水源热泵热水器实验研究

水源热泵技术利用少量电能将地表水或地下水的低品位能量转移至高品位,目前正成为节能领域的研究热点.针对水源热泵变冷凝参数的相关研究缺乏的现状,通过搭建水源热泵热水器实验台进行了相应实验研究.在水流量Q为0.7~1.3 m~3·h~(-1),进水温度t为15~30℃范围内,对系统功耗、制热量、制冷量、热泵性能系数COP等参数进行了测量.实验结果表明,在水流量为1.1 m~3·h~(-1),进水温度为20℃时,COP达到最大值,系统平均热泵性能系数COP_(ave)为3.23,此时系统处于最佳运行工况.由此可知,寻找系统的最佳运行工况对热泵系统设计和实际工程应用具有重要的意义.     

R290直膨式太阳能热泵供暖系统实验研究

为分析直膨式太阳能热泵耦合地板辐射供暖系统在北方寒冷地区的实际运行特性,设计并搭建以丙烷(R290)为工质的直膨式太阳能热泵供暖实验平台,分析冬季不同运行工况下环境参数对系统热力性能的影响。实验结果表明：系统可实现室内供暖的稳定性,实验测试期间平均室温保持在16.1～20.8℃之间,热泵系统性能系数(COP)保持在2.57～4.30之间,供暖系统COP保持在2.24～3.98之间。太阳辐照度每增加50 W/m²,热泵系统COP提升4.9%;环境温度每升高1℃,热泵系统COP提升2.4%。太阳辐照度对热泵系统的电子膨胀阀开度和工质质量流量影响较为显著。当终止水温从45℃提升至55℃时,热泵系统COP降低12.2%;而在终止水温为50℃时,供暖系统COP达到最大值3.37。     

直膨式太阳能热泵集热/蒸发器性能优化及其低温适应性研究

对直膨式太阳能热泵系统的集热/蒸发器结构进行优化,设计由六边形与四边形单元组合的流道结构,并进行仿真与实验研究。在上海地区,冬季工况下,将水温从10℃加热到50℃,系统COP可达到4.5;夏季工况下,将水温从30℃加热到55℃,系统COP可达到6.60。在此基础上,针对严寒地区冬季运行,研究了与喷气增焓循环耦合的低温型直膨式太阳能热泵系统。在环境温度为-10℃时,系统COP可达到3.79;环境温度为-20℃时,系统COP可达到3.69。依据实验与仿真数据,运用全生命周期经济性分析方法,以当量热价(LCoH)为评价指标,为太阳能热泵采暖经济性分析提供计算方法和理论依据。     

基于水蒸气工质新型压缩-吸收式热泵循环性能分析

针对常规热泵在工业余热利用领域应用温度范围受限的技术难题,该文对一种压缩-吸收式耦合热泵系统在大温升工况下制取约130 ℃热水或蒸汽开展研究。首先介绍耦合热泵循环的运行原理,构建耦合热泵的完整热力学模型,通过EES软件最优化函数计算发现吸收侧压力越低,循环性能系数（COP）越好,同时在溶液热交换器出口浓溶液温度高于结晶温度10 ℃及溶液放汽范围为5.0%~5.5%的约束条件下,以某工业余热回收工况为设计工况,其中余热热水进/出口温度为90/75 ℃,余热水流量为30 kg/s,高温热水进/出口温度为100/125 ℃,吸收与发生侧最优压力值分别为40和2.2 kPa,对应耦合热泵的COP为9.8。同理分析了不同余热热水出口温度及高温热水出口温度变化工况下系统的循环性能,验证了该循环在高制热温度下仍具有较好的性能系数。     

