螺旋盘管式水-水换热器传热与流动特性实验研究

对螺旋盘管式换热器的特性及国内外研究状况进行了综述,对一种新型的螺旋盘管式水-水换热器进行了传热与流动特性实验研究。实验结果表明,传热系数随冷、热水流速的增加呈现先增加后明显趋缓的变化,存在比较经济的流速数值;实验拟合得到管外流体的对流换热准则关系式,并且得到了一定流速范围内管程和壳程流体压降与流速的关联式,为螺旋盘管换热器的研究及产品设计提供了参考与依据。     

焦炉荒煤气显热回收换热器传热特性的实验研究

为了研究不同的换热器类型在焦炉荒煤气显热回收装置的传热效果,依据相似与模化原理,搭建了空气-水传热实验台,通过传热实验,对比分析了夹套管与螺旋盘管两种换热器在不同工况下的传热系数,并根据实验数据计算拟合出空气侧的传热关联式。结果表明:夹套管与螺旋盘管的换热系数随空气流量的增大而增大,受工质侧水流量的影响不大。螺旋盘管的换热系数受上升管内筒筒壁和螺旋盘管管壁之间的空气层热阻影响较大。在相同的工况条件下,夹套管的换热系数是螺旋盘管的1.5倍,结合现场参数进行热力计算,夹套管比螺旋盘管每小时可以多产生1.7 MPa的蒸汽57.1 kg。     

软土地区竖直地埋管换热器回填材料性能研究

竖直地埋管换热器回填材料性能对地源热泵换热系统的换热能力有直接影响。对不同配比的水泥基回填材料的导热性能进行测试分析。对不同配比的膨润土基回填材料的导热性能、抗渗性能以及充填性能进行测试分析。得出不同配比下导热系数、渗透系数、析水率的变化曲线,建立膨润土基回填材料导热系数与加压养护压力关系式及膨润土基回填材料水灰比与析水百分比关系式。     

碳纤维换热器换热性能实验研究

为了解决烟气余热利用中换热器低温露点腐蚀问题,提出了一种新型碳纤维换热器。并以碳钢换热器作为对比进行了实验,实验测量了碳纤维、碳钢两种材料换热管的导热系数;利用烟风换热实验监测系统动态模拟火力发电厂锅炉尾部烟道换热器换热过程,在相同工况下实验测试了两种材料换热器的换热性能。结果表明:本实验所用碳纤维换热管导热系数大于碳钢换热管;碳纤维换热器整体换热性能弱于碳钢换热器,原因是为防止碳纤维换热器渗水,外表面涂敷了一定厚度的树脂材料,导致碳纤维换热器整体换热性能下降。     

地埋管回填材料传热性能的研究与分析

当回填材料导热系数大于周围岩土层,对地埋管换热器换热性能提升效果开始逐步递减.研究回填材料增益效果递减的原因,对提高总系统运行效率具有重要意义.通过软件平台Workbench对地埋管换热器在回填材料导热系数不同的情况下进行模拟.结果 显示,回填材料在整个传热过程中主要起到疏导热量,扩大导热面积的作用.回填材料导热系数较...     

海水源空调用盘管换热节能效果分析

为了研究海水源空调用盘管换热器节能效果,采用现场实验的方法对盘管单位管长换热量进行测定.基于实验测试值,结合工程实例,对海水源空调系统冷却水采用盘管换热器获取方式和传统冷却塔在节能、经济和环境方面进行对比.研究结果表明,管内流速越大换热量越大,在流速为0.7 m/s时,PE32的换热管单位管长换热量为27.2 W/m.此外,夏季采用盘管与海水换热制备冷却水的海水源空调系统经济性和环境效益明显.     

浮动盘管换热器和U型管换热器在建筑热水中的应用

在建筑热水供应设备中,有浮动盘管换热器、U型管换热器、螺旋管换热器等种类。本文重点对浮动盘管换热器、U型管换热器的性能、特点进行分析和比对。1.浮动盘管换热器浮动盘管换热器是一种间接换热器,传热部分采用铜管,把传热管做成螺旋状浮动置于壳体内,所以称为浮动盘管。由于该换热器的传热管在壳体内,水流过时可上下浮动     

二甲醚气化系统中螺旋盘管换热器的理论设计

基于二甲醚盘管换热器的理论计算,获得了换热器的换热量、换热面积以及盘管的圈数.研究结果为大规模气化二甲醚提供了理论依据.     

