In a run around system, what is done with the heat absorbed from exhaust air?

In a run around system, the heat absorbed from exhaust air is transferred to inlet air. This process occurs in a heat exchanger, where the exhaust air, typically warmer due to containing waste heat, passes through a coil or tubing that's also inhabited by the inlet fresh air. As the two air streams pass by each other in the system, heat energy from the exhaust air is effectively transferred to the incoming air.

This method is highly efficient because it preheats the incoming air before it’s conditioned and circulated back into a space, thereby reducing the energy required by heating or cooling systems. This process not only enhances the efficiency of the system but also contributes to energy savings and improved environmental sustainability, as it utilizes waste heat rather than simply discharging it into the environment.

The other choices do not align with this operational principle. For example, while discarding heat or releasing it into the environment may happen in different systems, it is not the function of a run around system which creatively harnesses waste heat.