Chapter 9, Problem 9.23P

Interpretation Introduction

(a)

Interpretation:

The inlet-outlet enthalpy table for the given process is to be prepared and filled using elemental species as reference.

Concept introduction:

Specific heat capacity $\left(C_p\right)$ of a substance is the amount of heat needed for a unit mass of substance to raise its temperature by $1^{\circ }\text{C}$. It is temperature dependent and varies with temperature of the substance.

Specific enthalpy $\left(\hat{H}\right)$ of any substance at temperature $T^{\circ }\text{C}$ is given by:

$\hat{H}={\int }_{T_{ref}}^T{C}_{p}dT$    …… (1)

Here, $T_{ref}$ is the reference temperature taken for the calculations.

Interpretation Introduction

(b)

Interpretation:

The required rate (kW) of heat transfer to or from the reactor is to be calculated.

Concept introduction:

The equation for energy balance is:

$\Delta \dot{H}+\Delta {\dot{E}}_{\text{k}}+\Delta {\dot{E}}_{\text{p}}=\dot{Q}-{\dot{W}}_{\text{s}}$    …… (2)

Here, $\Delta \dot{H}$ is the rate of change in the enthalpy of the system, $\Delta {\dot{E}}_{\text{k}}$ is the rate of kinetic energy change of the system, $\Delta {\dot{E}}_{\text{p}}$ is the rate of potential energy change of the system, $\dot{Q}$ is the net rate at which energy is transferred to a system and ${\dot{W}}_{\text{s}}$ is the rate at which energy is transferred as shaft work.

Interpretation Introduction

(c)

Interpretation:

If molecular species are taken as reference for the calculations, then the difference in the results of part (a) and part (b) are to be stated.

Concept introduction:

For multiple reactions taking place in a reactor, $\Delta \dot{H}$ is calculated from the equation,

$\Delta \dot{H}=\sum _{\text{reactions}}{\dot{\xi }}_j\Delta {\hat{H}}_{rj}{}^{\circ }+\sum {\dot{n}}_{\text{out}}{\hat{H}}_{\text{out}}-\sum {\dot{n}}_{\text{in}}{\hat{H}}_{\text{in}}$    …… (3)

Here, ${\dot{\xi }}_j$ is the extent of the reaction.