Chemical Engineering - Heat Transfer - Discussion

Please someone explain this question.

What is the graph?

This depend upon the graph of cost vs Area.

How this can happen? Kindly give the detailed explanation.

It is about the insulation done on the bodies, as a graph of " heat loss vs radius of insulation".

Why cost per unit area decreases with increasing area?

This is due to economies of scale in heat exchanger manufacturing. The purchased cost of a shell-and-tube heat exchanger does not increase linearly with area; instead, it follows a power-law relationship:

Typically, for shell-and-tube exchangers, the exponent is approximately $n approximately 0.6$ .

Cost per unit area:
Since $n-1$ is negative, the cost per unit area decreases as area $A$ increases .

Practical reason:

Fixed costs (design, fabrication setup, shells, heads) are spread over more surface area
Larger exchangers use material more efficiently (less material per unit area)
Manufacturing and installation costs don't scale linearly.

So, the correct Answer is : Option B — decreases.

Please I need explain.

What does it mean to pass through maxima?

Please explain.

This is because the fixed costs of the equipment (such as the cost of the shell, tube sheets, and other components) are spread over a larger surface area, leading to economies of scale.

In my opinion, the increase of the heat transfer area may be a high cost.