Variation characteristics of aquifer parameters induced by groundwater source heat pump operation under variable flow

The variation characteristics of aquifer parameters,induced by groundwater source heat pump(GWSHP) operation under variable flow,were theoretically analyzed through a case study,in which the characteristics of building air conditioning load were considered.The results,compared with the constant flow operation,indicate that the influence on the variations of porosity,hydraulic conductivity and confined water head is decreased by 48%,51% and 71%,respectively,under variable flow operation.The security of variable flow operation is superior to that of constant flow.It is also concluded that the climate region and function of the buildings are primary factors which affect the suitability of variable flow operation in GWSHP.

Using Grey Relational Analysis to Evaluate Different Influencing Factors on Aquifer Parameters Variations with Groundwater Source Heat Pump Operation

The influence of particle migration induced by groundwater source heat pump( GWSHP) operation on aquifer parameters was theoretically analyzed. Then the sensitivity analysis of different influencing factors,which influenced aquifer parameters with GWSHP operation,was evaluated by using grey relational analysis method through a case study. The present study indicated that the erosion parameter, hydraulic conductivity and initial concentration were critical influencing factors which affected the aquifer parameters and the suitability of GWSHP. It also indicated that the discharge of single well should be controlled and the diameter of single well should be selected appropriately in order to decrease particle migration.

Effect of Heat-Setting on Structural Parameters and Mechanical Properties of PP Monofilament Hernia Patch

General surgery hernia is a common and frequently- occurring disease in the world. In the tension-free hernia repair surgery, polypropylene （PP） patch has been confirmed as the most popular surgical implants. In this study, domestic medical PP monofilament was selected as raw material whose diameter was 0.15 mm, and the patch was knitted in the warp knitting machine of 12E gauge with one bar. Using the method of orthogonal experiment with three factors and three levels, the best heat-setting process of PP mesh was determined at the temperature of 130 ~C with 10 min under tension-free conditions. The relationship between heat-setting tension and performance of the patch was discussed. Patches with different porosity were prepared, and then structural parameters including density, thickness, porosity, and mechanical properties including tensile breaking strength, bursting strength, tearing strength, flexural rigidity and suture pulling out strength were tested and compared. The experimental results show that： the smaller of the patch＇s density, the higher of the porosity; other properties including density, thickness, bending stiffness, tensile breaking strength, bursting strength, tear strength, and suture pulling out strength reduce in varying degrees. This different degree of reduction is worth summarizing.

Refrigerant Control Strategies for Residential Air-Conditioning and Heat-Pump System

This paper simulated the optimal refrigerant charge inventory of a refrigeration system in air-conditioning operation and heat-pump operation respectively,and studied the refrigerant control strategies in this system.The void fraction in two-phase fluid region was calculated by Harms model.And based on distributed parameter model and Harms model,the refrigerant charge inventory in condenser and evaporator were calculated and analyzed in air-conditioning conditions and heat-pump conditions,respectively.The calculating results of different refrigerant mass between refrigeration and heating conditions indicate that the optimal refrigerant charge inventory in heat-pump conditions is lower than that in air-conditioning conditions.To avoid the decrease of COP due to the surplus refrigerant in heating conditions,we introduced the liquid reservoir control method and associate capillary control method.Both of them could increase the heating capacity of the air-source heat pump.The difference of optimal refrigerant charge inventory in air-conditioning and heat-pump system can be controlled by the liquid reservoir or the associate capillary.

Operation Performance of Air Source Heat Pump System for Space Heating in Tianjin

An air source heat pump system (ASHPS) used in an office building is set up and studied experimentally. Its operating performance in winter is evaluated based on test data and a comparative discussion is given on the effect of climate conditions and heating load ratio on the operation behavior. Then heating capacity variation caused by evaporator frosting is analyzed as well. Finally, the defrosting parameters and the technical feasibility are studied for a constant heating demand. The experimental results indicate that both the outlet water temperature drop and the system COP should be taken into account when setting defrosting parameters, and ASHPS is a viable technology for space heating and hot-water production in winter in Tianjin, which can maintain the room temperature above 19 ℃ when the outdoor temperature is -2 ℃.

Case study of underground pipe ground coupled heat pump system

Aiming to give some advices on the ground coupled heat pump system design in Siehuan Province, China, a typical ground source heat pump （GSHP） system in Sichuan Province was tested in a whole operational year, and the parameters of temperature and flow rate in different parts of system were measured during this period. The seasonal energy efficiency ratio was calculated and the performance of heat pump system in summer was compared with that in winter. The result shows that the coefficient of performance of the system reaches 3.63 in summer and 3.49 in winter, respectively. The heat balance in underground rock mass is acquired basically throughout the year, and the heat accumulation in the earth tends to be zero.

