直线压缩机驱动的超高温双作用行波热声热泵

提出了一种直线压缩机驱动下的高温双作用行波热声热泵流程,并以kW级别的热泵系统进行了设计和优化。在热泵热端温度为150℃,环境温度为40℃时,计算模拟了其在不同回热器结构以及不同换热器结构下的性能。得出当回热器采用板叠式回热器,换热器采用管壳式换热器时能够获得较高的效率和较大的泵热量,获得的热端泵热量可达1 823.9 W,热泵系数COP为3.16,相对卡诺效率为82.3%。在此基础上,进一步计算了热泵在不同环境温度和不同热端温度下的工作性能,以模拟工业上热泵在不同环境下的工作状况。     

电驱动低温空气源双作用行波热声热泵

在环境温度低于0℃时,常规空气源热泵会出现压比过高、效率和制冷量急剧下降等问题。为了解决这些问题,提出了电驱动双作用行波热声热泵技术。通过数值计算优化了该新型热泵的结构尺寸,设计出一台电驱动低温环境下运行的双作用行波热声热泵。在环境温度253 K(-20℃),泵热温度323 K(50℃)的条件下,新型热泵的制热系数达到了2.93,相对卡诺效率接近64%,泵热量为4 722.6W,压比仅为1.19。热泵多种运行工况的计算结果表明该热泵能够在效率变化较小的情况下调节泵热量的大小;环境温度和泵热温度的改变对系统的运行状态影响不大;该系统制冷时亦有不俗的表现。双作用行波热声热泵在低环境温度情况下的这些优点使其非常有潜力成为高端热泵技术。     

热声驱动的气-液双作用行波热声制冷机

提出了一种热声驱动的气-液双作用行波热声制冷机,对其性能进行了数值模拟分析.计算结果表明,在平均工作压力3.0 MPa,发动机定壁温加热温度440℃工况下,系统谐振频率为12.76 Hz,在-20℃制冷温度以及环境温度为27℃的情况下获得0.708 kW制冷量,整机的制冷系数(制冷量除以加热量)为0.512.在350℃、440℃以及550℃定壁温加热下,系统能够达到的最低制冷温度分别为-62.3℃、-68.3℃以及-70.8℃.系统整机相对卡诺效率在制冷温度变化范围内存在最大值.较低的发动机加热温度更有利于系统的热声转换,当发动机加热温度为350℃时,系统在-45℃制冷温度下达到25.30％最大相对卡诺效率.     

基于传输管的三级级联脉管制冷机实验研究

为提高脉管制冷机制冷效率,通过引入一根特殊设计的传输管,将本应在前一级脉管制冷机脉管热端耗散声功回收,理论上多级级联脉管制冷机制冷效率可达卡诺效率。基于该理论,在已有两级级联脉管制冷机基础上串入第三级制冷机。实验结果显示,该三级级联脉管制冷机最高可获得253.6 W@233 K制冷量,较单级制冷机制冷效率增加39.9%,制冷效率进一步趋于卡诺效率。     

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。     

跨临界CO2双节流阀热泵系统的实验研究

介绍了一种带有双节流阀和平衡储液器控制装置的跨临界CO2热泵系统实验台,针对系统相对功率影响指数和相对制冷系数影响指数进行量化分析,论证了回热器对跨临界CO2热泵系统性能的影响。结果表明:在高压侧压力为10MPa以上,蒸发温度在0℃以下时,带回热器的系统功率相对较低。而蒸发温度在5℃以上,无回热器的系统性能系数将提高3%至5%。这种新的带有双节流阀和平衡储液器控制装置可有效平衡系统高、低侧压力波动对性能的影响。研究结果为跨临界CO2热泵的开发提供了实验依据。     

气-液耦合双作用行波热声制冷系统数值模拟研究

为解决传统热声制冷系统因采用气体谐振管导致整机效率较低的问题，本文提出一种新型气-液耦合双作用行波热声制冷系统，通过数值模拟优化了系统结构尺寸，并对其性能进行了数值模拟分析。首先，对三级气-液耦合双作用行波热声制冷系统的声功、压力及体积流幅值等重要参数的沿程分布进行了研究；然后，研究不同级数下系统的声功、热声转换效率等特性参数；最后，对比分析了各级系统的制冷量及COP随压力的变化特性。研究结果表明：在环境温度293 K、加热温度400 K、制冷温度270 K、平均压力1 MPa下，三级系统COP达到0.7，制冷量为0.78 kW，运行频率为13 Hz，系统相对卡诺效率为22.3%。系统级数增加，整机的功率密度提高，当平均压力为10 MPa时，六级系统制冷量达到最大值16.1 kW，COP为0.38。     

