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The oil-lampblack technique was employed to reveal the patterns of fluid flow in a shell-and-tube heat exchanger. Flow patterns were visualized adjacent to the shell wall, to the baffle plates, and to each tube of the array. From the flow patterns adjacent to the shell, three recirculation zones were identified. The patterns adjacent to the baffles were similar to those for cross flow over a tube bank, with curvature-related deviations near the shell. The flow patterns adjacent to the tubes showed, typically, a stagnation line/circumferential flow system on the upstream face of each tube and a recirculation tone dominating the tee side. Turn-related deviations from these patterns were in evidence at the window region. 相似文献
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An experimental study was conducted on the effects of the amount of working fluid on the performance of a two-row copper-R134a heat pipe heat exchanger at the air side. The heat pipe heat exchanger operates in the horizontal configuration, and five different fluid charges were studied to cover the underload and overload cases. Moreover, the calculated outlet temperature of the evaporator side, obtained from the heat exchanger simulation, was compared with the experimental results. Based on the present study, it was found that the optimum performance of the copper-R134a heat pipe heat exchanger can be achieved at a fluid charge slightly exceeding the amount required to saturate the wick. 相似文献
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Arturo Pacheco-Vega Claudia Ruiz-Mercado Kevin Peters Luis Enrique Vilchiz 《传热工程》2013,34(14):1208-1215
We have developed a fuzzy-rule-based controller to perform on-line temperature control of a concentric-tube heat exchanger facility. The rules for the controller were derived from dynamical values of the mass flow rates and fluid temperatures in the heat exchanger. The fuzzy controller was embedded in a closed-loop, single-input single-output system to control the outlet temperature of the cold fluid. The development of the controller was done in two phases, the difference between the phases being the information about the system that was used to build the corresponding control scheme. To validate this fuzzy controller, a series of experiments, corresponding to regulation and tracking of a setpoint, was carried out for maintaining specific values of the outlet temperature under different perturbations. Results from this investigation demonstrate that the fuzzy-rule-based controller is able to effect control of the system, and that the amount of information about the plant provided to it is important in terms of accuracy and efficiency. 相似文献
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Mario Antonio Cucumo Vittorio Ferraro Dimitrios Kaliakatsos Marilena Mele Antonio Galloro Rosario Schimio 《传热工程》2020,41(12):1026-1039
AbstractIn the article, a three-dimensional numerical solution of two real shell-and-tube heat exchangers, with different types of baffles, segmental, and pseudohelical, is presented, through the use of commercial codes, in order to evaluate the influence of the baffles type on heat exchanger performance. The parameters to be evaluated, which influence the efficiency of the thermal exchange and the maintenance and pumping costs, are the pressure drops, the heat transfer coefficient, and the fouling resistance. The fluid dynamic study of the shell-and-tube heat exchanger is conducted under stationary flow conditions. In the article, furthermore, the results of the thermohydraulic analysis, performed under stationary flow conditions, more "helical baffles" exchangers, with different baffles helix angle, are presented. Exchangers with pseudohelical baffles inclined by 7°, 20°, 30°, 40°, 45°, and 50° are analyzed. The simulations are carried out considering a real fluid, approximately incompressible, under laminar flow conditions. Finally, to verify the correctness of the results, they are compared with correlations in the literature. 相似文献
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Jean-François Portha Guillaume Henry Alexandra Père-Gigante Jean-Marc Commenge 《传热工程》2020,41(22):1869-1884
