Physics Asked by Dio on April 11, 2021
I’ve just seen these without any explanation of what the variables are or what are do they describe, I just know it should be something about convex lenses and starting fire with them.
$$Q_r=C^n(-Delta H_r)Ze^{-frac{E}{RT}}$$
I’m not sure if the triangle represents delta as change or if it’s a Laplace operator
$$C_prhofrac{partial T}{partial t}=Q_r-Q_c$$
Can anyone tell me what the variables are and what do these equations represent?
What is the source?
Broadly, the first is an Arrhenius equation, which provides the rate of a thermally activated process, i.e., one with an activation energy.
$Q_r$: a rate (based on the second equation, likely a heat flux)
$C^n$: some type of pre-exponential factor, where n may be the reaction order; problem specific
$-Delta H_r$: H often stands for enthalpy and r for reaction
$Z$: typically a collision frequency
$E$: the activation energy
$R$: the gas constant
$T$: the temperature
The second equation is a heat capacity equation describing how an object heats up from a net heat flux.
$C_p$: specific heat capacity at constant pressure
$rho$: density
$t$: time
$Q_r$: likely an input heat flux, with units of J/m³s
$Q_c$: likely an output heat flux, perhaps to a cold sink (c)
Put together, the equations provide an energy balance: the thermal energy generated from a reaction minus any output thermal energy goes into heating the system.
Correct answer by Chemomechanics on April 11, 2021
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