You're reading an old version of this documentation. For the latest released version, please have a look at v4.4.0.

Lumped rate model without pores (LRM)

The lumped rate model without pores [3, 4] deviates from the lumped rate model with pores (see Section Lumped rate model with pores (LRMP)) by neglecting pores completely. The particle phase \(c^p\) is removed and the porosity \(\varepsilon_t\) is taken as total porosity

(10)\[\begin{aligned} \varepsilon_t = \varepsilon_c + \left( 1 - \varepsilon_c \right) \varepsilon_p. \end{aligned}\]

The phase ratio is denoted by \(\beta_t = \varepsilon_t / (1 - \varepsilon_t)\) accordingly. The model equations are given by

\[\begin{aligned} \frac{\partial c^l_i}{\partial t} + \frac{1}{\beta_t} \frac{\partial}{\partial t} \sum_{m_i} c^s_{i,m_i} &= -u \frac{\partial c^l_i}{\partial z} + D_{\text{ax},i} \frac{\partial^2 c^l_i}{\partial z^2} + f_{\text{react},i}^l\left( c^l, c^s \right) + \frac{1}{\beta_t} f_{\text{react},i}^s\left( c^l, c^s \right), \end{aligned}\]

where \(\beta_t = \varepsilon_t / (1 - \varepsilon_t)\) denotes the (total) phase ratio. The equations are complemented by Danckwerts boundary conditions [8]

\[\begin{split}\begin{aligned} u c_{\text{in},i}(t) &= u c^l_i(t,0) - D_{\text{ax},i} \frac{\partial c^l_i}{\partial z}(t, 0) & \forall t > 0,\\ \frac{\partial c^l_i}{\partial z}(t, L) &= 0 & \forall t > 0. \end{aligned}\end{split}\]

Both quasi-stationary and dynamic binding models are supported:

\[\begin{split}\begin{aligned} \text{quasi-stationary: }& & 0 &= f_{\text{ads}}\left( c^l, c^s\right), \\ \text{dynamic: }& & \frac{\partial q}{\partial t} &= f_{\text{ads}}\left( c^l, c^s\right) + f_{\text{react}}^s\left( c^l, c^s \right). \end{aligned}\end{split}\]

By default, the following initial conditions are applied for all \(z \in [0,L]\):

\[\begin{aligned} c^l_i(0, z) &= 0, & c^s_{i,m_i}(0,z) &= 0. \end{aligned}\]

Note that by setting \(\varepsilon_t = 1\), removing all bound states by setting \(N_{\text{bnd},i} = 0\) for all components \(i\), and applying no binding model, a dispersive plug flow reactor (DPFR) is obtained. For the specification of flow rate and direction, the same holds as for the general rate model (see Section Specification of flow rate / velocity and direction).

For information on model parameters see Lumped Rate Model Without Pores.