双效溴化锂吸收式热泵余热回收系统数值模拟研究

溴化锂吸收式热泵机组可以有效回收利用工业和建筑中的各种形式低温余热,提高余热资源回收率,但设备参数对热泵性能影响很大。因此本文基于温度对口和梯级利用的原则,对蒸汽型双效溴化锂吸收式热泵机组内传热部件进行热力及传热分析,通过质量和能量守恒建立热泵机组数学模型,分析热网供水温度、蒸发器进口低温余热水温度和驱动热源温度这三个外部因素的变化对系统性能的影响。研究结果表明:热网供水温度在49℃左右,热泵系统COP最佳为2.67;蒸发器进口低温余热水温度在47℃左右时,热泵系统COP最佳为2.67;随着驱动热源温度的上升,热泵系统的COP呈上升趋势。为吸收式热泵实际运行过程中,合理设置设备参数提高热泵性能提供指导。     

水—乙二醇高温吸收式热泵系统的模拟及分析

本文对水/乙二醇高温吸收式热泵系统进行了变工况计算机模拟及分析,着重研究了废热温度,冷却水进出口温差,浓溶液浓度,循环倍率及回流比对系统性能系数和温升的影响,此外,还研究了吸收器进出口溶液浓度差及废热温度对系统(火用)效率的影响。     

复叠式空气源热泵热水器结霜工况下的机组运行参数研究

复叠式空气源热泵热水器可以在冬季低温(-25℃)下最高提供80℃热水,但是机组结霜问题对机组的效率和供热性能影响较大。通过研究复叠式热泵热水器的结霜规律以及结霜对机组性能的影响,为进一步研究并优化除霜控制方法提供依据。系统分为低温级循环和高温级循环,低温级循环为室外系统,高温级循环及蒸发冷凝器部分为室内系统,热泵循环低温级采用R410A作为循环工质,高温级采用R134a,热泵系统高温级冷凝温度为80℃,低温级的蒸发温度可达-40℃。通过在焓差实验室实验进行研究。测试复叠式热泵的结霜过程时间与结霜量,得到不同室外温湿度与结霜量之间的关系。结霜量通过测量低温级蒸发器进出口含湿量的方法获得,并分析结霜对于机组实际耗电量以及COP等性能参数的影响。     

利用生活废水余热的CO_2热泵系统

为了充分利用生活废水的余热,提出利用生活废水余热作为低温热源的CO2热泵系统,并分析生活废水温度、蒸发温度、气体冷却器出口温度、气体冷却器出口压力、吸气过热度、制取热水温度等参数对CO2跨临界循环热泵系统性能的影响,得出提高蒸发温度、降低气体冷却器出口温度、适当增加过热度会使系统的COP增大,且在生活废水温度为20℃,制取热水温度为60℃,蒸发温度为15℃的工况下,存在最优的气体冷却器出口压力(9.8 MPa),获得最大性能系数(5.5)。CO2热泵的能耗比空气源热泵、电加热器、燃气锅炉、燃油锅炉分别节约38.2%,80.7%,84.8%和82.7%,CO2热泵的年运行费用较低,空气源热泵、电加热器、燃气锅炉和燃油锅炉分别是其1.6倍、5.1倍、2.9倍和5.5倍。     

小型太阳能-热泵耦合系统供暖应用研究

设计具有多种运行模式的太阳能-热泵耦合系统,仅对以太阳能系统制取的低温热水为低温热源的水源热泵系统进行性能测试与数据分析,结果表明:太阳能集热效率最高可达52.8%,热泵COP最大可达3.5;该太阳能-热泵耦合系统可实现能源的综合利用。     

高温吸收式热泵的性能及研究

从热力学原理出发，研究分析了高温吸收式热泵的性能，提出了评价热泵性能的新参数ＣＯＰ·ΔＴ和Ｙｏｎｇ指标ＥＩ，探讨了不同操作条件对热泵性能的影响。     

水箱水温对CO2热泵热水器性能影响的实验研究

通过实验对比研究了循环加热和一次加热热水时,水箱水温对CO2热泵热水器性能的影响。循环加热工况时,随着水温的升高,压缩机的进、排气压力逐渐升高,功耗增加;气体冷却器的CO2进、出口温度升高,内侧CO2和外侧水的温差逐渐减小,换热量减小;CO2热泵系统的COP下降。一次加热工况时,进水温度一定,系统的各项运行参数稳定,COP基本保持不变。以水温度17℃为例,系统COP在3.5左右,远远高于循环加热的COP。实验结果表明水箱水温对系统的性能有一定影响。根据实验结果提出了水箱结构改进方案,使气冷器入口水温稳定在较低水平,可有效提高系统的性能。     

