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1950-51 Theatre Catalog, 9th Edition, Page 371 (349)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 371
Page 371

1950-51 Theatre Catalog, 9th Edition, Page 371

different one of the horizontal and vertical louvers for the rear to attain best results. Of course, two grilles will cost almost twice as much as the one grille with the same square footage, but it is felt that the added control is worth the extra expense.

Furthermore, some engineers point out that if air has to be exhausted through the entrance doors, or five feet above the patrons heads, some areas in the auditorium will have dead air spaces. This problem does not usually arise in theatres with less than 600 seats, for defiection of the air with the grilles can be controlled from 60' to 70'.

The prime difficulty is said to arise in theatres 100' or more long, where a way must be found to get the air low over the back seats, once control with the blower has been lost. This is usually done with large exhaust fans mounted on the roof of the theatre and long flat ducts run down against the wall. If it is at all feasible, these exhaust ducts should be situated approximately 7' above floor level. It is understood, of course, that the front doors are to be left open as often as possible to provide additional exhaust air.


While it is true that an evaporative cooling system functions at greater effectiveness in the warm and dry sections of the United States than in the relatively cool and moist areas, it can, contrary to popular belief, be successfully operated in those sections which have a designed summer wet-bulb temperature of approximately 790 or less (see Fig. 10), provided the system is properly engineered in every detail.

Special Cases

It is also true, however, that other factors concerned with general location should likewise be taken into consideration. In some cases, an evaporative cooling system may be operated with satisfaction in sections of the country where it is not ordinarily used, if such considerations as the size of the house and the time of its operation make such an installation feasible. For instance, in an area where the daytime temperatures are relatively warm, although the evening temperatures are quite cool, an evapora

FIGURE 7-Installation ot evaporative cooling system with screen rotors. (Photograph courtesy of Farr Co.)

tive cooling system could do an excellent job for night-time operation in small suburban theatres where the heat emission from the occupants might be quite high, in spite of relatively cool outside conditions.

FIGURE B-Typical theatre supply grille. (Phylogrnph courlesy of U. 5. Air Conditioning Corp.)

Table l-Results Obtainable with Evaporative Cooling Under 730 and 770 Wet-Bulb Conditions

Entering Air


Dry W'el Relative Bull: Bulb Bulb Humid- Depres Temp. Temp. ity sion

1050 730 20% 320 1000 730 27% 27c 950 730 33% 220 900 72 o 43% 170 850 730 56% 120

1000 77G 34% 230 95" '770 43% 180 900 77a 55% 130 880 770 60% 11D 850 770 69% 80 820 770 80% 5O


Leaving Air of Cooler

Dry Effer- [Vet Relative Bulb live Bull: Hunu'dTemp. Temp. Temp. ily

810 750 730 70% '79U 730 73a 75% 780 720 730 78% 770 710 730 82% 760 700 730 86%

1'330 77D 77'0 75% 82a 760 770 80% 810 75c '770 83% 800 740 770 87% 790 730 770 91% 780 720 770 96%


It should be pointed out that the term ffhumidityt, has been overworked and often misused in approaching cooling problems. For example, it is quite common to find a relative humidity of 85% or more with a temperature of 800 or less on mornings that appear to be cool and comfortable in most areas during hot Weather. When the humidity is up in high wet-bulb'areas, the temperature is low, so sufficient air movement with proper distribution should provide a comfortable condition in a theatre.

Specific Wet Bulb Data

Fig. 10 shows what the summer wetbulb temperature data are throughout the country, and indicates that evaporative cooling may be used on a wide scale. Of course, some differences, based on the air change method of computation, will exist in the engineering of systems installed in various sections of the United States. For example, a complete air change is required every two minutes in the western part of Oklahoma, Kansas, and Texas, but a 11/;minute change is needed in Dallas, Kansas City, Indianapolis, and Greenville, S. C. Similarly, a one-minute air change is required in St. Louis, Louisville, Cincinnati, Philadelphia, New York, and Boston, but a 34-minute one is needed in areas, such as Savannah, Ga., which have a designed wet-bulb of 790

Cooling Results in Two Cases

Table 1, which shows the temperatures of entering air and those of air leaving evaporative coolers under 730 and 770 wet-bulb conditions, exemplifies the satisfactory results which may be achieved with this type of system.

It should be noted, in connection with Table 1, that when the temperature is 820 with a 770 wet-bulb and a corresponding 80% relative humidity, proper air motion is all that is required to produce an effective temperature condition. Furthermore, when the dry-bulb temperature is 1000 with a wet-bulb temperature of 770, the outside air, after it
1950-51 Theatre Catalog, 9th Edition, Page 371