武汉与重庆典型地质结构下的地埋管换热性能

地埋管地源热泵换热器的换热性能受到不同地质结构的影响。以武汉和重庆地区的典型地质构成为边界条件,建立了三维地埋管的单孔双U管换热模型,通过模型计算,获得了两种地质条件下的地埋管换热性能,以重庆地区的地源热泵热响应测试结果以及工程运行数据出发,对模型的计算结果进行了验证,结果表明,模型吻合度较好,可以应用于工程分析。以模型为条件,进行地质结构对换热性能的影响度分析,预测了两地地埋管地源热泵的换热性能并计算得到换热器的平均换热系数分别为武汉地区K₁=1.65（W/m·K）,重庆地区K₂=1.51（W/m·K）。     

Numerical Analysis and Optimization of a Small Vehicle Heat Exchanger

This paper analyzes the fluid flow and heat transfer of the heat exchanger, and obtainsd the distribution of fluid field, heat field and pressure field in heat exchanger. According the analysis result, some modify measure is adopted, such as decreasing the number of tube bundle, the size of baffle plate and increasing the diameter of exchange heat tube. In the new heat exchanger, the resistance decreased 32.3%, is 103.2 Pa and the temperature of the exit is 130 K. The new heat exchanger satisfies the requirement of exchanging heat. The study indicates that adopting the numerical simulation method could get temperature, pressure and fluid - velocity of anywhere of the heat exchanger, and understand effecfing of structure parameter on fluid flied and heat flied of the heat exchanger. Therefore, it provides a new method for optimization design of heat exchanger.     

AN EXPERIMENTAL RESEARCH ON ENHANCEMENT OF HEAT TRANSFER OF FINNED TUBES IN REFRIGERANT HEAT EXCHANGER

In this paper,the comparative experimental research that air flows through theout-surface of a single row finned tubes is done in a drawing wind tunnel and the three differnetshapes of rectangluar finned tubes are compared with a plain finned tube that is usually used in therefrigerant heat exchanger, the useful results are obtained. The results show that,in the range ofwind velocity flowing through the marrowest area, W_(max)=2.5m/s to 8.5m/s,the average convec-tion heat transfer coefficient of the two-side V-groove finned tube is higher than that of rectangluarplain finned tube,It is a new type finned tube that has good heat transfer performance and it isworth poplarlzing.     

Heat Transfer Performance of Horizontal Enhanced Condenser Tubes

In this paper, experimental results on heat transfer performance of a low integral-fin tube, thermoexcel-C tube (C tube) and a new horizontal double-side enhanced condenser tube (GC tube) have been reported for condensation of R-11. Within our experimental scope,the overall heat transfer coefficient of the GC tube can increase more than 5 times that of the smooth tube . And the relevant friction factor inside the GC tube can be 7 times that of the smooth tube. The Second law of thermodynamics was applied to develop a new criterion to assess the heat transfer performance of the GC tube,the C tube,the low integral-fin tube,and the DAC tube[1] (another doubleside enhanced condenser tube). The result shows the heat transfer performance of the GC tube is superior to the other tubes from a thermodynamical viewpoint.     

The Key Parameters Method of Calculating Geothermal Heat Exchanger Length

The geothermal heat exchanger is the key component of ground coupled heat pump systems. We discuss the key parameters method of calculating geothermal heat exchanger length based on line source theory. Typical meteorological year data is used to determine the hottest month, the coldest month and annual average surface temperature. The building hourly load can be obtained by introducing the concept of equilibrium temperature. The cooling fraction and the heating fraction then can be calculated using building hourly load and performance parameters curve fit of a water source heat pump unit. The method for selecting the hottest and lowest entering fluid temperature and calculating the borehole and ground thermal resistance is given. A vertical U tube heat exchanger length calculation procedure is proposed.     

