For the heat transfer mode of radiation, the radiative property that provides a measure of how efficiently a surface emits energy relative to a blackbody is called what?
Explanation
Emissivity is the key surface property that determines the rate of thermal radiation emission from a real (non-ideal) surface at a given temperature.
Other questions
What is the fundamental definition of heat transfer provided in the text?
Which mode of heat transfer involves the transfer of energy from more energetic to less energetic particles of a substance due to interactions between the particles, and can be viewed as diffusion of energy?
An industrial furnace wall is 0.15 meters thick and has a thermal conductivity of 1.7 W/m·K. If the inner and outer surfaces are maintained at 1400 K and 1150 K respectively, what is the heat flux through the wall under steady-state conditions?
What two mechanisms comprise the convection heat transfer mode?
What is the key distinction between forced convection and free (or natural) convection?
According to Newton's law of cooling, the convective heat flux is proportional to what?
Which mode of heat transfer can occur most efficiently in a vacuum?
An uninsulated steam pipe with an emissivity of 0.8 is in a room where the walls are at 298 K (25 C). What is the irradiation on the pipe surface?
What is the primary difference between the disciplines of heat transfer and thermodynamics?
The first law of thermodynamics for a control volume (an open system) on a rate basis states that the rate of increase of stored energy must equal the rate of energy entering, minus the rate of energy leaving, plus what other term?
In a surface energy balance for a medium, where the control volume has no mass or volume, which two terms from the general conservation of energy expression (Equation 1.11c) are no longer relevant?
A person with a 3 mm thick skin/fat layer (k = 0.3 W/m·K) has an inner skin temperature of 308 K. They are in still air at 297 K where the convection coefficient is 2 W/m^2·K and the radiation coefficient is approximately 5.9 W/m^2·K. What is the skin surface temperature?
A coating on a plate absorbs 80 percent of a 2000 W/m^2 irradiation from an infrared lamp. The plate has an emissivity of 0.50 and is exposed to air at 20 C (293 K) and surroundings at 30 C (303 K). If the convection coefficient is 15 W/m^2·K, what is the cure temperature of the plate?
What is the primary function of cooling fins (heat sinks) attached to electronic components like microprocessors?
What are the four basic dimensions required for the development of heat transfer analysis?
In the SI system of units, what is the derived unit for Power, and what is its equivalent in base units?
What property of a material is defined by Fourier's law and is a measure of a material's ability to conduct heat?
Using the thermal circuit analogy, what is the expression for the thermal resistance for convection?
In a thermal circuit analogy for a plane wall, what does the quantity L/(kA) represent?
For a surface with emissivity (epsilon) and absorptivity (alpha), what is the net rate of radiation heat transfer from the surface per unit area, q''_rad, in an environment where it is surrounded by a large isothermal surface at T_sur?
An electrical current of 15 A passes through a PEM fuel cell with a cell voltage of 0.6 volts. If the corresponding thermal generation rate is 11.25 W, what is the generated electrical power?
What is the term for the conversion of mechanical energy to thermal energy associated with viscous forces acting in a fluid, which is important in high-speed or highly viscous flows?
In the systematic procedure for solving heat transfer problems, what are the first three recommended steps?
What physical quantity is represented by the symbol 'h' in the context of convection, and what are its typical SI units?
A long conducting rod with a diameter of D and electrical resistance per unit length R'_e has a current I passed through it. If the rod is of length L, what is the total rate of energy generation due to Ohmic heating?
A cubical container with a wall of thickness L and thermal conductivity k encloses a mass M of ice at its fusion temperature (0 C). If the outer surface of the wall is heated to a temperature T1 > 0 C, the time tm needed to melt the ice is proportional to what?
Which of these processes is an example of free or natural convection?
For a one-dimensional plane wall with linear temperature distribution T(x) from T1 to T2 over a length L, the temperature gradient dT/dx is given by which expression?
In a closed container of hot coffee, what heat transfer process is primarily responsible for energy transfer from the liquid coffee to the inner surface of the plastic flask?
In the SI system, what is the unit of thermal conductivity (k)?
A surface with an emissivity of 0.50 has an absolute temperature of 500 K. The Stefan-Boltzmann constant is 5.67 x 10^-8 W/m^2·K^4. What is the heat flux emitted by this real surface?
What is the region of fluid where the velocity varies from zero at a surface to a finite value in the main flow called?
For a gray surface where emissivity equals absorptivity (epsilon = alpha), what is the formula for the net radiation heat flux exchanged between a small surface at temperature Ts and large, isothermal surroundings at Tsur?
In the context of the conservation of energy, what does the term 'thermal energy generation' (E_dot_g) represent?
In a steady-flow open system with mass flow rate m_dot, what thermodynamic property is the sum of thermal energy per unit mass (u_t) and flow work per unit mass (pv)?
A fluid flows through a heated tube under steady-state conditions. The mass flow rate is 0.1 kg/s and the specific heat is 1000 J/kg·K. If the fluid enters at 20 C and leaves at 80 C, what is the rate of heat transfer to the fluid?
What is the primary reason that human skin temperature in 25 C water feels much colder than in 25 C air?
The total rate of heat transfer from a surface is the sum of the heat transfer by convection and radiation. If the convection coefficient is h and the linearized radiation coefficient is hr, what is the total heat rate (q) from a surface of area A at temperature Ts to surroundings at T_inf and T_sur?
The thermal energy generation in a gas turbine is a dominant aspect of its operation. What is a key reason that heat transfer analysis is critical for the turbine blades and vanes?
What is the primary role of the electrolytic membrane in a Proton Exchange Membrane (PEM) fuel cell?
How does the SI unit of kelvin (K) relate to the Celsius scale (C)?
In the summary of heat transfer processes (Table 1.5), the rate equation for conduction is q''_x = -k * dT/dx. What does the negative sign signify?
Which physical dimension corresponds to the SI unit of the mole (mol)?
According to the list of typical convection heat transfer coefficients, which process would have the highest 'h' value?
What term is used for the region of a fluid where the temperature varies from the surface temperature to the free stream temperature?
In a surface energy balance where heat is conducted to the surface from the interior and lost to the surroundings via convection and radiation, what is the correct energy balance equation on a per unit area basis?
What is the primary heat transfer concern in cryosurgery?
If a surface has an absorptivity of 0.7, and the irradiation incident on it is 1000 W/m^2, what is the rate of radiant energy absorbed per unit surface area?
The simplified steady-flow thermal energy equation, q = m_dot*c_p*(T_out - T_in), is NOT applicable for which of the following cases?
What is the prefix and abbreviation for the multiplier 10^-6?