ANS:D - all (a), (b) and (c).

The use of transverse baffles in a shell and tube heat exchanger serves multiple purposes, including: a) Increase the rate of heat transfer: Transverse baffles help enhance heat transfer by promoting turbulence and increasing the surface area available for heat exchange between the fluids flowing through the tubes and the shell. b) Increase flow velocity: Transverse baffles can alter the flow path of the fluid within the shell, leading to increased flow velocity. This increased velocity helps prevent stagnation of the fluid and improves the overall efficiency of heat transfer. c) Increase turbulence of shell-side fluid: The presence of transverse baffles disrupts the flow of the shell-side fluid, inducing turbulence. Turbulent flow enhances heat transfer by ensuring better mixing of the fluid and promoting greater interaction between the fluid and the heat exchange surfaces. Therefore, the correct answer is: d) all (a), (b) and (c). Transverse baffles serve to increase the rate of heat transfer, flow velocity, and turbulence of the shell-side fluid in a shell and tube heat exchanger.