地铁用间接蒸发冷却器换热性能影响因素

为解决地铁站冷却塔设置难题,提出了一种采用低速电机驱动旋转布水装置的间接蒸发冷却器,在两种布置方式下,对其换热性能进行了单因素实验,并运用正交实验法对较优布置方式下影响换热器换热的因素进行了分析。结果表明：两种布置方式下,喷嘴与蒸发冷却器的间距、两组换热管束间距均存在最佳值,喷嘴双侧旋转布水优于单侧旋转布水;换热器平行气流布置且喷嘴双侧旋转布水为较优布置方式,此时,换热器换热量随喷水量、转速、空气速度、冷却水进口温度的增加以及喷水温度、空气温度的降低而增大,其中,冷却水进口温度对换热器换热影响最为显著,其他因素对其换热的影响从主到次顺序为：喷水量、空气温度、空气速度、喷水温度、转速、冷却水流量。     

Experimental Studies of Forced Convective Heat Transfer and Pressure Drop of Ethylene Glycol in Tubes with Three Dimensional Internally Extended Surface

In this paper,the reSults are presented from experimental investigation on heattransfer performance in seven copper tu bes with three dimensional internally extended surface(3-DIEST)varying in axial pitch,circumferential pitch,height, width and arrangement form of fins. The forced con vective heat transfer and pressure drop of ethylene glycol flowing in the 3-DLESTShave been tested in the Revnolds number range from 250 to 6,000 and the Prandtl number rangefrom 60 to 90.The average stanton number in the most superior 3-DIEST can be increased about2.4times in the laminar flow.and4.5 times in the transitional flow and turbulent flow as com-pared with that in the smooth tube. And the friction factor between fluid and tube wall can be 1.7times in laminar flow. and 4 times in transitional flow andturbulent flow inside the 3-DIEST as much as those inside the smcoth tube.     

ALYSTS OF THREE-FLUID SEPARATE TYPE HEAT PIPE EXCHANGER

An analytical model for the separate type heat pipe exchanger with three different fluids is presented. A univeral basic temperature transfer matrix equation can be applied to predict the heat transfer performance of parallel-or counter-flow in which heat is transfered between one hot fluid and two cold fluids or between two hot fluids and one cold fluid. The calculation of a real engineering example proves the proposal model to be reliable.     

Analysis of coupled heat transfer between freezing soil,water and horizontal heat exchange tube

The research object is the coupled heat transfer effect between freezing soil,water and horizontal heat exchange tube,use finite volume numerical method to dispersed solving for continuity equation and heat transfer equation of unsaturated freezing soil,gives part of the temperature fields and freezing percentage distribution graphs,and analyzes the reason of the coupled heat transfer.The analysis result shows that:the temperature field of freezing soil are some horizontal lines parallelling to the ground surface.The peak value of solid-liquid phase change region appears in the upper part where there is backwater pipe,the low value appears in the place where there isn't horizontal heat exchange tube.The horizontal heat exchange tube makes the freezing front deviate towards the ground surface.The arrangement difference of inlet and outlet position of horizontal heat exchange tube will effect the size and position of the phase change region of freezing soil.Arranging the backwater pipe at one side or middle position is the optimized mode.     

Thermodynamic Analysis of River Water Fouling on Constant Wall Temperature Tube of Small Diameter

In order to improve utilization of cold and heat source from river, turbulence theory and entropy generation theory were adopted to analyze the effect of fouling on convective heat transfer performance in small diameter tube of constant wall temperature.It is found that the entropy generation caused by conduction of fouling plays a more important role in total entropy generation of heat transfer process through a duct than that in cveast rate of caused by temperature difference.The entropy generation caused by viscous flow is more than the entropy generation caused by temperature difference in flow with bigger Reynolds and small radius.The increase rate of entropy generation monotonically increase with Reynolds and the generation process of fouling resistance.Thereafter, the effect of fouling resistance on the heat transfer performance of water source heat pump heat exchanger should be paid more attention, when river water are used as the cold and heat source of heat pump.     

