Document Yr5kVyxV2JXnD6XZbJEkqRBEO

12 63. Gage 64. High Side Float 05. Imaorsioa Cooling Unit 66. Low Side Float 67. Motor-Compressor, Enclosed Crank, case, Reciprocat ing, Direct Con nected 68. Motor-Compressor, Enclosed Crank case', Rotary, Di rect Connected 69. Motor-Compressor, Sealed Crankcase, Reciprocating 70. Motor-Compressor, Sealed Crankcase, Rotary 71. Pressurestat 72. Pressure Switch 73. Pressure Switch With High Pressure CutOut 74. Receiver, Horisontal 76. Receiver, Vertical 76. Scale Trap 77. 8pray Pond J8. Thermal Bulb 79. Thermostat (Remote Bulb) 80. Valves 80.1 Automatic Expan sion 80.2 CompressorSuction Pressure Limiting, Throttling Type (Compressor Side) 80.3 Constant Pressure, Suction 80.4 Evaporator Pres sure Regulating, 8nap Action 80.6 Evaporator Pres sure Regulating, Thermostatic Throttling Type 80.6 Evaporator Pres sure Regulating, Throttling Type (Evaporator Side) 2 fl G-6 e-C <S> t=5 b- ir\AA m " I* !r' c-&- -r --(i 6- =- -6=^ CHAPTER 2 1960 Guide 80.7 Hand Expansion 80.8 Magnetic Stop JL 80.9 Snap Action 80.10 Suction Vapor Regulating 80.11 Thermo Suction 80.12 Thermostatic Ex pansion 80.13 Water 81. Vibration Absorber, Line it TS*- <s" -t- -CC3- IDENTIFICATION OF PIPING SYSTEMS BY COLOR The color scheme for identification of piping systems, based on material carried, as listed in the following table.and shown in Fig. 1, is reprinted from Part V, Fourth Edition, of the Engineering Standards of the Heating, Piping end Air Con ditioning Contractors National Association.7 Class F--Fire-protectiooD--Dangerous materials S--Safe materials Coton Red Yellow or Orange Green (or the achromatic col ors, white, black, gray or aluminum) and, when required P--Protective materials Bright blue V--Extra valuable materials Deep purple Fig. 1.... Mom Clossiflcotion by Color CHAPTER 3 THERMODYNAMICS Moss and Energy Balances; Thermodynamic Properties of Moist Air, Formulas and Tabhs; Thermodynamic Properties of Water, Formulas and Tables; Degree of Saturation; ASHRAE PSYCHROMETRIC CHART; Sofution of Air Conditioning Problems by Use of Tables and Psydirometric Chart; U. S. SlafKford Afmotpheres HERMODYNAMICS is that branch of natural science servation of Energy is to flow systems in which, generally, Twhich deals with energy and its transformations, includ both muss and energy cross the system boundary at pre ing tendencies for an energy change to take place and limitascribed rates. The simplest case, and one to which the present tions upon such a change, with particular reference to thermal treatment will be limited, is for steady flow, wherein the flow ;Pf)npn-w This chapter will be limited to thermodynamics in rates are constant. air-conditioning processes involving air and water as the sub Fig. 1 shows a steady-flow system with a single fluid stream stances. A working knowledge of fundamentals of thermody entering and leaving. Because of steady flow, no internal net namics is presumed for the reader, but it may be desirable to - storage of fluid can occur. Each unit mass of fluid crossing consult a recent textbook on the subject for a more complete the fixed system boundary at Sections 1 and 2 possesses three background treatment. kinds of energy: potential, kinetic, and enthalpy. The application of thermodynamic science to problems of The Principle of Conservation of Energy, for the steady- technology in air conditioning is usually called psyckrometrics. flow system, can thus be written Mass and Energy Balances A system is defined as any specified portion of the material universe which has been placed within a convenient boundary, or imaginary envelope, for.study. The First-Law of Thermodynamics is a statement of the Principle of Conservation of Encrgy;-it may be stated in the form: The energy added to a system is equal to the increase of the energy stored in the system plus the energy which leaves the system. For a completely contained nonflow system, wherein no mass crosses the boundary, the First Law is expressible as . U, - U, - iQi - (1) where iQi = energy added between the final state 2 and tbe initial state 1 of the system, tu. U -= internal energy of the system, Btu. it * work done by the system on tbe surroundings between states 1 and 2, Btu. Subscripts 1 and 2 refer to states of the system between which a change takes place. For any nonflow system in which the final and initial states are at the same pressure iQi Ht -- Hi (2) where H enthalpy of the system, Btu. Subscripts 1 and 2 are as above. GIS* + Fx. + h'O + .?> = G(m + Bn + A',) + ,W, (3) where G " mass flow rate, pounds per minute. Ef> = fluid potential energy, Btu per pound of fluid flowing. Bs = fluid kinetic energy, Btu per pound of fluid flowing. V = fluid enthalpy, Btu per pouad of fluid flowing. = rate of beat addition between 1 and 2, Btu per minute. ,W, = rate of work output of the system, between 1 and 2, Btu per minute. Equation 3 is applicable to any fluid or fluids, but in airconditioning it is applied most often to air and water aa the flow substances. It is conventional and convenient, when the fluid flowing is a mixture of air and water vapor, to use the flow rate of dry air. in the mixture as the quantity G in Equation 3. This is in accord with the fact' that the dry air-flow-rate at inlet and outlet to a piece of equipment usually is the same, while there may be a change in the flow rate of the water vapor in the mixture, depending upon whether humidification or dehumidification occurs. In the great majority of air-conditioning problems the kinetic energy and potential energy changes are negligible rel ative to the heat, work, and enthalpy changes in Equation 3; and, if so, the Bp and BK terms may be dropped. (If kinetic and potential energy changes are not negligible, then one ap proach is to define a so-called "total enthalpy" which is the sum Ep + Bk + A'.) Because this simplification usually ap plies in sir conditioning, the remaining discussions in this chapter will employ the steady-flow energy conservation equa tion in the form: The total internal energy and enthalpy are the products of the mass of the system and, respectively, the internal energy and enthalpy per unit mass. Equation 2 applies to nonflow air-conditioning problems such as the heating or cooling of a given mass or volume of material. The broadest practical application of the Principle of Con G*Ai + t?* * Gtht 4-1W (4) where Q* flow rate of dry air, pounds per hour. Under the assumption, which is quite adequate for present purposes, that negligible energy interchange is involved in' 13