Document ExqEvvpvnaEO1YVZvBma9QVpL

Heating Ventilating Air Conditioning Guide 1939 Dew-Point Temperature: The temperature corresponding to satura tion (100 per cent relative humidity) for a given moisture content. Direct-Indirect Heating Unit: A heating unit located in the room or space to be heated and partially enclosed, the enclosed portion being used to heat air which enters from outside the room. Direct Radiator: Same as Radiator. Direct-Return System (Hot water): A hot water system in which the' water, after it has passed through a heating unit, is returned to the boiler along a direct path so that the total distance traveled by the water is the shortest feasible, and so that there are considerable differences in the lengths of the several circuits' composing the system. Down-Feed One-Pipe Riser (Steam): A pipe which carries steam downward to the heating units and.into which the condensation from the' heating units drain. Down-Feed System (Steam): A steam heating system in which the supply mains are above the level of the heating units which they .serve.. , Draft Head (Side Outlet Enclosure): The height of a gravity convector between the. bottom of the heating unit and the bottom of the air outlet opening^ (Top Outlet Enclosure):. The height of a gravity convectorbetween the bottom of the heating unit and the top of the enclosure. ' Drip: A pipe, or a steam trap and a.pipe, considered as a unit, which, conducts condensation. from the steam .side of a piping system to the, water or return side of the system. , Dry Air: ,;Air with which no water vapor is.mixed. This term is used comparatively, since in nature there is always.spme water vapor included in air, and such water vapor, being a gas, is dry. - Dry-Bulb Temperature:. The temperature of the air indicated by any type of thermometer not affected by . the water vapor content or relative humidity of the air. ;K ; - Dry Return: A return pipe in a steam heating system which carries' both water of condensation and air. The dry return is above the level of the water line in the boiler in a gravity system. (See, Wet Return).. -y. . - 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. .v .'i:; i f-cvf v -v:- vr ; '.. Effective Temperature':An-arbitrary index of the degree of ,warmth;; ot cold fel t 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, arid air: motion into a single value. .The'numerical , value'ofixt-h.e':effeetive';temperature: spale.has been fixed iby tiie/temperature ful saturatedjcp? which .induces an identical sensation of warmth. -V; Enthalpy: Total heat or thermal potential. ' 838- Chapter .45.: Terminology. Entropy: A ratio, evaluated for practical purposes by dividing the heat content of a unit weight of a substance by its absolute temperature. Useful, in .examining changes during a heati cycle. 'Entropy is constant during a reyersible.adiabatic change of state., . Equivalent Evaporation: - The amount of water a boiler would evaporate; in pounds peri hour, if it received feed water at 212 F and jvaporized.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 pf 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). C 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 condition as to rest or motion. F = -W---V--. 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. Furnace: That part of a boiler or warm air heating plant in which combustion takes place. Also, a firepot. . Furnace Volume (total): The total furnace volume for horizontal- return tubular boilers and water-tube boilers is the cubical contents of the 5 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 waste- heat 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 1 chamber, up to the plane of first entry.into the tubes. (A .S.M E. Power i Test Codes, Series 1929). . .. . Gage Pressure: ..Pressure measured, from atmospheric pressure as a , base. Gage pressure may be indicated by a manometer which has one leg 839