US 3320724 A
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Description (OCR text may contain errors)
y 3, 1967 R. E. RICE 3,320,724
HEAT- STORAGE BREATHER SYSTEM Filed Aug. 24, 1964 INVENTOR. ldlardfl Zeke w iwrwy FM United States Patent Ofilice 3,320,724 Patented May 23, 1967 3,320,724 HEAT-STQRAGE BREATHER SYSTEM Richard E. Rice, Arlington, Mass, assignor to Comstock & Wescott, Inc, Cambridge, Mass, a corporation of Massachusetts Filed Aug. 24, 1964, Ser. No. 391,564 6 Claims. (Cl. 55269) This invention relates to heat-storage apparatus of the type comprising one or more closed containers of heatstorage material such as sodium hydroxide mixed with a small percentage of rust inhibitor, as for example apparatus such as disclosed in the copending application of Richard E. Rice and William E. Whitney, Ser. No. 391,- 676, filed herewith, now US. Patent No. 3,299,945. The aforesaid material may be cycled over a wide range, for example from a maximum of 900 F. when fully charged with heat to a minimum of 250 F. when almost discharged. Inasmuch as the heat-storage material when heated expands more rapidly than the containers, an air space must be left above the material at the top of each container, and the space must be vented to avoid excessive pressure during heating or sub-atmospheric pressure while heat is being withdrawn from the material. While the material is being heated air is exhaled and while the material is being cooled it is inhaled.
When in the solid state heat-storage material such as sodium hydroxide and other caustic alkalies adsorb moisture vigorously, though not appreciably in the higher ranges in which the material is liquid. Therefore when the apparatus is not being operated, as during the summer months, moisture would be adsorbed from the humid summer air if permitted to enter. The presence of moisture would not only have deleterious corrosive effects on the internal surface of the containers but, upon heating after a shut-down period, this moisture would be driven off and an objectionable evolution of steam would occur.
Furthermore the aforesaid caustic alkalies combine with carbon dioxide to form carbonates, and air normally contains .03% or more of carbon dioxide. If carbon dioxide were permitted to enter it would combine with the thin film of liquid caustic alkali which normally exists on the inner surfaces of the containers above the liquid level and within the heated portion of the vent tube. Inasmuch as the aforesaid carbonates have melting points higher than the highest temperature through which the heat-storage material is cycled (900 F. in the above example) solid accumulations might build up, eventually closing the vent tube and causing dangerous pressures.
A practical piece of heat-storage equipment for use in homes or in commercial or industrial buildings must be designed to operate without frequent maintenance for long periods of time. If the well-known methods of abscr bing carbon dioxide and moisture from air were applied, the quantities of the absorbents required would be very large adding substantially to the cost and to the bulk of the equipment.
Objects of the present invention are to provide a breather system for heat-storage apparatus which is simple and economical in construction, which requires a minimum amount of sorbent material, which is effective during periods when the apparatus is inactive, which requires minimum maintenance and which is durable and reliable in use.
According to this invention the apparatus comprises a container for the heat-storage material, means for circulating fluid along a passageway past the container to draw heat from the material, a wall of insulation around the container, and a breather tube leading from the interior of the container outside the aforesaid wall, the tube including a desiccant chamber disposed in the wall. The desiccant chamber should be located at a location intermediate the inner and outer surfaces of the wall such that, when the inner surface is near its maximum temperature, the desiccant is hot enough to release moisture and, when the temperature of the inner surface is near the lower end of the range, the desiccant is cool enough to adsorb moisture. Preferably the aforesaid chamber is juxtaposed to the inlet end of the aforesaid passageway so that when heat is being drawn from the material and air is being breathed into the chamber, the desiccant is kept cool enough to be effective. The preferred embodiment is further characterized by a liquid reservoir in the aforesaid tube between the chamber and the outer end of the tube, the reservoir being disposed below the chamber and outer end to collect condensation during large evolution of water vapor. Preferably the reservoir is disposed in the aforesaid wall close to its outer surface to remain below the boiling point of water throughout the range of temperature of the material. The preferred embodiment is further characterized by carbon dioxide absorber in the aforesaid tube between the reservoir and the outer end of the tube.
For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawings in which FIG. 1 is a top plan view with parts broken away;
FIG. 2 is a section on line 22 of FIG. 1; and
FIG. 3 is a section on line 33 of FIG. 1.
