Introduction to Thermal Systems Engineering - em

Introduction to Thermal Systems Engineering - em

List of Symbols

BiBiot number cspecific heat of an incompressible substance, centroid (FM)

cpspecific heat at constant pressure,)p cvspecific heat at constant volume,)v CDdrag coefficient CLlift coefficient

Ct thermal capacitance ddrag force

Dh hydraulic diameter e;Eenergy per unit mass (T); energy (T),electric potential (HT),emissive power (HT) EuEuler number grate of energy generation in,outrate of energy transfer in/out of control volume strate of increase of energy stored within a control volume F, F force vector, force

FoFourier number FrFroude number ffriction factor G irradiation GrGrashof number henthalpy per unit mass (T),convection heat transfer coefficient (HT) Henthalpy (T),head (FM),height (FM,HT) hLhead loss ielectric current

J radiosity kspecific heat ratio:cp cv(T),thermal conductivity (HT),Boltzmann’s constant (HT)

KLloss coefficient l lift m mass mass flow rate

Mmolecular weight,Mach number (FM),moment (FM) Mmass dimension nnumber of moles,polytropic exponent NuNusselt number p pressure pe;PEpotential energy per unit mass; potential energy PrPrandtl number qheat transfer rate (HT) rate of energy generation per unit volume (HT)q#

Qvolumetric flow rate rradial vector Rgas constant: M,radius (FM,HT) RaRayleigh number ReReynolds number universal gas constant

Rc electrical resistance Rffouling factor Rt thermal resistance

Rt,cthermal contact resistance s,Sentropy per unit mass (T),distance along a streamline (FM); entropy (T) s entropy function as used in ideal gas tables SGspecific gravity StStrouhal number t time T temperature u;Uinternal energy per unit mass (T); internal energy

(T),upstream velocity (FM),overall heat transfer coefficient (HT) u,v,wfluid velocity components v;Vspecific volume; volume V, V velocity Wwork,width of a slot nozzle (HT) w weight rate of work,or power x quality xccritical location for transition to turbulent flow xfd,hhydrodynamic entry length xfd,tthermal entry length ymass flow rate ratio,mole fraction yRdistance from free surface to center of pressure z elevation

Z compressibility factor

Greek Letters thermal diffusivity (HT),absorptivity (HT),angle of attack (FM) coefficient of performance for a refrigerator (T), diameter ratio (FM),coefficient of volume expansion (HT) coefficient of performance for a heat pump (T), specific weight (FM) hydrodynamic boundary layer thickness tthermal boundary layer thickness εheat exchanger effectiveness (T,HT),pipe wall roughness (FM),emissivity (HT) εffin effectiveness

#Undesignated symbols are used consistently throughout the book. The following denote particular sections where symbols have special meanings T thermodynamics FMfluid mechanics HTheat transfer efficiency, similarity variable ffin efficiency temperature difference, angle wavelength absolute (dynamic) viscosity kinematic viscosity pi term; dimensionless quantity density, reflectivity (HT) entropy production (T),normal stress (HT), Stefan-Boltzmann constant (HT) rate of entropy production relative humidity (T) shear stress (FM),transmissivity (HT) humidity ratio (T),angular velocity (T),shedding frequency (FM)

Subscripts adry air abs absorbed ad adiabatic bboundary (T),base of an extended surface (HT), blackbody (HT)

B bouyancy cproperty at the critical point (T),compressor (T), combined system (T),critical (transition) (FM), centroid (FM),cross-sectional (HT),cold fluid (HT) cvcontrol volume cwcooling water Ccold reservoir,low temperature CF counterflow D drag, diameter estate of substance exiting a control volume (T), emission (HT) fproperty of saturated liquid (T),temperature of surroundings (T),final value (T),film temperature (HT),fin conditions (HT) fgdifference in property for saturated vapor and saturated liquid,heat of vaporization gproperty of saturated vapor h hydrodynamic, hot fluid Hhot reservoir,high temperature istate of a substance entering a control volume (T), tube inlet condition (HT),initial condition (HT) iinitial value (T),property of saturated solid,inner (HT)

I irreversible ig,ifdifference in property for saturated vapor (saturated liquid) and saturated solid isol isolated int revinternally reversible jportion of the boundary Lbased on characteristic length lbased on plate length lmlog mean condition mmean value over a tube cross section ocenter or midplane condition,tube outlet condition, outer p pump p particle rad radiation refreference state or value (T),reflected radiation ( res reservoir R reversible R resultant s isentropic s streamwise direction, surface conditions sat saturated sur surroundings t turbine t thermal tptriple point tr transmitted v vapor w water, wall xlocal conditions spectral

Superscripts dot over symbol denotes time rate * dimensionless quantity ‘fluctuating quantity (HT) -overbar denotes property on a molar basis (T), surfaceaverage conditions (HT) property at standard state or standard pressure

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