$2.$

$($a$)$ Write a brief technical note on the main types of contact and non$-$contact heat exchangers employed in food processing applications. Illustrate your answer with neat sketches where appropriate.

$($b$)$ Steam in the condenser of a process plant is to be condensed at a temperature of $30$C with cooling water which enters the tubes of the condenser at $14$C and leaves at $22$C$.$ The surface area of the tubes is $45$ m$2$ and the overall heat transfer coefficient is $2,100$ W m$-2$C $-1.$ The heat of vaporisation of water at $30$C is $2,430$ kJ kg$-1.$

Determine the mass flow rate of the cooling water required and the rate of condensation of the steam in the condenser.