理想溶液时吸收式热泵的理想过程模型

本文基于吸收式热泵内部实际发生的物理过程,建立了一个不同于目前通用的热泵-热机等效模型的吸收式热泵的理想模型。基于此理想模型,研究了吸收式热泵实现热量变换的基本性能。定义了热量的温度提升系数,即吸收-蒸发过程源侧热量的升温程度与发生-冷凝过程源侧热量的降温程度之比。提出用热量的品位提升系数和制冷COP(蒸发器制冷量与发生器输入热量之比)两个相对独立的参数来刻画吸收式热泵理想过程的基本性能。推导出了恒温热源下单效单级、多效、多级吸收式热泵的理想过程的温度提升系数、理想COP的表达式,可分别从热量的温度提升和输入输出热量比两个方面认识吸收式热泵实现热量变换的本质。     

真实溶液下吸收式热泵的理想过程模型

本文给出了真实溶液下吸收式热泵的理想过程模型。首先讨论了真实溶液溶液流量无限大的工况,推导出其温度提升系数,与理想溶液相比,用修正系数kr进行修正,kr主要取决于发生器溶液和吸收器溶液的活度系数,对于第一类吸收式热泵,kr大于1,对于第二类吸收式热泵,kr小于1;分别讨论了第一类吸收式热泵和第二类吸收式热泵的COP,第一类吸收式热泵的COP相比理想溶液过程降低,第二类吸收式热泵的COP相比理想溶液有所升高。在溶液循环量无限大的结果的基础上,讨论了有限循环流量的真实溶液工况,定义了有限流量时的温度提升系数,与真实溶液溶液流量无限大相比,修正系数kr还受溶液放气范围的影响,溶液放气范围越大,修正系数kr越低;当溶液流量有限时,kr小于溶液流量无限大的工况,COP也低于溶液流量无限大的工况;真实溶液下溶液流量无限大或者有限均满足COP1TaTe/TgTc(第一类热泵),COP20.5TaTe/TgTc(第二类热泵)。最后应用本文提出的真实溶液理想过程模型分析了两个实际案例。从这些案例可以看到,采用本文的分析方法,不需要计算内部复杂的溶液循环过程就能得到吸收式热泵的外部性能参数。本文给出的理想过程模型从新的角度出发对吸收式热泵的热量变换过程给出了清晰的描述。     

油田污水源热泵系统研究及Aspen仿真分析

针对油田污水资源丰富的特点并基于溴化锂吸收式热泵工作原理,设计一种回收油田污水余热替代水套加热炉对原油进行直接加热的第一类溴化锂吸收式热泵系统。使用化工过程仿真模拟软件Aspen对其进行建模计算,分析影响系统性能的几种因素。结果表明,随着蒸发器蒸发压力增大、浓稀溶液换热器冷流出口温度升高、机组放气范围增大,热泵系统性能系数COP随之增高。研究结果可为工程样机的设计提供参考。     

LiBr-H2O吸收式热泵的热力学分析

本文建立了LiBr-H2O吸收式热泵系统的理论模型，对热泵系统的热力学循环进行模拟计算。分析了不同操作参数（包括循环倍率、低温废水入口温度、热水入口温度、高温蒸汽入口温度）对热泵的性能系数（COP）、火积效率、?效率和熵产这4种性能评价指标的影响规律，对比了这4种性能评价标准下的系统性能变化的一致性，并探讨了作为新指标的火积效率是否适用于吸收式热泵分析。模拟结果表明：当循环倍率、热水入口温度和高温蒸汽入口温度增加时，热泵系统性能均变差，只有低温废水入口温度升高时，系统性能才逐渐提高。计算结果表明：在不同的操作参数条件下4种性能评价指标变化并不一致，有些甚至相反，但COP和火积效率的变化趋势却始终保持了很好的一致性，因此说明火积效率也可以用于吸收式热泵的性能分析。     

