![]() ![]() In efforts to reduce climate change, processes that use waste heat for other needs are becoming more relevant. ![]() In almost all industrial processes, more than half of the input energy is turned into waste heat. The hot coolant is cooled by the air stream flowing into the grill, and once sufficiently cooled it is returned to the engine to repeat the process. Once it is hot, it flows to the radiator (as shown in Figure 2) which is located at the front grill of the car. Most vehicles use liquid cooling systems, which send coolant through passages in the engine block and picks up heat from the engine. This isn't a failure of engineering, but rather a limit due to the Second law of thermodynamics (given by the Carnot efficiency). The thermal efficiency ( \eta) which describes the ratio of the useful work to input energy can be found in terms of this waste heat, by the equation:Ĭars generate about 2x more waste heat than actual useful work (with \eta\approx 25\%) which must be rid of in order for the engine to remain at a safe temperature to ensure it doesn't destroy itself. ![]()
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