Jordan Gracia 32 sub and 5 videos
2 answers:
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Answer:
and
Explanation:
Given
Represent the height as h, the length as l and the width as w.
From the question:
Volume of a box is calculated as:
This gives:
Substitute 9 for V
Make h the subject:
The surface area is calculated as:
Recall that:
Recall that:
So:
To minimize the surface area, we have to differentiate with respect to w
Set A' to 0
Add to both sides
Multiply both sides by
Make the subject
Solve for w
Recall that : and
Hence, the dimension that minimizes the surface area is:
and
Answer:
a)
b)
Explanation:
From the properties of Super-heated Refrigerant 134a Vapor at ,
; we obtain the following properties for specific enthalpy and specific entropy.
So; specific enthalpy
specific entropy
Also; from the properties of saturated Refrigerant 134 a vapor (liquid - vapor). pressure table at ; we obtain the following properties:
Given that the power input to the compressor is 2 hp;
Then converting to Btu/hr ;we known that since 1 hp = 2544.4342 Btu/hr
2 hp = 2 × 2544.4342 Btu/hr
2 hp = 5088.8684 Btu/hr
The steady state energy for a compressor can be expressed by the formula:
By neglecting kinetic and potential energy effects; we have:
b) To determine the entropy generation; we employ the formula:
In a steady state condition
Hence;