heat transfer

[...]... mechanism, radiation that allows the propagation of heat through a vacuum 2 This mechanism is restricted to heat propagation through stagnant matter In the case of fluids in motion, the heat transfer mechanism is convection 3 Conduction is the only possible heat transfer mechanism in opaque solids 2-7-2 Convection Description of the Mechanism Convection is a heat transfer mechanism present in fluids in motion... (2-6-4) HEAT TRANSFER FUNDAMENTALS HEAT TRANSFER FUNDAMENTALS 9 (In this book we will only use the specific heat at constant pressure, so we will drop the subscript and will designate it as c.) The specific heats may be considered approximately constant within certain temperature ranges It is then possible to put them into tables or graphs that are useful tools for hand calculations Specific heat values... both heat and mass transfer simultaneously, such as the condensation of multicomponent mixtures 2-2 HEAT AND THE FIRST LAW OF THERMODYNAMICS Heat can be defined as energy that is transferred because of the existence of a temperature difference between two systems or between two parts of a system When we speak about heat, we always refer to energy in transit It cannot be said that a system accumulates heat. .. CHAPTER 3 HEAT CONDUCTION IN SOLIDS Conduction is a heat transfer mechanism resulting from the energy exchange between neighbor molecules as a consequence of molecular contact In conduction heat transfer, atoms or molecules interact by elastic and inelastic collisions to propagate the energy from regions of higher temperature to regions of lower temperature Conduction is the only possible heat transfer. .. auxiliary variable is the latent heat of vaporization of a pure substance λ This is defined as the enthalpy difference between the saturated vapor and the liquid at its boiling temperature and same pressure Latent heats of vaporization for different substances are also included in App I 2-7 HEAT TRANSFER MECHANISMS It is normally accepted that there are three basic heat transfer mechanisms—conduction,... flux, A is the area perpendicular to the heat flux, and k is a proportionality constant In this expression, the negative sign means that the direction of the heat flow is the direction in which temperature decreases C In the rest of the book we will work frequently with heat- flux denTA sities, meaning heat transferred per unit time and per unit area The TB heat flux density will be designated as q... boiling heat transfer coefficient, some programs use correlations based on critical properties Other programs do not use the critical properties and calculate boiling heat transfer coefficients based on properties that are difficult to predict, such as surface tension of the boiling liquid This means that some variables that are important in some programs are not important in others Boiling heat transfer. .. profile is imposed externally on the system independent of the heat transfer However, in the absence of fluid movers, if heat is applied to a fluid, the temperature gradients provoke density differences that cause the fluid to move This movement is the result of heat flux and is called natural convection This means that every time heat is transferred to or from a fluid, the mechanism will be convection,... pumping of the fluid by means of pump B The heat exchange in heat exchanger C The phase separation in separator D The condensation of vapor in condenser E Each of these units is a unit operation Unit operations normally are classified in three groups, which generally are studied separately They are • Momentum -transfer operations • Heat transfer operations • Mass -transfer operations The first group includes... temperature of the contained liquid is Ti , whereas the temperature of the exterior air is To Heat will flow from the liquid to the exterior through the composite solid wall (Fig 3-4) The heat- flux density qz will be constant through the wall Heat is transferred from the liquid to the internal wall by convection For heat transfer to exist, a temperature difference between the bulk of the liquid and the solid . Fundamentals of Heat Transfer Between Fluids 79 5-1 The Enthalpy Balance / 79 5-2 Heat Transfer Area and Heat Transfer Coefficient / 81 5-3 Expression of the Overall Heat Transfer Coefficient. Exchangers versus Shell-and-Tube Heat Exchangers / 265 9-7 Typical Heat Transfer Coefficients / 266 9-8 Heat Transfer and Pressure-Drop Correlations for Plate Heat Exchangers / 267 9-9. Overall Heat Transfer Coefficient and Pressure Drop for Double-Tube Heat Exchangers / 94 5-6 Heat Exchanger Process Specifications / 98 5-7 Design Procedure for a Double-Tube Heat Exchanger