A magnetic resonance magnet system comprising:
a superconducting magnetic resonance magnet;
the heat exchanger system according to claim 1 .

9. A method of cooling a superconducting magnet comprising:
starting at room temperature with gaseous helium sealed in a closed loop of thermally conductive tubing at 65-105 bar;
starting at room temperature with gaseous helium hermetically sealed in an interconnected
thermally conductive cylinder around which the closed loop of tubing is wrapped in thermal communication therewith,
a cooling column disposed higher than the thermally conductive cylinder,
a cryogen coldhead adjacent a top of the cooling column, and
an expansion tank connected with the cooling column and the coldhead,

cooling the gaseous helium contained in the cooling column with the cryogen coldhead;
as pressure in the cooling column drops due to the cooling, receiving more helium from the expansion tank and causing the gaseous helium to condense into a liquid state and fall by gravity to a bottom of the cooling column;
allowing the liquid state helium to flow by gravity from the bottom of the cooling cylinder to the thermally conductive container;
transferring heat from the gaseous helium sealed in the closed loop of thermally conductive tubing to the liquid state helium in the thermally conductive container causing some of the liquid state helium to form gaseous helium;
transferring heat from the superconducting magnet to the gaseous helium in the thermal conductive tubing;
allowing the gaseous helium from the thermally conductive cylinder to rise by thermal gradients to the cooling column and up the cooling column to the coldhead to be recondensed to the liquid state.

10. The method according to claim 9 , wherein the gaseous helium sealed in the closed loop of thermally conductive tubing forms a thermosiphon which circulates the gaseous helium using thermal gradients without moving parts.

11. The method according to claim 10 , further including:
quenching the superconducting magnet;
in response to the quenching, the superconducting magnet heating to at least 70° K which heats the first pool of helium to at least 70° K;
heating the liquid state and gaseous helium in the thermally conductive cylinder with the gaseous helium in the closed loop of thermally conductive tubing causing pressures of gaseous helium in the thermally conductive cylinder and the cooling column to rise;
with the rise in pressure, flowing the gaseous helium from the cooling column into the expansion tank without venting any of the gaseous helium to the atmosphere.

12. The method according to claim 11 , further including:
continuing to cool the gaseous helium in the cooling column with the coldhead;
as the pressure in the cooling column drops due to the cooling, condensing the gaseous helium to the liquid state and allowing the liquid state helium to flow by gravity into the thermally conductive cylinder;
transferring heat from the gaseous helium sealed in the closed loop of thermally conductive tubing to the liquid state gaseous helium in the thermally conductive cylinder;
transferring heat from the superconducting magnet to the gaseous helium in the closed loop of thermally conductive tubing;
when sufficient heat is transferred from the superconducting magnet to reach its superconducting temperature, restarting the superconducting magnet.

13. A heat exchanging system comprising:
a hermetically sealed interconnected combination of a thermally conductive cylinder, a cooling column disposed higher than the thermally conductive cylinder and fluidically connecte

Assignees

• Koninklijke Philips Nv

Inventors

• Ackermann Robert Adolph
• Menteur Philippe
• Dhar Manmohan

Classifications

• G01R33/3804

  Additional hardware for cooling or heating of the magnet assembly, for housing a cooled or heated part of the magnet assembly or for temperature control of the magnet assembly · CPC title

• F25B25/005 Primary

  using primary and secondary systems · CPC title

• F25B9/10

  with several cooling stages · CPC title

• F25D19/00

  Arrangement or mounting of refrigeration units with respect to devices {or objects to be refrigerated, e.g. infrared detectors} · CPC title

• G01R33/3815

  with superconducting coils, e.g. power supply therefor · CPC title