Q1: Which of the following is directly concerned with psychrometry ?

ANS:A - Lewis reltionship

The Lewis relationship is a concept used in the field of mass transfer, particularly in the context of diffusion in fluid systems. It describes the relationship between the mass diffusivity (often represented by the symbol 𝐷D) and the thermal diffusivity (often represented by the symbol 𝛼α) of a substance. Mathematically, the Lewis relationship is expressed as: Lewis Number=Thermal DiffusivityMass Diffusivity=𝛼𝐷Lewis Number=Mass DiffusivityThermal Diffusivity​=Dα​ It essentially quantifies the ratio of thermal diffusivity to mass diffusivity in a given fluid system. This dimensionless number is significant in processes where both heat and mass transfer occur simultaneously, such as in chemical reactors, distillation columns, and various other industrial and natural processes. The Lewis number helps in understanding how temperature gradients in a fluid affect the transport of mass within it and vice versa. For example, in a system where heat and mass are being transferred, a low Lewis number indicates that thermal diffusion dominates over mass diffusion, meaning that temperature gradients play a more significant role in the transfer process. Conversely, a high Lewis number suggests that mass diffusion is dominant over thermal diffusion. Understanding the Lewis relationship is crucial for optimizing processes involving simultaneous heat and mass transfer, as it provides insights into how changes in temperature and concentration gradients affect overall system performance.