太阳能制冷与供暖系统的设计与比较

根据上海的气候条件，以上海地区某写字楼为对象，提出4种太阳能驱动的溴化锂吸收式与电动蒸汽压缩式热泵联合制冷与供暖系统。这4种系统分别由热管式真空管集热器或抛物面槽形聚光集热器，单效或双效溴化锂吸收式制冷机，以及风冷热泵或水源热泵构成。分析比较这4种系统的节能型和经济性的结果表明，采用抛物面槽形聚光集热器＋双效溴化锂吸收式制冷机＋风冷热泵组成的系统，同时具备较好的节能性与经济性，一次能源利用率可降低约50％。     

燃气热电联产系统余热挖潜方式研究

针对燃气蒸汽联合循环热电联产机组的烟气和乏汽余热,介绍了3S离合技术、吸收式热泵技术、压缩式热泵技术、吸收式热泵+压缩式热泵技术及基于Co-ah循环供热技术(吸收式换热的热电联产集中供热技术)5种余热利用技术,对其供热能力提升、节能性和经济性进行了定量分析。通过对供热能力提升程度的分析得出,利用5种技术均可以提升供热能力,其中基于Co-ah循环供热技术提升供热能力最大。通过节能性分析得出,5种技术均有节能效果,其中基于Co-ah循环供热技术节能效果更为显著。通过经济性分析得出,增加单位供热能力(1MW)的情况下,在电厂应用吸收式热泵技术和基于Co-ah循环供热技术初投资略高,但运行费用节省也较为明显。综合考虑供热能力提升和经济性两方面因素,基于Co-ah循环供热技术更具优势。     

单双效结合运行的溴化锂第一类吸收式热泵

在传统的单效和双效溴化锂第一类吸收式热泵的基础上,开发单双效结合运行的溴化锂第一类吸收式热泵机组。当用户需求热水温度较低时,机组以双效模式运行;反之,机组则以单效模式运行。克服了溴化锂第一类吸收式热泵供热系统中机组模式单一化、运行效率低的缺点,实现了一台机组两种模式运行的方案,提高了设备和资源的利用率,具有良好的节能效益和经济效益。     

高效利用地热水的系统型式及其经济分析

讨论了解决当前地热水严重浪费问题的几种技术方案。分析了三种系统型式：用于普通热水锅炉给水的系统；有蒸气锅炉和溴化锂吸收式热泵的复合系统；有电动蒸汽压缩式热泵的系统。证明地热水供热系统中使用热泵具有节能与经济意义。     

吸收式热泵机组在北方某垃圾焚烧厂的应用经济分析

介绍了吸收式热泵机组余热利用的技术特点及在热电厂内余热利用的原理。通过实例,分析了吸收式热泵机组代替传统换热机组进行全厂供热的经济性及合理性,为吸收式热泵机组在垃圾焚烧厂的选择应用提供了借鉴。     

电厂集中供热领域中吸收式热泵与压缩式热泵的经济性比较

从电厂供热改造经济性出发,讨论了采用吸收式热泵、压缩式热泵时供热量及相应收益的变化情况。理论分析结果显示,采用两种热泵都存在着最大余热利用量。同时,针对某300MW抽凝机组进行了供热计算,结果显示,在增加相同供热量时,吸收式热泵的年增加收益约为压缩式热泵的2倍,即使考虑两者设备的投资差距,电厂进行余热回收供热改造时,也宜采用吸收式热泵。     

压缩式和吸收式热泵回收电厂循环水冷凝热经济性分析

采用压缩式或吸收式热泵技术回收电厂循环水冷凝热用于城市集中供热,是我国重点节能推广技术.从热泵制热性能系数COP出发,分析了热泵节能机理,并首次构建了压缩式和吸收式两种形式热泵在回收电厂循环水冷凝热工程中热经济性优劣的判定模型,对于指导热泵选型具有重要的指导意义.     

溴化锂吸收式热泵的研究及应用

主要探讨第I类和第Ⅱ类溴化锂吸收式热泵的性能,并从节能的角度分析了这两类热泵回收利用低温热源的经济性。     

基于吸收式热泵的循环水余热利用技术在大型抽凝机组热电联产中的应用

为了降低燃煤电厂的能耗,该文提出了一种基于吸收式热泵的循环水余热利用技术,提取发电机组的循环水余热用于城市供暖,在热电厂内设置溴化锂吸收式热泵站,利用机组循环冷却水作为热泵的热源水,提取余热加热热网水,从而显著提升热电厂的供热能力及热效率,进一步降低综合供电煤耗,实现节能减排的目的.     

