Techno-economic analysis of single U-tube and double U-tube heat exchangers in Chongqing area

On the basis of practical projects in Chongqing,the thermal performance of heat exchangers (single U-tube type and double U-tube type) of the ground-source heat pump (GSHP) system in the hot summer was obtained and analyzed. The data obtained from test could match with the result deduced from theoretical calculation. From the test results,the cooling capacity of double U-tube is 1.6 times that of single U-tube. Taking cost per depth per watt Clq as the evaluation standard,Clq of single U-tube is 4.69 RMB$/W,and Clq of double U-tube is 3.14 RMB$/W. The double U-tube heat exchangers usage should be prioritized.

Numerical simulation on heat transfer performance of vertical U-tube with different borehole fill materials

Heat exchange performance of vertical U-tube heat exchanger was studied with two different borehole fill materials and CFD software. Borehole surface temperature and water temperature distribution were simulated on the condition of continuous operation for 8 h in winter with inlet water temperature being 10℃. The results show that there is no obvious difference on heat exchanger performance between the two different borehole fill materials.

Performance enhancement of filled-type solar collector with U-tube

In order to increase the efficiency of solar collector, a methodology is proposed based on the analysis of its influencing factors, such as thermal conductivity of filled layer, structure forms of filled layer and heat loss coefficient. The results of analysis show that the heat transfer between pipes in evacuated tube is one of the most important factors, which can lead to the decrease of the outlet temperature of working fluid. In order to eliminate the negative influence of the heat transfer between pipes, the hollow filled-type evacuated tube with U-tube(HUFET) was developed, and the heat transfer characteristics of HUFET were analyzed by theoretical and experimental studies. The results show that the thermal resistances decrease with the increase of the thermal conductivity of filled layer. When the thermal conductivity is over 10 W/(m·K), the change of thermal resistances is very little.Furthermore, the larger the thermal conductivity of filled layer, the less the rate of the energy transfer between the two pipes to the total energy transfer, which is between the absorber tube and the working fluid. There is a little difference between the efficiencies of HUFET and UFET, with the efficiency of HUFET 2.4% higher than that of UFET. Meanwhile, the validation of the model developed was confirmed by the experiment.

An Analytical Model for the Thermal Assessment of a Vertical Double U-Tube Ground-Coupled Heat Pump System in Steady-State Conditions

An analytical model was built to predict the thermal resistance of a vertical double U-tube ground-coupled heat pump that operates under steady-state conditions.It included a geometry obstruction factor for heat transfer throughout the backfill medium due to the presence of the second loop.The verification of the model was achieved by the implementation of five different borehole configurations and a comparison with other correlations in the available literature.The model considered a U-tube spacing range between(2)and(4)times the U-tube outside diameter producing a geometry configuration factor range of(0.29-0.6).The results of the model were utilized for the assessment of the DX ground heat exchanger coupled heat pump system.For similar geometrical configurations,the borehole thermal resistance experienced a decrease as the geometry factor increased.The single U-tube borehole thermal resistance was higher than that of the double U-tube heat exchanger by(10-27)%for the examined geometry configurations.The borehole thermal resistance at tube spacing of twice the tube diameter was higher than the predicted value at the triple diameter and fell in the range of(18-34)%.

Thermal performance of a single U-tube ground heat exchanger:A parametric study

In this research,the thermal performance of a single U-tube vertical ground heat exchanger is evaluated numerically as a function of the most influential flow parameters,namely,the soil porosity,volumetric heat capacity,and thermal conductivity of the backfill material,inlet volume flow rate,and inlet fluid temperature.The results are discussed in terms of the variations of the heat exchange rate,the effective thermal resistance,and the effectiveness of the ground heat exchanger.They show that the inlet volume flow rate,inlet fluid temperature,and backfill material thermal conductivity have significant effects on the thermal performance of the ground heat exchanger,such that by decreasing the inlet volume flow rate and increasing the backfill material thermal conductivity and inlet fluid temperature,the outlet fluid temperature decreases considerably.On the contrary,the soil porosity and backfill material volumetric heat capacity have negligible effects on the studied ground heat exchanger’s thermal performance.The lowest inlet fluid temperature reaches a the maximum effective thermal resistance of borehole and soil,and consequently the minimum heat transfer rate and effectiveness.Also,multilinear regression analyses are performed to determine the most feasible models able to predict the thermal properties of the single U-tube ground heat exchanger.

