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.     

The Effect of Contact Thermal Resistance on Temperature Distribution in the Tube-Mouth Region of High Temperature Heat Exchange Equipment

Heat transfer in the tube-mouth region of high temporature heat exchangeequipment was further analysed. The finite difference method(FDM)was employed for investigat-ing emphatically the effects of contact thermal resistance on heat transfer.Temperature distributionin the tube-mouth region with the different contact thermal resistance was found.The computation-al results were compared with that which were obtained with no contact thermal resistance,and thecorresponding heat transfer mechanism was fully analysed.     

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.     

INFLUENCE OF THE GEOMTRIC PARAMETERS OF LOW FINNED TUBE ON BOLHING HEAT TRANSFER AND OPTIMIZATION OF THE PARAMETERS

On the basis of the mechanism of the boiling heat transfer on low finned tube, the influence of the geometric parameters of low finned tube on boiling heat transfer is synthetically analyzed and relevant criteria which affect the optimal structure of low finned tube is deduced in this paper. The boiling heat transfer experiment on low finned tube is conducted. Distilled water and R-113 are used as test fluids The experiment is performed at local atmospheric pressure. Synthesizing a large amount of experimental data, the semiempirical equations for the optimal geometric parameters of lowfinned tube are established     

彩钢板屋顶高大平房仓仓顶喷涂反射隔热涂料的应用效果

分析了彩钢板屋顶高大平房仓喷涂太阳热反射隔热涂料对仓顶温度、仓温、粮温的影响,为彩钢板屋顶高大平房仓控温储粮寻找一种有效方法。试验结果表明,喷涂太阳热反射隔热涂料对控制彩钢板屋顶高大平房仓仓温效果明显,同时可以达到延缓仓顶彩钢板老化、改善仓内工作环境和节能减排的目的。     

高大平房仓围护结构隔热试验

夏季高温时期,太阳对墙体的热辐射以及外界热量通过仓房围护结构的传导向粮堆传递,使墙体周边的粮温上升较快,向阳面最高部位可达30℃以上,超过了控温储粮的最高限量目标。介绍采用隔热保温材料对仓房围护结构的隔热试验,为提高高大平房仓的隔热保温性能提供科学的参考依据。     

谷物呼吸热值测定研究

谷物呼吸热值测定是粮食通风散热课题的核心问题.本文利用气体分析仪和恒温水槽测定谷物呼吸对氧气的消耗量和二氧化碳的生成量,作者首次提出了同时考虑有氧呼吸和无氧呼吸两因素,对呼吸方程进行配平,从而由呼吸生成物与呼吸反应物之间生成??值之差来精确计算出呼吸热. 数据处理全过程由微机完成.     

EXPERIMENTAL INVESTIGATION ON BOILING HEAT TRANSFER OUTSIDE THE LOW FINNED TUBE WITH SHROUD

Based on analysis of pool boiling characteristics outside low finned tube, this paper describes a simple method, using enhancing shroud to improve the performance of boiling heat transfer outside the low finned tube. The experiment results show that the boiling heat transfer coefficient can be 7-up to 10-fold enhanced by using shroud. The efficiency of a shroud is related to the size of two windows, heat flux and physical characteristics of test fluids.     

四种隔热材料隔热效果研究

采用聚氨酯发泡材料、聚苯乙烯泡沫板、棉胎、PEF保温隔热板4种隔热材料在高大平房仓中进行隔热效果试验。试验结果表明所采用的4种隔热材料均有一定的隔热效果，可在一定程度上延缓高温季节粮温的回升及减缓粮食品质的变化。4种隔热材料中聚氨酯覆盖仓顶隔热效果明显，采用聚苯乙烯泡沫板和棉胎在粮面压盖隔热效果稍差。     

EXPERIMENTED INVESTIGATION OF EFFECT OF THE INCLINATION ON HEAT TRANSFER ON TUBE

The present paper discribes experiment research of effect of the inclination on heat transfer on 9 kinds of plain tubes in atomosphere, working fluids are distill water and ethanel. Experinent result show very obvious effect of inclination of pool boiling heat transfer. The larger heat transfer increases, the larger the inclination does. The correlation obtained on 524 experiment data can be used for reference to engineering design in prospect of heat transger coefficient.     

