Heat exchanger beds composed of thermomagnetic material

Abstract

Provided is a packed heat exchanger bed composed of thermomagnetic material particles having a mean particle diameter of 50 μm to 1 mm. The packed bed has porosity of 30-45%. A thermomagnetic material is a metal containing material such as (A y B 1-y ) 2+δ C w D x E z , La(Fe x Al 1-x ) 13 H y or La(Fe x Si 1-x ) 13 H y , La(Fe x Al y Co z ) 13 or La(FeSi y Co z ) 13 , LaMn x Fe 2-x Ge, Heusler alloys, Gd 5 (Si x Ge 1-x ) 4 , Fe 2 P-based compounds, manganites of the perovskite type, Tb 5 (Si 4-x Ge x ), XTiGe, Mn 2-x Z x Sb, or Mn 2 Z x Sb 1-x , wherein A- E, P, and Z represent various metal atoms.

1 . A packed heat exchanger bed composed of thermomagnetic material particles which have a mean diameter in the range from 50 μm to 400 μm and give rise to a porosity in the packed bed of from 30 to 45%. 
     
     
         2 . The heat exchanger bed according to  claim 1 , wherein the material particles have a mean diameter of from 50 μm to 200 μm. 
     
     
         3 . The heat exchanger bed according to  claim 1 , wherein the material particles are in spherical form, pellet form, sheet form or cylinder form. 
     
     
         4 . The heat exchanger bed according to  claim 1 , wherein the porosity of the packed bed is 36 to 45%. 
     
     
         5 . A heat exchanger bed composed of a thermomagnetic material monolith which has continuous channels with a cross-sectional area of the individual channels of from 0.001 to 0.2 mm 2  and a wall thickness of 50 to 300 μm, a porosity of from 10 to 60% and a ratio of surface to volume of from 3,000 to 50,000 m 2 /m 3 , or which has a plurality of parallel sheets with a sheet thickness of 0.1 to 2 mm and a sheet separation of 0.05 to 1 mm. 
     
     
         6 . The heat exchanger bed according to  claim 5 , wherein the porosity is 20 to 30%. 
     
     
         7 . The heat exchanger bed according to  claim 5 , wherein the cross-sectional area of the individual channels is from 0.01 to 0.03 mm 2  and the wall thickness is from 50 to 150 μm. 
     
     
         8 . The heat exchanger bed according to  claim 1 , wherein the thermomagnetic material is at least one selected from the group consisting of (1)-(8):
 (1) at least one compound of the formula (I)
   (A y B 1-y ) 2+δ C w D x E z    (I),
 
    wherein    A is Mn or Co,    B is Fe, Cr or Ni,    C, D and E at least two of C, D and E are different, have a non-vanishing concentration and each independently is selected from the group consisting of P, B, Se, Ge, Ga, Si, Sn, N, As and Sb, where at least one of C, D and E is Ge or Si,    δ is a number of from −0.1 to 0.1,    w, x, y, z each independently is from 0 to 1, wherein w+x+z=1;   (2) at least one La- and Fe-based compound of the formulae (II) and/or (III) and/or (IV)
   La(Fe x Al 1-x ) 13 H y  or La(Fe x Si 1-x ) 13 H y    (II)
 
    wherein    x is a number of from 0.7 to 0.95,    y is a number of from 0 to 3;
   La(Fe x Al y Co z ) 13  or La(Fe x Si y Co z ) 13    (III),
 
    wherein    x is a number of from 0.7 to 0.95,    y is a number of from 0.05 to 1−x,    z is a number of from 0.005 to 0.5;
   LaMn x Fe 2-x Ge   (IV),
 
    wherein    x is a number of from 1.7 to 1.95, and   (3) at least one Heusler alloy of the MnTP type, wherein T is a transition metal and P is a p-doping metal having an electron count per atom e/a of from 7 to 8.5,   (4) at least one Gd- and Si-based compound of the formula (V)
   Gd 5 (Si x Ge 1-x ) 4    (V)
 
    wherein x is a number of from 0.2 to 1,   (5) at least one Fe 2 P-based compound,   (6) at least one manganite of the perovskite type,   (7) at least one compound which comprises at least one rare earth element and has the formulae selected from the group consisting of (VI) and (VII)
   Tb 5 (Si 4-x Ge x )   (VI),
 
    wherein x=0, 1, 2, 3, or 4,
   XTiGe   (VII),
 
    wherein X=Dy, Ho, or Tm,   (8) at least one Mn- and Sb- or As-based compound of the formulae (VIII) and (IX)
   Mn 2-x Z x Sb   (VIII)
 
   Mn 2 Z x Sb 1-x    (IX)
 
    wherein    Z is Cr, Cu, Zn, Co, V, As, or Ge,    x is from 0.01 to 0.5,    wherein Sb may be replaced by As when Z is not As.   
     
     
         9 . The heat exchanger bed according to  claim 8 , wherein the thermomagnetic material is at least one quaternary compound of the formula (I) which, in addition to Mn, Fe, P and optionally Sb, further comprises Ge; Si; As; Ge and Si; Ge and As; Si and As; or Ge, Si, and As. 
     
     
         10 . A process for producing heat exchanger beds according to  claim 1 , comprising subjecting a powder of the thermomagnetic material to shaping to form the thermomagnetic material particles and subsequently packing the material particles to form the heat exchanger bed. 
     
     
         11 . A process for producing heat exchanger beds according to  claim 5  by extrusion, injection molding or molding of the thermomagnetic material to form the monolith. 
     
     
         12 . A refrigerator, an air conditioning unit, a heat pump, or a thermomagnetic generator comprising the packed heat exchanger bed according to  claim 1 .