Heating surface

“ To utilize advantageously the heat thus generated, a large heating surface must be provided and this can only be obtained by passing the products of combustion through a great number of tubes of small diameter. ”

“ Water-ways thin enough to heat water rapidly. Quality and position of heating surface must not allow for waste of heat. 65% of heating surface should be in direct contact with heat, 35% in flue surface. Response to your dampers will show you if you have 65% of your heating surface in direct contact with flame! Go and see the best hot water boiler in your vicinity—before you buy consult your engineer and ask about others. ”

“ Having selected the system of heating to be employed according to the needs of the building in hand, and having proportioned the radiator surface according to the requirements of the various rooms, it then remains to lay out the system of piping and arrange the various details of construction. ”

“ Amongst the essentials are a receptacle capable of containing the water and the steam produced by its evaporation, and strong enough continuously to withstand with safety the highest pressure of steam for which the boiler is intended. Another essential is a furnace for burning the fuel, and a further one is the provision of a sufficiency of heating surface for the transmission of the heat produced by the combustion of the fuel to the water which is required to be evaporated. ”

“ In buildings of the second class, such as residences, office buildings and hotels, we have been, as a rule, satisfied with sufficient heat, and have relied upon such ventilation as is secured by the natural circulation methods. In such buildings, therefore, the system of heating most used is that known as "direct radiation," in which radiators, or some form of radiating surface, are located in each room, and connected by an arrangement of piping to a central source of steam or hot-water supply. ”

“ We can best realise what this statement implies by finding the amount of coal which would produce the same quantity of heat. It can be shown that the heat given out by each square foot of the solar surface in one minute will be equivalent to that produced in the combustion of forty-six pounds of coal. If the sun’s heat were sustained by combustion, every part of the sun’s surface as large as the grate of an ordinary furnace would have to be doing at least one hundred times as much heating as the most vigorous stoking could extract from any actual furnace. ”

“ In proportioning heating surfaces and gas passages for waste heat work there are so many factors bearing directly on what constitutes the proper installation that it is impossible to set any fixed rules. Each individual installation must be considered by itself as well as the particular characteristics of the gases available, such as their temperature and volume, and the presence of dust or tar-like substances, and all must be given the proper weight in the determination of the design of the heating surfaces and gas passages for the specific set of conditions. ”

“ He first calculates the amount of heat lost from the room in question and then the amount of radiating surface necessary to offset this heat, using coefficients for heat transmission which he substitutes in his formula. According to Prof. Carpenter's method, the heat in British thermal units lost from a room for every degree difference in temperature between the inside and outside air is , in which , , and represent the quantities previously assigned them, and is the number of times the air of the room is to be changed per hour. ”

“ With low temperature gases, to obtain a heat transfer rate at all comparable with that found in ordinary boiler practice, the lack of temperature must be offset by an added velocity of the gases in their passage over the heating surfaces. ”

“ The heating is a single-pipe steam system, the heat generated by a boiler in each building. The principal rooms are heated by radiators, with heating risers used elsewhere. The hardware and lighting fixtures are simple and substantial. ”

“ This comprises about the whole system of arrangements in the construction for warming the house with heat radiated from the floors and interior walls.
Its mode of operation simply consists in the body of warmed air passing from the heating-chamber upward, through the walls and under the floors, and in its passage giving up its surplus heat to the surfaces of these flues. As the air becomes reduced in temperature, it naturally descends through the pipe and trunk passage-ways provided for its return to the heating-chamber, where it is again recharged with heat. ”

“ There are a number of methods available for adoption in the heating of buildings, but it is a matter of considerable difficulty to suit the method of warming to the class of building to be warmed. Heating may be effected by one of the following systems, or installations may be so arranged as to combine the advantages of more than one method: open fires, closed stoves, hot-air apparatus, hot water circulating in pipes at low or at high pressure, or steam at high or low pressure. ”

“ As long as the temperature at the heated side of the furnace wall is kept constant, the temperature gradient and the rate of heat conduction also remain constant. Increasing the thickness of the wall lengthens the path through which the heat must travel, decreasing the temperature gradient and the rate at which heat appears at the outside surface. Raising the temperature in the furnace increases the temperature gradient and the rate of heat conduction, much as raising the inlet pressure increased the rate of flow of water in the pipe. ”

“ In the case of houses heated by furnaces, some moisture is furnished by the water-pans of the furnace; but in the case of heating by hot air and steam pipes, there is less circulation of air, the air is very much drier, and generally of a very much higher temperature. ”

“ Conduction of heat is a commonplace occurrence in our daily lives, in industrial processes, and in nature. If a metal spoon is dipped in a cup of hot coffee, the spoon handle soon becomes warm and then hot—some of the heat in the coffee is conducted along the spoon. Heat from a burner on a stove is conducted through the bottom of utensils to cook food. In a steam engine or hot-water heating system, heat from burning fuel is transferred by conduction through the iron or steel of the boiler to heat water. ”

“ Must be heated, where artificial heating is necessary to prevent freezing, by steam or hot-water systems, the heater to be located in a separate building, and no open flames to be permitted within generator enclosures. ”

“ For large public buildings, factories, &c., heating by steam is generally adopted on account of the rapidity with which heat is available, and the great distance from the boiler at which warming is effected. ”

“ As soon as the bricks have become red hot, the current is diverted to an adjacent chamber or pair of chambers, and the acquired heat is removed by a current of cool gas or air passing towards the furnace, where it arrives at a temperature sufficiently high to ensure the greatest possible heating effect in combustion. ”

