The only thing strange about that description is you're calling them funny; otherwise, it's quite a good one. Heat recovery systems, in essence, aim to the capture of heat which would generally be considered as waste and then reuse it for other parts of the building. Using their afterdust, vents, or any other industrial process, instead of just discarding excellent energy, these systems take back the lost energy and make it serve different purposes.
For example, in manufacturing plants, a lot of equipment generates excess heat during operation. Without a recovery system, that heat simply escapes into the atmosphere. With heat recovery systems in place, the captured energy can be used to preheat air, warm water, support production processes, or reduce the workload on heating equipment.
One reason engineers like these systems is that they improve overall energy efficiency. When a facility can reuse existing heat, it often consumes less fuel or electricity to achieve the same results. This allows the reduction of operating costs and the elimination of energy consumption largely.Industries apply different heat recovery systems which are mainly dependent on their requirements. Some obtain heat from the exhaust air whereas others capture thermal energy from the cooling systems or industrial tools. The selected method is dependent on a number of parameters like temperature, production, and layout of the facility.Because of this, though "leftovers" may be a laughable word, it effectively portrays the main concept. Heat recovery systems ensure that the lost energy can be exploited. Instead of disposing of heat, which represents that energy which was paid for, companies can reprocess the heat and get more benefits from the energy that they use daily.