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It would then have been necessary to admit into and withdraw from the room erery hour the enormous amount of
-= 2,703,000 cubic feet of air, or 751 cubic feet a second, which corresponds to a complete renewal of the air of the room effected
= 13.52 times an hour.
By means of chimneys extending to the roof, a velocity of discharge equal to at least 7 feet a second could have been obtained, and their sectional area and that of the openings into them would have to be 114 square feet. Supposing five of the latter to be placed in the ceiling, each would require to be 23 square feet in area.
However great the amount of air to be removed and the areas of flues may seem, there need be no serious difficulty in obtaining them.
115. Throne-room. This room has the following dimensions: length, 94 feet; breadth, 36 feet; height, 26 feet; cubical capacity, 88,000 cubic feet; floor-surface, 3,380 square feet. It accommodates 95 guests at a table 77 feet long by 13 feet wide, having, therefore, a circumference of 180 feet, which gives each guest but 1.9 feet of space.
The number of servants is about 25. There are then 120 persons in the room. The cubical space to each person is
-= 733 cubic feet.
= The floor-surface to each person is
100 = 28 square feet. Under these circumstances, it is lighted up by12 chandeliers of 96 candles....
.................. 1,152 4 candelabra of 25 candles .....
100 On the table.........
......... or, 17 candles to a guest.
Allowing, as before, that a candle gives out 476 units of heat an hour, the same as a person, the total number of units of heat given out an hour would be
(120+1622) x 476 = 829, 192 units. Supposing that the air bad been introduced at a height of 20 feet, and at a temperature of 590, and that this air, after having become heated to 950, had escaped through openings in the ceiling, every cubic foot of air introduced would have carried away, as in the preceding case, .6536
It would then be necessary to admit into, and discharge from, the room every hour the amount of
.0536 =1,268,000 cubic feet, or 352 cubic feet a second, which corresponds to a complete renewal of the air of the room effected 14.27 times an hour. If the velocity of discharge reaches 64 feet a second, the total sectional area of the openings should be 54 square feet.
The amount, 1,268,000 cubic feet, is about that which can easily be withdrawn from the lecture-rooms of the Conservatory, and introduced there at a mean height of less than 20 feet without inconvenience to, the audience.
116. Dining-room.—This room has the following dimensions : length, 49 feet; breadth, 23 feet; height, 25 feet; cubical capacity, 28,000 cubic feet; floor-surface, 1,120 square feet.
It accommodates 54 guests at a table 42 feet long by 10 feet wide, hav. ing therefore a circumference of 104 feet, and giving to each guest but 2 feet of table-space.
The number of servants is about 14. There are then 68 persons in the room. The cubical space for each person is
=410 cubic feet. The floor-surface to each person is
68 =16 square feet. It is lit up by1 chandelier ...
60 candles, 14 chandeliers of 20 candles each..
280 candles, Portable candelabras..............
170 candles, Total ........
........ 510 candles, or 9.44 candles to a guest.
Admitting the same bases of calculation as before, the total number of units of heat developed in an hour by the people and the candles will be
(68+510) x 476=275,128 units, and the amount of air to be admitted and withdrawn every hour would be
=421,000 cubic feet, or 117 cubic feet a second, which corresponds to a complete renewal of the air of the room effected 15.23 times an hour.
The amount, 421,000 cubic feet, is less than that which is constantly admitted into and withdrawn from the small lecture-room at the Conservatory.
Under the arrangements at present in use, it is not uncommon to find at the close of a ineal a temperature of 860 without any change of air,
which is very unpleasant, and the supposition that it will be 950 near the ceiling is probably below the truth.
The three preceding examples present extreme difficulties ; and it is besides evident that if the proportions referred to be adopted, it would be necessary to reserve means of regulating and of moderating, according to circunstances, the amounts of air to be adınitted and carried off. For the winter season, the latter should be taken from places near the rooms where a suitable temperature can be maintained.
117. What has already been said in regard to dining-rooms applies equally to large reception-rooms, where many lights serve to a great extent to heat and vitiate the air.
There, as in evening drawing-schools, it will not be sufficient merely to produce a change of air proportioned to the number of persons present; it is necessary at the same time to carry off the hot gases of com. bustion through the ceiling under the influence of the draught which they produce, and to establish at the same time if possible an outward draught near the floor, which will draw to it a part of the fresh air. The fresh air should be introduced at a considerable height, and as far as possible from the people in the room.
In such cases, it will be advisable to secure the complete renewal of the air six or eight times an hour.
Observations made at the school in the Rue des Petits-Hôtels having shown that, with an external temperature of 500 and an internal temperature of 799, there will be produced from free openings, disconnected from any chimney, a velocity of about 3 feet a second, the surfaces of the openings to be made above may be calculated by assuming that 75 per cent. of the amount of air to be removed escapes through these openings; and that the balance, or 25 per cent., will be drawn off at the bottom, with a velocity also equal to at least 3 feet a second.