寒冷地区空气源吸收式热泵性能提高途径及对比分析

空气源吸收式热泵对于北方供暖的意义重大。为了提高空气源吸收式热泵在低温环境下的可靠性和能效,提出了双级吸收式热泵、双级耦合吸收式热泵和增压吸收式热泵。通过建模和模拟分析,对这三种途径在不同环境温度下的性能进行了对比分析。若采用风机盘管末端,当采暖期内气温低于-25℃的时间很少时,双级耦合热泵的性能最好;否则可以考虑采用双级空气源吸收式热泵。室外设计温度为-15℃和-30℃时,空气源吸收式热泵的一次能源效率分别比燃煤锅炉高28%和19%。若采用地板辐射末端,则增压吸收式热泵的能效最高,室外设计温度为-15℃和-30℃时,一次能源效率可达0.953和0.874,分别比燃煤锅炉高36%和25%。考虑整个采暖期内气温较高时热泵的性能较好,则增压空气源吸收式热泵用于地板辐射采暖的节能潜力更为可观。     

空气源-水环热泵联合系统性能分析

建立空气源-水环热泵联合系统的模型,通过改变空气源-水环热泵联合系统的空气源热泵冷凝温度及蒸发温度,得到联合系统不同工况下的最佳性能系数。研究结果表明:在供水温度分别为45℃和50℃时,系统性能系数均在空气源热泵冷凝温度16℃时达到最大值,分别为2.128和1.954,供水温度为55℃时,系统性能系数在空气源热泵冷凝温度18℃时达到最大值1.805;供水温度分别为45℃,50℃和55℃时,单级系统(仅运行空气源热泵系统)、双级系统(空气源-水环热泵联合系统)相互切换的最佳蒸发温度分别为-2℃,-13℃和-23℃。指出根据不同工况及时调整热泵系统的运行方式能够提高系统能效。     

传热规律对内可逆四热源吸收式热泵循环性能的影响

建立了传热规律为Q∝△(T^n)时内可逆四热源吸收式热泵循环模型,导出了循环泵热率和泵热系数的一般关系;并导出了传热服从线性唯象定律时的基本优化关系、循环中工质的最佳工作温度和换热器传热面积的最佳分配关系;通过数值算例分析了传热规律对循环性能的影响规律,比较了传热面积最优分配前后循环的最优性能。     

采用离子液体-水工质对的GAX吸收式制冷循环性能研究

热驱动的吸收式制冷技术是太阳能利用和工业余热回收的重要途径,其中GAX(吸收发生换热)吸收式循环具有高效、效率可随热源温度变化的特点。本文提出采用无结晶风险的离子液体工质对,并使用NRTL模型对离子液体工质对性质进行计算,并对GAX吸收式制冷循环进行性能计算。结果表明:采用1,3-二甲基咪唑磷酸二甲酯盐([DMIM][DMP]/水工质对可以使用GAX吸收式循环,且在发生温度较高的情况下COP能够达到约1.02,比相同特定工况下的单效循环COP提升27.5%,比采用溴化锂/水工质对的吸收式循环具有更加优异的性能。     

低温环境下中温水复叠热泵性能研究

在低温环境下,为提高R410A/R410A复叠热泵的制热性能,通过试验调节水流量改变热泵冷凝侧进出水温差,分析在不同工况下各个参数随冷凝侧进出水温差的变化规律。结果表明:复叠热泵在低蒸发温度下能够稳定运行,蒸发温度为-33℃、-30℃、-27℃、-24℃、-21℃时,进水温度33℃,进出水温差由8℃降至2℃时,COP增长率分别为13.1%、17.2%、19.0%、19.7%、20.1%,制热量增长率为7.0%、9.4%、11.6%、13.1%、15.6%,降低冷凝侧进出水温差能够在一定程度上减缓蒸发温度下降对热泵系统COP和制热量的不利影响。在同一进出水温差下,在蒸发温度为-30℃,出水温度为35℃时,其COP可达2.34,随着出水温度上升,制热系数及制热量均下降,对于采用R410A制冷剂的热泵更适合用于中温水工况。     

