Document 3eZnqJqa9dXqVYyEXgROq64mJ

22 CHAPTER 2 1951 Guide 76. Scale Trap 77. Spray Pond 78. Thermal Bulb 79. Thermostat (Remote . . Bulb). , 80. Valves . .80.1 Automatic Expan sion 80.2 Compressor Suction Pressure Limiting, s ` Throttling Type (Compressor Side) 80.3 Constant Pressure, , Suction 80.4 Evaporator Pressure Regulating, Snap Action 80.5 Evaporator Pressure Regulating, Thermo static Throttling Type .-Qr 80.6 Evaporator.Pressure Regulating, Throt tling Type (Evapo rator Side) 80.7 Hand Expansion 80.8 Magnetic Stop _5lL> $ (") 80.9 Snap Action 80.10 Suction Vapor Regulating 80.11 Thermo Suction 80.12 Thermostatic Ex pansion x*- 80.13 Water 81. Vibration Absorber, lane IDENTIFICATION OF PIPING SYSTEMS BY COLOR The color scheme for identification of piping systems, based bn material carried, as listed in the following table and shown in Fig. I, is reprinted from Part V, Fourth Edition, of the Engineering Standards of the Heat ing, Piping and Air Conditioning Contractors National AssociationJ ' Class F--Fire-protection . D--Dangerous materials S--Safe Materials and, when required Red Colob Yellow or Orange Green (or the achromatic, colors, white, black,! gray or aluminum) P--Protective materials V--Extra valuable materials Bright blue , Deep purple Fiq. 1. Main Classification bt Colob 1 See Scheme, tor Identification of Piping Sjretema, A13-1928, American Standard! Atsociation. CHAPTER 3 THERMODYNAMICS Mass and Energy Balances; Thermodynamic Properties of Moist Air; Formulas and Tables' Thermodynamic Properties of Water, Formulas and Tables; Degree of Saturation; A.S.H.V.E. Paychrometric Chart; Solution of Air. Conditioning Problems by Use of Tables and Paychrometric Chart; U. S. Standard Atmosphere THERMODYNAMICS is that branch of natural science which deals with energy and its transformations into various forms. In this chapter the discussion will be limited to thermodynamics as it affects the arts of heating and air conditioning. This will necessarily presume some knowledge of the fundamentals of the science on the part of the reader who may also find it desirable to refer to a standard text on the subject, preferably one published after 1930. MASS AND ENERGY BALANCES The First Law of Thennodynamics is a statement of the Principle of Conservation of Energy. It may be stated as follows: The energy added to a system is equal to the increase or decrease of the energy stored in the system, plus the energy which leaves the system. For a completely contained, or non-flow system, this may be restated as: The heat added to a non-flow system is equal to the change in the internal energy of the system, plus the work done by the system. iq=U,-U, + w (1) For a constant pressure process iq *= Hi -- H, (2). tohere ,q, = energy added between points 1 and 2. U = internal energy, of system. . w = work done by system. H = enthalpy of system. ... Subscripts 1 and 2 refer to sections of the system between which a change takes place. For engineering problems, a more important application of the First Law is its use in cases in which, in addition to energy, one or more fluids are crossing the boundaries of the system. The most simple of these is the steady flow system, in which the rates of energy and mass flow across the boundaries of the system are constant, and no mass or energy is stored or released by the system. Consider a system as illustrated in Fig. T. The fluid crossing the boundaries of the system carries with it potential energy by reason of its elevation above some convenient datum,;kinetic energy by reason of its 23