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52 Cards in this Set
- Front
- Back
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Specific volume, v |
= V/M = 1/ rho |
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Specific gravity, S.G |
= rho/rhoH2O |
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State postulate |
The state of a simple compressible system is completely specified by two independant INTENSIVE properties |
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Pure substance |
No change in chemical composition throughout the system |
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Ideal gas, P |
= rho. R T |
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Diathermic |
Walls that allow heat to pass through |
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Adiabatic |
Insulated walls, impassible to heat |
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Boltzmann distribution |
distribution of atoms over allowed energy states |
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Population of energy state, E/ Population of energy state, 0 |
E/0 = e^(betaE) |
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Beta (boltzmann distribution) |
= 1/ kT (k is boltzmann constant) |
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Work is the... |
motion against an opposing force |
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Heat is the ... |
energy transferred as a result of temperature difference between systems and surroundings |
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Enthalpy is the ..... |
total energy of a system |
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Enthalpy, H |
= U + pV |
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Total energy, E |
= U + KE + PE |
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for specific quantities of energy |
divide by mass, e = u + (v^2/2) + gz |
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Mass flow rate, mdot |
= rho. Vdot = rho.Av |
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1st law of thermodynamics equation |
(Qin-Qout)+(Win-Wout)+(Em,in-Emout)= delta U+deltaKE+deltaPE |
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Qin-Qout = |
heat transfer |
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Win-Wout = |
work transfer |
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Emass,in-Emass,out = |
mass flow |
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Performance = |
Desired output / Required output
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Combustion, n | |
= Q/ HV
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For closed system, no mass transfer so ... |
(Qin-Qout) + (Win-Wout) = 0 |
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Specific heat capacity, cp |
= cv+ Rg |
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Conduction is defined as... |
heat transfer through walls |
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Conduction equation, Qdot |
= -kA . dT/dx |
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Forced conduction is defined as .... |
heat transfer by movement of turbulent eddies |
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Newton's law of cooling, q(dot) |
=h ( Tw - Tb ) |
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Radiation is defined as.... |
energy emitted by matter as electromagnetic waves |
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Max rate of radiation at absolute T, black body |
Qdot(emit) = sigma. A . (Ts)^4 sigma = stefan boltzmann constant |
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Max rate of radiation, real surface |
Qdot(emit) = epsilon.sigma.A.Ts^4 epsilon = emissivity |
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Clausius statement of 2nd law |
"Heat does not pass from a body at a low temperature to one at high temperature without an accompanying change elsewhere" |
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Kelvins statement of 2nd law |
"No cyclic process is possible in which heat is taken from a hot source and converted completely into work" |
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Change in entropy = |
Heat supplied reversibly / Temperature delta S = Q / T |
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Generic statement of 2nd Law |
"The entropy of the universe increases in the course of spontaneous change" |
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Thermal efficiency, nth |
= (Wout - Win) / Qin |
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Carnot efficiency, nmax |
= 1 - (Tout/Tin) |
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Coefficient of performance, COP |
= desired output/required input = Ql / Win |
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COPmax |
= 1 / ((Th/Tl) - 1) |
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COP heat pump = |
Qh / Win = Qh / (Qh - Ql) |
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Entropy S, dS |
= dQ/T (for reversible processes) <- do not exist |
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Irreversible, 3 cases |
- Heat transfer across a finite temperature difference - Unrestrained expansion of gas - Friction |
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Entropy balance equation, integral form |
S2 - S1 = integral( deltaQ / T) + sigma |
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Entropy balance equation, differential form |
dS = (deltaQ / T) |
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Gibbs equation |
T.dS = du + pdv |
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Helmholtz Energy, A (Arbeit) german for work |
deltaA = deltaU - TdeltaS |
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Helmholtz energy is the .... |
thermodynamic potential of a closed system |
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delta A is the .... |
change in internal energy due to work only |
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Gibbs energy, deltaG |
= deltaA + pdeltaV |
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3rd law states that .... |
No finite sequence of cyclic processes can succeed in cooling a body to absolute zero temperature |
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3rd law absolute zero postulate |
The entropy of every pure perfectly crystalline substance approaches the same value as temperature approaches absolute zero |
