 # A rigid container equipped with a stirring device contains 2.5 Ben Shaver 2021-12-16 Answered
A rigid container equipped with a stirring device contains 2.5 kg of motor oil. Determine the rate of specific energy increase when heat is transferred to the oil at a rate of 1 W, and 1.5 W of power is applied to the stirring device.
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Step 1
Given
1) mass of oil $m=2.5Kg$
2) Heat transfer ${\stackrel{˙}{Q}}_{\in }=1W$
3) Power $\stackrel{˙}{W}=1.5W$
Required
Determine the rate of specific energy increase
Assumptions
This is a closed system since on mass enters or leaves
Step 2
Solution
We take the oil in the container as our system.The energy balance could be defined as the following
${E}_{\in }-{E}_{out}=\mathrm{\Delta }{E}_{sys}$
${\stackrel{˙}{Q}}_{\in }+{\stackrel{˙}{W}}_{\in }=\mathrm{\Delta }\stackrel{˙}{E}$˙
The rate of energy increase could be defined as the following
$\mathrm{\Delta }\stackrel{˙}{E}=1+1.5=2.5W$
The rate of specific energy increase could be defined as the following
$\mathrm{\Delta }\stackrel{˙}{e}=\frac{\mathrm{\Delta }\stackrel{˙}{E}}{m}$
$\mathrm{\Delta }\stackrel{˙}{e}=\frac{2.5}{2.5}=1\frac{J}{K}g.s$

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