Tribological Properties of Cylinder Block/Valve Plate Interface of Axial Piston Pump on the Tribometer

The tribological properties of cylinder block/valve plate is an important consideration in the design of axial piston pump.The effect of materials and heat treatment on friction and wear properties has been studied in depth.Engi-neering experiences show that the speed and load also affect the tribological properties,but these have not been systematically analyzed.The purpose of this paper is to evaluate the tribological properties of the commonly used materials(CuPb1 5Sn5 and 38CrMoAl/42CrMo)for cylinder block/valve plate with different heat treatment and con-tact pressure at different speed.During the test,tribometer is used to simulate the contact pattern between the valve plate/cylinder block in axial piston pump,the friction coefficient,wear rate and surface topography are analyzed to evaluate the tribological properties of different types of friction samples at different speed.Results indicate that:(1)contact surface of the samples at 1800 r/min is more prone to adhesive wear than those at 500 r/min;(2)in the terms of wear resistance,quench-tempered and nitrided 38CrMoAl(38CrMoAl QTN for short)is better than quench-tem-pered and nitrided 42CrMo,although they are all commonly used materials in the axial piston pump;(3)2.5 MPa is the critical contact pressure of the interface between valve plate made of 38CrMoAl QTN and cylinder block made of CuPb1 5Sn5 on the tribometer,which implies the pressure bearing area at the bottom of the cylinder block should be carefully designed;(4)the valve plate/cylinder block made of 38CrMoAl QTN/CuPb15Sn5 exhibits good tribological properties in a real axial piston pump.This research is useful for the failure analysis and structural optimization design of the valve plates/cylinder block.

Prediction of mechanical properties of A357 alloy using artificial neural network

The workpieces of A357 alloy were routinely heat treated to the T6 state in order to gain an adequate mechanical property.The mechanical properties of these workpieces depend mainly on solid-solution temperature,solid-solution time,artificial aging temperature and artificial aging time.An artificial neural network（ANN） model with a back-propagation（BP） algorithm was used to predict mechanical properties of A357 alloy,and the effects of heat treatment processes on mechanical behavior of this alloy were studied.The results show that this BP model is able to predict the mechanical properties with a high accuracy.This model was used to reflect the influence of heat treatments on the mechanical properties of A357 alloy.Isograms of ultimate tensile strength and elongation were drawn in the same picture,which are very helpful to understand the relationship among aging parameters,ultimate tensile strength and elongation.

Numerical and experimental evaluation on methods for parameter identification of thermal response tests

Several parameter identification methods of thermal response test were evaluated through numerical and experimental study.A three-dimensional finite-volume numerical model was established under the assumption that the soil thermal conductivity had been known in the simulation of thermal response test.The thermal response curve was firstly obtained through numerical calculation.Then,the accuracy of the numerical model was verified with measured data obtained through a thermal response test.Based on the numerical and experimental thermal response curves,the thermal conductivity of the soil was calculated by different parameter identification methods.The calculated results were compared with the assumed value and then the accuracy of these methods was evaluated.Furthermore,the effects of test time,variable data quality,borehole radius,initial ground temperature,and heat injection rate were analyzed.The results show that the method based on cylinder-source model has a low precision and the identified thermal conductivity decreases with an increase in borehole radius.For parameter estimation,the measuring accuracy of the initial temperature of the deep ground soil has greater effect on identified thermal conductivity.

基于恒热流法和恒温法的岩土热物性试验分析研究

目前岩土热物性测试仪采用的方法包括两种:恒热流法和恒温法,通过介绍两种测试方法的区别及模型算法,以北京市某公建项目岩土热物性测试结果为基准,利用TRNSYS软件分别模拟了恒热流法和恒温法的测试工况,针对模拟结果展开分析研究。经对比,试验时间至48 h时,两种测试方法利用软件模拟出的延米换热量与现场测试结果的误差在10%以内,表明若已知项目周边的地层热物性参数如地层的导热系数、热扩散率等,可将软件模拟结果作为前期地埋管系统设计的依据,并作为后续热物性勘察结果验证的参考数据。此外,根据模拟结果,由于夏季地埋管流体在设计工况下与土壤的温差值较大,为了使流体尽快达到设计工况点,恒温法测试时应选用较大的功率,否则48 h内的测试值结果与实际值偏差较大。