基于当量抽汽压力的大型热电联产供热模式研究

建立了大型热电联产机组变工况分析模型,揭示出不同热网回水温度和热网回水温升条件下,单效溴化锂吸收式热泵驱动热源饱和蒸汽压力和热力系数的变化规律.提出2种不同供热模式选取的判据,即当量抽汽压力.以某300 MW直接空冷抽凝供热机组为例,进行了变工况计算及分析.结果表明:随热网回水温升的增大以及热网回水温度的升高,驱动热源饱和蒸汽压力升高,而吸收式热泵热力系数则减小;对于300 MW等级及以上供热改造机组,由于汽轮机中低压缸抽汽压力高于对应的当量抽汽压力,采用吸收式热泵供热模式更节能.     

A review of the applications of heat pipe heat exchangers for heat recovery

The waste heat recovery by heat pipes is accepted as an excellent way of saving energy and preventing global warming. This paper is a literature review of the application of heat pipes heat exchangers for the heat recovery that is focused on the energy saving and the enhanced effectiveness of the conventional heat pipe (CHP), two-phase closed thermosyphon (TPCT) and oscillating heat pipe (OHP) heat exchangers. The relevant papers were allocated into three main categories, and the experimental studies were summarized. These research papers were analyzed to support future works. Finally, the parameters of effectiveness of the CHP, TPCT and OHP heat exchangers were described. This review article provides additional information for the design of heat pipe heat exchangers with optimum conditions in the heat recovery system.     

地源热泵的套管式地下换热器传热研究

地源热泵是一种节能、对环境无害的绿色空调设备,可成为下个世纪冷暖技术的核心,采用能量平衡,建立了地下浅埋套管式换热器传热平衡式,进行求解,并分析了影响传热的各关联因子,提出了需研究的强化地下换热的措施,根据求解结果,给出了相应的函数关系图。对实验设计和工程实践有一定的指导作用。     

Frosting of heat pump with heat recovery facility

This paper aims to prolong the heat pump frost time and reduce its growth with heat recovery facility, which should mix the exhausted indoor and outdoor air before entering the evaporator. An ideal mathematic model is developed for heat transfer, frost generation and airside pressure drop. The properties of the mixture would be obtained by solving the mass and energy conservation equations. A parametric analysis is performed to investigate the effects of air inlet temperature, relative humidity and air mass flow rate on total heat transfer coefficient, frost thickness and airside pressure drop, respectively. The results show that rationalizing the ratio of indoor and outdoor air could prolong frosting time and reduce the frost thickness greatly. The total heat transfer coefficient, frost thickness and airside pressure drop increase monotonically with time going, but are not proportional. Decreasing the mixture inlet air temperature and relative humidity could essentially reduce frost growth on the tube surfaces. This can also be observed when increasing the air mass flow rate.     

Analysis of three-dimensional heat transfer in micro-channel heat sinks

In this study, the three-dimensional fluid flow and heat transfer in a rectangular micro-channel heat sink are analyzed numerically using water as the cooling fluid. The heat sink consists of a 1-cm² silicon wafer. The micro-channels have a width of 57 μm and a depth of 180 μm, and are separated by a 43 μm wall. A numerical code based on the finite difference method and the SIMPLE algorithm is developed to solve the governing equations. The code is carefully validated by comparing the predictions with analytical solutions and available experimental data. For the micro-channel heat sink investigated, it is found that the temperature rise along the flow direction in the solid and fluid regions can be approximated as linear. The highest temperature is encountered at the heated base surface of the heat sink immediately above the channel outlet. The heat flux and Nusselt number have much higher values near the channel inlet and vary around the channel periphery, approaching zero in the corners. Flow Reynolds number affects the length of the flow developing region. For a relatively high Reynolds number of 1400, fully developed flow may not be achieved inside the heat sink. Increasing the thermal conductivity of the solid substrate reduces the temperature at the heated base surface of the heat sink, especially near the channel outlet. Although the classical fin analysis method provides a simplified means to modeling heat transfer in micro-channel heat sinks, some key assumptions introduced in the fin method deviate significantly from the real situation, which may compromise the accuracy of this method.     