谐振管几何形状对热声发动机工作性能的影响

谐振管作为热声发动机的重要部件之一,其几何参数的变化对热声系统的工作性能有重大影响,在驻波型热声发动机系统上对锥形谐振管和圆直谐振管进行了初步的实验对比,以探明谐振管的形状对热声发动机系统性能的影响.实验结果表明,在系统的工作频率固定在130 Hz的情况下,无论是压比、输出声功,还是相对卡诺效率,采用锥形管的系统都要比采用圆直管的系统具有更大的优势.     

热声斯特林发动机热动力学特性的CFD研究第二部分:热声转换特性及热声声流的研究

研究了热声斯特林发动机的声场特性和热力特性,计算了波动压力和体积流率振幅及两者的相位差、截面平均温度以及声功流在系统内的沿程分布,与实验及预期的趋势相符合.对热声斯特林发动机内部的Gedeon声直流进行了研究.通过监测系统内截面的质量流率周期分布特性观测到Gedeon直流的存在,计算了直流量的大小及在系统内的分布特性,并采用风扇模型抑制了直流,给出了直流抑制过程中的系统性能变化.进一步验证了CFD研究的有效性.     

热端管长度对涡流管性能影响的实验研究

研制了不同热端管长度的涡流管,并以空气作为工作介质,通过实验研究了热端管长度对涡流管能量分离性能的影响.实验结果表明:对于常温涡流管,在入口压力为0.5MPa的情况下,相同冷流率时,随着热端管长度的增加,涡流管的制冷温度效应、单位制冷量和制冷系数增加,而其制热温度效应无显著的规律;对同一热端管长的涡流管,随着冷流率的增加,涡流管的制冷温度效应、单位制冷量和制冷系数增加,且在冷流率为40%～50%时出现峰值,而制热温度效应随冷流率的增加而增加,在冷流率范围内未出现峰值.     

Theoretical and experimental study of a gas-coupled two-stage pulse tube cooler with stepped warm displacer as the phase shifter

A compact and high efficiency cooler working at liquid hydrogen temperature has many important applications such as cooling superconductors and mid-infrared sensors. This paper presents a two-stage gas-coupled pulse tube cooler system with a completely co-axial configuration. A stepped warm displacer, working as the phase shifter for both stages, has been studied theoretically and experimentally in this paper. Comparisons with the traditional phase shifter (double inlet) are also made. Compared with the double inlet type, the stepped warm displacer has the advantages of recovering the expansion work from the pulse tube hot end (especially from the first stage) and easily realizing an appropriate phase relationship between the pressure wave and volume flow rate at the pulse tube hot end. Experiments are then carried out to investigate the performance. The pressure ratio at the compression space is maintained at 1.37, for the double inlet type, the system obtains 1.1 W cooling power at 20 K with 390 W acoustic power input and the relative Carnot efficiency is only 3.85%; while for the stepped warm displacer type, the system obtains 1.06 W cooling power at 20 K with only 224 W acoustic power input and the relative Carnot efficiency can reach 6.5%.     

Numerical investigation on a 300 Hz pulse tube cryocooler driven by a three-stage traveling-wave thermoacoustic heat engine

A 300 Hz pulse tube cryocooler (PTC) driven by a three-stage traveling-wave thermoacoustic heat engine (TSTHE) has been proposed and studied in this paper. In the configuration, three identical thermoacoustic heat engine units are evenly incorporated in a closed traveling-wave loop, in which three pulse tube cryocoolers are connected to the branch of each thermoacoustic heat engine. Compared with the conventional thermoacoustic heat engine which involves a traveling-wave loop and a long resonator, it has advantages of compact size and potentially high thermal efficiency. A TSTHE–PTC system was designed, optimized and studied in detail based on the thermoacoustic theory. Firstly, numerical simulation was conducted to design the system thus the optimum structure parameters of the system were obtained. With the operating condition of 4 MPa mean pressure and high working frequency, a cooling power of 7.75 W at 77 K and an overall relative Carnot efficiency of 11.78% were achieved. In order to better understand the energy conversion characteristics of the system, distributions of key parameters such as acoustic work, phase difference, dynamic pressure, volume flow rate and exergy loss were presented and discussed. Then, the coupling mechanism of the system was investigated. In addition, influence of coupling position on the system performance was further studied.     

