【作者】 雷萌；

【导师】 马新灵；

【作者基本信息】 郑州大学 ， 化工过程机械， 2021， 硕士

【摘要】 随着“十四五”的到来,我国能源结构会做进一步的调整,更要尽可能提高能源的综合利用率。有机朗肯循环(Organic Rankine Cycle,简称ORC)作为回收中低温余热的有效技术,已经得到广大学者的高度认可。而板式换热器因传热效率高、占地面积小等优势而被作为ORC系统中的蒸发器和冷凝器,其性能直接影响ORC系统的整体性能。本文通过Aspen Plus和Aspen EDR软件模拟了板式换热器和ORC系统的性能,并在不同运行参数下进行了实验研究。具体内容如下:(1)用Aspen Plus软件建立了ORC系统的模型,研究了换热器传热面积对系统性能的影响,并从多个角度考虑,确定了R245fa、R1233zd(E)及R1234ze(E)为工质时系统的最优蒸发器/冷凝器的传热面积。在此基础上,通过Aspen Plus和Aspen EDR的交互功能,研究了板式换热器人字形波纹角及板片厚度对系统性能的影响。结果表明:一定范围内波纹角越大、板片厚度越薄,则系统的净输出功率越大,但对热效率的影响较小。经综合考虑,确定了板式换热器的波纹角、板片厚度以及下一步模拟研究所使用的工质。(2)以R245fa为工质,模拟研究了不同运行参数对系统热力性能的影响。结果表明:随着工质流量的增加,系统的热效率先保持不变然后逐渐增加,而系统的（火用）效率则先减小后增大;热源流量的增加使系统的净输出功率增大、热效率和（火用）效率降低;此外,工质的冷凝压力越低、蒸发压力越高,系统的热力性能越好,蒸发压力为0.6 MPa时系统的净输出功率最大。(3)以R245fa为工质,在基于向心透平的ORC发电平台进行了实验研究。结果表明:热源、冷源一定时,有机工质流量的增加使蒸发器内的气相区逐渐减小,直至蒸发器的面积优先供给工质完成预热和蒸发过程;最佳工质流量为800 kg/h,此时蒸发器内传热面积的分配相对均衡,系统各方面性能指标也最佳。而不同工质流量下冷凝器内两相区的UA值始终最大,且有足够的传热面积完成单相传热,因而其传热面积的分配始终相对均衡。相比之下,工质流量变化时系统中冷凝器的稳定性优于蒸发器。(4)基于最佳工质流量,分别研究了导热油流量及冷却水流量对换热器及系统性能的影响。结果表明:导热油流量过大也会导致蒸发器内传热面积分配不均衡。最佳导热油流量为4 m~3/h,此时的净输出功率、热效率和（火用）效率分别为1.62 k W、2.63%和9.38%。冷却水流量增加的过程中,冷凝器内有足够的传热面积用于相变以及单相传热。冷却水流量最大时系统性能最佳,此时的净输出功率、热效率和（火用）效率分别为2.13 k W、3.43%和12.2%。综上可知,ORC系统中冷凝器在不同运行参数下的稳定性优于蒸发器。更多还原

【Abstract】 With the arrival of the"14th five-year Plan",China’s energy structure will be further adjusted and energy utilization efficiency will be also improved as much as possible.As an effective technology for the recovery of medium and low temperature waste heat,Organic Rankine cycle has been highly recognized by the majority of scholars.Plate heat exchanger is often used as evaporator or condenser in ORC system because of its high heat transfer efficiency and small occupation,which directly affects the overall performance of ORC system.In this paper,plate heat exchanger and ORC system are simulated by Aspen Plus and Aspen EDR.And experiments are carriedout under different operating conditions.The main research contents are as follows:(1)The model of ORC system is established by using Aspen Plus software,and the impacts of heat transfer area of heat exchangers on system are studied.From two different aspects,the optimal heat transfer area of evaporator/condenser is determined when R245fa,R1233zd(E)and R1234ze(E)are selected as working fluid of the system,respectively.Then,the impacts of chevron angle and plate thickness of the plate heat exchanger on the performance are studied through the interactive function of Aspen Plus&Aspen EDR.The results show that the larger the chevron angle and the thinner the thickness of the plate in a certain range,the greater the net output work of the system,but it has almost no effects on the thermal efficiency and exergy efficiency.After comprehensive consideration,the chevron angle and plate thickness of plate heat exchanger and working fluid used in the next simulation study are determined.(2)With R245fa as working fluid,the impacts of different operating conditions on the thermodynamic performance of the system was simulated.Results show that the thermal efficiency of the system firstly remains unchanged and then increases gradually with the increase of working fluid flow rate,while the exergy efficiency decreases and then increases.The increase of heat source flow rate reduces the thermal efficiency and exergy efficiency of the system;In addition,the lower the condensing pressure and the higher the evaporating pressure,the better the thermodynamic performance of the system.The net output power is the largest when the evaporation pressure is 0.6 MPa.(3)With R245fa as working fluid,the related experiments were carried out on the ORC experimental platform based on turbine.The results show that the increase of working fluid flow rate will gradually reduce the gas phase area in the evaporator until the area of evaporator is given to complete the preheating and evaporation processes with priority when the conditions of heat source and cold source are constant.Distribution of heat transfer area in the evaporator is relatively balanced when the working fluid flow rate is 800 kg/h,and the optimal system performance is obtained.Under different working fluid mass flow rates,the UA value of the two-phase region in the condenser is always larger than that of the single-phase region,and there is enough heat transfer area to complete the heat transfer in single-phase regions.So the distribution of heat transfer area is always relatively balanced.In contrast,thestability of the condenser is better than that of the evaporator under different working fluid flow rates in the ORC system.(4)Based on the optimal working fluid flow rate,the impacts of heat transfer oil flow rate and cooling water flow rate on the UA value and system performance were studied.The results show that the excessive flow rate of heat transfer oil will also lead to the uneven distribution of heat transfer area in the evaporator.The optimal net output work,thermal efficiency and exergy efficiency are 1.62k W,2.63%and 9.38%when the optimal heat transfer oil flow rate is 4 m~3/h,respectively.With the increase of cooling water flow rate,there is sufficient heat transfer area for heat transfer in any regions.The optimal performance is obtained when the cooling water flow rate is maximum and the net output work,thermal efficiency and cooling efficiency are2.13k W,3.43%and 12.2%,respectively.To sum up,the stability of condenser in ORC system is better than that of evaporator under different operating parameters.更多还原