As more fully disclosed in the aforesaid application the apparatus comprises an enclosure having inner and outer walls 1 and 2, a bottom 3 and a removable top 4. As shown in FIG. 1 the inner walls 1 are disposed on only two opposite sides of the enclosure and as shown in FIG. 2 they terminate short of the top 4 to provide openings 6 and 7 interconnecting the passageways 8 and 9 between the inner and outer walls with the space between the inner walls containing the storage units 11. As shown in FIG. 1 the units 11 have peripheral flanges around one side which fit into grooves in the inner walls 1, the units slipping into the grooves from the top when the cover 4 is removed. The space between the inner walls is divided into two parts by means of a baffle 12 which is slotted from the bottom to fit over the units and divide the space between the units except for an opening 13 at the bottom of the enclosure to permit circulation of air from one side of the baffle to the other. The enclosure is entirely surrounded by a housing 19 having a removable cover 21, with a wall of insulation 22 filling the space between the enclosure and housing. Communicating with the passageway 8 is an inlet duct 28 and communicating with the passageway 9 is an outlet duct 29. Disposed in the outlet duct is a blower 39 to produce circulation of air through the inlet 28, passageway 8, openings '6, 13 and 7, passageway 9 and outlet duct 29.
The storage units 11 may be filled with any suitable heat-storage material but they preferably contain sodium hydroxide mixed with a small percentage of rust inhibitor. The units are preferably filled with mateial in liquid form before they are inserted in the enclosure. After the units are inserted the filling caps are removed and replaced with caps 53 connected to a tube 54 which leads to chambers 56, 57 and 58 and thence to an outlet 59 to the atmosphere. The chamber 56 contains material to adsorb moisture, such as silica-gel or activated alumina, or a molecular sieve. Chamber 57 serves to collect condensed moisture removed by the material in chamber 56, and chamber 58 contains material to absorb carbon dioxide, for example calcium hydroxide or a caustic alkali, such as lithium hydroxide, potassium hydroxide or barium hydroxide or both, preferably a mixture of calcium hydroxide, sodium hydroxide and a color indicator, such as Sodasorb made by Dewey & Almy Chemical Co.
As air is inhaled during cooling periods carbon dioxide is absorbed in chamber 58 and moisture is adsorbed in chamber 56. As air is exhaled in the upper end of the temperature range, the condensed moisture in chamber 57 is evaporated and carried out to the atmosphere. While the heat-storage material is at high temperature the desiccant is ineffective but this is immaterial because the material cannot adsorb moisture at the higher temperatures. In apparatus operating through the aforesaid range of 250 F. to 900 F. and using activated alumina as the desiccant and having a wall of Johns- Manville Spintex eight inches thick, the desiccant chamber 56 is preferably located about five inches from the inner surface of the insulation so that the desiccant adsorbs moisture while the heat-absorbing material is cool enough to adsorb moisture and evaporates the moisture in the upper end of each temperature cycle.
While a particular embodiment has been shown by way of illustrationit should be understood that the invention includes all modifications and equivalents falling within the scope of the appended claims.
1. In a heat-storage system of the type employing heatabsorptive material which has aflinity for water when cool, the combination of a container for said material, mean fors circulating fluid along a passageway past said container to draw heat from the material, a Wall of insulation around said container, and a breather tube leading from the interior of said container outside said wall, said tube including a desiccant chamber disposed in said wall.
2. The combination of claim 1 wherein said chamber is juxtaposed to the inlet end of said passageway so that when heat is being drawn from said material and air is being breathed into said chamber, the desiccant is kept cool enough to be efiective.
3. The combination of claim 1 further characterized by a liquid reservoir in said tube between said chamber and the outer end of the tube, the reservoir being disposed below said chamber and outer end to collect condensation during large evolution of water vapor.
4. The combination of claim 3 wherein said reservoir is disposed in said wall close to its outer surface to remain below the boiling point of water throughout the range of temperatures of said material.
5. The combination of claim 1 further characterized by carbon dioxide absorber in said tube between said chamber and the outer end of the tube.
6. The combination of claim 3 further characterized by carbon dioxide absorber in said tube between said reservoir and the outer end of the tube.
References Cited by the Examiner UNITED STATES PATENTS 3,144,756 8/1964 Arnold et. al. 55268 FOREIGN PATENTS 260,899 11/1926 Great Britain.
REUBEN FRIEDMAN, Primary Examiner.
C. N. HART, Assistant Examiner.