AME Int. Heat Trans. D. B. Go 1 Different Coordinate Systems cartesian cylindrical spherical

AME Int. Heat Trans. D. B. Go 2 Work Examples F CM ΔxΔx [1] Sliding Block work done to the control mass so it is energy gained [2] Shear Work on a Fluid Belt  CM Liquid Bath W vxvx work done to the control mass so it is energy gained shear stress × speed × area

AME Int. Heat Trans. D. B. Go 3 Work Examples p1p1 p0p0 CM W [3] Boundary Displacement ΔzΔz work done by the control mass so it is energy lost boundary work Gas Expansion Strain (Compression/Expansion) CM1 F ΔzΔz work done to the control mass so it is energy gained boundary work (constant area)

AME Int. Heat Trans. D. B. Go 4 Work Examples [4] Shaft/Propeller [5] Electrical Work (Heat Generation) W CM torque × angular speed work done to the control mass so it is energy gained CM + - W Joule (or resistive or Ohmic) heating work done to the control mass so it is energy gained V R

AME Int. Heat Trans. D. B. Go 5 Work Examples [6] Surface Tension surface tension × area change work done to the control mass so it is energy gained Soap bubble air CM straw CM movable wire Soap film inside a wire ΔAΔA

AME Int. Heat Trans. D. B. Go 6 Work Examples [7] Spring Compression F ΔxΔx

AME Int. Heat Trans. D. B. Go 7 Enthalpy We can literally define a new specific property enthalpy as the summation of the internal energy and the pressure × volume (flow work) Porter, 1922 Thus for open systems, the first law is frequently written as

AME Int. Heat Trans. D. B. Go 8 Heat Transfer Heat Transfer is the transport of thermal energy due to a temperature difference across a medium(s) –mediums: gas, liquid, solid, liquid-gas, solid-gas, solid-liquid, solid-solid, etc. –Thermal Energy is simply the kinetic energy (i.e. motion) of atoms and molecules in the medium(s) Atoms/molecules in matter occupy different states –translation, rotation, vibration, electronic –the statistics of these individual molecular-level activities will give us the thermal energy which is approximated by temperature Heat Transfer, Thermal Energy, and Temperature are DIFFERENT. DO NOT confuse them. Heat generation (electrical, chemical, nuclear, etc.) are not forms of heat transfer Q but forms of work W – Q is the transfer of heat across the boundary of the system due to a temperature difference

AME Int. Heat Trans. D. B. Go 9 Definitions Thermal Energy Temperature Heat Transfer Energy associated with molecular behavior of matter U [J] – extensive property u [J/kg] – intensive property Means of indirectly assessing the amount of thermal energy stored in matter QuantityMeaning Symbol/Units T [K] or [°C] Thermal energy transport due to a temperature gradient (difference) various Heat Heat Rate/Heat Flow Heat Flux Thermal energy transferred over a time interval ( Δt > 0) Thermal energy transferred per unit time Thermal energy transferred per unit time per unit surface area Heat Transfer

AME Int. Heat Trans. D. B. Go 10 Modes of Heat Transfer Conduction & convection require a temperature difference across a medium (the interactions of atoms/molecules) Radiation transport can occur across a vacuum