Document Lp5y2VN6aGZZDp011vobRQM9w

American Society of Heating and Ventilating Engineers Guide, 1937 Chapter 44--Terminology Air Infiltration: The inleakage of air through cracks and crevices and through doors, windows and other openings, caused by wind pressure or temperature difference. Air Inlet and Air Outlet: Used to designate that point or location in an air handling device or system where air enters or leaves. These terms are misleading and meaningless standing by themselves; must be accompanied by other words to designate location, space, or device which 1the air is entering or leaving. Thus, air inlet to a room may be opening in end of a duct leading from the air outlet of a fan. Air Washer: An enclosure in which air is forced through a spray of water in order to cleanse, humidify, or dehumidify the air. Anemometer: An instrument for measuring the velocity of moving air. Atmospheric Pressure: The pressure exerted by the atmosphere in all directions, as indicated by a barometer. Standard atmospheric pressure is considered to be 14.7 lb per square inch, which is equivalent to 29.92 in. of mercury. Baffle: A plate or wall for deflecting gases or fluids. I Blast: This word was formerly used to denote forced air circulation, particularly in connection with central fan systems using steam or hot water as the heating medium. As applied in this sense, the word blast is now obsolete. Boiler: A closed vessel in which steam is generated or in which wateris heated. Boiler Heating Surface: That portion of the surface of the heattransfer apparatus in contact with the fluid being heated on one side and the gas or refractory being cooled on the other, in which the fluid being heated forms part of the circulating system; this surface shall be measured on the side receiving heat. This includes the boiler, water walls, water screens, and water floor. (A.S.M.E. Power Test Codes, Series 1929.) Boiler Horsepower: The equivalent evaporation of 34.5 lb of water per hour from and at 212 F. This is equal to a heat output of 970.2 X 34.5 = 33,471.9 Btu per hour. British Thermal Unit: The mean British thermal unit is-7577 of the loU heat required to raise the temperature of 1 lb of water from 32 F to 212 F. It is substantially equal to the quantity of heat required to raise 1 lb of water from 63 F to 64 F. One Btu = r-h kwhr. 3415 By-pass: A pipe or duct, usually controlled by valve or damper, for short-circuiting fluid flow. Calorie: The mean calorie is of the heat required to raise the temperature of 1 gram of water from Zero C to 100 C. It is substantially equal to the quantity of heat required to raise one gram of water from 14.5 C to 15.5 C. Central Fan System: A mechanical indirect system of heating, ventilating, or air conditioning, in which the air is treated or handled by 788 equipment located outside the rooms served, usually at a central location, and is conveyed to and from the rooms by means of a fan and a system of distribution ducts. See Chapters 9 and 10. Chimney Effect: The tendency in a duct or other vertical air passage for air to rise when heated, owing to its decrease in density. Coefficient of Transmission: The amount of heat (Btu) transmitted from air to air in one hour per square foot of the wall, floor, roof or ceiling for a difference in temperature of 1 F between the air on the inside and that on the outside of the wall, floor, roof or ceiling. Column Radiator: A type of direct radiator. This radiator has not been listed by manufacturers since 1926. Comfort Line: The effective temperature at which the largest per centage of adults feel comfortable. Comfort Zone (Average): The range of effective temperatures over which the majority (50 per cent or more) of adults feel comfortable. Comfort Zone (Extreme): The range of effective temperatures over which one or more adults feel comfortable. (See Chapter 3.) Concealed Radiator: A heating device located within, adjacent to, or exterior to the room being heated but so covered or enclosed or con cealed that the heat transfer surface of the device, which may be either a radiator or a convector, does not see the room. Such a device transfers its heat to the room largely by convection air currents. Conductance:. The amount of heat (Btu) transmitted from surface to surface in one hour through one square foot of a material or construc tion, whatever its thickness, when the temperature difference is 1 F between the two surfaces. Conduction: The transmission of heat through and by means of matter unaccompanied by any obvious motion of the matter. Conductivity: The amount of heat (Btu) transmitted in one hour through one square foot of a homogeneous material 1 in. thick for a difference in temperature of 1 F between the two surfaces of the material. Conductor (heat): A material capable of readily conducting heat. The opposite of an insulator or insulation. Constant Relative Humidity Line: Any line on the psychrometric chart representing a series of conditions which may be evaluated by one percentage of relative humidity; there are also constant dry-bulb lines, wet-bulb lines, effective temperature lines, vapor pressure lines, and lines showing other physical properties of air mixed with water vapor. Control: Any manual or automatic device for the regulation of a machine to keep it at normal operation. If automatic, it is considered that the device is motivated by variations in temperature, pressure, time, light, or other influences. Convection: The transmission of heat by the circulation of a liquid or a gas such as air. Convection may be natural or forced. Convector: A heat transfer surface designed to transfer its heat to surrounding air largely or wholly by convection currents. Such a surface may or may not be enclosed or concealed. When concealed and enclosed 789 >. I