Performance of U-tube Solar Water Heaters Facing Different Directions

System performance of solar water heaters depends upon collector and storage tank designs, solar radiation intensity and ambient temperature, amongst others. Evacuated glass tube collectors with U-tubes inside are less prone to leakages than the all-glass or the heat pipe types. U-tube solar water heaters suspended on walls and balconies could help overcome present day roof space restriction and increasing apartment-style housing. As such, their performance would depend upon its orientation when mounted in a vertical position. This paper reports the results of outdoor tests conducted on natural convection U-tube solar water heaters oriented towards different directions. Long and short term test procedures were employed to allow us to compare their performances as if they were tested simultaneously side-by-side.

亨通光电成功研发A-Dry^(TM)全干式光缆及U-Tube^(TM)超细气吹微缆

近日,亨通光电成功研发A-Dry^（TM）全干式光缆及U-TubeTM超细气吹微缆,既可满足海外电信市场不同层次的网络建设需求,又可为国内电信市场提供多样化的产品选择,进一步推进公司＂从本土企业向国际化企业、从生产型企业向研发生产型企业、从产品供应商向系统集成服务商转型＂的战略转型,为实现＂打造行业领军企业,加快推进国际化进程＂的战略目标提供强力支撑,进一步提升亨通光电在行业中的技术研发领先地位。

A novel distributed solar refrigeration system based on evacuated U-tube solar collector and elastocaloric refrigerator

Refrigeration challenges in regions with electricity shortages significantly decrease the quality of life for residents. In response to the prevalent refrigeration challenges in power-deficient areas, a novel distributed solar refrigeration system, comprising an evacuated U-tube solar collector and elastocaloric refrigerator, is theoretically introduced. Theoretical formulations for the energy efficiency and cooling power of the solar refrigeration system are presented to facilitate predictive assessments of the performance properties. Under typical conditions, the energy efficiency and cooling power of the solar refrigeration system are,respectively, 4.84% and 200.15 W. Subsequently, an extensive parameter study is conducted to comprehensively uncover key performance influencers and identify avenues for improvement. In addition, local sensitivity analyses identify that the length ratio is the top influential parameter, while the heat transfer fluid flow rate is the least sensitivity. A pragmatic case study,conducted with the weather data of Ningbo City, China, serves to empirically predict the performance of the hybrid system within the constraints of practical circumstances.

揿针联合清肺健脾汤治疗脾气亏虚兼痰热壅肺型老年社区获得性肺炎临床研究

目的:观察揿针联合清肺健脾汤治疗脾气亏虚兼痰热壅肺型老年社区获得性肺炎(CAP)的临床疗效。方法:选取脾气亏虚兼痰热壅肺型老年CAP患者100例,按随机数字表法分为治疗组与对照组各50例。2组均接受抗感染、化痰、止咳、退热、营养支持等西医常规治疗;治疗组加用揿针联合清肺健脾汤治疗。比较2组临床疗效,以及治疗前后降钙素原(PCT)、C-反应蛋白(CRP)、T淋巴细胞亚群(CD3^(+)、CD4^(+)、CD8^(+))、血清胃泌素水平变化。结果:治疗后,治疗组总有效率为98.00%,对照组为86.00%,组间比较,差异有统计学意义(P<0.05)。治疗后,2组PCT、CRP水平均治疗前降低(P<0.05),且治疗组PCT、CRP水平低于对照组(P<0.05)。治疗后,2组CD3^(+)、CD4^(+)水平较治疗前提高(P<0.05),CD8^(+)水平较治疗前降低(P<0.05);且治疗组CD3^(+)、CD4^(+)水平高于对照组(P<0.05),CD8^(+)水平低于对照组(P<0.05)。治疗后,2组胃泌素水平较均治疗前降低(P<0.05),且治疗组胃泌素水平低于对照组(P<0.05)。结论:揿针联合清肺健脾汤治疗脾气亏虚兼痰热壅肺型老年CAP临床治疗效果显著,能有效下调炎症反应水平,提高机体免疫力,改善肠胃功能。

