Simulation and Experiment on Heat Exchanger for Automobile Thermoelectric Generator
|Keywords||automobile exhaust thermoelectric generation heat transfer enhancement numerical simulation finned pipes|
The vehicle production of China is more than1900million in2010. The rapiddevelopment of automobile industry made us become the automobile manufacturingindustrial nation.30%-40%of the energy is discharged to the atmosphere in the form ofhigh temperature exhaust gas when the car is running. Its low energy efficiency has poseda serious energy crisis and serious environmental pollution.Thermal power generation technology enables converse the heat energy into electricalenergy directly. If this kind of technology is applied in automobiles to converse the heatenergy from exhaust into electrical energy, not only improve the efficiency of the gasoline,but also reduce the heat pollution.Thermoelectric conversion efficiency mainly depends on the performance of thethermoelectric materials and the temperature difference between thermoelectric generationmodule cold/hot sides. To improve thermoelectric generation module cold and hot sidetemperature difference is the research focus at the present stage under the premise thatthermoelectric materials research breakthrough is not achieved. In this paper, advancing anew kind of flat thermoelectric heat exchange channel, which is attached the rectangularfins in the inner surface to the convective heat transfer intensity and improve the channeloutside wall temperature. By this way to increase the temperature difference, improve thethermoelectric conversion efficiency.Based on the study research status of thermoelectric generators, the study identifiedthe flat thermoelectric heat exchanger channel dimensions, while to determine structuralparameters of the fins attached the inner wall surface (length l, the spacing d and height h).Using computational fluid dynamics software GAMBIT and FLUENT to modeling andsimulation, finding that the heat transfer performance of finned pipe is superior to smoothpipe. Through the optimizing of fins on the structural parameters obtain the overall enhancement ratios of different trends along the pipe. Get the fin heat pipe structureparameters makes the best performance: l=400mm, d=20mm, h=50mm.Its overallenhancement ratio is1.25when the inlet flow rate is10m/s.According to the simulation results, choose three kinds of pipes includes smooth pipe,best performance finned pipe (type Ⅱ finned pipe) and normal finned tubes (typeⅠfinned pipe)as the automobile thermoelectric generator heat exchange channels to build abench. Measure the average temperature of the heat exchange channels outside surfaces,the open circuit voltage, the load voltage, and pressure losses of pipes. The experimentalresults show that the finned pipes outside surface average temperature, the open circuitvoltage, the load power is higher than the smooth pipe, wherein the type Ⅱfinned pipe isthe highest. Compared with the smooth pipe, the average wall temperature was increasedby22.7%, the open circuit voltage was increased by28%,and the load power wasincreased by30%when the inlet temperature was200℃, flow rate of30m/s. Theexperiment results are consistent with the simulation results, verifying the correctness ofthe simulation results.Found by calculating the output power of thermoelectric generators are low, this paperanalyzes and summarizes the factors leading to this result, providing a foundation forsubsequent improved further study.