浅层岩土体热物性参数测定的影响因素分析

浅层地热勘查中,岩土体的热物性是区域评价和工程应用的重要参数。为提高热物性参数测定的准确性,建立了具有单项因素误差影响计算功能的传热模型,分别研判岩土体热物性测试的影响因素。结果显示:不同温度的泥浆,成孔停待10d后,热导率值基本稳定;加载功率波动时,可根据波动周期规律选择合适的加载时间与数据舍弃时间,以减少求解误差;如加载过程出现中断,运用线热源简化法计算的热导率有较大误差,中断开始时间越晚、中断时间越长,误差越大;无负荷循环测试时,15min的观测时间可得到岩土体初始平均温度;岩土体温度受四季气温影响深度主要在15m以内,最低平均温度在2、3月份,最高平均温度在8、9月份,均较当地气温约滞后2个月。

结构参数对石英纤维针刺毡防隔热和力学性能的影响

为开发具有良好防隔热和力学性能的高性能石英纤维毡,基于传热数学方程,预测了石英纤维毡的厚度对其隔热性能的影响规律;为提高纤维毡的力学性能,探究了在纤维毡中添加不同层数的石英纤维布对其力学性能的影响规律;此外还探讨了针刺密度对石英纤维毡隔热性能和力学性能的影响。结果表明:石英纤维毡传热模型与实验吻合度可达94.8%;石英纤维毡厚度提升2 mm,其隔热性能提高20℃左右;添加石英纤维布可以显著提高纤维毡断裂强力和撕破强力;针刺密度可以提升纤维毡力学性能,但针刺密度过大会破坏纤维毡结构,使其力学性能下降。

低温工质对R1336mzz(Z)/TEGDME的饱和蒸气压、密度、黏度、比热容及比焓

随着氢燃料电池产业加速发展,其低温余热(约70℃)利用成为了亟需解决的问题,而传统的LiBr/H_(2)O工质对的发生温度过高,无法利用较低品位的热能以及低温下易结晶,因此提出了新型低温工质对R1336mzz(Z)/TEGDME,并进行了饱和蒸气压、密度、黏度、比热容的测量,通过NRTL模型计算了其混合焓和比焓。使用最小二乘法对以上数据均进行了回归,实验值与拟合值的相关系数的平方均大于0.999,吻合较好,可使用拟合公式进行新型低温工质对的余热制冷热力循环的设计计算。相较LiBr/H_(2)O工质对,低温工质对R1336mzz(Z)/TEGDME的发生温度降低了约12℃,黏度降低了约30%,可以利用低温燃料电池余热制冷,具有很强的实际应用意义。

不同烟气CO_(2)含量下近等温相变捕集工艺调节策略模拟分析

CO_(2)相变捕集工艺具有较低的再生能耗,但在实际生产中,上游工艺产生的烟气中CO_(2)含量(物质的量分数,下同)不稳定,可导致工艺的整体能耗发生变化,因此需研究不同烟气CO_(2)含量下该工艺参数的调节策略。通过Python语言调用AspenPlus对近等温CO_(2)相变捕集工艺进行了模拟计算,分析了不同CO_(2)含量下吸收塔温度(ta)、解吸塔温度(td)、液/气比(v)、胺浓度(c)、解吸液循环比(s)对再生能耗和CO_(2)捕集率的影响以及相应的调节策略。结果表明,td对CO_(2)捕集率的影响最显著,当CO_(2)含量为5.00%时,其相关性系数最高(74.78%);ta对再生能耗的影响最显著,当CO_(2)含量为20.00%时,其相关性系数最高(-55.26%)。在维持CO_(2)捕集率大于等于90.00%的条件下,随着CO_(2)含量从5.00%升高至20.00%,再生能耗从2.35GJ/t降低至2.13GJ/t。此外,应根据CO_(2)含量对ta、td、c和v进行相应调节,以确保CO_(2)捕集率大于等于90.00%并且再生能耗最低。

跨临界CO_(2)热泵系统最优风量实验研究

为探究在压缩机固定转速下风量对跨临界CO_(2)循环系统性能的影响,以及确定使系统达到最大COP的最优风量,搭建了跨临界CO_(2)热泵系统实验台。研究了室内、外风量对系统制热性能的影响,并总结出确定最优风量的方法。结果表明:跨临界CO_(2)热泵系统在制热模式下运行,当室内风量固定时,随着室外风量的增大,排气压力与室内出风温度均呈现出先升高后趋于平稳,系统制热COP随着室外风量的增大存在一个最优值;为准确预测最优室外风量,引入最优排气压力偏离度σ和参数变化率δ作为最优室外风量的判断依据,当σ=0.48%,δ=1.4%时,系统处于最优室外风量,即对应系统在最大的COP下运行。经过实验验证,最优室外风量预测值误差在5%以内,该方法具有较高的准确性。