沼气池内PEX螺旋盘管换热性能实验研究

建立PEX螺旋盘管加热沼气池的实验平台,对影响盘管换热的运行参数(热媒入口温度、平均流速)和设计参数(螺旋管直径、螺距)进行实验研究。对比分析不同因素对沼气池内温度变化、盘管换热量和传热系数等参数的影响。结果表明:入口水温对螺旋盘管换热性能的影响大于管内平均流速,提高螺旋盘管入口水温可显著缩短沼气池的预热时间,将入口水温由40℃升至70℃后,对应的预热时间由15 h以上缩至5.4 h;螺旋盘管的平均传热系数随螺旋直径的增大、螺距的减小而减小;改变螺旋直径对水平方向上的沼液温度分布影响较小。     

垂直螺旋盘管地源热泵供暖制冷实验研究

结合一实际用户建立垂直螺旋盘管地源热泵实验系统，在供暖制冷工况下测量地下盘管的进出水温度，盘管从地下的取热量、排热量，从而分析系统性能、供热、制冷系数。     

Experimental performance evaluation of a closed‐loop vertical ground source heat pump in the heating mode using energy analysis method

An experimental study is performed to determine the performance of a ground source heat pump (GSHP) system in the heating mode in the city of Erzurum, Turkey. The GSHP system using R‐134a as refrigerant has a single U‐tube ground heat exchanger (GHE) made of polyethylene pipe with a 16 mm inside diameter. The GHE was placed in a vertical borehole with 55 m depth and 203.2 mm diameter. The average coefficients of performance (COP) of the GSHP system and heat pump in heating mode are calculated as 2.09 and 2.57, respectively. The heat extraction rate per meter of the borehole is determined as 33.60 W m^?1. Considering the current gas and electric prices in Erzurum city, the equivalent COP of the GSHP system should be 2.92 for the same energy cost comparing with natural gas. The virgin ground in Erzurum basin has high permeability and low thermal conductivity. In order to improve the thermal efficiency of GHE and thus improve COP of a GSHP in the basin, the borehole should be backfilled with sand as low‐cost backfill material and a 1 to 2 m thick surface plug of clay should be inserted. Copyright © 2007 John Wiley & Sons, Ltd.     

竖直埋管地热换热器钻孔内的传热分析

准三维模型为竖直埋管地热换热器的结构优化提供了较为精确的理论基础。利用准三维模型对竖直埋管地热换热器进行分析与研究得出，不同的行程布置对双U型埋管地热换热器的传热性能有较大影响。就钻孔内热阻的对比，双U型埋管比单U型埋管钻孔内的热阻低，因而双U型埋管地热换热器较单U型埋管地热换热器更为合理。     

Heat and mass transfer model of a ground heat exchanger: validation and sensitivity analysis

Validation of ground heat exchanger (GHE) model is presented using the experimental data obtained for both single and double pipe horizontal GHE. Sensitivity analysis of the GHE model shows the influence of the variation in the soil thermal conductivity, specific heat and density on the thermal performance of a GHE. Finally, the thermal performance of a GHE is analysed using both heat and mass transfer models, and conduction only model, as well as the influence of the initial soil moisture content on the thermal performance of a GHE. © 1998 John Wiley & Sons, Ltd.     

Experimental performance investigation of a horizontal ground source compression refrigeration machine

In this paper, the effect of various system parameters on horizontal ground source compression refrigeration machine (CRM) performance is studied experimentally in Bursa, Turkey. A ground heat exchanger (GHE) system connected to CRM in a test room in the air conditioning and refrigeration laboratory of Uludag University has been designed and constructed. This system was tested for space cooling in August and September 2004 and performance tests were performed during this period. Overall, system mainly consists of the GHE (GHE–water circuit) and CRM (CRM–refrigerant circuit). Refrigerant is R134a. Hourly variations of inlet and outlet water temperatures, extracted heat from test room, rejected heat to ground, compression ratio, total power consumption, and coefficient of performance (COP) values for both whole system and only CRM are obtained. Thermal properties of soil are also estimated by using experimental data and theory. Cooling load of test room and rejected heat to ground, and all COP values are also presented. Finally, heat rejection rate to ground with respect to leaving water temperature from GHE is given. The COP of the overall system changes between 2 and 2.5, also CRM COP values are in the range of 3 and 3.86. Copyright © 2007 John Wiley & Sons, Ltd.     

