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.     

Analysis of Heat Transfer and Optimal Parameters of Multi-louvered Fin Condenser

The authors conduct the experimental study and optimal computing for the condenser of automobile air conditioner. The especially the properties of heat transfer and flow at the side of air when using shutter fin. The authors the influence of several combinations of fin's geometry parameter to heat transfer and flow resistance. The maximal heat transfer is used as a criterion relation to select the fin's geometry parameters in the same facing air area of condenser. Furthermore, a program is designed to conduct optimal computing, and the computing results are basically consistent with experimental results. It shows that the optimal method is reasonable and the results can be applied to engineering practice.     

NUMERICAL STUDY OF FLOW AND HEAT TRANSFER IN AN INCLINED RECTANGULAR FIN GROOVE

Flow and heat transfer are numerically studied in a rectangular fin groove when the fin base is heated with contsant temperature. Rayleigh number, inclination , aspect ratio, thick ness and conductivity of the fin are systematically changed to examine their effects. Five flow patterns are found, local and average characteristics are given, and the mechanism of heat transfer is discussed. The results can be used as a reference for fin designs.     

GGH heat transfer enhancement and a new type heat exchangerin the desulphurization system of wet flue gas

This paper conducts in-tube heat transfer experiments in a three dimensional fin tube with 102 mm outer diameter.Compared with the smooth tube,the heat transfer enhancement ratio is between 1.65 and 1.7,and the pressure drop ratio is between 1.65 and 1.7.Based on the analysis of the heat transfer and tube surface temperature,a new type heat exchanger is put forward.Moreover,the design and calculation method is explored.The engineering example indicate that not only the tube surface temperature is higher than the smooth tube,but also the quantity of heat is increased by about 20% than the smooth tube.Compared with other types,the new type heat exchanger has a overall better performance.     

An Experimental Investigation of Condensation Heat Transfer of HC600a-Oil Mixture in a Horizontal Micro-fin Tube

Experimental study of condensation heat transfer of HC600a-oil mixture in a horizontal micro fin tube is performed to investigate the inflence of oil percentage, saturated pressure and mass flux on condensation heat transfer.The empirical correlation according to this study is well correlated by the experimental data. By comparing with other refrigerants, HC600a has no inflence on ozone depletion and better heat transfer characteristcs than CFC12 and HCFC134a. It is a promising substitute for CFC12.     

Numerical Calculation of Fin Efficiencies and Performances of Rectangular Flat Fins with Modified Geometry

Numerical calculation with FEM was carried out for the fin efficiencies of common rectangular flat fin and three flat fins with modified geometry The result shows that the general heat tasfer performance of fin B2 is higher than that of common flat fin, but the fin efficiency is lower. Both the performances of heat transfer and fin efficiences of fin C and fin D are higher than those of common flat fin. The work of this paper is valuable for optimization design of high efficient fin.     

Experimental investigation of electrothermal defrost tubes’ arrangement on heat transfer and flow resistance characteristics of evaporator

The paper presents new arrangement types of electrothermal defrost tubes and manufactures four evaporator samples. Through a wind tunnel refrigeration experimental test-bed, relatively experiments for every sample are carried to study heat transfer and flow resistances characteristics of evaporator. The experiment results show that in experimental face velocity range from 1.5 m/s to 4.3 m/s compared with flat-fin evaporator, the unit area of cooling capacity of DK-8 evaporator increased 28.1% to 36.2%, the fin surface coefficient of heat transfer raises 79.2% to 83.5%, the compressor COP (Coefficient of Performance) improves 38.2% to 46.9%, and the air side flow resistance decreases 5.29% to 18.3% in the same experimental condition and geometric size. The increase amplitude of COP is obviously higher than air side flow resistance. The experimental investigation results prove that it is completely feasible optimized combing defrost design with heat transfer enhancement design.     

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.     

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.     

Dropwise Condensation Heat Transfer Coefficient on the Horizontal Circular Surface with Radial Gradient Surface Energy

A theoretical model is developed for the dropwise condensation heat transfer on the horizontal circular surface with radial gradient surface energy based on the heat transfer model of individual condensate drop and the size distribution model of condensate drop on homogeneous condensation surface.The effect of variation of contact angle on the gradient surface on condensation heat transfer and condensate drop size distribution is taken account of in this model.The theoretical calculation method was obtained to predict the dropwise condensation heat transfer coefficient on the horizontal circular surface with radial gradient surface energy under various wall subcooled temperature,contact angle profile on wall surface,and working fluid.The effects of surface energy gradient,wall subcooled temperature,and thermophysical properties of condensate on the condensation heat transfer are discussed respectively.The calculation results show that the condensation heat transfer coefficient increases slightly with the increase of wall subcooled temperature.As latent heat and surface tension increasing,the condensation heat transfer coefficient increases.A larger surface energy gradient induces a larger condensation heat transfer coefficient.     