电动汽车热泵系统低温工况的制热性能实验研究

为研究低温时电动汽车热泵空调系统的制热性能,本文通过搭建空气源热泵空调系统实验台,实验研究了电动汽车热泵空调系统在环境温度为-10~0℃的低温工况下的制热性能,分析了压缩机转速(2000~5000 r/min)、HVAC总成进风量(300~400 m^3/h)和环境温度对该热泵系统性能的影响,最后通过推导公式,估算电动汽车在使用空调系统后的续航里程。实验结果表明:随着压缩机转速的增加,压缩机排气温度、排气压力和系统制热量均增加,而COP下降;当保持压缩机转速和环境温度不变时,HVAC总成进风量从300 m^3/h增至400 m^3/h,制热量增加约13.3%~26.0%,COP增加约0.03~0.80;在其他条件不变时,当环境温度从-10℃升至0℃,热泵空调系统的制热量增加约60.9%~71.0%,COP增加约0.51~0.63;通过公式进行计算,当环境温度为-10~0℃时,在达到相同制热量条件下,热泵空调系统可在PTC加热器的基础上使续航里程提高13.5%~20.8%。     

基于Aspen Plus的自复叠热泵模拟

自复叠热泵的变工况运行对其性能影响很大。应用Aspen Plus软件,对冷凝器入口水温从40～55℃的4个工况下的自复叠热泵进行了流程模拟,并对流程中各点参数变化进行了分析,对节流阀的流态进行了计算分析。结果表明,自复叠热泵在两个节流阀开度不变时,随着冷凝器入口水温的升高,压缩机耗功增加,主流与支流流量增大,蒸发压力升高,压缩机入口比容减小,循环的质量流量增大;两个节流阀均未达到雍塞流。     

Development of high efficiency Stirling-type pulse tube cryocoolers

Thermoacoustic theory is a powerful tool to understand the working mechanism of regenerative thermodynamic systems. In this paper, a modified thermoacoustic model is employed to design three single-stage Stirling-type pulse tube cryocoolers. The first one (PTC-10) is designed with in-line configuration and the second one (CPTC-10) is designed with co-axial configuration. Both of them are able to provide about 10 W cooling power at 77 K with a relative Carnot efficiency of about 18.6%. The third one (PTC-20), designed with in-line configuration, has a twice cross section area of the PTC-10. It can provide more than 20 W cooling power at 77 K with a relative Carnot efficiency of 22%.     

地源热泵系统双U型埋管换热器的测试实验

建立双U型垂直埋管试验井测试实验装置,通过现场测试采集当地的岩土热物性参数,从而确定土壤的原始地温、单位井深的散热量等参数,对地源热泵设计有一定的参考价值.结果表明,土壤的原始地温为19.2℃;夏季工况下,地下换热器的进、出口水温度分别为35"C和31℃时,单位井深的散热量为62.55W/m.     

空气源热泵热水机(器)的出水温度及能效标准讨论

对分别用于采暖和生活热水的空气源热泵,前者的出水温度可以根据使用情况自行确定,而生活热水由于卫生要求的杀菌温度,对于后者我国规定是55℃。然而日常使用的生活热水,往往40℃或45℃就可以满足要求。显然,空气源热泵热水机(器)出水温度越低,COP越高。本着这个原则,本文讨论产生合理的热水温度且满足卫生要求的空气源热泵热水机(器)的出水温度,并提出不同出水温度下空气源热泵热水机(器)的能效标准。     

Electroosmotically induced hydraulic pumping on microchips: differential ion transport

The theory behind and operation of an electroosmotically induced hydraulic pump for microfluidic devices is reported. This microchip functional element consists of a tee intersection with one inlet channel and two outlet channels. The inlet channel is maintained at high voltage while one outlet channel is kept at ground and the other channel has no electric potential applied. A pressure-induced flow of buffer is created in both outlet channels of the tee by reducing electroosmosis in the ground channel relative to that of the inlet channel. Spatially selective reduction of electroosmosis is accomplished by coating the walls of the ground channel with a viscous polymer. The pump is shown to differentially transport ions down the two outlet channels. This ion discrimination ability of the pump is examined as a function of an analyte's electrophoretic velocity. In addition, we demonstrate that an anion can be rejected from the ground channel and made to flow only into the field-free channel if the electrophoretic velocity of the anion is greater than the pressure-generated flow in the ground channel. The velocity threshold at which anion rejection occurs can be selectively tuned by changing the flow resistance in the field-free channel relative to the ground channel.