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THERMODYNAMICS AND ENERGY

Lecture # 2. THERMODYNAMICS AND ENERGY. The name thermodynamics stems from the Greek words therme (heat) and dynamics(power), which is most descriptive of the early efforts to convert heat into power. One of the most fundamental laws of nature is the conservation of energy principle.

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THERMODYNAMICS AND ENERGY

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  1. Lecture # 2 THERMODYNAMICS AND ENERGY • The name thermodynamics stems from the Greek words therme (heat) and dynamics(power), which is most descriptive of the early efforts to convert heat into power. • One of the most fundamental laws of nature is the conservation of energy principle. • Today the same name is broadly interpreted to include allaspectsof energy and energy transformations, including power generation, refrigeration, and relationships among the properties of matter

  2. The first law of thermodynamics is simply an expression of the conservation of energy principle, and it asserts that energy i s a thermodynamic property. • The second law of thermodynamics asserts that energy has quality as well as quantity, and actual processes occur in the direction of decreasing quality of energy.

  3. SYSTEMS AND CONTROL VOLUMES • A system :is defined as a quantity of matter or a region in space chosen for study. • The real or imaginary surface that separates the system from its surroundings is called the boundary. • The surroundings: is The mass or region outside the system . • A closed system :(also known as a control mass) consists of a fixed amount of mass, and no mass can cross its boundary. • An open system: or a control volume It usually encloses a device that involves mass flow such as a compressor, turbine, or nozzle

  4. PROPERTIES OF A SYSTEM • Any characteristic of a system is called a property. • Intensive properties :are those that are independent of the mass of a system, such as temperature, pressure, and density. • Extensive properties are those whose values depend on the size—or extent—of the system.

  5. DENSITY AND SPECIFIC GRAVITY • Density: is defined as mass per unit volume

  6. specific gravity, or relative density: is defined as the ratio of the density of a substance to the density of some standard substance at a specified temperature.

  7. STATE AND EQUILIBRIUM State: • Consider a system not undergoing any change. • At this point, all the proper-ties can be measured or calculated throughout the entire system, which gives us a set of properties that completely describes the condition, or the state

  8. Equilibrium • The word equilibrium implies a state of balance. • A system in equilibrium experiences no changes when it is isolated from its surroundings. Thermal equilibrium Mechanical equilibrium. Phase equilibrium Chemical equilibrium

  9. PROCESSES AND CYCLES • Any change that a system undergoes from one equilibrium state to another is called a process,

  10. isothermal process Isobaric process isochoric (or isometric) process

  11. A system is said to have undergone a cycle if it returns to its initial state at the end of the process. That is, for a cycle the initial and final states are Identical. • Temperature Scales: • Celsius scale • Fahrenheit scale • Kelvin scale. • Rankine scale

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