低温环境下复叠式燃气机热泵的供热性能研究

为了提高燃气机热泵在低环境温度下的制热性能,本文将燃气机热泵技术与复叠式热泵技术相结合,提出了应用于低环境温度下的复叠式燃气机热泵（CGEHP）系统。使用MATLAB软件,建立了CGEHP数学模型。分析了燃气发动机转速、环境温度和系统进水温度对系统供热性能（总供热量、制热性能系数（COP）以及一次能源利用率（PER））的影响规律。结果表明：当环境温度分别为﹣20、﹣15和﹣10 ℃,以NH3-LiNO3作为吸收式热泵系统工质,发动机转速为1 500 r/min时,PER分别为1.0、1.02、1.04,比常规空气源电热泵系统分别提高了24%、15%、5%。     

我国空调与热泵的能效和标准现状与分析

本文总结了我国空调热泵的能效标准,阐述了季节能效比SEER、综合部分负荷值IPLV和热泵热水机组全年能源消耗效率APF之间的关系,分析我国能效(分级)标准发展历程。其中,空调与热泵的能效标准,风冷从单一工况的制冷能效比EER或性能系数COP,发展到SEER和供热季节性能系数HSPF;水冷从单一工况COP,发展到综合部分负荷系数IPLV。提出低环境温度空气源热泵IPLV(H)的3级能效划分建议值。同时,指出能效标准的共性与问题,如理论工作还有待加强,评价指标不统一,部分能效标准缺失,能效标准未能及时与产品标准相对应等,并对今后能效标准的研究思路和方向给出了建议。     

空气源热泵自然冷源过冷制热性能实验研究

冬季我国北方室外环境蕴含大量天然冷源,热力学分析表明热泵工质过冷释放的热量可以在蒸发器的等温吸热过程中获得补偿。为了研究大气自然冷源对热泵制热性能的影响,增设室外过冷器,搭建利用自然冷源过冷的空气源热泵实验装置。实验结果表明：当室外环境温度大于0 ℃,冷凝温度小于45 ℃的条件下,自然冷源过冷对热泵制热量与制热COP影响均较小,系统制热量维持在6.22 ~ 6.70 kW,制热COP维持在3.03,压缩机排气温度维持在103 ℃以下;当室外环境温度小于 -10 ℃,冷凝温度大于50 ℃时,随过冷度的增加,压缩机功率增加、排气温度显著增高,系统制热量呈先缓慢增加后减小趋势,制热COP降至2.3。基于上述研究提出一种空气源热泵过冷融霜新型除霜方式,融霜同时不停止制热。     

Experimental study of sensible heat recovery of heat pump during heating and ventilation

Indoor space requires heating, cooling and ventilating for maintaining human occupant space to a comfortable level. Heat pump system is now widely used since it has the capabilities of providing both cooling and heating with a single unit. Ventilation, which exhausts the contaminated indoor air and brings in the fresh outdoor air is essential for maintaining pleasant indoor air quality. Ventilation, however, causes energy loss since air-conditioning is necessary to change the state of outdoor air to that of indoor. When outdoor air is introduced into the interior space, it must be cooled or heated to bring it to the indoor space condition. In this work, three methods of recovering sensible heat during heating and ventilation process of heat pump have been studied experimentally. Those methods are by a separate sensible heat exchanger, introduction of indoor air to the evaporator (single heat recovery), and finally a combination of fore-mentioned two methods (double heat recovery). An air-source heat pump system with none, single and double heat recovery capabilities has been built and tested in two constant-temperature and constant-humidity thermal chambers that simulate the indoor and outdoor environments. From the experiment performed under standard heating condition with a ventilation ratio of 23.1%, coefficient of performance for none, sensible heat exchanger, single and double heat recoveries were 2.88, 3.20, 3.18 and 3.28, respectively. Double heat recovery heat pump that has the ventilation and double heat recovery functions integrated into a single unit showed the best COP performance.     

Regenerated air cycle potentials in heat pump applications

Air (reversed Brayton) cycle has been utilized in the area of refrigeration and cryogenics for several decades, but its potentials in heat pump applications were longtime underestimated. In this paper, a thermodynamic model for the regenerated air heat pump cycle with practical compressor, expander and regenerated heat exchanger was developed. Based on the model, the relations between the system performance and the operating parameters were analyzed. The optimal heating COP (coefficient of performance) and the corresponding pressure ratio were derived. Then, air heat pump cycles (regenerated cycle and basic cycle) and vapor-compression heat pump cycles (CO₂ trans-critical cycle and R410A subcritical cycle) were numerically compared. The results indicated that the regenerated air heat pump cycle not only gets the heating capacity in line with the heating load under different operating conditions but also achieves higher COP over trans-critical CO₂ heat pump cycle in applications of large temperature difference.     