血清Ⅳ型胶原、透明质酸及板层素对肝纤维化的诊断价值

本文用放射免疫法检测了２２０例各型肝病患者血清Ⅳ型胶原（Ⅳ－Ｃ）、透明质酸（ＨＡ）及板层素（ＬＮ）水平。结果显示各类肝病患者血清Ⅳ－Ｃ、ＨＡ及ＬＮ水平随病情进展而逐渐升高，以Ⅳ－Ｃ≥１３０μｇ／Ｌ、ＨＡ≥２６０μｇ／Ｌ、ＬＮ≥１６０μｇ／Ｌ为诊断肝纤维化的临界点，其敏感度、特异性、准确率分别达８０％以上，联合检测以Ⅳ－Ｃ与ＨＡ联合较为理想，说明三者可作为肝纤维化诊断较为敏感的指标，其中Ⅳ－Ｃ对早期肝纤维化的诊断优于ＨＡ和ＬＮ。

干旱胁迫对不同株型玉米光合特性及产量性状的影响

在大田干旱胁迫条件下,对3种株型玉米品种即平展型豫玉22号、中间型沈单16号和紧凑型先玉335的形态、光合特性和产量要素进行了分析研究。研究结果表明:(1)干旱胁迫导致3个不同株型玉米叶片叶绿素含量显著降低,先玉335的叶绿素含量受干旱胁迫的影响最小,豫玉22号影响最大。(2)3个品种的Pn、Tr、Gs、Ci随干旱胁迫程度加大而显著减小,但WUE的变化规律与之相反,即胁迫程度越深,WUE越大。WUE和Pn的大小排序均表现为先玉335>沈单16号>豫玉22号。(3)干旱胁迫下,3种株型玉米品种的株高降低、穗长缩短、秃尖变长、穗行数、穗粗、行粒数和千粒重显著减少,经济产量显著下降,且胁迫程度越大,减产越严重,豫玉22号减产幅度最大,先玉335最小,沈单16号居中。

艾灸治疗腹泻型肠易激综合征临床研究

目的观察艾灸对腹泻型肠易激综合征的临床疗效。方法将符合纳入标准的60例患者随机分为2组:治疗组(30例)和对照组(30例)分别采用艾灸和西药洛哌丁胺治疗。观察两组临床疗效、治疗前后症状积分变化。结果治疗组总体临床疗效显著优于对照组(P<0.05)。治疗后对照组腹痛、腹胀或不适、大便性状、大便次数积分显著降低(P<0.01),治疗组腹痛、腹胀或不适、大便性状、大便次数、黏液便、胃纳减少、大便不尽感积分均显著降低(P<0.05,或P<0.01)。治疗前后胃纳减少、大便不尽感、腹痛、腹胀或不适的积分差值比较,治疗组显著高于对照组(P<0.05,或P<0.01)。结论艾灸对腹泻型肠易激综合征的临床疗效优于西药洛哌丁胺。

孤立湿地研究进展

孤立湿地作为湿地的重要组成部分,在人类社会发展中作用逐渐凸显。对术语"孤立湿地"的定义国外进行较早,美国官方将孤立湿地定义为与可流动水体不相邻或不通过地表水相联系的湿地,而我国仅提出了与孤立湿地相关的概念,如"环型湿地"、"碟型洼地"、湿地的"景观破碎化"等。孤立湿地的类型与特征研究相对较少,没有形成完整的理论体系,仅提出孤立性、水文连通性、生物连通性等特征。孤立湿地的功能研究是孤立湿地研究的重点,从孤立湿地的气候、水文和水质、生境等功能进行阐述。对于孤立湿地的保护,国外已有明确的法律和相应的措施,而我国在此方面需要进一步完善。通过对孤立湿地的定义、类型、特征、功能和保护进行了综述,并对未来我国孤立湿地研究的热点和方向进行了初步展望。

