VENTILATING FLUE allowed to escape, and the thorough mixing of the pure incoming air with the air already in the room. If any one doubts the correctness of the action of air as herein described, let him fill the incoming flue with smoke that can be readily seen, and watch its course as it enters, flows upward and outward, and see where the great mass of it goes. The dotted lines on these sketches indicate the breathing point of a person sitting. It may be well to explain that in these experiments that I have made, the outlets have been at least twice as large as the inlets, and that there has always been heat in the outgoing flues to produce a strong up-current, as I believe this to be the only sure way to produce a constant outward flow of air. In Fig. 4, the flues have been placed on about the same level, Fie 4 but with no better results. In Fig. 5, the outgoing flue has been placed at the floor with the results shown in the sketch. In Fig. 6, both flues are at the floor-level with better results than have yet been obtained, but still far from satisfactory. I have thus tried to show the general action of incoming and outgoing currents of air by the placing of the introduction-flues on the outer walls, and the outlets on the inner. The second method in general use is the placing of the coilboxes upon the inner wall, and the removal of the foul air at the opposite or outer side of the rooms. I consider the placing of the coil-boxes on the inner wall a great improvement on the other method, as by this plan they are centralized, extensive piping is saved, and the danger of freezing obviated. The placing of the exhaust-flues on the opposite side of the room I believe to be open to the same objections that I have described in the first method. The action of the hot air from the points where it is introduced towards the various outlets is the same as in the sketches already shown, and will be readily understood by the reader. In the Bridgeport school the coil-boxes for the heating of the various rooms have all been placed in the main ventilating shafts in the centre of the building, and the air conveyed from them through these shafts to the rooms by means of metal tubes. The air enters the inner corner of the room about eight feet from the floor, the corner being clipped so as to form a flat surface for the register opening; underneath the register the space is utilized for a closet for the use of the teacher. The outgoing flue has been placed directly under the platform, which is located in the same corner as the introduction Aue. This platform is 6 X 12 feet, and is supplied with castors, so that it can be moved at any time it is necessary to clean under it. Its entire lower edge is kept about 4 inches from the floor to give a full circulation of air under it at all points. The action of the incoming air is rapidly upward and outward, stratifying as it goes toward the cooler outer walls, thence flowing down their surfaces to the floor, and back across the floor to the outgoing register on the inner corner of the room. By this method, all the air entering is made to traverse with a circular motion (see Fig. 7) the entire room, before it reaches the exhaust-shaft, and there is a constant movement and mixing of the air, in all parts of the room, continually going on. All the heat entering is utilized, and I believe that if the supply- and exhaust-flues are properly balanced as to size, there can be but a very small loss of heat. The inlets are all intended to be large, and the flow of air through them moderate and steady. The air is not intended to be heated to a very high temperature: the large quantity introduced is expected to keep the thermometer at about 68° at the breathing-level. The school-rooms contain on an average about 13,000 feet of air, or 260 cubic feet per pupil. It is proposed to supply each pupil with 30 cubic feet of air each minute, or 1,800 cubic feet per hour. Allowing fifty pupils to each room, this will necessitate the introduction of 90,000 cubic feet of air into the room each hour, and will change the air of the room 6.92 times within the hour, or once in about eight minutes. These calculations are based on a difference of 30° in temperature. In the exhaust flues there are placed coils to produce a strong up current at all times; heat is also obtained from radiation from the introduction and boiler-flues, which run through the foul-air shafts. Trouble has always been found in regulating the supply of warmed air obtained by the indirect system, owing to the inability to control the heating surfaces. The usual way of constructing the apparatus has been to place in the coil-boxes sufficient steam-pipe to heat the room in the coldest weather. The VENTILATING FLUE pure, cold air passing over the pipes becomes heated to the desired temperature, and is then carried to the rooms; this answers very well during the coldest weather, but as the weather moderates and less heat is required, the only way to regulate it has Ric 7 been to close the registers. This not only lowers the temperature of the room, but shuts off the supply of pure air entering. This fault has been remedied in the Bridgeport school-house as follows: The heating surface for each room is enclosed in separate cases or jackets (see Fig. 8) of metal, and are then subdivided into five sections, so arranged that any number of sections, or the whole, may be used at pleasure, that is to say, that any one, two, or three parts may be used at discretion. In extreme cold weather the whole five sections are in use; in moderate weather, two or three; and when a small amount of heat is required, only one. By this plan the supply of pure air remains always the same, but the degree to which it is heated is changed by the opening or closing of a valve. (See sketch.) The above method of regulating the temperature of a room or a building, when warmed by steam, is at once simple and effective, and does away with many reasons against its use, for in practice it has been found almost impossible to adapt the system to the varied conditions of our climate. We often have a difference of twenty to thirty degrees of temperature in twenty-four hours, and with a single coil of steam-pipes it is not practicable |