- Kitchen fire.
- Chimney.
- Hot air Chamber. This is a cast-iron box, which forms the back of the kitchen grate.
- Cold air pipe, or passage; made with brick, or stone, or iron piping, communicating with the open air for the purpose of feeding the hot air chamber with an ascending current of fresh air.
- Hot air pipe, receives the ascending current of air, which becomes heated by passing over the back of the fire. At the top this pipe branches off at right angles, and terminates near the floor in the two sleeping rooms above.
- Gratings to admit the warm air from the hot-air pipe into the bed-rooms. The addition of sliding valves over the face of the gratings would serve to cut off the current of warm air during the summer, and when not otherwise required.
- Sitting-room, into which sufficient heat is radiated from the hot air chamber, not only to warm the apartment, but even to dry wet linen.
By means of one common fire in a stove of the above description, a four-roomed cottage can be comfortably warmed, and kept dry throughout.
Warming Buildings by Steam.
The arrangements for warming rooms and buildings by steam are very different from those in which stoves are employed. They are generally such as the following. At a convenient part of the building, and as low as possible, there is placed a close steam-boiler of the ordinary construction. From this boiler a small steam-pipe is carried to the parts of the building which are to be warmed; the pipe being wrapped round with a thick layer of flannel, to prevent the heat from radiating before it arrives at the destined place. Pipes of a larger size are laid round the rooms above the floor, or under a perforated floor, or in any other convenient position. The steam issues into these larger pipes, from the surface of which heat radiates into the room, and thus the steam is condensed into water. Small pipes of lead or tin are provided for convoying the water back into the boiler, a gentle slope being given to all the pipes to facilitate this object. This water, again flowing into the boiler, is again converted into steam, again ascends to the pipes which surround the apartment, again gives out heat to the air of those apartments, and again flows back to the boiler in the form of water. Thus the same supply of water circulates over and over again through the pipes, carrying heat from the fire below to the rooms above. In some cases the steam-pipes in the apartments, instead of being laid round the sides, are grouped together in a compact form, and have an ornamental character imparted to them.
Instead of pipes, the steam is sometimes made to circulate between parallel sheets of copper or iron, in such manner that every sheet of metal shall have steam on one side of it, and air on the other, the air in that position receiving heat from the steam through the metal.
Warming Buildings by Hot Water.
Lastly we have to notice the method of warming by hot water. In this method there is usually a boiler communicating by an upper and lower pipe, with an upright pipe the same height as the boiler. On the application of heat to the boiler, the column of water becomes lighter than that in the upright pipe; therefore the pressure on the water in the lower pipe being less at the end nearest to the boiler than it is at the other end, a portion of the water in this lower pipe moves forward towards the boiler, which causes a corresponding quantity to pass along the upper pipe in a contrary direction. This motion will necessarily continue as long as the column of water in the boiler is hotter, and therefore lighter than that in the upright pipe; and this must be the case so long as the boiler continues to receive heat from the fire, and the pipes to part with their heat to the air, and thereby cool the water contained in them. In whatever form the hot water apparatus is constructed, this difference of pressure of the two columns of water is the cause of the circulation.
In this form of apparatus some part or other of the water is open to the atmosphere, either at the top of the boiler or at the top of one of the pipes, so that there is no danger from the bursting action of water heated above the boiling temperature. But, on the other hand, the water cannot well be conveyed to rooms at different elevations in the building. To increase the efficacy of the arrangement in this respect, the following adaptation has been suggested. A pipe is made to dip into an open boiler, reaching only an inch or two below the surface of the water, and passing round the room to be warmed, returns again to the boiler and dips again into the water, descending quite to the bottom of the boiler. An air-pump is connected with this pipe by a small tube; and the air in the pipe being exhausted by this means, the water rises into the pipes above the level of the boiler by atmospheric pressure, and the circulation then takes place by the hot water ascending through the pipe at the top of the boiler, and passing through the whole circuit of the pipe, it returns through the upper end of the pipe which reaches to the bottom of the boiler.
In the last-described form of apparatus the water will rise in the syphon pipe to a height of about thirty feet above the boiler, being that elevation which is due to the action of the atmosphere on liquid flowing through a vacuum. But when a whole house or building is warmed by hot water in all the different floors or heights, a modification of the system, called the high-pressure system, is adopted.
The apparatus on this system consists of a spiral coil of small iron pipe built into a furnace, the pipe being carried from the upper part of the coil, and entwined round the room intended to be warmed, forming a continuous pipe when again joined to the bottom of the coil. The size of the pipe is usually only half an inch in diameter internally, and an inch externally. A large pipe of about two and a half inches diameter is connected, either horizontally or vertically, with the small pipe, and is placed at the highest point of the apparatus. This, which is called the “expansion pipe,” has an opening near its lower extremity, by which the apparatus is filled with water, the aperture being afterwards secured by a strong screw; but the expansion pipe itself cannot be filled higher than this opening. After the water has been introduced, the screw is securely fastened, and the apparatus becomes completely closed in all parts. The expansion pipe, which is thus left empty, is calculated to hold about one-tenth or one-twelfth as much water as the whole of the small pipes; this being necessary in order to allow for the expansion that takes place in the volume of the water when heated, and which otherwise would inevitably burst the pipes, however strong they might be.