Thermodynamic Properties of Steam Fluid H（蒸汽流体的热力学性质H）.pdf

Steam Basics by Fluid Handling Inc. Session 1, Thermodynamics of Steam, 2/17/07 Thermodynamic Properties of Steam Purpose of This Session The purpose of this session is to understand the thermodynamic properties of steam, which affect the design and operation of steam heating systems and process steam systems. An understanding of the basic thermodynamics of steam allows us to properly size equipment and to design piping systems. It also allows us to make informed decisions affecting the energy usage of the system. Principles of Steam Water exists in three forms: a) Solid (ice), b) liquid (water) and vapor (steam). For our purposes, the definition of steam is: “the vapor form of water”. As steam system designers, we are not really concerned about the solid state, except when water inadvertently freezes in a system. Proper piping design prevents this and we will touch on that later. In our study of the Thermodynamics of Steam, we will concentrate on the liquid and vapor phases of water. The Key Principle, “Saturation” To properly select steam products and to design a successful steam system, we must thoroughly understand the principal of saturation temperature and pressure. We define the saturation temperature as the temperature at which water boils at a given pressure. Refer to the steam tables to discover the first key principle of saturation: o For each pressure, there exists one corresponding temperature and for each temperature, there exists one corresponding pressure. Examples 1-3 (Refer to Steam Tables) 1. What is the saturation temperature of 2 PSIG steam? The saturation temperature at 2 PSIG is 219° F 2. What is the saturation temperature at 0 PSIG steam? At what temperature would water boil on the stove from an open pan at sea level? The saturation temperature at 0