光伏-直膨太阳能热泵系统在变水温工况下的实验研究

提出了一种新型光伏-直膨太阳能热泵(PV-DXSAHP)的系统原理,建立了PV-DXSAHP系统试验台。对PV- DXSAHP系统在水温从15℃升高到55℃工况下的动态性能进行了测试和分析,结果显示,在水温升高到55℃时,PV-DXSAHP系统COP为4.1,测试过程的平均光电效率为13.2%。研究表明PV-DXSAHP系统具有优越的热泵性能和光电转换效率。     

水源热泵机组性能测试不确定度分析

依据水源热泵机组的性能测试方法和测量不确定度评定方法的相关标准,对水源热泵机组的制冷量和制热量进行了测试并建立了数学模型,分别对测量A类和B类不确定度进行了评定,得出测量相对误差为制冷工况2.2%和制热工况1.9%。分析了制冷(热)量测量不确定度主要来源于水温和水流量测量,建议采用系统整体标定方法进行削弱,以提高测试结果的准确度。     

乏汽吸收式热泵动态特性实验研究

采用吸收式热泵利用汽轮机乏汽余热供暖已逐渐成为火电厂的主要节能措施之一,但由于机组负荷变化频繁,使热泵经常偏离设计工况,运行效率低,供热性能差。为对热泵实施优化调节和控制,提高热泵运行效率,实验研究了热泵动态特性,结果显示,在驱动热源流量、低温水流量和低温水入口温度阶跃降低10%的情况下,在400s内,热泵制热量分别减少了18kW、2.1kW和14kW,冷却水出口温度分别降低了4℃、0.35℃和2.5℃,并通过仿真获得了动态响应过程的传递函数,为热泵优化控制提供了技术支持。     

江水源热泵系统温排水对江水水温及水质的影响

针对江水源热泵系统取水量大可能对江水水质产生影响的问题,以嘉陵江重庆主城段水体为研究对象,采用物理模拟的方法对江水源热泵系统温排水进行了系统的试验研究.结果表明,温排水对排放口近水域水温和水质均有一定程度的影响.在模拟大型江水源热泵系统运行工况的条件下,温排水导致排放口附近水域水温上升约3.3℃,间歇运行时水温能得到有效恢复;温排水导致排放口局部水域溶解氧降低8%～12%;并能加快水中营养物质的循环,从而使水体的高锰酸盐指数升高;温排水有利于水体中的有机氮转化为氨氮,加速氮循环,从而使水体氨氮和总氮含量升高,但对总磷影响不显著.     

变工况下热泵供热及膨胀机供热的热力性能对比分析

通过对各设备进行建模,以某300 MW热电联产机组为例,对热泵供热及利用小型膨胀机发电后排汽供热两种方案进行变工况分析。结果表明,对于热泵供热方案,在不同的主蒸汽流量下,都存在一个最佳出口热网水温,使系统煤耗最低;采用热泵最佳参数与膨胀机方案进行变工况对比,发现在采暖抽汽参数较低时,热泵方案的煤耗高于膨胀机方案,随着采暖抽汽参数的增大,当热泵出口最佳热网水温超过70℃时,热泵方案的煤耗开始低于膨胀机方案;同样,在采暖抽汽参数较低时,热泵供热效率比膨胀机方案低,当热泵出口最佳热网水温超过64℃时,热泵方案供热效率开始超过膨胀机方案;提出等效节能量指标,并通过计算表明该指标可用于对比两方案的节能效益。     

空气源热泵热水器的优化策略及性能分析

空气源热泵热水器具有运行工况广、冷凝温度时变的特点,机组在运行至较高水温时系统效率会有明显下降。针对这一问题通过实验比较不同外部工况下系统性能的变化规律,分析热泵热水器的实际运行特性和制热性能劣化的原因,并依此提出以控制电子膨胀阀开度和压缩机启停时机的优化策略来提升系统性能。实验结果表明,系统性能分别提升了24.8%和14.3%。同时分析了两种策略的优势与差异性,以期使空气源热泵热水器在实际应用中的制热效率得到最大程度地优化。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Contents in Volume 23,2014

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Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.