Chapter 8, Problem 8.65P

Interpretation Introduction

(a)

Interpretation:

The outlet water temperature is to be calculated. Also, compare it with the outlet temperature of propane.

Concept introduction:

Saturated vapor is the vapor at temperature of its boiling point corresponding to a particular pressure and it is on the verge of condensing with removal of heat from it.

Saturated liquid is the liquid at temperature of its boiling point corresponding to a particular pressure such that any addition of heat to it leads to its vaporization.

Interpretation Introduction

(b)

Interpretation:

The rate of the heat transferred from the propane to the water in the heat exchanger and the flowrate of water stream are 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:

$\text{input+generation-output-consumpumtion=accumulation}$

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.

The equation for energy balance is:

$\Delta \dot{H}+\Delta {\dot{E}}_{\text{k}}+\Delta {\dot{E}}_{\text{p}}=\dot{Q}-{\dot{W}}_{\text{s}}$ ...… (1)

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.

For an adiabatic system, the heat lost by one component in the system is the heat gained by another component in that system. Thus,

${\dot{Q}}_{lost}={\dot{Q}}_{gain}=\left(\dot{m}{C}_p\Delta T\right)$ ...… (2)

An ideal gas is the gas which obeys ideal gas laws which is a simplified equation of states.

A real gas behaves as an ideal gas at higher temperature and lower pressure. At STP, a lb-mole of an ideal gas has a volume of $359.5{\text{ ft}}^3$.