AERFERRISI

Impianti e ricambi per il riscaldamento e il condizionamento di ambienti

Fan Heating System for Theaters

Many of these rooms require their systems to be renewed, not only to update them according to recent requirements, but also with the most appropriate and rational graduation of the parameters that control wellbeing in the different areas. These are many and all have their own characteristics.
Let us start with the entrance, that will have to have an intermediate temperature between the external temperature and the temperature inside the theater; then there is the problem of the frequent opening and closing of the entrance doors with consequent bothersome air movements and cold currents.
In the box office there is personnel who has to sit still, while the public entering from outside is still dressed with coats and furs, waiting to leave them at the cloakroom. Gathering hundreds of articles of clothing, the cloakroom will need changes of air to avoid the accumulation of odors. Summing up, the entrance needs air changes and overpressure, in order to prevent undesired cold air from entering and help the expulsion of air from the cloakroom. The entrance will thus be heated by using only external air, with continuous temperature control and modulating valves. Temperature will be around 16-18°C.
For the box office and the personnel working there, the temperature may be increased with warm platforms, where they can rest their feet, or elements to heat with a radiating effect. In the cloakrooms, the proper air extractors will avoid air stagnation, guaranteeing about 3-5 changes per hour; more air will exit, by overpressure, from the entrance doors, thus opposing the cold air and working as a thermic barrier.
Let us enter the actual theater hall, and more specifically the stalls, where the conditions will be the same as any other building intended for public shows, such as theaters and movie theaters.
Therefore, we will give 20°C and 32 cu m per person, as is befitting. The heating will be obtained by means of re-circulation fan heaters that can simply provide the necessary calories, while the air change will be entrusted to other machines located in other areas, as we will see.
The regulation could also be an “all-or-nothing” type, but it is advisable to be able to modulate it, just to avoid the sensations of air movement that are inevitably felt with an “all-or-nothing” regulation.
It is a known fact that heat rises and so, on first consideration, there should be no problem with heating the boxes, at least as it was done in early systems; being by their nature closed, theater boxes need their air to be changed, and the air is taken from the emptiness of the room and, after “washing” the box, it goes into the corridors of the different storeys through air transit vents. Every corridor will be heated through simple units embedded into the wall and hidden to the sight, while one or more air extractors (per storey) suck in and expel the air directly or (a better solution, if the heights allow it) by lowering the ceiling, or through a suction canalization from the different boxes.
Since the storeys are many, each will have its individual extraction that will have to be regulated, with respect to the air flow, according to the height of the storey. The total cubic meters extracted, divided, as mentioned above, first among the different storeys in a graduated form, must match the total number of present people multiplied by 32 (that represents the minimum amount of cubic meters required by law for each person). Naturally, it would be best to plan for a larger air flow, to be used not only for changing the air, but also for cooling during the spring and autumn, with the possibility in both cases to graduate the volume at various steps. This would allow to extract the exact amount of air without any waste, depending on the actual public attendance; this solution would not be possible if the air flows were fixed, with a consequent waste of calories.
We suggest to take all the air needed for the change from the roof, and for various reasons. First of all, air suction will be easier; then, the air will be cleaner than it is at street level; finally, being pumped from above, it will oppose the rise of hot air inside the building, preventing stratification.
Of course, the air will not be completely cold when pumped in. First, it will be filtered, and then heated up to the right level with three-way motorized valves. Evidently, if the air were too hot, its tendency would be to remain up high, while if it were cold, it would fall towards the stalls, causing the inconvenience of air currents. Only a precise and measured regulation will guarantee a right flow of changed air, that will be used up and eliminated by the suction from the different tiers of boxes.
Another area that needs to be treated is the stage. It does not need large air changes; it needs different temperatures from the spectators’ room, as the actors and singers often wear scene clothing, at times light and at times heavy. Moreover, the considerable height of the room due to the backdrops that have to be lifted up and down requires low recovery vents to avoid stratifications.
We should also pay attention to air distribution, avoiding the possibility that uncontrolled air movements may cause the backdrops to fluctuate.
An external air inlet is not necessary, due to the low number of the people present, and because of the width of the stage, that directly communicates with the theater room.
Other rooms concerned with air treatment are the actors’ dressing rooms, that require the possibility of changing the temperature according to the desires of the occupants, and therefore with each room independent from the others. Also, air changes are important to guarantee health conditions and eliminate the smell of flowers, perfumes, and the various cosmetic ingredients of make-up.
Another room with particular characteristics is the foyer. How should this room be treated with fan heating? Obviously the most appreciated machines are the ones that have a greater air flow intensity, both with respect to air delivery and extraction, since they allow to graduate the air changes according to the number of present people and to the moment. When the room is more crowded and the coffee machines work at maximum capacity, at that point the air extractors will provide the highest air flow, while before the spectators arrive they will be turned off and only air recirculation will be working. Also in this case must the regulation be modular, in order to adjust to these rather unusual, sudden, and occasional utilization curves. The air changes are the ones provided for by law, but it is advisable to have a 50% supply more; in fact, the temperature may rise very fast, due to the sudden contribution from the spectators, and thus in order to maintain a good level of wellbeing it could be helpful to expel great quantities of endogenous heat before climatic conditions are stabilized.
We have practically toured the whole theater, and in every zone we have ensured the right temperature, correct air change, and the most suited position for air delivery, recovery, and expulsion with each machine.
Let us say, in addition, that the control of humidity in winter is not very important, first of all because of the limited time people stay in these buildings; then, because of the contribution of humidity by people themselves, and because of the consequent air change with air taken from outside.
Concerning summer air conditioning, it must be said that it is not often required, since the opera season is mostly in the winter or springtime. However, it must be pointed out that the summer cooling conditions are more easily obtained. First of all, the problem of winter stratification does not exist, and then the heat loads are basically just the ones relevant to the air changes, since dispersions are very small and the sun’s irradiation is practically absent.
Considering the above, with a few calculations it will not be difficult to make a study for this type of rooms; only, it will be necessary to pay attention to the position that must be given to each fan heating machine, and above all to choose the most silent models, with the option of setting different air flows, so that it can be possible to adapt to various situations and uses.

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