| Latent heat storage technology attracts much attention due to high heat storage density,heat release at a fixed temperature,and repeatable utilization.Nevertheless,researches about latent heat storage system(LHSS)used for high temperature application,especially above 1273.15 K,have been rarely reported and basically limited to molten salts.Moreover,the reports about LHSS filled with all metal phase change capsules for high temperature applications are fewer.The mechanisms of heat storage and heat filter of LHSS filled with all metal phase change capsules are scarce.In this dissertation,Cu@Cr@Ni,concrete,Ni,and MgCl2@304 L stainless steel are used as heat storage materials(HSMs).The high temperature converter gas is used as heat transfer fluid(HTF).The fixed bed heat storage system is adopted.The performances of heat storage and heat filter of heat storage system are investigated from four aspects including the packed forms of HSMs,the ratio of the length and diameter of the container,the inlet velocity of HTF,and the inlet temperature fluctuation period and amplitude of HTF.A fixed bed heat storage system filled with spherical HSMs has two packing forms,including specially packed bed(SPB)and randomly packed bed(RPB).The performances of heat storage and heat filter of SPB and RPB heat storage system were numerically simulated and compared.The concept of the attenuation ratio is proposed and used to evaluate the attenuating fluid temperature fluctuation performance of the heat energy storage system.The calculation results show the turbulent perturbation becomes more intense and the velocity of HTF becomes faster in the RPB heat storage system due to the staggered arrangement of the HSMs,resulting in a better ability of heat exchange between HTF and heat storage materials(HSMs),higher rate of temperature rise,shorter time needed by completing phase transition,higher heat storage efficiency and better performance of attenuating the HTF temperature fluctuation amplitude.In addition,the heat storage system filled with Cu@Cr@Ni capsules has the best performance of recovering waste heat and regulating HTF temperature fluctuation among all heat storage system filled with different HSMs.The effect of the ratio of the structure of the container on the performances of heat storage and heat filter of the RPB heat storage system filled with Cu@Cr@Ni capsules was investigated.The calculation results show that the flow velocity of HTF decreases with the decrease of the ratio of the length and the diameter,resulting in the decrease of the heat exchange rate between Cu@Cr@Ni capsules and HTF,the increase of the time needed by the completed phase transition of Cu@Cr@Ni,and the decrease of the performances of heat storage and heat filter of LHSS.The attenuation ratios of the containers with l/d=1566/340 and l/d=340/1566 are 92.2% and 87.8%,respectively.The effects of the HTF velocity and temperature fluctuation period and amplitude on the performances of heat storage and heat filter of the RPB heat storage system filled with Cu@Cr@Ni capsules were investigated and analyzed by numerical simulation.In this system,the outlet temperature of HTF increases and the energy transfer efficiency between PCMs and HTF decreases with the increase of the inlet velocity of HTF under the condition that the inlet temperature of HTF is 1600 K.When the inlet temperature of HTF is fluctuated in the sine wave way,the fluid temperature fluctuation period has little effect on the fluctuant amplitude of the outlet temperature of HTF,the fluctuant amplitude is about 15.7 K,and the higher fluctuant amplitude of the inlet temperature leads to the higher fluctuant amplitude of the outlet temperature after the outlet temperature fluctuation of HTF reaches a steady state.However,the attenuation ratio of the latent heat storage system filled with Cu@Cr@Ni capsules is about 92.2% and independent of the fluctuant period and amplitude of the inlet temperature of HTF. |
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