| 摘要 |
<p>The auxiliary filter admits air to a chamber to which the whistle is connected. The air flow resistance of the whistle is considerably higher, pref. 10X higher, than that of the auxiliary filter, and the whistle only operates when a predetermined air speed through it is reached. A flute mouth-piece is suitable as the whistle. The auxiliary filter is pref. a portion of the main filter. As the flow through the auxiliary filter is initially very much smaller than that through the main filter, through the difference in resistances, very little clogging of the auxiliary filter occurs in use; its resistance remains substantially constant. When the main filter resistance rises due to clogging, the resultant pressure drop increases the flow through the auxiliary filter and the whistle until the speed is sufficient to sound the whistle. The device is used with filters in air conditioning plant in which heat recovery is practised. The exhaust air is cleaned before passage, through heat exchanges, which would otherwise become clogged. The filters need regular replacement and the simplicity of the warning device makes it use on all filters in the plant economic.</p> |
