Chapter 3, Problem 3.33P

Interpretation Introduction

Interpretation:

The feed rate of logs $\left(\text{logs}/\text{min}\right)$ to produce dry wood pulp is to be calculated.

Concept introduction:

In a system, a conserved quantity (total mass, mass of a particular species, energy or momentum) is balanced and can be written as:

$input+generation-output-consumpumtion=accumulation$

Here, ‘input’ is the stream which enters the system. ‘generation’ is the term used for the quantity that is produced within the system. ‘output’ is the stream which leaves the system. ‘consumption’ is the term used for the quantity that is consumed within the system. ‘accumulation’ is used for the quantity which is builds up within the system.

All the equations which are formed are then solved simultaneously to calculate the values of the unknown variables.

Specific gravity $\left(\text{SG}\right)$ is a relative term used to express the ratio of density of a substance to the density of the reference substance. Since it is the ratio of same quantity, specific gravity is dimensionless.

From mass flowrate, volumetric flowrate is calculated if the density of the substance is given as:

$\stackrel{•}{V}=\frac{\stackrel{•}{m}}{\rho }$   ........ (1)

Here, $\stackrel{•}{V}$ is the volume of substance per hour in ‘ $\text{L/min}$ ’, $\stackrel{•}{m}$ is the mass of the substance in ‘ $\text{kg/min}$ ’ and $\rho$ is the density of the substance in ‘ $\text{kg/L}$ ’.

Volume of a cylinder is calculated as:

$V=\pi r^{2}h$   ........ (2)

Here, $V$ is the volume of the cylinder in ${\text{m}}^3$, $r$ is the radius of the cylinder in $\left(\text{m}\right)$ and $h$ is the height of the cylinder in $\left(\text{m}\right)$.