Chapter 1: Introduction Definition of Thermodynamics: Thermodynamics is a science that deals with heat and work and those properties of substances that bear a relation to heat and work. Macroscopic description (homogeneous, isotropic, molecular activities neglected). Static, equilibrium states.
What to be studied? System is used to identify the subject of the analysis Automobile engines Turbines Compressors, pumps Fossil and nuclear-fueled power stations Propulsion systems for aircraft and rockets Combustion systems Cryogenic systems, gas separation, and liquefaction Heating, ventilating and air-conditioning systems Vapor compression-and absorption refrigeration Heat pumps Cooling of electronic equipment Alternative energy' systems Fuel cells
What to be studied? Thermoelectric and thermionic devices Magnetohydrodynarnic (MHD) converters Solar-activated heating, cooling, and power generation Geothermal systems Ocean thermal, wave, and tidal power generation Wind power, Biomedical applications Life-support systems Artificial organs
Some common systems related to thermodynamics System is used to identify the subject of the analysis
Some common systems related to thermodynamics System is used to identify the subject of the analysis
Some common systems related to thermodynamics System is used to identify the subject of the analysis
Some common systems related to thermodynamics System is used to identify the subject of the analysis
Types of systems Closed system:
Types of systems Open systems or control volume:
The concepts of properties, state, and processes A property is a macroscopic characteristic of a system such as mass, volume, energy, pressure, and temperature to which a numerical value can be assigned at a given time without knowledge of previous behavior (history) of the system ( a point function and independent of a process). The word State refers to the condition of a system as described by its properties. A Process is a transformation from one state to another. Extensive properties depend on the size or extent of a system, mass, volume, energy,... Intensive properties are independent of the size or extent of a system, temperature, pressure, specific volume,...
Phase and Pure Substance The term phase refers to a quantity of matter that is homogenous throughout in both chemical composition and physical structure. A substance may typically have three phases: solid, liquid, and vapor (or gas). Water: ice, liquid, and vapor A pure substance is one that is uniform and invariable in chemical composition. A pure substance can exist in more than one phase; but its chemical composition must be the same
Equilibrium In mechanics, equilibrium means a condition of balance maintained by an equality of opposing forces. In thermodynamics, several types of equilibrium must exist individually to fulfill the condition of complete equilibrium; among these are mechanical, thermal, phase, and chemical equilibrium. At equilibrium, properties, such as temperature, pressure, density, and chemical composition, must be uniform throughout the system.
Specific Volume, Pressure, and Temperature - measurable properties Specific volume v --- The volume per unit mass
Pressure - Thermodynamic pressure
Temperature We are aware of "temperature" as a sense of hotness or coldness. However, the sense of hotness or coldness is highly unreliable (different persons may have different senses of hotness or coldness). For this reason, we need a reference (a judge or an arbitrator) to independently determine the hotness or coldness – Temperature. It is possible to arrive at an objective understanding of equality of temperature by using the fact that when the temperature of a body changes, other properties (such as volume or pressure) also would also change. A thermometer based on the change of other properties of a substance is used to measure the temperature. Then the question is that will the temperature measured by the thermometer be unique?
Temperature The Zeroth Law of Thermodynamics: Two bodies have equality of temperature with a third body, they in turn have equality of the temperature with each other. (The third body may be a Thermometer) Importance: The temperature can be uniquely defined.
Temperature Scales
Normal boiling water temperature at atmosphere: