Thermo Lecture 4

• closed system - form of heat or work
• open system - (control surface) heat, work, and mass transfer

• (total energy entinering the system) - (total energy leaving the system) = (change in total energy of the system)
• or delta (E = U + KE + PE)

• E = U + KE + PE
• internal + kinetic + potential

U - dependent on the state and mass of the system

• System not moving with velocity/changing elevation
• delta E = delta U

Q - caused by temperature difference between system and surroundings. Heat transfer into system is energy increase, out of system is decrease. Adiabatic system, Q = 0.

W - energy transfer at a system boundary, the force acting through a distance or energy to lift a weight. Transfered into system energy increases, out of system energy decreases.

m - mass flowing into system, energy increases by the amount of energy carried with the mass. m = 0 for closed systems.

• 1. Boundary phenomena
• 2. systems posses energy, not heat/work
• 3. Associated with process, not state
• 4. path function

• Calculated by following the process path and adding differential amounts along the way
• δQ = Q₁₂ or δW = W₁₂

• positive - heat transfer to a system/work done by a system
• negative - heat transfer from a system/done done on a system

heat transfer in progressive exchange of energy btwn the molecules of a substance

• 
• k - thermal conductivity [W/mK]
• dT/dx - temp gradient, direction of heat flow

heat transfer of the energy transfer btwn a solid surface and adj liquid or gas in motion, and involves combined effects of conduction and fluid motion.

• 
• h - convection heat transfer coe [W/m²K]
• T_s - surface temp, T_f - bulk fluid temp

energy in transition from the surface of one body to the surface of another due to electromagnetic radiation.

• 
• sigma - Stefan-Boltzmann constant, 5.57x10^-8 W/m²K⁴
• epsilon - emissivity

• rate of electrical work done by electrons crossing a system boundary
• P = VI

• force of a distance vs. energy to lift weight
• 
• angle bten force and displacement vector
• delta means it is path dependent

shaft, spring, elastic solid bars, stretching liquid film, raise/accelerate a body