| 摘要 |
Anhydrous sodium sulfate has been shown to have higher thermal content than any other low cost solid material because of its high density, high specific heat, and additional reversible latent heat of solid-to-solid crystal phase change at around 465 DEG F. By compressing anhydrous sodium sulfate into pellets and then forming a bed of these pellets and passing a heated fluid through the bed a relatively great quantity of heat energy may be economically stored in a relatively small volume. Moreover, a rapid rate of heat transfer into or out of the pebble bed can be achieved, up to 400,000 Btu per hour per cubic foot. The same heat transfer fluid may be used to withdraw the heat from the bed for use in space heating or other purposes. The fluid may be air, other inert gases, or a non-acqueous heat transfer liquid which does not react with sodium sulfate, such as a modified terphenyl or a high temperature oil. Advantageously, a thermal storage system embodying this invention can store a relatively great quantity of heat energy per unit volume, for example up to at least 45,000 Btu per cubic foot in a pebble bed containing thirty percent voids, and even higher when the pebbles are smaller and the percentage of voids is lower. This amount of stored heat energy per unit volume with rapid charging and discharging rates is considerably greater than in any practicable arrangement heretofore proposed.
|
