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1950-51 Theatre Catalog, 9th Edition, Page 368 (346)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 368
Page 368

1950-51 Theatre Catalog, 9th Edition, Page 368

Evaporative Cooling for Theatres

A Simple and Inexpensive Air Conditioning Method Proves Suitable for Operation in Many Localities

A satisfactory cooling and ventilating system is an absolute requisite for any theatre which professes to be modern, for wherever a large number of people are congregated there must be sufficient circulation of air, particularly during the warm months of the year. Due to the publicls Widespread acceptance of air conditioning as a prime comfort agent, patrons of today instinctively expect to find a pleasantly cool atmosphere in the theatres which they visit. Those houses which have failed to install efiicient cooling systems have inevitably suffered painful losses at the boxofiice.

Several different types and styles of summertime cooling and air conditioning are available to the theatre. Varying widely in basic design and equipment requirements, they provide a complete range of ventilation or cooling results commensurate with the size and type of theatre to be conditioned.

First of all, just plain ventilation with sufficient air movement to effect a perceptible reduction in effective temperature is still utilized in many of the smaller houses. For those theatres in cooler localities, and where night-time operation is customary, plain ventilation can accomplish some remarkably good results.

Secondly, evaporative cooling, one of the most frequently employed systems now installed in theatres, provides not only that same drop in effective temperature, but an actual reduction in drybulb temperature as well.

Next, cooling by means of well water; either through air washers or coils, is a commonly found type of system wherever cold water at temperatures of 550 or lower is available.

BRIEF: There are . . . at the present time . . . hundreds of theatres equipped with evaporative cooling . . . which involves a simple exchange of energy between air and water . . . without actual loss or gain of heat in an engineering sense . . . Although particularly suitable for theatres containing up to 800 seats, there are a number of larger houses . . . in the 1,000 to 1,200-seat class . . . that have been successfully cooled by this method.

Curiously enough . . . in spite of the fact that evaporative cooling has been in general use by theatres for over 20 years . . . many exhibitors and builders still know little about its basic characteristics . . . It is hoped that the following article . . . published to remedy this lack of knowledge . . . will lead to a better understanding of this cooling method with regard to: operational principles . . . equipment . . . installation . . . area considerations, etc.

Finally, refrigeration systems of many types, ranging from small packaged installations to large central station assemblies, are utilized at a steadily increasing rate.

The choice of the proper type of air conditioning or cooling system to be used in any theatre is dependent upon many factors. The results desired, the size of the house to be cooled, the amount of capital investment and operating expense commensurate with net earnings, and the locality of the theatre itself all have a direct bearing on the question. It is not the purpose of this article to promote any one type of system about

FIGURE l-How dry-bulb temperature is reduced while wet-bulb remains static in evaporative method.

others, but merely to describe in a factual manner the methods of operations and results to be expected from one particular type of system-evaporative cooling.


Evaporative cooling is that type of temperature reduction made possible through the evaporation of water when exposed to air. The rate of such evaporation depends upon the comparative dryness of the air, the amount of air motion, and other factors. The evaporative cooling system takes advantage of these basic physical principles and adapts them to its cooling cycle, accomplishing in turn a temperature reduction which is both actual and effective. It does not, in this process, remove heat in an engineering sense, although it does reduce the temperature.

Theory of Cooling Cycle

It is most interesting to examine the evaporative cooling cycle and see how it actually works. After all, it is the same cycle which the human body uses to keep cool (at least in part) on a hot day and has been employed in literally thousands of variations ever since man became a conscious individual. The actual physical principles involved in its operation are not overly complex, and, Without getting too technical, we can easily see what takes place.

As is generally known, matter exists in three statesesolid, liquid, and gas. Whenever any material changes from one of these states to the other a heat transfer is necessary. Such absorption or usage of heat is necessary to that change of state; the change cannot take place without it.

When a pound of water changes from liquid to a gas at ordinary temperatures, approximately 1,100 b.t.u. are required to make the change. This heat is obtained from the water itself, from the air which is absorbing the gaseous water, or from a heating medium, such as the fire under an ordinary coffee pot. However, for every condition of air, there exists what is known as a wet-bulb temperature, below which the water in contact with that air can never fall in temperature unless through some outside cooling medium. In evaporating, therefore, the necessary heat to make that evaporation possible cannot come from the water, but must come from the air into which that moisture is passing.

Illustrative Example

An excellent conception of the aforementioned process in operation is portrayed by Fig. 1. Here, air at a temperature of 900 dry bulb and '700 wet bulb is admitted into an evaporative system.

1950-51 Theatre Catalog, 9th Edition, Page 368