Q1: The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (K_c) for the same sytem is

ANS:B - 10

The increase in the Reynolds number for a laminar falling film would lead to an increase in the mass transfer coefficient (𝐾𝑐Kc​) according to the penetration theory. However, the relationship between Reynolds number and mass transfer coefficient is not necessarily linear. In gas-liquid contacting systems, such as falling film evaporators, the mass transfer coefficient is influenced by various factors including fluid properties, flow conditions, and equipment geometry. While an increase in Reynolds number typically enhances mixing and increases mass transfer, the relationship between Reynolds number and mass transfer coefficient can be complex and may not always follow a simple linear relationship. Given that the Reynolds number was increased 100-fold, a reasonable estimate for the fold increase in the mass transfer coefficient (𝐾𝑐Kc​) would likely be less than 100. However, without specific information on the system and its characteristics, it is difficult to determine the exact fold increase in 𝐾𝑐Kc​ accurately. Therefore, based on general trends, a fold increase of around 5 to 10 seems reasonable. So, considering the options provided, a fold increase in the mass transfer coefficient (𝐾𝑐Kc​) of 5 to 10 would be a reasonable estimate for the same system with a 100-fold increase in Reynolds number.