Lecture 2 Flashcards
What is heat transfer?
The study of energy flow caused by difference in temperature.
Why do we study heat transfer after thermodynamics?
To study the mechanism and rate of energy transfer.
Define convection, conduction and radiation.
Convection is the movement of heat through liquid. Conduction is the movement of heat through solids and radiation is the movement of heat through waves.
What are the 2 mechanisms of heat transfer?
- Direct interactions.
- Emission and absorption of electromagnetic waves.
What is microscopic energy?
The forms of energy related to the molecular activity.
What is internal energy? Relate it to microscopic energy. What are the two energies that make up internal energy?
Internal energy is the sum of all microscopic energy in a system. Internal energy is made up of kinetic and potential energy.
What is nuclear energy?
The internal energy associated with the bonds in the nucleus of an atom.
What happens during phase change?
Enough energy is added or rejected from a solid, liquid or gas to overcome molecular forces.
For thermal systems involving fluid flow h (enthalpy) is equal to.
Enthalpy = internal energy + pressure x specific volume
h=u + Pv
Change in enthalpy (H) and (h) are equal to.
Change H = mCpavg(change temp)
Change h= Cpavg(change temp)
Change in internal energy (U) and (u) are equal to what?
Change U = m x Cvavg x (change T)
Change u = Cvavg x (change T)
Which is greater. Cp or Cv?
Cp
Mass flowing in and out of a system is called.
Control Volume
Energy in British thermal units
BTU
Energy in international system (SI) units.
Joule
What is the definition of a calorie?
The energy required to raise one gram of water at 14.5 degrees centigrade by 1 degree centigrade.
What is the definition of a British Thermal Unit (BTU)
The energy required to raise 1 pound mass of water at 60 degrees Fahrenheit by one degree Fahrenheit.
What is newtons law of cooling?
Qconvection = hconvection x surface area (Tsurface - T alpha)