R515B在中高温热泵系统中的性能研究

对低GWP制冷剂R515B在双螺杆单级蒸汽压缩式热泵系统中的性能进行了研究。通过实验对比研究R515B直接替换R134a时系统的性能变化,结果表明：R515B的制热量比R134a降低27%左右,消耗功率比R134a降低约28%,制热COP比R134a平均提高1%,排气温度降比R134a低约15℃。同时建立热泵系统仿真模型,预测R515B在较高冷凝器出水温度下热泵系统的性能,结果表明：R515B具有优良的热力学性能和循环性能,在采用单级蒸汽压缩循环的中高温热泵系统中可实现88℃以下的高冷凝器出水温度。     

中低温废热水驱动吸收式装置的试验研究及节能效果分析

本文介绍了溴化锂吸收式制冷和供热两用装置，在６５℃－９０℃废热水驱动下，实施制制冷循环及Ⅱ型热泵循环的试验研究结果，文内给出了吸收制冷循环和Ⅱ型热泵循环的热力系数，系统一次能源利用率、稀溶液浓度和放汽范围及负荷水温度的变化关系。并分析了不同驱动热水温度下的经济运行工况，制冷循环制冷量与Ⅱ型热泵循环供热量间的区配关系及系统的节能效果。     

溶液换热器传热效率对高温吸收式热泵性能的影响

溶液换热器是吸收式热泵的重要部件之一,它的传热效率与强化对提高热泵系统性能,降低热泵循环系统的设备费和操作费非常重要,本文分析计算了不同传热效率对水／乙二醇高温吸收式热泵系统性能的影响,并分析了换热器传热温差和用损与传热效率的关系,通过回归分析得出评价热泵系统性能的关联式。     

Experimental study on the performance of a vapor injection high temperature heat pump

In this study, a vapor injection technique was applied in a high temperature heat pump (HTHP) for providing hot water at temperatures up to 88 °C. A prototype HTHP system with economizer vapor injection was developed and its performance was experimentally investigated under various operating conditions. Results showed that the vapor injection pressure had a large effect on heating capacity and on refrigerant temperature at the inlet of the electronic expansion valve (EEV). As the injection pressure increased from 0.82 to 0.98 MPa, the vapor injection flow ratio increased from 7.3% to 22.61% and the heating capacity increased by 7%. The system COP did not show significant change although the COP trend showed an optimal value for the injection pressure. The refrigerant temperature at the EEV inlet showed a subcooling of more than 16 °C under all studied conditions, which improved the EEV operating reliability.     

DME或R600a与角鲨烷为工质对的吸收式制冷循环性能分析

本文分析了R600a/角鲨烷和DME/角鲨烷工质对在单效和压缩辅助吸收式制冷循环中的热力学性能.利用NRTL模型关联了两种工质对的汽液相平衡数据,分析了发生温度、蒸发温度和压缩机压比对循环性能系数(COP)、 效率和循环倍率的影响.结果表明:R600a工质对的性能更优.相比于单效循环,压缩辅助循环性能明显更高.在蒸发温...     

跨临界CO2气冷器火积耗散分析

跨临界CO2系统已成为热泵及空调领域的研究热点,本文以CO2气冷器为研究对象,管内外两种流体因温差传热与流动阻力引起系统火积耗散,通过建立的CO2气冷器跨临界区二维分布参数模型求解系统火积耗散数 。分析系统火积耗散数产生的主要原因及沿程分布,讨论CO2、水入口状态参数对系统火积耗散数的影响。结果表明系统火积耗散数主要由温差传热引起,温差越大,系统火积耗散数越大。各微元段火积耗散数与CO2温降幅度呈反比关系,在临界点 达到最大值。随着CO2质量流率、压力的增大,系统火积耗散数逐渐增大;随着水质量流量的增大,系统火积耗散数逐渐减小,减小幅度随着压力的增大而减小。系统火积耗散数随着CO2入口温度的增大而减小,CO2入口温度越大,减小幅度逐渐降低。水入口温度对系统火积耗散数的影响非常小。     

混合工质回热式大温跨供热热泵循环的理论分析

物料干燥、印刷、印染纺织、电镀等领域普遍需要65~100℃的热源供应,常规热泵技术难以实现。本文充分利用非共沸混合工质相变过程中的大温度滑移,实现与水侧更好的热当量匹配,提出一种混合工质回热式大温跨热泵循环,建立了热力学模型,分析了运行压力、混合工质组分、环境温度、出水温度等关键参数对系统性能的影响,基于遗传算法优化了系统吸排气压力和工质配比,结果表明:混合工质回热式热泵可在常规空调压缩机的正常工况内运行,在环境温度为25℃、入水温度为15℃、出水温度为90℃时,系统理论COP最高可达5. 5,与同工况下CO2跨临界热泵性能相当。     

