QUESTION

$5$

Ambient air at

$30$

oC dry bulb temperature and

$30$

$\%$

$$relative humidity is heated to

$120$

oC dry

bulb temperature. The heated air is introduced into a spray drier where it is used to dry a food

sample. The food sample enters the spray drier at a feed rate of

$5$

$$kg

$/$

h

$,$

$$has an initial moisture

content of

$70$

$\%$

$$and leaves the spray drier with a moisture content of

$5$

$\%$

$$after drying. After

the drying process, air exits the spray drier at

$60$

oC dry bulb temperature.

$5\mathrm{.}1$

$$Estimate the dew point and wet bulb temperature of the air after the drying process.

$(4)$

$5\mathrm{.}2$

$$Calculate the mass flow rate of air through the drier in kg dry air per minute correct to the

nearest whole number.

$(11)$

$[15$

$$MARKS

$]$