Exhaust Heat Recovery
Although public awareness of the finiteness of fossil fuel reserves has receded into the background somewhat since it was raised in the 1970s, the impact of pollutant and CO2 input into the earth’s atmosphere is again making the need for a longer range en
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Exhaust Heat Recovery Franz Hirschbichler
14.1.1
Preliminary Remarks
Although public awareness of the finiteness of fossil fuel reserves has receded into the background somewhat after being raised in the 1970s, the impact of pollutant and CO2 input into the earth’s atmosphere is again making the need for a longer range environmentally compatible energy policy with concrete goals evident. In the future, both challenges – conserving resources and protecting the environment – will increasingly require an approach that endeavors to take full advantage of the ample potentials to save energy and additionally intensify the utilization of renewable, i.e. inexhaustible, energy sources. Both goals will have to be pursued simultaneously, i.e. in parallel, rather than sequentially. This will necessitate research on the types of waste heat that accumulate during diesel engine combustion as well as expedient recovery methods for the purpose of conserving primary energy and protecting the environment.
14.1.2
While exhaust gas heat is dissipated by gas exchange in the exhaust process, all other waste heat must inevitably be dissipated with the aid of a coolant (water, oil or air). Heat that accumulates in various points of an engine (Fig. 14-1) is transferred to water as the heat transfer medium for recovery of varying complexity. While cooling energy is transferred to water/water or air/water heat exchangers without any problem, the transfer of exhaust gas heat loaded with particulate matter and soot particulates to a gas/water heat exchanger proves to be somewhat more complicated (see Sect. 9.2.5.5).
Residual heat
Exhaust gas cooling
Diesel Engine Waste Heat
Exhaust gas heat
Basics of Waste Heat Recovery
Turbine cooling
The following types of waste heat can be distinguished on the basis of their origin: – waste heat from exhaust gas generated by gas exchange, – waste heat produced as cooling energy to protect metallic walls, e.g. cylinder cooling, piston cooling and, where applicable, cooling of turbocharger turbine housings and oil cooling of bearings and interior walls, – waste heat from intercooling, which serves to boost engine power and net efficiency, and – waste heat emitted from the engine surface to the environment as radiation and convection heat.
Cylinder cooling
Cooling water heat
14.1
Shaft power Oil cooling
Intercooling System boundary
F. Hirschbichler (*) Mu¨nchen, Germany e-mail: [email protected]
Fig. 14-1 External heat balance and waste heat of a diesel engine
K. Mollenhauer, H. Tschoeke (eds.), Handbook of Diesel Engines, DOI 10.1007/978-3-540-89083-6_14, Springer-Verlag Berlin Heidelberg 2010
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F. Hirschbichler
Radiation and convection heat emitted by an engine is usually dissipated by aerating and ventilating the underhood environment. In principle, it may also be dissipated with the aid of an air/water heat pump and recovered. This has been implemented in very few cases though. In addition to being dissipated and exchanged differently, the different types of diesel engin
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