Questions $(40$ pts$)$:

Define the main types of heat exchangers $($Counter$-$Current, Co$-$Current, Parallel Flow$).$ Provide examples of their applications. $(8$ pts$)$

Which type of exchanger is more efficient, the Counter$-$Current or Co$-$Current? Explain why using graphs and formulas. $(8$ pts$)$

Between the two rays $($A and B$),$ which one is more energetic? Explain your answer with formulas. $(8$ pts$)$

Explain the process of how a ray is received by a body. What proportion contributes to increasing the body's energy? $(8$ pts$)$

What is the difference between a black body and an opaque body in the context of radiation? $(8$ pts$)$