Fluid Properties PDF

Fluid- a substance that exists, or is regarded as existing, as a continuum characterized by low resistance to flow and the tendency to assume the shape of its container. Substance - something that is locally made up of molecules. Pure Substance - homogenous in composition and homogenous and variab...

Fluid- a substance that exists, or is regarded as existing, as a continuum characterized by low resistance to flow and the tendency to assume the shape of its container. Substance - something that is locally made up of molecules. Pure Substance - homogenous in composition and homogenous and variable in chemical aggregation Simple Substance - one whose state is defined by two independently variable intensive thermodynamic properties Types of System: Closed System - one in which there is no exchange of matter with the surroundings. - mass does not cross its boundaries. Open System - is one across whose boundaries there is a flow of mass. Each may have energy crossing its boundaries. Isolated System- is completely impervious to its surroundings. - neither mass or energy cross its boundaries. Properties Macroscopic Properties: (pressure, temperature, density, specific volume) Intensive Properties - independent of the mass. - temperature, pressure, density, and voltage. Extensive Properties - dependent of the mass of the system and are total values such as total volume and total internal energy. Specific Properties - are those for a unit mass, and are intensive by definition such as specific volume. Mass- is the absolute quantity of matter in an object Weight -- the force of gravity on the body Pressure - Kinetic Theory Pressure of a gas - is caused by pounding of a large number of gas molecules on the surface. Elementary kinetic theory - the volume of the molecule is negligible, have negligible forces on one another, and the molecules are rigid spheres that do not have elastic collisions. (Pressure is a consequence of rate of change of momentum of molecules striking the surface) Barometers - used to measure atmospheric pressure (Standard reference atmospheric pressure: 760 mm Hg or 29.92 in. Hg at 32°F, or 14.696 psia (14.7 for slide rule), or 1 atm) gauge pressure = difference in pressure. Absolute pressure = atmospheric pressure ± gage pressure Measuring Temperature 1\. Change in volume 2\. Change in pressure 3\. Change in electrical resistivity 4\. Change in electrical potential Thermopcouple- device that measures temperature by the electromotive force Seebeck effect - emf is a function of the temperature difference between the junctions 5\. Optical changes Stefan-Boltzmann law: Q = eσT^4^ Zeroth Law When two bodies, isolated from other environment, are in thermal equilibrium with a third body, the two are in thermal equilibrium with each other. process - if any one or more properties of a system change. Isobaric process - undergo constant pressure. Isometric process - undergo constant volume. Cycle - When a certain mass of fluid in a particular state pass through a series of processes and return to its original state. Conservation of Mass The law of conservation of mass states that mass is indestructible, except nuclear processes. Two-dimensional flow - fluid velocity at every point is parallel to a fixed plane. The flow properties like velocity and pressure vary only in 2d space. One-dimensional flow - flow properties like velocity, pressure, density vary only along one dimension. Heat Reservoir A heat reservoir is a thermodynamic system that generally serves as a heat source or heat sink for another system. It is considered to be stable, homogenous in temperature and composition, and uniform in pressure at any level in the gravitation field. Heat Engines A heat engine is a thermodynamic system that operates continuously with only energy (heat and work) crossing its boundaries. The boundaries are impervious to the flow of mass. Steady-Flow System-an open system in which there is no change of stored mass Adiabatic Surface, Process An adiabatic surface is one that is impervious to heat. It implies perfect insulation. A process that occurs within a system enveloped by an adiabatic surface is called and adiabatic process - there can be no heat flow.