基于预测的复合地源热泵系统控制方法实现

在冬冷夏热且夏季冷负荷远大于冬季热负荷的地区常采用带有冷却塔的复合式地源热泵系统,其控制策略存在极大的优化空间。文章提出了直接比较冷却塔和与土壤换热器相连的板式换热器的出口温度的控制方法,并通过人工神经网络预测板式换热器机组侧的出口水温来实现此控制方法。通过FLUENT软件建立复合式地源热泵系统动态数值模型,获取建立神经网络的数据,采用3层BP网络,建立了多个预测板式换热器机组侧出口温度的模型。研究结果表明,采用神经网络可以准确实现此预测,绝对误差不超过0.4℃。     

U型波纹埋管对于增强土壤源热泵换热性能的研究

为了增强土壤源热泵系统地下埋管换热器的换热性能,通过CFD方法,探讨改用波纹管对地下换热所产生的影响,首次提出采用波纹管代替光管作为强化地下埋管换热器换热效率。     

直埋闭式地源热泵回填土性能研究

回填土的性能对直埋式地源热泵的设计有一定的影响．对直埋闭式地源热泵用回填土的性能参数中的密度、含水率、饱和度以及导热系数进行了数学定义，并指出影响导热系数的主要因素是密度和含水率。用平板探针原理的室内试验的方法研究了各种物质组成情况、时间以及不同温度对导热系数的影响，并对试验的结果进行了详细的分析，得出了随各种影响因素而变化的曲线。试验结果表明，膨润土不适合单独用于回填材料，需与水泥配合并推荐使用非饱和态。导热系数随水灰比的减小而增加。掺人大颗粒的骨料是提高导热系数的有效途径，砂含量的增加使导热系数往往呈线性增长。当水灰比为0．45且砂的置换率为80％时回填材料具有较满意的导热性能，值得推荐使用。     

地下水流动对地下埋管换热器影响的实验研究

为确定地下水渗流对竖直地下埋管换热器的影响,该文从实验角度出发,分别对无渗流土壤、饱和土壤中地下埋管换热器热负荷对其周边土壤温度场的影响,有渗流土壤中地下水流速、土壤初始温度以及埋管热负荷对土壤温度场的影响进行了实验,从而得出在夏热冬冷地区或亚热带地区应用土壤源热泵时,宜采用冷却塔-土壤源热泵混合系统形式或将地下埋管换热器埋设在地下水流速较大地区,以期土壤源热泵的长期良好运行。     

A two-region simulation model of vertical U-tube ground heat exchanger and its experimental verification

Heat transfer around vertical ground heat exchanger (GHE) is a common problem for the design and simulation of ground coupled heat pump (GCHP). In this paper, an updated two-region vertical U-tube GHE analytical model, which is fit for system dynamic simulation of GCHP, is proposed and developed. It divides the heat transfer region of GHE into two parts at the boundary of borehole wall, and the two regions are coupled by the temperature of borehole wall. Both steady and transient heat transfer method are used to analyze the heat transfer process inside and outside borehole, respectively. The transient borehole wall temperature is calculated for the soil region outside borehole by use of a variable heat flux cylindrical source model. As for the region inside borehole, considering the variation of fluid temperature along the borehole length and the heat interference between two adjacent legs of U-tube, a quasi-three dimensional steady-state heat transfer analytical model for the borehole is developed based on the element energy conservation. The implement process of the model used in the dynamic simulation of GCHPs is illuminated in detail and the application calculation example for it is also presented. The experimental validation on the model is performed in a solar-geothermal multifunctional heat pump experiment system with two vertical boreholes and each with a 30 m vertical 1 1/4 in nominal diameter HDPE single U-tube GHE, the results indicate that the calculated fluid outlet temperatures of GHE by the model are agreed well with the corresponding test data and the guess relative error is less than 6%.     

A study on the performance of a geothermal heat exchanger under coupled heat conduction and groundwater advection

Being environmental friendly and with the potential of energy-efficiency, more and more ground-source heat pump (GSHP) systems are being widely used. However, the influence of groundwater advection on the performance of the geothermal heat exchanger (GHE) in a GSHP is not still clearly known. In this paper, the configuration of a vertical dual-function GHE used in an integrated soil cold storage and ground-source heat pump (ISCS&GSHP) system, which charged cold energy to soil at night and produced chilled water in daytime in summer, and hot water for heating in winter, is firstly presented. This is then followed by a report on a mathematical model for the GHE considering the impact of the coupled heat conduction and groundwater advection on the heat transfer between the GHE and its surrounding soil. The GHE model developed was then integrated into a previously developed simulation program for an ISCS&GSHP system, and the operating performances of the GHE in an ISCS&GSHP system having a vertical dual-function GHE have been studied by simulation and reported. These simulation results, firstly seen in open literature, are much helpful to the design of a GHE buried in soil and widely used in GSHP systems or ISCS&GSHP systems.