| A large amount of energy is discharged with the engine exhaust during the driving process,which makes the fuel energy efficiency low,resulting in a great waste of energy and environmental pollution.On account of the Seebeck effect,the thermoelectric technology can straightly translate heat into electricity.It has the advantages of no noise and no chemical reaction.So it becomes a good way for waste heat recovery.Therefore,it is generally used in the fileds,such as automobile exhaust waste heat recovery,solar energy waste heat recovery and so on.However,solar heat,industrial waste heat and automobile exhaust all have the characteristics of frequent temperature changes and instability,which will cause great damage to the thermoelectric generation system,seriously affect its output performance,and even directly cause the thermoelectric generation module to fail.In order to reduce the influence of unstable heat sources on the thermoelectric power generation system,this paper uses the characteristics of phase change materials that can store heat in intermittent heat sources.A phase change material-thermoelectric generation(PCM-TEG)system is designed and compared with the common TEG system.The influence of the PCM on the hot side temperature,cold side temperature,and output performance of TEG is analyzed.The effect of PCM on the hot and cold end temperature and output performance of TEG module is studied,and the influences of different cold end heat dissipation intensity and pulse transient boundary conditions of different fluctuation frequency on the output performance of PCM-TEG system are analyzed.In addition,in order to improve the output performance of the PCM-TEG system,the phase change energy storage unit is simulated based on FLUENT software.The influence of different fin thickness and number on the internal heat transfer characteristics and wall temperature of the phase change energy storage unit are explored.The core research contents of this paper are as follows:(1)The PCM used in the experiment is erythritol.The latent heat capacity and phase change temperature of PCM are measured by differential scanning calorimetry(DSC).The result show that the latent heat capacity and the phase change temperature is 330.3k J/kg and 117.7 ?,respectively.The PCM-TEG system and the common TEG system are built to explore the influence of PCM on the temperature of the hot and cold sides of the TEG and its output performance.The results show that PCM plays an important role in reducing the influence of unstable heat sources on the temperature of the hot and cold sides of the TEG.PCM can effectively reduce the fluctuation of the output voltage of the TEG and the TEG can produce more stable output power.In addition,although the total electrical energy generated by the common TEG system is more than that of the PCM-TEG system,the PCM-TEG system generates more electrical energy due to the release of latent heat and sensible heat stored in the PCM when there is no heat input.(2)Based on the PCM-TEG system,the effects of different cold side heat dissipation intensity and different frequency pulse transient boundary conditions on the PCM-TEG system are studied.When the transient boundary condition of the heat source pulse is constant,the stronger the cold side heat dissipation capacity,the later the PCM starts to melt,the greater the temperature fluctuation range of the hot and cold side of the TEG,the greater the fluctuation range of the output voltage,output current and output power generated.When the heat dissipation intensity of the cold side of the PCM-TEG system is kept constant,the greater the fluctuation frequency of the transient boundary conditions of the heat source pulse,the greater the fluctuation of the internal temperature of the PCM,the greater the temperature fluctuation of the hot and cold side of the TEG module,and the greater the fluctuation of the load voltage,output current and output power generated by the TEG module.(3)The simplified model of phase change energy storage unit is established by simulation software,the fin number and fin thickness of phase change energy storage unit are explored.The influence of different fin number and thickness on PCM liquid rate,PCM average temperature and wall temperature of phase change energy storage unit are analyzed.The results show that the increase of the number of fins has a positive effect on the heat transfer of the phase change energy storage unit.When the thickness of the fin is constant,the liquid phase rate changes,and the heat storage rate of the phase change energy storage unit increases with the increase of the number of fins.The wall temperature of the phase change energy storage unit decreases with the increase of the number of fins.The thickness of different fins has a certain influence on the heat transfer of PCM.The average temperature of the PCM varies over time and the rise rate of the liquid phase rate increase with the thickness of the fins. |
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