粮食仓房隔热性能对低温储粮效果的影响

研究分析了不同粮食仓房围护结构、隔热保冷性能对粮温变化的影响。提出了对于不同的地区、不同类型的粮仓、不同围护结构的要求；并提供了一般建筑结构的粮食仓房隔热性能及改造的常用技术。     

不同储粮区域储备粮仓的保温隔热

本文通过热平衡计算及对影响仓温因素分析，推出仓温计算公式。在达到最佳储粮效果下，从而定性的对不同储粮区域仓房进行不同的隔热保温处理。     

AN EXPERIMENT ON HEAT TRANSFER BY MICROWAVE THAWING IN A FOOD ANALOGUE MATERIAL

The one-dimensional heat transfer of microwave thawing in a food analogue material is experimentally studied. The results show that the phase change region is narrow and the latent heat is quickly released due to the effect of the microwave energy. Besides, in the rising section of the temperature after thawing. the internal heat source makes the temperature at the central point rise more quickly than that at other parts of the tested element.     

太阳能辅助热泵干燥粮食的数值模拟研究

粮食的干燥过程实质上是多孔介质热湿耦合传递的过程.基于多孔介质热质传递理论,通过数值模拟的方法,针对利用太阳能辅助热泵干燥粮食时热风随时间变化的情况,采用综合温度和空气绝对湿度作为瞬态边界条件来对干燥过程中粮食内部温度和水分的变化进行模拟研究.模拟结果显示小麦水分在干燥150 h后达到安全水分13.6％(干基),而实验结果显示小麦水分在干燥135 h后达到安全水分13.6％(干基),二者对比相差不大,并且模拟温度与试验温度吻合较好.     

HATURAL CONVECTION HEAT TRANSFER JN AN ENCLOSURE WITH A LOCAL INTERNAL HEAT SOURCE

Numerical analysis is made for the unsteady and steady, two-dimensional laminar natural convection in an enclosure caused simultaneously by the external heating and a local internal heat source. The velocities and temperature profiles are given, the average and local Nusselt numbers for the hot and cold surfaces obtained, and the equivalent relative intensity of the internal heat source, the critical equivalent relative intensity of the internal heat source and the transient control regime defined. The results show that there exist five flow patterns with changing the external or internal Rayleigh number, and the heat transfer performance for each flow pattern region is different.     

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.     

高大房式仓粮面压盖隔热试验

利用聚苯乙烯泡沫板、腈纶棉被、稻壳、麻袋等压盖物 ,分别对高大平房仓粮堆表面进行压盖 ,经过度夏试验的结果表明 ,用隔热性能较好的材料压盖 ,能有效地控制粮温上升幅度 ,克服了高大房式仓屋面隔热性能差、上层粮温易升高的缺点 ,有效地控制了虫霉危害发生 ,达到控温储藏、延缓粮食品质陈化的目的     

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.     

THERMODYNAMIC ANALYSIS AND PERFORMANCE EVALUATION OF CONVECTIVE HEAT TRANSFER THROUGH DUCTS

A second law analysis is carried out on convective heat transfer in fully developed region with constant wall temperature through circular, trianglar and rectangular ducts. Besides, the entropy generation rate expression is obtained and the loss rate of available energy in convective heat transfer processes is defined as well. At the same time, the influence of initial temperature difference between fluid and wall as well as the influence of fluid friction on the loss rate of available energy is discussed. Then, the thermodynamic performances of several typical ducts are compared. Finally , the optimum initial temperature difference with the minimum loss rate of available energy is also obtained.