新世纪跨季节显热储热项目发展现状与分析

发展跨季节储热技术对实现我国供热领域的绿色低碳转型具有重要意义。本文从跨季节储热项目角度出发,分别对跨季节储热的原理及分类、国内外发展现状、项目统计与参数分析等方面进行了综述。重点对所统计的44个国内外跨季节显热储热项目进行了典型技术经济参数分析、热源分析与材料分析。最后指出国内外跨季节储热项目数量增多、储热规模持续扩大,发展大容量跨季节水体储热、实现跨季节储热热源多能互补、规模化应用热泵、进一步开发适用于跨季节储热系统的新型材料可能是未来跨季节储热发展的重要方向。

常温闭环脉动热管性能影响因素研究综述

常温闭环脉动热管依靠工质在管内脉动和相变传热,具有传热效率高、结构简单、成本低等优点,广泛应用于电子元件散热。将影响脉动热管启动和传热性能的因素分为3类展开综述:结构参数、操作参数和工质物性参数。首先对结构参数中管径、截面形状、弯头数以及各段长度比等因素的研究进行总结,其次分析操作参数中加热功率、倾斜角度和充液率的影响,最后将工质物性参数分为影响流动和传热两方面进行归纳。为提升脉动热管启动和传热性能,未来需对临界弯头数开展深入研究;为适应小倾角和负角度工况,需要提升热管抗重力性能;为描述工质物性对热管性能的影响,需构建物性参数综合评价指标。

百米U75V钢轨在线热处理工艺优化

百米U75V钢轨是我国铁路建设的主型钢轨,在线热处理是其主要强韧化手段,纵向(长度方向)性能均匀性差和生产效率低是其热处理生产存在的主要问题。百米U75V钢轨的在线热处理过程分为2个冷却阶段,共包含4个冷却工艺参数:开淬温度(T_(i))、相变阶段冷却速度(V_(s))、相变冷却结束温度(T_(f))以及相变后冷却速度(V_(a))。通过热模拟试验研究了各参数对百米U75V钢轨组织和性能的影响。随着工艺参数的变化,珠光体片层间距(S)在100.7~209.1 nm范围内变化;T_(i)和V_(s)对S具有特别显著影响,T_(f)和V_(a)对S没有显著影响;T_(i)不一致是百米U75V钢轨纵向性能不均匀的主要原因之一。采用“先慢后快”的两段式冷却方案,即在轧后钢轨表面温度冷却至相变终冷温度(约500℃)之前,以接近但不超过珠光体转变临界冷却速率的速度进行冷却,之后提高冷却速度(不超过10℃/s),有利于同时提高生产效率和百米U75V钢轨纵向性能的均匀性。

Dehydration property of Shrimp(Pandalus borealis)undergoing heat-pump drying process

Peeled,headed or whole shrimp(Pandalus borealis)was dried in a heat-pump dryer at-2-0℃and 20℃,respectively,and desorption isotherms characterizing the dehydration property of each shrimp sample group were determined.Desorption isotherms of shrimp handled differently and dried at different temperatures(-2-0℃or 20℃)could be well described by Oswin’s model(X=a(1-a_(w)/a_(w))).The regression model of peeled,headed or whole shrimp was established,which is reliable for predicting the desorption isotherms of shrimp undergoing heat-pump drying.The handling methods of shrimp exhibit measurable influence on desorption isotherms of shrimp,whereas drying temperature(-2-0℃or 20℃)has little influence on the constants of a and n in Oswin’s model,of whole shrimp,even though it has certain influence on these constants of peeled and headed shrimp.For heat-pump drying,headed shrimp may have a better stability than peeled or whole shrimp due to the best stability.

含气量对混凝土流变参数及力学性能的影响

为了研究影响混凝土的流变参数,通过掺入引气剂改变混凝土含气量对混凝土流变性能及力学性能的影响进行分析。根据混凝土拌和物性能标准,利用混凝土流变仪、塌落度桶试验,测试混凝土的塌落度、扩展度、含气量以及流变参数,并对混凝土拌和物的流变学参数与力学性能进行分析。结果表明:在保证混凝土强度的前提下,掺用适量引气剂在混凝土拌和物内形成适量微小的封闭球状气泡,可以降低集料颗粒间的相互作用力(摩擦阻力),从而可降低屈服剪切应力和粘度、改善拌和物流变性能;引气剂掺量过大,混凝土强度下降明显。结合流变参数和抗压强度测试结果,引气剂掺量控制在0.1/10000~0.5/10000之间较为合适;提高混凝土含气量可以改善其流动性,降低泵送混凝土单位长度的压力损失。