Review of advanced absorption cycles: performance improvement and temperature lift enhancement

The objective of this study is to propose and evaluate advanced absorption cycles for the coefficient of performance (COP) improvement and temperature lift enhancement applications. The characteristics of each cycle are assessed from the viewpoints of the ideal cycle COP and its applications. The advanced cycles for the COP improvement are categorized according to their heat recovery method: condensation heat recovery, absorption heat recovery, and condensation/absorption heat recovery. In H₂O–LiBr systems, the number of effects and the number of stages can be improved by adding a third or a fourth component to the solution pairs. The performance of NH₃–H₂O systems can be improved by internal heat recovery due to their thermal characteristics such as temperature gliding. NH₃–H₂O cycles can be combined with adsorption cycles and power generation cycles for waste heat utilization, performance improvement, panel heating and low temperature applications. The H₂O–LiBr cycle is better from the high COP viewpoints for the evaporation temperature over 0°C while the NH₃–H₂O cycle is better from the viewpoint of low temperature applications. This study suggests that the cycle performance would be significantly improved by combining the advanced H₂O–LiBr and NH₃–H₂O cycles.     

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...     

混合吸收式制冷循环的(火用)分析

新型混合吸收式制冷循环[1] 的特点是能够运用中低温热源 ,热源的可利用温差大 ,制冷系数较高。本文利用效率法对新型混合吸收式制冷循环进行了分析 ,得出新型混合吸收式制冷循环的效率比两效吸收式循环高 ,可达 0 .2 92。同时得出系统各个部件的损失 ,分析吸收式制冷系统在能量的转移过程中的薄弱环节 ,为混合吸收循环系统的优化提供了前提。     

广义不可逆卡诺热泵的有限时间(火用)经济性能优化

本文研究了牛顿定律系统广义不可逆卡诺热泵的有限时间炯经济性能，导出了存在热阻、热漏和其它内不可逆性时卡诺热泵的最优利润率解析式以及相应的供热系数界限，并用数值算例分析了热漏等因素对利润率和炯经济性能界限的影响。     

制冷与热泵产品的能效标准研究和循环热力学完善度的分析

为了建立评价冷水机组和水源热泵的EER或COP等能效指标的公共平台,提出了热力学完善度的分析方法,并计算了我国的房间空调器、冷水机组和水源热泵等制冷装置的热力学完善度的数据范围。大多水冷产品的热力学完善度在0.3至0.5之间,高效产品可以达到0.6,但风冷产品热力学完善度在0.2左右,空气源热泵热水机等介于两者之间。热力学完善度可用于同类产品或相似产品在不同工况下的性能比较。分析可见热力学完善度表征着当前产品设计制造的综合水平,是制定相关产品能效标准的限定值、节能值及能效等级的依据。     

Development of a vapor compression cycle with a solution circuit and desorber/absorber heat exchange

A vapor compression cycle with a solution circuit and desorber/absorber heat exchange (DAHX) has been investigated experimentally using the ammonia/water mixture. A breadboard heat pump was designed and built to measure the cycle performance. COPs in the range of 1.2–1.8 were obtained experimentally for a temperature lift between 60 and 80°C. The cooling capacities were between 7 and 12 kW, which increased with an increase of the ammonia concentration. The pressure ratios encountered were in the range of 2–6. A COP of 1.44 at the temperature lift of 79°C was recorded with a cooling capacity at 10.25 kW. The experimental results are compared to that of the single-stage and two-stage cycle. The two-stage system had the highest temperature lift (110–120°C) and the lowest COP (0.69–1.04). The single-stage system has the highest COP (2.2–3.5) but the lowest temperature lift (40°C). Also, a solution bypass between the Absorber I outlet and Desorber II inlet was proposed to improve the cycle performance. The experimental results showed that the COP varied in the range of 1–2%, while the temperature lift increased by the range between 0 and 6°C. In addition, the analysis of the test result uncertainties was made.