# US 4,392,356 A · Magnetic heat pumping

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- Number: US 4,392,356 A
- Document ID: US4392356A
- Status: Granted
- Kind: A
- Application number: 06/235,868
- Filed: 1981-02-19
- Granted: 1983-07-12
- Earliest claimed: 1977-08-31
- Assignees: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
- Inventors: Gerald V. Brown
- Web page: https://patentgrep.com/patent/US4392356A

## CPC

- F25B 21/00: Machines, plants or systems, using electric or magnetic effects
- F25B 2321/0021: with a static fixed magnet
- Y02B 30/00: Energy efficient heating, ventilation or air conditioning [HVAC]
- Y10S 505/889: Utilizing rare earth material
- Y10S 505/891: Magnetic or electrical effect cooling
- Y10S 505/892: Magnetic device cooling
- F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

The method of the invention employs ferromagnetic or ferrimagnetic elements, preferably of rare-earth based material, for example gadolinium, and preferably employs a regenerator. The steps of the method comprise controlling the temperature and applied magnetic field of the element to cause the state of the element as represented on a temperature-magnetic entropy diagram repeatedly to traverse a loop. The loop may have a first portion of concurrent substantially isothermal or constant temperature and increasing applied magnetic field, a second portion of lowering temperature and constant applied magnetic field, a third portion of isothermal and decreasing applied magnetic field, and a fourth portion of increasing temperature and constant applied magnetic field. Other loops may be four-sided, with, for example, two isotherms and two adiabats (constant entropy portions). Preferably, a regenerator may be employed to enhance desired cooling or heating effects, with varied magnetic fields or varying temperatures including three-sided figures traversed by the representative point.

## Claims

### Claim 1

A magnetic heat pump comprising:
a working component which is essentially a single ferromagnetic or ferrimagnetic material selected from the group consisting of rare earth elements and intermetallic compounds and alloys containing rare earth elements;
means for subjecting said component successively to a magnetic field to first, second, third and fourth strengths, and then back to said first strength; and,
means for changing said element successively from a first to a second temperature, then to a third temperature; then to a fourth temperature; and then back to said first temperature, said first, second, third and fourth temperatures coinciding with said first, second, third and fourth strengths of said magnetic field.

### Claim 2 (depends on 1)

The apparatus as claimed in claim 1, in which said first and second temperature are the same whereby heat is rejected by said element in a substantially isothermal manner as the magnetic field applied to said element is changed from first to second strength.

### Claim 3 (depends on 1)

The apparatus as claimed in claim 1, in which said third temperature equals said fourth temperature whereby heat is absorbed by said element in a substantially isothermal manner as the magnetic field applied to said element is changed from third to fourth strength.

### Claim 4 (depends on 1)

The apparatus as claimed in claim 1 including means whereby said element is thermally isolated during the change from said second to said third temperature.

### Claim 5 (depends on 4)

The apparatus as claimed in claim 4, in which said component is thermally isolated during the change from said fourth to said first temperature.

### Claim 6 (depends on 4)

The apparatus as claimed in claim 4 in which heat is absorbed by said element during the change from said fourth to said first temperature.

### Claim 7 (depends on 1)

The apparatus as claimed in claim 1 in which the Curie temperature of said component is in or near the temperature range between said first and fourth temperatures.