| 摘要 |
<p>The unit is provided with an envelope having a front face, a rear face, a top, a bottom and peripheral side walls. The front face and the peripheral side walls define an inner enclosure. The unit is also provided with a medial shield having front face, a rear face, a top, a bottom and peripheral side walls. The medial shield is mounted within the inner enclosure defined by the envelope and spaced apart therefrom. The rear face and peripheral side walls of the medial shield and the front face and peripheral side walls of the envelope define a ventilation passage having top and bottom openings in communication with ambient air. The medial shield preferably has an intermediate opening communicating with the ventilation passage. The unit is also provided with a cover having a front face, a rear face, a top and a bottom. The cover is fixed over the medial shield. The cover has top and bottom openings in communication with the ambient air. The top and bottom openings of the cover communicate with the top and bottom openings of the ventilation passage. The rear face of the cover and the front face of the medial shield define a convection passage between the top and bottom openings of the cover.</p> |
