El inicio de convecci?n t?rmica esta descrito por el n?mero de Rayleigh

equation

Para un sistema entre dos placas con las temperaturas inferior T_b y superior T_t la convecci?n se iniciar? al alcanzar un n?mero de Rayleigh de 1708. Para el caso de dos superficies libres el valor cr?tico es 657.51. Para un sistema de un borde fijo y el otro libre 1,100.65.

$v_c=\sqrt{\displaystyle\frac{2hg(\rho_m-\rho}{C_W\rho_m}}$

Como la velocidad de acenso es igual a

equation=4869

y en condiciones isobaricas se cumple

equation=8835

la ecuaci n para la velocidad se puede tambi n escribir en funci n de la temperatura

equation


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The mixing ratio of water vapor with air is defined as the ratio of the masses of each component present in a volume:

$\displaystyle\frac{M_v}{M_a}=\displaystyle\frac{n_vM_{mol,v}}{n_aM_{mol,a}}=\displaystyle\frac{p_v}{p_a}\displaystyle\frac{M_{mol,v}}{M_{mol,a}}\sim 0.01$

Where $M_v$ and $M_a$ are the masses of water vapor and air respectively, $n_v$ and $n_a$ are the moles of water vapor and air, $M_{mol,v}$ and $M_{mol,a}$ are the molar masses of water vapor and air, $p_v$ and $p_a$ are the relative pressures of water vapor and air, and $r$ is the mixing ratio. Therefore, we have

kyon

In the specific case of water vapor in air, the mixing ratio is proportional to the relative pressures, which can be quantified using the vapor pressure of water $p_v\sim 1500 Pa$ and the air pressure $p_a\sim 10^5 Pa$. By applying the ideal gas equation and the definition of molar mass, it can be determined that the mixing ratio is approximately $0.01$. This means that the amount of water vapor compared to air is low under normal conditions.


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