双作用高温行波热声热泵的热力特性研究

提出了一种双作用热声热泵的流程,利用热声软件DeltaEc模拟计算了在进出口体积流率相位差为120°时各个结构尺寸的改变对系统性能的影响,并对影响其改变的原因做了分析讨论。设计优化了一种高性能高温行波热声热泵,在热端温度为100℃、环境温度为30℃时,其热端泵热量可达1037.7W,热泵系数COP为3.2,相对卡诺效率为59.7%。在此基础上进一步研究了在进出口体积流率相位差在不同值时热泵系统的性能,发现在相位差为129°时,相对卡诺效率可达最高,为60.1%     

Thermodynamic assessment of high-temperature heat pumps using Low-GWP HFO refrigerants for heat recovery

Reducing energy consumption by utilizing heat recovery systems has become increasingly important in industry. This paper presents an exploratory assessment of heat pump type heat recovery systems using environmentally friendly refrigerants. The coefficient of performance (COP) of 4 cycle configurations used to raise the temperature of heat media to 160 °C with a waste heat at 80 °C is calculated and compared for refrigerants R717, R365mfc, R1234ze(E), and R1234ze(Z). A multiple-stage “extraction” cycle drastically reduces the throttling loss and exergy loss in the condensers, resulting in the highest COP for R1234ze(Z). A cascade cycle using R1234ze(Z) and R365mfc has a relatively high COP and provides practical benefits. Even under adverse conditions, the primary energy efficiency is greater than 1.3 when the transmission end efficiency of the electric power generation is 0.37. The assessment demonstrated that high-temperature heat pumps are a promising approach for reducing primary energy consumption for industrial applications.     

节能除湿型热泵空调机的性能研究

研究了进水温度、进风工况对节能除湿型热泵空调机性能的影响,实验结果表明:(1)在除湿模式下,进风工况对机组的制冷量、除湿量、压缩机功耗及其COP的影响比进水温度的影响要明显。(2)在热泵模式下,进水温度对机组的制热量、出风干球温度、压缩机功耗及其COP的影响比进风工况的影响要明显。     

A theoretical study on a novel combined power and ejector refrigeration cycle

A new combined power and refrigeration cycle is proposed for the cogeneration, which combines the Rankine cycle and the ejector refrigeration cycle by adding an extraction turbine between heat recovery vapor generator (HRVG) and ejector. This combined cycle could produce both power output and refrigeration output simultaneously, and could be driven by the flue gas from gas turbine or engine, solar energy, geothermal energy and industrial waste heats. Parametric analysis and exergy analysis are conducted to examine the effects of thermodynamic parameters on the performance and exergy destruction in each component for the combined cycle. The results show that the condenser temperature, the evaporator temperature, the turbine inlet pressure, the turbine extraction pressure and extraction ratio have significant effects on the turbine power output, refrigeration output, exergy efficiency and exergy destruction in each component in the combined cycle. It is also shown that the biggest exergy destruction occurs in the heat recovery vapor generator, followed by the ejector and turbine.     

Exergy analysis of gas turbine trigeneration system for combined production of power heat and refrigeration

A conceptual trigeneration system is proposed based on the conventional gas turbine cycle for the high temperature heat addition while adopting the heat recovery steam generator for process heat and vapor absorption refrigeration for the cold production. Combined first and second law approach is applied and computational analysis is performed to investigate the effects of overall pressure ratio, turbine inlet temperature, pressure drop in combustor and heat recovery steam generator, and evaporator temperature on the exergy destruction in each component, first law efficiency, electrical to thermal energy ratio, and second law efficiency of the system. Thermodynamic analysis indicates that exergy destruction in combustion chamber and HRSG is significantly affected by the pressure ratio and turbine inlet temperature, and not at all affected by pressure drop and evaporator temperature. The process heat pressure and evaporator temperature causes significant exergy destruction in various components of vapor absorption refrigeration cycle and HRSG. It also indicates that maximum exergy is destroyed during the combustion and steam generation process; which represents over 80% of the total exergy destruction in the overall system. The first law efficiency, electrical to thermal energy ratio and second law efficiency of the trigeneration, cogeneration, and gas turbine cycle significantly varies with the change in overall pressure ratio and turbine inlet temperature, but the change in pressure drop, process heat pressure, and evaporator temperature shows small variations in these parameters. Decision makers should find the methodology contained in this paper useful in the comparison and selection of advanced heat recovery systems.