Thermal Ratchet Stopping Shovel Wall

Abstract

The thermal ratchet stopping shovel wall solves the problem of thermal ratcheting in packed bed heat storage units. It uses protrusions from the wall containing the packed bed to stop net downward rearrangement of the bed's solid granules. The protrusions limit the downward movement of packed bed granules during one part of a thermal cycle and, in another part of the cycle, the protrusions, with movement relative to the packed bed, “shovel” fallen granules back up to near their positions one cycle earlier.

I claim: 
     
         1 . A cycling process in granular media, packed bed heat storage units comprising:
 providing a granular media, packed bed heat storage unit including a packed bed of granular media of granules, and a heat transfer fluid, wherein this fluid can flow through the interstitial passages between the granules in the packed bed, and one or more walls, wherein these walls contain and are in contact with both of the packed bed and the heat transfer fluid, and a plurality of protrusions that protrude from the walls into the packed bed, and one or more force applying devices for forcing the heat transfer fluid to flow through the interstitial passages between the granules;   driving thermal charging and discharging cycling in the heat storage unit;   responsive driven wall thermal cycling in the heat storage unit;   during wall gap widening half cycles, with relative movement between the walls and the packed bed, widening of gap spaces between the walls and some packed bed granules in regions close to the walls, such that some of the granules fall into the widened wall gap spaces;   during wall gap widening half cycles, limiting the falls of any of the granules to regions (a) bounded by the walls and (b) bounded above by either the top of the packed bed or one of the protrusions and (c) also bounded below by either the bottom of the packed bed or another of the protrusions, but bounded by less than the complete vertical distance between the top and bottom of the packed bed; and   during wall gap narrowing half cycles, with relative movement between the packed bed and the walls and narrowing of the gaps between granules of the packed bed and the walls, the pushing upwards by the protrusions of granules, so that, over repeating wall gap cycles, there is little or no net vertical movement of the granules.   
     
     
         2 . The process of  claim 1  wherein the protrusions have sloping upper sides. 
     
     
         3 . The process of  claim 1  wherein the tips of the protrusions are embedded in the packed bed at all times. 
     
     
         4 . The process of  claim 1  wherein the walls with protruding protrusions can have vertical sections or non-vertical sections or both. 
     
     
         5 . The process of  claim 1  wherein the protrusions are made of material that can withstand the mechanical wear on the protrusions due to contact with and relative movement with the granules of the packed bed. 
     
     
         6 . The process of  claim 5  wherein the protrusions can be made from a material selected from the group consisting of carbon steel with a carbon content between 0.6 and 2.0 percent, cast iron with a carbon content above 2.0 percent, tungsten, alumina porcelains with alumina content above 30 percent and alumina plus silica contents above 80 percent and zirconia porcelains with zirconia content above 30 percent and zirconia plus alumina plus silica contents above 80 percent, silicon nitride, tantalum carbide, silicon carbide, tungsten carbide, titanium carbide and boron carbide. 
     
     
         7 . The process of  claim 1  wherein the protrusions are either firmly attached to or integral to the remainder of the walls. 
     
     
         8 . An apparatus for preventing thermal ratcheting in granular media, packed bed heat storage units comprising of at least:
 a packed bed of granular media of granules; heat transfer fluid wherein this fluid can flow through the interstitial passages between the granules; one or more walls wherein these walls contain and are in contact with both of the packed bed and the heat transfer fluid, one or more force applying devices for forcing the heat transfer fluid to flow through the interstitial passages between the granules, a plurality of protrusions that protrude from the walls into the packed bed, wherein the protrusions have sloping upper sides and the tips of the protrusions are embedded in the packed bed at all times.   
     
     
         9 . The apparatus of  claim 8  wherein the protrusions are made of material that can withstand the mechanical wear on the protrusions due to contact with and relative movement with the granules of the packed bed. 
     
     
         10 . The apparatus of  claim 9  wherein the protrusions can be made from a material selected from the group consisting of carbon steel with a carbon content between 0.6 and 2.0 percent, cast iron with a carbon content above 2.0 percent, tungsten, alumina porcelains with alumina content above 30 percent and alumina plus silica contents above 80 percent and zirconia porcelains with zirconia content above 30 percent and zirconia plus alumina plus silica contents above 80 percent, silicon nitride, tantalum carbide, silicon carbide, tungsten carbide, titanium carbide and boron carbide. 
     
     
         11 . The apparatus of  claim 8  wherein the protrusions are either firmly attached to or integral to the remainder of the walls.