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Homework Help: Checking partial derivative

  1. Oct 14, 2012 #1
    1. The problem statement, all variables and given/known data


    I have to derivate the two phase multiplier R which is a function of the following parameters: [itex]\dot{x}[/itex] the steam quality, [itex]\rho_b[/itex] and [itex]\zeta_b[/itex] the density and the friction coefficient at the bubble point respectively, [itex]\rho_d[/itex] and [itex]\zeta_d[/itex] the density and the friction coefficient at the dew point respectively

    2. Relevant equations

    The two-phase multiplier equation is:
    [tex] R = 1 + \dot{x} \left( \frac{\rho_b \zeta_d}{\rho_d \zeta_b} -1 \right) + 3 \dot{x}^{2,637}(1-\dot{x})^{0,565} \left( \frac{\rho_b-\rho_d}{\rho_d} \right) [/tex]

    3. The attempt at a solution

    My attempt:

    [tex] \frac{{\partial R}}{{\partial \dot{x}}} = \left( \frac{\rho_b \zeta_d}{\rho_d \zeta_b} -1 \right) - 3 \left( \frac{\rho_b-\rho_d}{\rho_d} \right) \dot{x}^{1,637} (1-\dot{x})^{0,565-1} (2,637 (\dot{x}-1)+0,565 \dot{x}) [/tex]

    [tex] \frac{{\partial R}}{{\partial \rho_b}} = \dot{x} \left( \frac{\zeta_d}{\rho_d \zeta_b} \right) + 3 \dot{x}^{2,637} (1 - \dot{x}) ^{0,565} (\frac{1}{\rho_d}) [/tex]

    [tex] \frac{{\partial R}}{{\partial \rho_d}} = -\dot{x} \frac{\rho_b \zeta_d}{\rho_d^2 \zeta_b} - \frac{3 \rho_b \dot{x}^{2,637} (1 - \dot{x}) ^{0,565}}{\rho_d^2} [/tex]

    [tex] \frac{{\partial R}}{{\partial \zeta_d}} = \frac{\dot{x} \rho_b}{\rho_d \zeta_b} [/tex]

    [tex] \frac{{\partial R}}{{\partial \zeta_d}} = - \frac{\dot{x} \rho_b \zeta_d}{\rho_d \zeta_b^2} [/tex]
  2. jcsd
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