PROBLEM $1($REQUIRES SUPPLEMENTARY BOOKLET$)$

$[$ TOTAL MARKS : $15]$

An adiabatic dryer is operated as shown in the figure below. The entire system operates at $1$

atmosphere $($absolute$).$ The feed $($Stream $1)$ contains $100k\frac{g}{h}$ of "dry" solids and $122k\frac{g}{h}$ of

water. The solids are dried to $8wt\%$ water $($Stream $2)$ by contact with hot air $($Stream $4).$ Fresh

air $($Stream $3)$ at $21C$ is heated to $52C($Stream $4),$ with an absolute humidity of $0\mathrm{.}011kg$

water$/$kg Dry Air. The warm, moist air which has dried the solids is vented to the atmosphere

$($Stream $5).$

a$)$ Determine the total and water mass flows of stream $2.[$kg$/$h$].[4$ MARKS$]8\mathrm{.}7k\frac{g}{h}$

b$)$ The dryer works adiabatically. The wet air leaving the dryer has a relative humidity of

$90\%.$ Show $($and label$)$ streams $3,4$ and $5,$ on the chart, and indicate the path the air

stream follows from point $3$ to $5.$ Determine the absolute humidity of stream $5.$

$[5$ MARKS$]$

c$)$ Determine the flow rate of dry air required to perform the drying $[$kg$/$h$].[3$ MARKS$]10,790kg$

d$)$ How much energy $kW$ must be added to the heater?

$[3$ MARKS$]$

$94kW$