Heat transfer performance analysis of lithium bromide solution falling film evaporation in vertical tube

For making the refrigeration system directly driven by low temperature waste flue gas heat more efficiently,an experimental research on the heat transfer of vertical in tube laminar falling film with different heat fluxes and different concentrations of lithium bromide solution is conducted.The outcome of falling film evaporation experiments show that the heat transfer coefficient increases with the decrease of inlet concentration of lithium bromide solution and significantly increases with the increase of heat flux.Based on multiple linear regression calculation of experimental data,an experimental correlation of falling film heat transfer coefficient is obtained.A falling film generator of lithium bromide absorption chiller is designed from the correlation,and the immersed generator whose heat load is equal to the falling film generator is designed.The comparison of the two generators on heat transfer coefficient,weight and volume of heat transfer components shows that the falling film generator has great advantages.     

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）。     

Simulation of a steady temperature field and analysis of factors affecting a worm gear

To obtain the distribution characteristic of the temperature on the surface of worm gear, a numerical simulation using heat transfer theory, tribology theory, and mesh theory is given to calculate the heat transfer coefficient and heat flux of rolling gea     

Experimental Study on Refrigeration Performance of Fin-tube With Circular Hole Under the Frost Condition

The performance of heat transfer of fin-tube with circular hole is better than fin-tube without hole if there is no frost,but what is the situation if under the frost condition.Tthe comparison study on performance of heat transfer and refrigeration is carriedout under the frost condition for the heat exchanger with three kinds of fins: circular and half circular hole,circular hole,plane form.The experiment process is finished through the refrigeration system of icebox.In the course of experiment,the influence of frost process to the diameter of circular hole;is analyzed The real refrigeration amount,heat transfer coefficient and real refrigeration coefficient of the three kinds of fins are compared;compare the effect of energy saving of enforced fins is given.The fin efficiency is calculated method and make out the real convection coefficient to disclose the situation of heat transfer of fins is lnade out.Results: compared with plane form fin,the following results are for fin-tube with circular hole: average heat transfer coefficient rise 11.53%,convection coefficient rises 18.84%,real refrigeration coefficient rises 6.83%,virtual refrigeration amount rises 6.02%,electricity saving is 6.39%.Fin-tube with circular hole is the best form for the three kinds of fins.     

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。     

Numerical Study of FLow and Heat Transfer in Rectangular CHannel with Dimpled SUrface

This authors uses a physical model of the rectangular channel with dimpled surface to simulate the flow and heat transfer situation. On the basis of actual flow and heat transfer in the channel, it made the interrelated hypothesizes and built up the math model. They adopted the turbulent model, appliy the algorithm to resolve the pressure-velocity coupling and use the experimental data model to check up the feasibility of the model. By the study, the thesis shows the principle of the flow and heat transfer in narrow channel with a dimple surface and gets the factors and the conditions that affect the flow and heat transfer. The results show that the geometry structure and rank distributing of dimple affect the capability of heat transfer evidently. When Reynolds number is low, the capability of heat transfer becomes better as the number increases, and when Reynolds number is bigger than a critical point, there is a little influence.     

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.     

Heat Transfer Characteristics of the Melting Process of the Metal Foam/Paraffin Compound Material

In order to enhance the heat transfer in the phase change heat storage device, a rectangular cavity filled with metal foam / paraffin wax is made. The melting heat storage experiment of foam metal / wax composite phase change material was carried out in the transverse wall temperature conditions. The temperature change curve is drawn according to different heating temperatures. Both the effects of natural convection in rectangular cavity on temperature distribution and the impact of heat transfer temperature difference on the thermal storage time are analyzed. The results show that the melting process of the paraffin in the body cavity is reinforced by the high thermal conductivity of copper foam. The remaining solid paraffin is accelerated to melt by the natural convection of the liquid paraffin formed near the heating surface; and the greater the heat transfer temperature difference is, the greater the natural convection is and the shorter the time for heat storage is.     

CONDENSATION HEAT TRANSFER ON THE THREE-DIMENSIONAL EXTENDED SURFACE TUBE ATTACHED BY A POROUS DRAINAGE STRIP

An experimental study was carried out for the condensation heat transfer on the three dimensional extended surface tube attached by a porous drainage strip. The results show that the combination of the three dimensional extended surface and the porous drainage strip is the effective method enhancing condensation heat tiansfer on the horizontal tube. The change of the shape arid depth of the axial grooves results in a 10% vaitation of condensation heal transfer coei ficienls. In the range of the experiments, for aocohol as the working fluid, the enhancement is up to 152%, and for water, 185% as compared with the horizontal low-finned tube.     

苏北地区日光温室能量分配动态研究

为了进一步提高日光温室保温性能,减轻温室内低温寡照灾害发生,以苏北（徐州）番茄日光温室为研究对象,利用采集的2010年12月-2011年4月温室小气候数据及番茄发育数据,根据日光温室小气候形成的物理过程与机理,系统研究了冬春季节不同天气类型及不同叶面积指数对温室能量分配的影响。结果表明：日光温室内潜热、显热随着室内总辐射量的改变而发生变化,阴天以显热消耗为主,潜热消耗量全天低于显热;晴天日光温室内用于作物蒸腾的能量显著多于阴天,阴天室内外贯流传热消耗的能量远远多于晴天;随着叶面积指数增大,到达地面的太阳辐射减少,地面升温慢,室内空气与地表的显热交换量减少,同时室内空气与墙体的显热交换增加。本研究结果可为温室的结构优化及冬春季节日光温室管理提供科学依据。