“ The heat conductivity of fluids, liquids and gases is very low, practically zero, but heat is transferred in them by convection. The particles in direct contact with the source of heat are heated above the temperature of the rest, and an increase in temperature of any liquid or gas invariably decreases its specific gravity and causes an upward current of the hot particles, which brings the colder particles in turn in contact with the hot body, thus maintaining a circulation which tends to raise the temperature of the entire mass. ”

“ Buildings of all kinds had from the earliest days been heated by open fireplaces, in which logs, and later coal, were burned in considerable quantities, while the larger proportion of the heat escaped up the flue. ”

“ How Food Is Heated
Heat is a form of energy which flows from hot to cold substances. This flow occurs by convection, conduction, and radiation. In a pressure canner, convection and conduction are the primary methods of heat transfer.
Convection heating occurs in thin liquids and in gases like air and steam. As molecules are heated, they become lighter and rise to the top of the jar, displacing cooler ones toward the bottom. This movement is visible in water that is being heated in a clear glass container. Convection heating occurs best in liquids like fruit and vegetable juices or broths. ”

“ A Lesson from the Coal-Pits.
We require in our houses an artificial temperate climate which shall be uniform throughout, and at the same time we need a gentle movement of air that shall supply the requirements of respiration without any gusts, or draughts, or alternations of temperature. Everybody will admit that these are fundamental desiderata, but whoever does so becomes thereby a denouncer of open-grate fireplaces, and of every system of heating which is dependent on any kind of342 stoves with fuel burning in the rooms that are to be inhabited. ”

“ The object of all heating apparatus is the transference of heat from the fire to the various parts of the building it is intended to warm, and this transfer may be effected by radiation, by conduction or by convection. An open fire acts by radiation; it warms the air in a room by first warming the walls, floor, ceiling and articles in the room, and these in turn warm the air. Therefore in a room with an open fire the air is, as a rule, less heated than the walls. ”

“ Now, we may suppose that its descent is accomplished in two stages; that, first of all, it falls upon a platform from the height of 424 metres, and gets heated in consequence, and that then the heated mass is allowed to fall other 424 metres. It is clear that the water will now be doubly heated; or, in other words, the heating effect in such a case will be proportional to the height through which the body falls—that is to say, it will be proportional to the actual energy which the body possesses before the blow has changed this into heat. ”

“ Why would you apply the heat at the top, in this experiment?
Because in heating water it expands and rises. The boiling of water is caused by the heated water ascending from the bottom, and the colder water descending to occupy its place. If the heat were not applied at the top, it would be distributed quickly by convection, but not by conduction. ”

“ Charles Hood, the English authority, states that one square foot of glass will cool 1.279 cubic feet of air one degree per minute per degree difference in temperature. This is equivalent to a coefficient of heat transmission of about 1.40 British thermal units per hour. ”

“ Hot-air Warming.—In small houses the warming of the various rooms and halls can be accomplished by placing the stove or furnace in the cellar, heating a large quantity of air and conveying it through proper tubes to the rooms and places to be warmed. ”

“ Molecular structure affects temperature change Heat measurement units, as we have seen, are defined in terms of a temperature change brought about by heating. But the same amount of heat applied to different materials does not necessarily bring about the same temperature change—it is well known that some materials can be heated or cooled more quickly than others. ”

“ It is true that a house of a given size cannot as soon be brought to the required temperature after the fire is first lighted, as by other modes of heating, but when once in full operation greater regularity is maintained, and if the fire should by any neglect go out, heat is still radiated, often for several hours, before the pipes become entirely cold. ”

“ From light we pass to its twin phase of energy, heat, for a glance at the forms of devices which enable us to use heat with economy. When we wish a furnace, crucible, or cooking vessel to maintain the highest possible temperature, we give it as little surface as possible. On the contrary when a warming apparatus is devised, its surface is freely extended. The traditional fireplace, for all its cheerfulness, yields but little heat. ”

“ Hot air stoves have been so generally condemned and discarded as a means of heating glass structures, that we shall not discuss their faults or merits, but confine ourselves to heating by flues, steam, and hot water in pipes and tanks. ”

“ Heated air, heated water and steam were all in turn experimented with as a means of distributing heat, and systems employing them have been rapidly and scientifically evolved to meet various requirements, and are to this day very widely used. ”

“ Heating Unit. The heating unit of a hot-water system is like any stove consisting of a fire pot and grate. Some are adjustable so that different kinds of fuel may be [66] used. A gas burner is sometimes placed in the fire pot and used for heating a furnace, but this is one of the most wasteful ways of using gas. A real gas furnace is much more economical. The fire and heat from the fire circulate around the coils containing the water. If the coils are not constantly kept full of water, they will be injured by the heat. ”

“ With these the heating is accomplished entirely by convection, while with direct radiators the radiant heat rarely amounts to 40 per cent., generally not over 30, and often in practice considerably less. For a radiator in any particular location the radiant heat is constant for the same conditions of temperature of the radiator and surrounding objects, and is independent of currents of air. ”

“ Thus you see, taking the air at 10° and heating up to 70°, the ordinary temperature of our rooms, requires about nine times the moisture contained in the original external atmosphere, and if heated to 100°, as most of our hot-air furnaces heat the air, it would require about twenty-three times the amount in the external atmosphere. ”

“ Let us suppose now that, instead of heating one degree the air subjected to a constant pressure and able to dilate freely, we inclose it within an invariable space, and that in this condition we cause it to rise one degree in temperature. The air thus heated one degree will differ from the air compressed only by its greater volume. So then the quantity of heat that the air would set free by a reduction of volume of is equal to that which would be required to raise it one degree Centigrade under constant volume. ”