Undergraduate Course: Thermodynamics 3 (MECE09010)
|School||School of Engineering
||College||College of Science and Engineering
|Credit level (Normal year taken)||SCQF Level 9 (Year 3 Undergraduate)
||Availability||Available to all students
|Summary||The course presents thermodynamics as a real world subject and insists that there is a pattern to working with thermodynamics which is summarised as Principles, Properties, Processes. This pattern is applied to a variety of machines and devices including turbines, reciprocating compressors, nozzles, power cycles, air conditioning systems and cooling towers. A final separate section introduces the basic ideas of heat transfer.
The course is divided into seven "Topics" on various aspects of applied Thermodynamics in Mechanical Engineering. These Topics are not of the same length and have differing numbers of lectures devoted to them. They may not be presented in this order.
Topic 1: Revison.
Revision of material introduced in Thermodynamics 2. First Law applied to closed systems, isentropic processes, Carnot cycle. Thermal efficiency of Carnot cycles.
Topic 2: First Law applied to open (flow) systems.
Conservation of energy in flow systems. Gas turbines and combined cycles. Air-standard models for flow power cycles.
The Brayton cycle as a model for gas turbines: thermal efficiency and comparison with the Carnot cycle.
Turbine, pump and nozzle efficiencies.
Compressor interstage cooling and resulting reduction of compressor work. Work of compression.
Digression: introduction to reciprocating compressors.
Improvements to the Brayton cycle: reheat and regeneration.
Regenerative cycles: regenerator effectiveness. Efficiency and limitations of regenerative cycles. Optimum pressure ratio for reheat.
Topic 3: Gas mixtures.
Amagat's and Dalton's laws. Thermodynamic properties of ideal gas mixtures. Entropy change of mixing. Gas separation processes. Properties of water and steam. Vapour-liquid equilibrium. Critical properties and phase diagrams.
Digression: conditions and limitations of the ideal gas assumption. Non-ideal gases. Law of corresponding states.
Gas-vapour mixtures: dew point, relative humidity, vapour pressure, partial pressure and saturation pressure. Absolute humidity and specific volume. Adiabatic saturation: wet and dry bulb temperatures, the psychrometric chart. Humidification and dehumidification, cooling towers and spray intercooling.
Topic 4: Steam and combined cycles.
The ideal Rankine cycle and comparison with the Carnot cycle. Analysis of the boiler, turbine, condenser and water feed pump. Condensation in the turbine.
Deviations from ideality and their effect. Increasing Rankine cycle efficiency: superheating of feed steam, decreasing condenser pressure, increasing average temperature of heat addition. Supercritical Rankine cycle. Reheat cycles and regenerative cycles: open and closed feed water heaters. Combined cycles: approach and pinch temperature difference.
Topic 5: Refrigerators and heat pumps.
Definition of coefficient of performance for each. Gas Carnot refrigeration cycle. Reversed Brayton refrigeration cycle. Ideal and non-ideal vapour compression refrigeration cycle. Multi-stage and multi-level refrigeration systems. Absorption refrigeration. Refrigerants.
Topic 6: Compressible flows.
Speed of sound. Velocity of sound and Mach number. Stagnation properties. Ideal gas results. The Pitot tube. Velocity and Mach number from Pitot tube measurements. Conservation of energy using stagnation properties. Nozzles. Effect of changing area on flow parameters for sub- and supersonic flows. Choked flow. Flow through converging-diverging nozzles: effect of back pressure. Shock waves.
Topic 7: Heat Transfer.
Conduction: Fourier's Law. Heat conduction in various geometries.
Convection: Newton's Law.Regimes of heat transfer.
Radiation: The Stefan-Boltzmann equation. Emissivities: radiation heat transfer coefficient.
Thermal resistance: addition of thermal resistances in series. The electrical analogy. Plane and cylindrical geometries. Overall heat transfer coefficient.
Shell and tube heat exchangers. Log mean temperature difference for countercurrent and cocurrent flow. Flow regimes in tubes: effect of turbulence. Reynolds, Nusselt and Prandtl numbers. Correlations for Nusselt number. Fluid temperature change in a heated pipe. Developing flows. Biot number and lumped parameter systems. Unsteady-state heat transfer. Radiative heat transfer overview. Shape factors.
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On completion of this course, the student will be able to:
- Use simplified theoretical models for reciprocating and rotary compressors, and for turbines, to estimate the performance of these machines, and to explain the limitations of the theory.
- Apply the First and Second laws of Thermodynamics to simple closed and steady-flow systems, such as power plant and refrigeration systems, using appropriate property data from tables, charts and equations.
- Use one-dimensional compressible flow theory to determine the gas velocities and flow rates in choked and un-choked nozzles.
- Use the simple theory of mixtures of ideal gases and vapours to calculate the performance of such plant as air-conditioning systems and cooling towers, and to have some appreciation of circumstances in which gases do not behave ideally.
- Carry out simple heat transfer calculations involving conduction, convection and radiation.
|Course organiser||Dr Donald Glass
Tel: (0131 6)50 4870
|Course secretary||Mrs Lynn Hughieson
Tel: (0131 6)50 5687