Study on Heat Transfer Characteristics in Waste Gas of the Exchanger

By the calculation and experiment,analysed the heat transfer characteristies in waste gas of the high temperature exchanger.The results which the reasonable vertical and horizontal distances were obtained,these turned out that the metallic rediation net was the effectve method intensified heat transfer in hot waste gas.The infulence of the velcity and temperature of waste gas on the multiple heat transfer caefficrent of the exchanger was studied by the experiment data.     

Coupled Conduction-convective Heat Transfer in the Louvered Fin Heat Exchanger

The heat transfer process in the louvered fin heat exchanger is analyzed,and the corresponding physical and mathematical models on the coupled conduction-convective heat transfer for the louver fin geometry are proposed.The control volume-based finite element method(CVFEM) is employed to solve numerically the problem.The computed(results) reveal the flow structure and heat transfer in the geometry in detail.Compared with the empirical correlation of heat transfer and friction coefficients previously proposed,the computed results show better consistency with the experimental results.     

Convection Heat Transfer Coefficient Distribution Over the Single Rectangle Fin Surface

Rectangle fin is widely used in different kinds of heat exchangrs. Convection heat transfercoefficient distribution over the fin surface is one of the theorehcal problems in research on enhancement of heat transfer. In this paper, a tube with an attached rectangular fin is used for a model and thefin surface is divided into a network of nodes by the finite difference techinque. When the wind velocityis u= 4. 5 m/s. the temperature distribution of discretization is obtained by experimental measurement,then the convection heat transfer coefficient of all nodes are soved by using the methed of inverse heatconduction problem. Through checking with heat balance methed, the results show that the solution cancorrectly express the actual heat transfer situation.This result is useful to experimental research onenhancement of heat transfer for finned for heat exchangers.     

Experimental Study of Flow and Heat Transfer in Heat Exchanger with Small Channels

The experimental study of the flow resistance and heat transfer characteristics are conducted for water and ethylene glycol solution (66% Wt) flowing in the heat exchanger with small rectangular microchannels . The heat exchanger having the channels of 0.4 mm in width, 2.0 mm in height, and 20 mm in length is heated by a hearing rod at the bottom surface, the upper and two side surfaces are adiabatic. During experiments, the Reynolds number are ranged from 2 to 2 500. The experimental results show that the flow friction factor decreases and Nusselt number increases with increasing Reynolds number for water and ethylene glycol solution. At a fixed Reynolds number, the Nusselt number for ethylene glycol solution with larger Prandtl number is greater than that for water. Meanwhile, the correlations of flow resistance and heat transfer in the heat exchanger with small channels are obtained for engineering application.     

Degital Simulation for the Direct Torque Control of Induction Motors Using the Circle Flux Path

This paper introduces the importance of developing the Ground-Source Heat pump and describes the prospects of it.with the method used abroad to acquire the temperature profiles within surrounding soil of the underground heat exchanger with buried tubes, in this paper the line heat source theory and thermal resistance network analysis method were used to set up the heat transfer model.The original temperature of the ground is determined by calculation and is compared with test results. Experiments of running single tube and running three series connection tubes are carried out on the built underground exchangers of vertical buried tube type.And the data which can provide reference for the Ground-Soure Heat pump technique are acquired.     

THE EFFECT OF THE CONVECT1VE HEAT TRANSFER IN THE ENTRANCE REGION OF THE TUBE ON THE HEAT TRANSFER IN THE TRBE -MOUTH REGION OF THE HIGH TEMPERATURE HEAT EXCHANGE EQUIPMENT

The effect of the convective heat transfer in the entrance region of the tube on the temperature field and the maximum temperature of the tube material in the tube -mouth region of the high temperature heat exchange equipment is examined by numerical analysis. The computations on the basis of four different formulas for convection heat transfer coefficient are performed. The computed results indicate that the efect can not be ignored as for heat protection of the tube -mouth region and it is resapnable and secure that the mean convective heat transfer coefficient with taking account of the effect of the entrance region is used in the thermal design of the tube -mouth region.     