异氟醚对肺泡Ⅱ型细胞表面活性物质相关蛋白A的影响

目的 通过原代培养的正常及受H2 O2 损伤的肺泡Ⅱ型上皮细胞 (ATⅡcell) ,探讨异氟醚 (Iso)对肺泡Ⅱ型上皮细胞表面活性物质相关蛋白A(SP A)的影响。方法 肺泡Ⅱ型上皮细胞培养 32小时后 ,被分为六组 :对照组 (不加任何药物 )、0 2 8mmol/LIso组、2 8mmol/LIso组、75 μmol/LH2 O2 组、75 μmol/LH2 O2 +0 2 8mmol/LIso组和 75 μmol/LH2 O2 +2 8mmol/LIso组 ,继续培养 3小时。通过酶联免疫吸附法 (ELISA)检测Ⅱ型上皮细胞内和培养液中SP A含量。结果 Iso降低正常肺泡Ⅱ型上皮细胞内和培养液中SP A含量 ;经H2 O2 作用后 ,SP A含量亦显著减少 ,异氟醚增强H2 O2 的作用。结论 Iso可降低肺泡Ⅱ型上皮细胞合成SP A的功能 ,尤其是在过氧化环境中。

甘肃省肃南县雪泉铜(锌)矿床找矿勘查思路探讨

雪泉塞浦路斯型富铜(锌)块状硫化物矿床地处北祁连山西段奥陶纪弧后盆地火山岩带内,矿床的形成受火山热液喷流中心控制,每个喷流中心的成矿遵循"蘑菇"状的成矿模式,目前已发现矿区存在多个热液喷流中心,与此相对应的矿体表现出呈群出现,分段集中的特点。结合矿区地形特点,笔者提出矿床下一步的找矿勘查应按照"面上展开——利用地质测量、物探扫面进行探寻热液喷流中心;分段深入——在每个热液喷流中心主要利用硐探工程进行探矿验证"的思路开展工作。

冠心病合并2型糖尿病患者经皮冠状动脉介入术的护理研究

目的:探讨综合护理对冠心病合并2型糖尿病(2-DM)并接受冠状动脉介入术患者围手术期预后的影响。方法:连续选取冠心病合并2型糖尿病并接受冠脉介入术患者127例作为研究对象,根据患者病情进行综合护理,观察患者围手术期预后情况。结果:127例患者手术成功率为100%,11例出现围手术期并发症,经积极处理均得到有效控制。结论:对冠心病合并2型糖尿病患者实施综合护理对提高手术成功率、减少围手术期并发症和改善患者预后具有重要意义。

生物系统冗余结构的Type-2型数学模型

生态系统本身就是一个自组织的进化系统,生物与环境的交流和相互作用中,生物利用自身的冗余结构和冗余补充,使整个系统的进化始终朝着有利于生物发展的方向进化。本文利用Type-2模糊系统建立了生物群落冗余结构的数学模型,提出了生物群落稳定性的度量方法,研究了生物群落冗余结构与生物进化可靠性和稳定性的关系。

2型糖尿病合并高血压病药物治疗方案分析

目的调查了解门诊2型糖尿病合并高血压患者的血糖、血压控制情况及药物治疗现状,总结其合理治疗经验,促进患者药物治疗安全有效。方法随机抽取2013年12月-2014年5月在医院门诊就诊的2型糖尿病合并高血压患者200例,采用问卷调查方法调查分析其服用药物情况及治疗效果。结果 200例糖尿病合并高血压患者的平均空腹血糖为7.38mmol/L,平均血压为137/83mm Hg。主要使用的降糖药物为二甲双胍、胰岛素、阿卡波糖、磺脲类药物等,使用较多的降压药物为钙通道阻滞剂、复方制剂、血管紧张素受体阻滞剂。随着病程的延长,联合用药的趋势明显。结论目前糖尿病合并高血压患者的血糖、血压水平控制尚可。在用药方面,降糖和降压药物选用较为合理。但仍需要继续严格控制血糖、血压及加强宣传教育,以期尽早实现血糖及血压控制达标,提高生活质量。