Applied Thermodynamics – ME432 Unit -1: Chapter-1: Pure Substance PROPERTIES OF PURE SUBSTANCES: Formation of steam, Phase changes, Properties of steam, Use of Steam Tables, Study of P-V, TS and Mollier diagram for steam, Dryness fraction and its determination, Study of steam calorimeters (Barrel, Separating, Throttling and combined). Non-flow and Steady flow vapour processes, Change of properties, Work and heat transfer. VAPOUR POWER CYCLE: Carnot cycle, Rankine cycle, Comparison of Carnot cycle and Rankine cycle, Efficiency of Rankine cycle, Relative efficiency, Effect of superheat, boiler and condenser pressure on performance of Rankine cycle. By RAVIKUMAR R ASSISTANT PROFESSOR
Pure Substance A pure substance is one that is homogeneous and is having invariable chemical composition. It may exist in more than one phase, but the chemical composition is the same in all phases. A pure substance will have a constant boiling and freezing point temperatures. Examples: 1. Liquid water 2. A mixture of liquid water and water vapor 3. A mixture of ice and liquid water
Phase change process
1. P-V diagrams 1.1 Vapour – Liquid – Solid phase equilibrium in pure substance • Consider 1 kg of ice at -10 oC and 1 atm pressure. • Ice is heated slowly so that it is having uniform temperature through out. The changes in volume of ice as it is heated is shown in the P-V diagram. 1. Process 1 – 2: Temp. increases from -10 oC to 0 oC. Volume of ice increases due to thermal expansion. At state 2 ice will start to melt. 2. Process 2 – 3: Ice melts to water at constant temperature of 0 oC . At state 3 melting ends . There is a slight reduction in volume due to anomalous expansion of water (peculiarity of water).