AN EXPERIMENTAL STUDY OF BOILING HEAT TRANSFER ON SMOOTH TUBE BUNDLES

This paper introduces the clarifying influence of the intertube spacing, the tube arrangement,the heat flux and the working fluid on boiling heat tra(?)sfer of smooth tube bundles. The tube bundles include the arrangements of twin tubes, triple tubes, seven tubes and thirteen tubes. The relative intertube spacing of the tube bundles is from 0. 9 to 3. 3. Experimental results show that the tube position and intertube spacting have no effect on boiling curves for the region of fully-devoloped boiling. And they considerably affect the heat transfer coefficient for the transition region between natural convection and nucleate boiling. In general,the heat transfer coefficient in the transition region for the upper tubes can be enhanced by 0. 5 to 1. 5 times.     

Pressure Drop and Evaporative Heat Transfer Characteristics of Air-water Bubbling Flow

A new kind of evaporative heat transfer experiment for the cooling process of condensers is conducted. The test coil is immersed in an air-water bubbling layer. The air-water two-phase flow passes through the heating tubes of the coil. Due to the motion of the air bubbles in the water, a thin water film forms on the surface of the heating tubes. As the air bubbles passing by the tubes the water is evaporated into the air. The tubes of coil reject heat to the water film, and the evaporation of the water film then rejects heat to the air bubble stream. This heat transfer mode significantly increases the heat transfer coefficient between tubes and air. The consumption of the power of a water pump can be decreased. Moreover, the airflow rate required is less than that of an air-cooled condenser.The pressure drop of air through air-water bubbling layer and the heat transfer between the tubes and water are experimentally investigated in the paper. The results show that the factors affecting the pressure drop and the heat transfer coefficient involve the pore geometry of sieve plate, the height of the air-water bubbling layer, the air flow rate through the sieve plate and the heat flux of tubes. The heat transfer coefficient between tube and water is two times larger than that of falling film of water on the outer surface of tube.     

Influence of heat storage mode of domestic hot water on the performance of ground heat exchanger in ground-source heat pump system

The vertical U-tube ground-coupled heat pump system provides cold and heat for the controlling of indoor environment. Under the air-conditioning condition, the vertical U-tube ground-coupled heat pump system with heat recovery can provide domestic hot water. The influence of supplying domestic hot water on the heat transfer performance of ground heat exchangers is different under different operating modes in summer and winter. Through a project design of ground-source heat pump system, the influence of supplying domestic hot water under heat storage mode on the heat transfer performance of ground heat exchangers in summer and winter is respectively analyzed. The dynamic performance of heat exchangers under different working conditions is analyzed, and through numerical calculation, the heat transfer performance parameters of ground heat exchangers under different operating modes are obtained. From the calculation results, the adjusting methods based on the load characteristics of this project represent.     

Investigation on the flow field in the connection sectionbetween two heat exchangers of a condensate gas water heater

This paper investigates a new type of condensate gas water heater,which consisted of a burner,a high temperature heater exchanger (i.e.rut exchanger) and a low temperature heater exchanger (i.e.subjoin exchanger or condensate exchanger).These components are set vertically one by one with a same rare plane.The subjoin exchanger is set at top and smaller in width than the rut exchanger and burner.A lean plane with some holes is set in the connect channel between the two exchangers aslant.As the flue gas flow crows the subjoin heater exchanger,the gas temperature will be below the dew point,and the same steam in the gas condensed into water.These blobs drip to the lean plane and are collected through the holes on the plane.The flow field of the connect channel and subjoin exchanger affected by the dip angle and holes distribution of the lean plane is investigated with CFD.The results show that there is a suitable configuration about the dip anger,hole's diameter and distribution of the lean plane.With that configuration,the flue gas can wash the tubes of the subjoin heat exchanger homogeneously in a higher velocity than the rut exchanger does.