ENGINEERING TRIPOS PART IB - 2011/2012

PAPER 4 - Thermofluid Mechanics

Thermofluid Mechanics

Leaders: Dr MP Juniper / Dr R Miller / Dr S Scott

Timing: Weeks 1-5 Michaelmas term (Dr MP Juniper),
week 6-8 Michaelmas and weeks 1-2 Lent term (Dr R Miller), weeks 3-5 Lent term (Dr S Scott)

Structure: 26 lectures, 2 lectures/week

AIMS

The aims of the course are to:

• Review inviscid flow in three dimensions and derive the Euler equation.
• Examine the effects of viscosity on fluid flow.
• Introduce the phenomena of laminar and turbulent flow and of boundary layers.
• Explore the issues associated with scaling fluid flows and conducting model tests.
• Introduce the concept to availability.
• Show how irreversibilities affect the performance of gas power cycles.
• Introduce the properties of working substances other than ideal gases.
• Describe and analyse simple steam power plant, including the effect of irreversibilities
• Introduce and analyse refrigeration and heat pump cycles.
• Describe how to evaluate the properties of gas and gas/vapour mixtures.
• Show how the First Law may be applied to Combustion
• Develop analysis tools for 1D heat condition, and simple transient conduction problems.
• Examine heat transfer by convection.
• Introduce heat transfer by thermal radiation, including radiation in the environment.
• Describe common types of heat exchanger, and perform an elementary analysis of performance

OBJECTIVES

At the end of the course students should be able to:

• Be able to set up the equations governing laminar viscous flow, and solve them for simple problems.
• Understand how irreversibilities arise in fluid flow and be able to make estimates of loss, drag, etc.
• Describe qualitatively the basic characteristics of boundary layers in internal and external flows.
• Understand the relevance of non-dimensional groups in determining the qualitative nature of fluid flow and how to apply this to model testing.
• Understand the effects of irreversibilities in gas, steam power cycles, and heat pump/refrigeration cycles.
• Understand and be able to use tables of properties for common working substances.
• Understand how to evaluate the properties of arbitrary mixtures of perfect gases, and gas/vapour mixtures, and apply this understanding to problems in psychrometry and combustion.
• Be able to analyse simple problems in conduction, convection and radiation heat exchange.
• Understand the physical principles underlying heat transfer correlations and be able to use these to estimate heat transfer coefficients.

SYLLABUS

Fluid Mechanics: lectures 1-10

1. Properties of a fluid (1L)

• Molecular picture vs. continuum picture
• Partial derivatives
• Law of conservation of mass
• Incompressible flow

2. Incompressible inviscid flow (1L)

• The material derivative, D/Dt
• Euler's equation
• Bernoulli's equation
• Streamline curvature
• Determination of the pressure field from the streamlines of a flow

3. Incompressible viscous flow and boundary layers (2L)

• Viscosity: momentum transfer through molecular motion
• Couette flow and Poiseuille flow
• The Navier-Stokes equation
• Boundary layers
• Pressure gradients in boundary layers
• Boundary layer separation

4. Turbulence and the Pipe Flow Experiment (1L)

• Laminar flow in a pipe with circular cross-section
• Turbulent flow
• Mixing, momentum transport and eddy viscosity
• Roughness

5. Network analysis (1L)

• Static pressure and stagnation pressure
• Stagnation pressure losses across pipe components
• Stagnation pressure changes across pumps and compressors
• Network analysis

6.The Boundary Layer Experiment (1L)

• Reynolds number in a boundary layer
• Transition to turbulence in a boundary layer
• Effect of turbulence on a boundary layer
• Comparison of transition and separation
• Boundary layer re-attachment

7.The External Flow and Drag Experiment (1L)

• Lift and drag
• Flows at very low Reynolds number (creeping flow)
• Flows at low Reynolds number
• Flows at high Reyholds number
• Mechanisms of drag reduction
• Vortex shedding
• Inviscid flow and Hele-Shaw cells

8.Dimensional analysis, scaling and model testing (1.5L)

• Dimensional analysis: the philosopher's, Mathematician's and engineer's approach
• Orific plate example
• Aeroplane example
• Ship example

9.Introduction to Compressible Flow (0.5L)

• The Steady Flow Energy Equation
• Stagnation enthalpy and stagnation termperature
• Viscous dissipation and irreversibility
• Transfer form thermal energy to mechanical energy.
• Incompressible flows and stagnation pressure.

Heat transfer: lectures 11-16

1. Heat Transfer by Conduction (2L)

• Conduction in solids - Fourier's law
• Energy balance in 1D
• Overall resistance to heat transfer
• Dimensional analysis
• Lumped heat capacity model

2. Heat Exchangers (0.5L)

• Description of major types
• Analysis, effectiveness, LMTD

3. Heat Transfer by convection (2L)

• Energy considerations for flows with heat transfer
• Forced convection, Reynolds and Prandtl, Nusselt and Stanton numbers
• Reynolds analogy
• Natural convection. Grashoff and Rayleigh numbers

4. Heat Transfer by Radiation (1.5L)

• Radiation from black bodies
• Emissivity and radiation from grey bodies
• View factors
• Radiation networks.

Thermodynamics: lectures 17-26

1.Introduction, review of previous material (1L)

• 1st & 2nd laws applied to steady flow device
• The ‘quantity’ and ‘quality’ of energy
• Irreversible entropy creation
• Examples of steady-flow devices

2. Maximum available power(1L)

• The different value of work and heat
• The maximum available power in a steady flow device
• The dead state
• How to apply availability to a steady flow device
• Lost power potential due to irreversible

3. Gas turbines(1L)

• Compressor and turbine irreversibilities
• Combustion changes in gas composition
• First law analysis of gas turbines
• Land based gas turbines and aeroengines
• Second law analysis of gas turbines:Availability

4. Working fluids(2L)

• p-v-T data for water and normal fluids
• Saturation lines, the triple point, the critical point
• Evaluating properties, dryness fraction
• Working with tabulated data

5. Power Generation (2L)

• Vapour power plant
• The Rankine cycle
• Reheating and superheating
• Isentropic efficiency
• Combined gas-vapour power cycles
• 1st law analysis of Rankine cycles
• 2nd law analysis of Rankine cycles
• HRSG analysis

6.Refrigeration cycles (1L)

• Refrigerators and heat pumps
• Coefficient of performance
• Real refrigeration cycles
• The T-s and p-h diagram
• Choice of refrigerants
• Practical cycles

7. Properties of Mixtures (1L)

• Describing mixture composition
• Dalton's law
• Amagat's law
• p,v,T relations for a mixture of ideal gases
• Evaluations of U,H & S for a mixture of ideal gases
• Analysis of gas,vapour mixtures
• Saturated mixtures
• Specific humidity & relative humidity
• Dew point
• Air conditioning

8. Combustion (1L)

• Chemical equations
• Lambda and equivalence ratio
• First law applied to combustion
• Phase change of reactants

REFERENCES

Please see the Booklist for Part IB Courses for references for this module.

Last updated: August 2011