Quiz 3 Flashcards
Measure of the amount of energy possessed by the molecules of a substance.
Temperature (T)
Energy in transit. Energy as the result of temperature difference
Heat (Q)
Force acting through a distance
Work
Modes of transferring heat
Conduction and Convection and Radiation
Transfer of heat by the interactions of atoms or molecules.
Conduction
Transfer of heat by the mixing and motion of macroscopic portions of a fluid.
Convection
Example of Convection
Sea and Land Breeze
Transfer of heat by electromagnetic radiation
Radiation
Heat transfer per unit area
Heat Flux
Measure of substances ability to transfer heat through solid by conduction
Thermal Conductivity
The thermal conductivity of most liquids and solids varies with ______ ; for vapors, it depends upon ____
Temperature ; Pressure
Sometimes referred as a film coefficient and represents the thermal resistance of a relatively stagnant layer of fluid between a heat transfer surface and the fluid medium.
Convective Heat Transfer Coefficient
Combines the heat transfer coefficient of the two heat exchanger fluids and the thermal conductivity of the heat exchanger tubes.
Overall heat transfer coefficient
For flow adjacent to a hot or cold surface, bulk temperature is the temperature of the fluid that is _______ from the surface.
Far
For boiling or condensation, temp bulk is equal to ______
saturation temperature
Heat transfer by conduction is dependent upon the _______ of temperature difference and the _______ to heat transfer
driving force ; resistance
The ______ to heat transfer is dependent upon the _______ and ________ of the heat transfer medium.
resistance , nature, dimension
All heat transfer problems involve the ________, _________ and ________ of the object being studied.
temperature difference, geometry, physical properties.
The heat transfer rate is analogous to ______ in electric circuit.
current flow
The combination of x, k and A is analogous to _____ in electric circuit
resistance
The temperature difference is the ______ or driving function for the heat flow
potential (EMF)
Across a cylindrical wall, the heat transfer surface area is continually _______ or ______
increasing, decreasing
It involves the transfer of heat by the motion and mixing of macroscopic portions of a fluid.
Convection
Type of convection when mixing is caused by density variations resulting from temperature difference within the fluid
Natural Convection
Type of convection if the motion and mixing is caused by an outside force, such as pump
Forced Convection
Factors that affect the stagnant film thickness:
Fluid velocity
Fluid viscosity
Heat flux
Surface roughness
Type of flow (single-phase/two-phase)
For flow in pipe, bulk temp is the average temperature at a particular ______ of the pipe
cross-section
The convective heat transfer coefficient is dependent on:
Physical properties of the fluid and physical situation
Many applications involving convective heat transfer take place within ____, ______ or some similar______
pipes, tubes, cylindrical device
Many of the heat transfer processes encountered in thermal facilities involve a combination of both _____ and ______
conduction, convection
The convection heat transfer process if strongly _____ upon the properties of the fluid being considered.
dependent
