A $1-2$ shell and tube heat exchanger will be used to heat $4$ kg$/$s of a liquid food $($density $1020$ kg$/$m$^3,3850$ J$/$kg K$,$ p$=0\mathrm{.}5$x$10$ Pa$.$s$,$ k$=0\mathrm{.}68$ W$/$m$.$K$)$ from $5\backslash$deg C to $75\backslash$deg C by $10$ kg$/$s of liquid water at an intet temperature of $95$ C$.$ Heating medium flows through the shell$-$side. The fouling coeficient for the shell side is estimated as $0\mathrm{.}004$ m$^2$ KW$.$ The heat transfer coefficient for the shell side will be assumed as $10000$ W$/$m$^2$K$.$ The pipe has inner and outer diameter of $22\mathrm{.}1$ mm and $25\mathrm{.}4$ mm$,$ respectively. SS $5$ cm$.$

Number of tubes is $86$ What type of heat transfer mechanism occurs in that system, give your reasings by explaing the mechanism briefly and drawing the thermal resistance diagram.