118. Application to the Hall of Marshals in the Tuileries.—This reception-room is 63 feet long, 53 feet wide, having therefore 3,340 square feet of floor-surface, and 48 feet in mean height, the cubic content being about 160,000 cubic feet. It accommodates at most six hundred people at balls, or about one person to every 5 square feet.
It is lit up on reception-days b y 548 candles and by 166 lamps, (equivalent to 498 candles,) which would develop together about 500,000 units of heat an bour.* The illumination corresponds then to
600 =1.74 candles to an individual. If it is desired that the air be renewed in this hall six times, it will be necessary to admit and discharge
6 x 160,000 = 960,000 cubic feet an hour,
* Études sur la ventilation, 2° vol., pp. 301-302.
of which .75X 960,000 = 720,000 cubic feet an hour, or 200 cubic feet a second, will be carried off at the ceiling, and .25 x 960,000 = 240,000 cubic feet an hour, or 67 cubic feet a second, by the openings near the floor. As the velocity of discharge near the ceiling may be as high as 3 feet a second, the openings to be made there-as far as possible directly above the main chandelier-should have
= 67 square feet of clear passageway, deduction being made for solid parts; and the velocity of draught near the floor being also 3 feet a second, the corresponding openings should bave a clear area of
= 22 square feet. The grating in use bas an area of but 116 square feet of total surface, including solid portions, and scarcely presents 43 square feet of clear passage.
Above the openings in the ceiling should be placed external ventilators, having together the same clear area, which will increase the velocity of discharge.
In regard to the ventilating openings at the floor-level, they may easily be made around the contour of the rooms under the steps on which the seats are placed; and their pipes should be carried in the piers of the vaults of the lower vestibule to the cellar, where they should join the collecting passages terminating in a general ventilating-chimney, at the bottom of which a coal fire or a namber of gas-burners should be kept burning.
The dimensions of these pipes should be calculated by the general rules previously given. If there are serious difficulties in the way of producing this down-draught, an up-draught may be used, produced by the aid of gas-burners placed in vertical flues made in the thickness of the walls.
119. Introduction of air.-But it is not sufficient merely to secure the discharge of the foul air; it is necessary to provide for the admission of an equal amount of fresh air at a proper temperature.
This air, which in winter should be warmed to a temperature of about 68°, may be admitted through au interjoist in the balcony, which is 20 feet above the floor. It should flow horizontally below the chandeliers, above and away from the occupants, and its horizontal velocity of admission may, without inconvenieuce, be 3 feet a second. Its volume being 954,000 cubic feet an hour, or 265 cubic feet a second, the total sectional area of the interjoist and of the conducting passages should be 81 square feet.
The length around the inner edge of the balcony being about 200 feet, it will suffice to give the openings
but on account of the ornaments which break up the passage it will be necessary to make them 10 inches either in height or in developed profile.
These arrangements will insure the renewal of 954,000 cubic feet of air an hour, or 1,590 cubic feet to each person, if there are 600 present, sufficient in all seasons to secure the healthful condition of the room and to moderate its temperature; but it is not necessary that they be isolated and confined to one of the reception rooms of the palace. It will be equally necessary to adopt similar arrangements for the two adjoining rooms, which often coutain many persons, and also for the large gallery, frequently used as a ball room. It may not be uunecessary to add that for evening parties the two large fire places which are in the grand gallery may, by means of gas-burners placed within them, serve as ventilating-chimneys; and if there is any difficulty in cutting in the side-walls descending flues leading to the basement, ascending flues may be made, separate, or communicating with a single ventilator placed in the roof over each room.
The fresh air should enter above the cornice, and in a borizontal direction.
Each of the principal saloons in the palace should thus have its own ventilators provided with regulating-valves; they should be independent of the others, and this will prevent the unpleasant currents which would otherwise arise as the guests take their departure.
HALLS OF ASSEMBLY AND LECTURE-ROOMS.
120. These places of temporary resort, where there is often more than one person to every square foot of floor-surface, should be ventilated at the rate of 1,000 cubic feet of air an hour to each person.
The arrangements which I have adopted for the maiu lecture-ball of the Conservatory of Arts and Trades, and of which the satisfactory results have been seen every day for five years, appear to me worthy of imitation.
The foul air is drawn off through openings in the risers behind the feet of the auditors, and their total clear area for the passage of the air -deduction being made for the solid portions of tbe grating, if there are any-should be calculated so that the air will only attain a velocity of 28 or 30 inches a second. This surface also should be distributed as uniformly as possible among the steps.
The basement under the lecture-room, kept as clear as possible, should communicate with a ventilating-gallery, placed underground or at the ground-floor level if possible, the sectional area of wbich should be calculated so that the velocity of the air shall not be greater than 4 feet a second.
This gallery should terminate in a ventilating-chimney, the mean sec. tion of which should be determined on the condition that the velocity of the air shall reach 5 or 7 feet a second in order to secure the permanence of the current.