Supply inlets combined with exhausts

A. supply inlet could be designed with or without an exhaust. There should naturally be an exhaust opening in the room. If the influence of the exhaust on the supply inlet is low, then it requires no special design, but if the influence of the exhaust is large it must be taken into account. The inlets could be combined with specific exhaust hoods to enhance their efficiency (see Section 10.4). There are many ways to design supply inlets and also to combine different supply inlets just a few inlets are described in this section. 

All supply inlets without a specific exhaust have the same problem, the spreading of contaminants in the room outside the supply air zone. When the inlets are used to create a cleaner zone in a normal workroom this is usually no problem. When a supply inlet is used to blow away some hazardous contaminant it is necessary to combine it with a specific exhaust, or the rest of the room will be contaminated. 

These systems can be inside large halls and may have no fixed limits for their influence, except for some parts of the system (inlet device surface, etc.) They can also be situated inside small rooms, where walls, floors, and ceilings are the natural boundaries. The systems usually consist of one exhaust hood and one supply inlet, which interact. There are also special combinations, as two or more inlets and one exhaust hood, or one supply inlet and two or more exhausts. All of these combinations need careful design and an accurate relation between supply and exhaust flow rates and velocities. Some systems also need stable temperature conditions to function properly. All combinations are dependent on having a defined contaminant concentration in the inlet air. This usually implies clean supply air, but some systems may use recirculated air with or without cleaning. 

There are many different combinations of supply inlets and exhaust enclosures, where the system has been designed as a whole. Two of these enclosures are described in some detail abrasive blasting rooms with a person working inside the enclosure, and hospital isolation rooms. 

A fixed-bed setup for calcination has been realized at the authors institute (Figure 11.4) 64 fixed-bed reactors are placed inside four ovens. The reactor inlets are connected by flexible lines with four gas supplies. Solid and liquid reaction products are condensed after the reactor outlets and the gases are led to the exhaust. By combination of four different gas compositions and four heating regimes (calcination temperatures, heating ramps, times) one can easily study the influence of calcination conditions on catalyst structure and performance. Moreover, gas composition can also be changed during the calcination procedure, which allows multistep calcination protocols. 

---