Document yrrGkDN3mgRYq0pNE6Jy7N6V6

American Society of Heating and Ventilating Engineers Guide, 1934 any type of thermometer not affected by the water vapor content or relative humidity of the air. Dry Return; A return pipe in a steam heating system which carries both water of condensation and air. See wet return. Dust: Solid material in a finely divided state, the particles of which are large and heavy enough to fall with increasing velocity, due to gravity in still air. For instance, particles of fine sand or grit, the average diameter of which is approximately 0.01 centimeter, such as are blown on a windy day, may be called dust. Dynamic Head or Pressure: The total or impact pressure. This is the sum of the radial pressure and the velocity pressure at the point of measurement. Effective Temperature: An arbitrary index of the degree of warmth or cold felt by the human body in response to temperature, humidity, and movement of the air. Effective temperature is a composite index which combines the readings of temperature, humidity, and air motion into a single value. The numerical value of the effective temperature scale has been fixed by the temperature of saturated air which induces an identical sensation of warmth. Equivalent Evaporation: The amount of water a boiler would evaporate, in pounds per hour, if it received feed water at 212 F and vaporized it at the same temperature and atmospheric pressure. Estimated Design Load: The load, stated in Btu per hour or equiv alent direct radiation, as estimated by the purchaser for the conditions of inside and outside temperature for which the amount of installed radiation was determined. It is the sum of the heat emission of the radiation to be actually installed plus the allowance for the heat loss of the connecting piping plus the heat requirement for any apparatus requiring heat con nected with the system. (A.S.H.V.E. Standard Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers--edition of April 1932). Estimated Maximum Load: Construed to mean the load stated in Btu per hour or equivalent direct radiation that has been estimated by the purchaser to be the greatest or maximum load that the boiler will be called upon to. carry. (A.S.H.V.E. Standard Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers--edition of April 1932). Extended Heating Surface: See heating surface. Extended.Surface Heating Unit: A heating unit having a relatively large amount Of extended surface which may be integral with the core containing the heating medium or assembled over such a core, making good thermal contact by pressure or by being soldered to the core or by both pressure and soldering. (An extended surface heating unit is usually placed within an enclosure and therefore functions as a convector). Fan Furnace-System: See warm air heating system. Force: The action on a body which tends to Change its relative conWV d.iti.on.as to rest or motion. F = --gt--. Fumes: Particles of solid matter resulting from such chemical pro cesses as combustion, explosion, and distillation, ranging from 0.1 to 1.0 micron in size. 590 Chapter 42--Heating and Ventilating Standard Terms Furnace: That part of a boiler or warm air heating plant in which combustion takes place. Also, a fire-pot. Furnace Volume (Total): The total furnace volume for horizontal return-tubular boilers and water-tube boilers is the cubical contents of the furnace between, the grate and the first plane of entry into or between tubes. It therefore includes the volume behind the bridge wall as in ordinary horizontal return-tubular boiler settings, unless manifestly in effective (i.e., no gas flow taking place through it), as in the case of wasteheat boilers with auxiliary coal furnaces, where one part of the furnace is out of action when the other is being used. For Scotch or other internally fired boilers it is the cubical contents of the furnace, flues and combustion chamber, up to the plane of first entry into the tubes. (A.S.M.E. Power Test Codes, Series 1929). Grate Area: The area of the grate surface, measured in square feet, to be used in estimating the rate of burning fuel. This area is construed to mean the area measured in the plane of the top surface of the grate, except that with special furnaces, such as those having magazine feed, or special shapes, the grate area shall be the mean area of the active part of the fuel bed taken perpendicular to the path of the gases through it. For furnaces having a secondary grate, such as those in double-grate down-draft boilers, the effective area shall be taken as the area of the upper grate plus one-eighth of the area of the lower grate, both areas being estimated as defined above. (A.S.H.V.E. Standard and Short Form Heat Balance Codes for Testing Low-Pressure Steam Heating Solid Fuel Boilers). Gravity Warm Air Heating System: See warm air heating system. Grille: A perforated covering for an air inlet or outlet usually made of wire screen, pressed steel, cast-iron or plaster. (Grilles may be plain or ornamental). Heat: A form of energy generated by the transformation of some other form of energy, as by combustion, chemical action, or friction. [Accord ing to the molecular theory, heat consists of the kinetic and potential energy of the. molecules of a substance. The addition of heat energy to"a body increases the temperature or the kinetic energy of motion of its' molecules (sensible heat) or increases their potential energy of position but does not increase the temperature, as when melting or boiling occurs (latent heal).] Heat Capacity: The amount of heat (Btu or calories) required to raise the temperature of a body (of any mass and variety of parts) one degree (Fahrenheit or centigrade). This will depend on the masses and specific heats of the various parts of the body. Therefore 5 = m, Ji + mj where + m, j,.. . . etc. 5 is the heat capacity and mi, mi, m>, and s, si, St stand for the masses and cor responding specific heats of the parts, respectively. Heating Medium: A substance such as water, steam, air, electricity 591 1