Refrigeration and Freezing

Plank's equation for estimating the freezing time $t_f$ of a food slab of thickness $a$ is:

Options:

• (A) $t_f = \frac{\rho_f \lambda}{T_F - T_a} \left[\frac{P a}{h} + \frac{R a^2}{k_f}\right]$
• (B) $t_f = \frac{\lambda}{\rho_f} \left(\frac{a}{h}\right)$
• (C) $t_f = \frac{k_f a}{\rho_f \lambda}$
• (D) $t_f = \frac{P a + R a^2}{h}$