Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 98
Apparent Density
ОглавлениеThe apparent density (bulk density) is the weight per unit volume of a material, such as coal, which includes the voids that exist in the tested material (Table A-22).
Table A-22 Measurement of the apparent density of materials.
| Method | Use | Test |
|---|---|---|
| A | For fine granules and powders that can be poured through a small funnel. | Test is performed by pouring the material through a funnel into a cylinder of known volume. The apparent density is calculated by dividing the weight of the material in the cylinder by the volume of the cylinder. |
| B | For coarse, granular materials that either cannot be poured or that pour with difficulty through the funnel from Method A. | Test is performed by pouring the material through a funnel into a cylinder of known volume. The apparent density is calculated by dividing the weight of the material in the cylinder by the volume of the cylinder. |
| C | For coarse flakes, chips, cut fibers, or strands that cannot be tested with Methods A or B. | Test is performed by pouring the material into a graduated cylinder and allowing a 2300-g plunger to pack the material for 1 minute. The apparent density is taken as the mass of the material divided by the settled volume. |
The bulk factor is the ratio of the density of a material after molding to the density of the raw material and provides a measure of the volume change that can be expected during processing.
The apparent density is not an intrinsic property of a material; it can change depending on how the material is handled. For example, a powder poured in to a cylinder will have a particular bulk density; if the cylinder is disturbed, the powder particles will move and usually settle closer together, resulting in a higher bulk density. For this reason, the bulk density of powders is usually reported both as “freely settled” and “tapped” density (where the tapped density refers to the bulk density of the powder after a specified compaction process, usually involving vibration of the container.