Second-law performance of heat exchangers for waste heat recovery

Exergy change rate in an ideal gas flow or an incompressible flow can be divided into a thermal exergy change rate and a mechanical exergy loss rate. The mechanical exergy loss rates in the two flows were generalized using a pressure-drop factor. For heat exchangers using in waste heat recovery, the consumed mechanical exergy is usually more valuable than the recovered thermal exergy. A weighing factor was proposed to modify the pressure-drop factor. An exergy recovery index (η_II) was defined and it was expressed as a function of effectiveness (?), ratio of modified heat capacity rates (C^∗), hot stream-to-dead-state temperature ratio, cold stream-to-dead-state temperature ratio and modified overall pressure-drop factor. This η_II–? relation can be used to find the η_II value of a heat exchanger with any flow arrangement. The η_II−Ntu and η_II−Ntu_h relations of cross-flow heat exchanger with both fluids unmixed were established respectively. The former provides a minimum Ntu design principle and the latter provides a minimum Ntu_h design principle. A numerical example showed that, at a fixed heat capacity rate of the hot stream, the heat exchanger size yielded by the minimum Ntu_h principle is smaller than that yielded by the minimum Ntu principle.     

Investigation of heat transfer characteristics in plate-fin heat sink

The present study applies the inverse method in conjunction with the experimental temperature data to investigate the accuracy of the heat transfer coefficient on the fin in the plate-fin heat sink for various fin spacings. The commercial software is applied to solve the governing differential equations with the RNG k–? model in order to obtain the heat transfer and fluid flow characteristics. Under the assumption of the non-uniform heat transfer coefficient, the entire fin is divided into several sub-fin regions before performing the inverse scheme. The average heat transfer coefficient in each sub-fin region is assumed to be unknown. Later, the present inverse scheme in conjunction with the experimental temperature data is applied to determine the heat transfer coefficient and fin efficiency. In order to determine a more reliable heat transfer coefficient, a comparison between the present inverse and numerical results and those obtained from the existing correlations will be made. The numerical fin temperatures will also be compared with the experimental data.     

Mass and heat transfer enhancement of chemical heat pumps

An inert additive, expanded graphite (EG), has been prepared and used to enhance the heat and mass transfer process of chemical heat pumps. The effects of mixing ratio and mixing method on the chemical reaction time are investigated.     

Hierarchic modeling of heat transfer processes in heat exchangers

An alternate approach based on hierarchic modeling is proposed to simulate fluid and heat flow in heat exchangers. On the first level, the direct simulations have been performed for the geometry that is similar to a segment of the examined heat sink. Based on the obtained results, the Reynolds number dependencies of the scaling factors f and StPr^2/3 have been established. On the second level, the integral model of the whole heat sink has been built using the volume averaging technique (VAT). The averaging of the transport equations leads to a closure problem. The direct model Reynolds number dependencies f and StPr^2/3 have been used to calculate the local values of the drag coefficient and the heat transfer coefficient , which are needed in the integral model. The example calculations have been performed for 14 different pressure drops across the aluminum heat sink. The whole-section drag coefficient and Nusselt number have been calculated and compared with the experimental data [M. Rizzi, M. Canino, K. Hu, S. Jones, V. Travkin, I. Catton, Experimental investigation of pin fin heat sink effectiveness, in: Proc. of the 35th National Heat Transfer Conference Anaheim, California, 2001]. A good agreement between the modeling results and the experiment data has been reached with same discrepancies in the transitional regime. The constructed computational algorithm offers possibilities for geometry improvements and optimization, to achieve higher thermal effectiveness.     

长距离环路热管传热性能实验研究

基于航空航天等领域对环路热管长距离传热的需求,设计制造了一套传热距离8.1m的圆柱型蒸发器环路热管,试验了不同加热功率、不同冷凝温度下该环路热管的启动和变工况运行性能,并对其热阻及最大传热能力进行了分析。研究结果表明：当其他条件一致、初始气液分布相同和不同时,加热功率由100W增大至160W后,本研究中的环路热管启动时间和启动温升均发生一定程度的下降;加热功率100W时,冷凝温度由10℃降低至-10℃使得环路热管启动时间增加,加热功率160W时,冷凝温度由10℃降至-10℃对环路热管的启动时间影响不大。在冷凝温度0℃下,该环路热管在100~500W范围内均能稳定运行,且200W时环路热管传热效率最高,传热温差最小,稳定运行温度最低;另外,由于系统传输距离较长,每个工况达到稳定所需要的时间也较长,分布于1000至3500S内。随着加热功率的增大,环路热管热阻先减小后逐渐增大,该环路热管传热热阻最大不超过0.09℃/W,最小为0.024℃/W;随着传热距离的增大,管路的热损失增加,总压降和热阻也变大。当传热距离基本相同时,蒸发器容积的大小、冷凝器的冷凝能力及气液管线的布置形状均在一定程度上影响环路热管的最大传热能力。     

Experimental research on heat transfer of pulsating heat pipe

Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper, and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fall ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters.