Chapter 4, Problem 4.48P

Interpretation Introduction

Interpretation:

The heating cost in $\frac{\text{\$}}{\text{million}\text{(btu)}}$ and $\frac{\text{\$}}{\text{MJ}}$ for a propane-fired water heater should be calculated with efficiency $\text{80\%}$ of the standard heat of combustion of the propane at ${\text{25}}^{\text{o}}\text{C}$ and products as carbon dioxide and water in gas. If price of propane is given as $\frac{\text{\$2}\text{.20}}{\text{gallon}}$ at ${\text{25}}^{\text{o}}\text{C}$ .

Concept Introduction:

The standard heat of combustion can be calculated as:

$\Delta H^{\circ }{}_f=\Delta H^{\circ }{}_P-\Delta H^{\circ }{}_R$........ (1)

And generalize correlations for $V^l$ in liquids:

$V^{liq}=V_c{Z}_c{}^{{(1-T_r)}^{2/7}}$.......(2)

And for rest problem, the concept used in this problem is based on unit consistency. The given values are used to balance the unit for unknown value which is $\frac{\text{\$}}{\text{million}\text{(btu)}}$ and $\frac{\text{\$}}{\text{MJ}}$ .