Abstract The use of Milli-Channel Heat Exchangers (MCHE) presents numerous assets: efficient heat transfer, huge compactness, and limited pressure drop. For an engineer, the Fanning friction factor and the convective heat transfer coefficient are two main parameters to describe the performance of a heat exchanger. A brazed MCHE with rectangular channels in stainless steel made by the Institut für Mikrotechnik Mainz (IMM, Mainz, Germany) has been characterized experimentally and theoretically in a counter-current configuration. The selected working fluids are deionized water and oil without any phase change during experiments. The pilot unit ensures measurements of pressure drops, temperatures, and volumetric flow rate of each fluid flowing in laminar regime. A one-dimensional model has been developed. The temperature and pressure profiles of each fluid are represented by differential equations associated with boundary conditions. The system of coupled equations consists in a two-point boundary value problem solved numerically by the Matlab software. The parameters of a Nusselt number correlation are identified together with those of a Fanning friction factor one by minimizing a sum of squared differences between experimental and predicted data. The calculated temperature and pressure profiles present a good agreement with measurements. A statistical analysis shows that each optimized parameter is significant. 相似文献
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DUSáAN P. SEKULICá 《传热工程》2013,34(1-2):83-88
The entropy generation (irreversibility) concept founded on the second law of thermodynamics may be applied in heat exchanger analysis. In this paper the quantity termed enthalpy exchange irreversibility norm (EEIN) is the measure of the internal heat exchanger irreversibilities. The behavior of EEIN as a function of the heat exchanger thermal size is discussed for an arbitrary flow arrangement and more precisely for two characteristic limiting cases: cocurrent and countercurrent heat exchangers. 相似文献
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为了提高新型高效紧凑式换热器设计的功能性,并使其满足热力学性能需求,对绕管的结构参数及桥接布管方式进行设计。采用一种新型的变径变线桥接方式,在体积有限的情况下实现密集的管束布置形式;对该新型换热器设计进行全尺寸流域建模及CFD数值模拟;并将三维建模结果与一维程序计算结果对比,进行可靠性验证。计算结果表明:三维计算的各项热力学性能结果与一维计算仅有较小偏差,总传热系数相对误差仅为3.74%,总传热量相对误差仅为1.04%,验证了该三维计算模型具有较好的准确性;结合温度云图证明了换热区域基本集中在绕管段,为简化复杂换热器的计算提供了思路;该新型高效紧凑式换热器设计实现了管侧双股流可独立运行且同层间不存在无效换热区,整体换热平顺进行,壳侧流阻较小,换热能力保持较好;在工况范围内整机换热体积功率达到4.67 MW。 相似文献
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板翅式换热器是舰载燃气轮机首选换热器形式。针对平直型翅片的矩形通道的结构特点,建立了流动换热分析的耦合计算模型,采用计算流体动力学(CFD)方法对间冷器的通道流场进行了数值模拟。给出并分析了计算区域内多个截面的温度、压力、速度、局部传热系数等参数的分布图形和变化趋势,并考察了不同工况下间冷器的工作能力。 相似文献
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Abstract An analysis of the thermal response of a finned-tube, liquid-to-gas cross-flow heat exchanger due to a step change in the liquid inlet temperature is performed. Closed-form solutions for the liquid and gas temperatures as functions of space and time are obtained via the Laplace transform technique for both small and large arguments of the modified Bessel function of the first kind. Using four physically important dimensionless parameters, the response of the liquid and average gas outlet temperatures are studied and presented in the time domain. The analysts is extended to a single-row serpentine coil geometry by accounting for U-tube bends. Using a typical heat exchanger geometry, the effects of the tube bends are shown to be significant. Relevant applications include automotive and HVAC heat exchangers and systems. 相似文献
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为了开发用于液体食品杀菌的新型换热器,通过实验研究了螺旋折流板波纹管换热器用于海鲜酱杀菌过程中的传热与流动性能。研究结果表明:在水-海鲜酱的热交换中,螺旋折流板波纹管换热器总传热系数比波纹管换热器提高了10%~50%,比光管换热器提高了30%~130%;管侧海鲜酱综合性能系数α/Δp值波纹管大于光管,壳侧水的综合性能系数α/Δp值螺旋折流板波纹管结构换热器比波纹管结构的和光管结构的都大,证明了螺旋折流板波纹管换热器用于液体食品杀菌具有良好的应用前景。 相似文献
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In this work, a modified analysis of a parallel-flow plate heat exchanger that takes into account a volumetrically uniform heat source in the hot fluid is presented. New expressions for the number of transfer units (NTU) and effectiveness of the heat exchanger are derived. These expressions are verified against the conventional effectiveness–NTU relations in the limit of zero heat source rate. This situation is of interest in applications such as the ammonia–water absorption absorber heat exchanger where a heat source is generated in the solution side. The model studies two cases based on the minimum and maximum heat capacities of the hot fluid. The results show that the number of transfer units and the effectiveness of the heat exchanger are the same for both cases. The analysis is applied to the absorber heat exchanger. Expressions of effectiveness and number of transfer units of a counterflow heat exchanger with a heat source in the hot fluid stream are also given from minimum and maximum heat capacities points of view. 相似文献
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螺旋管式换热器适于处理粘度大的流体或含固体颗粒的泥浆,被广泛应用。文章对一种高效、紧凑型的螺旋管换热器的结构设计作了讨论,对螺旋管换热管等具有过冷情况的热力计算方法作了探讨。 相似文献
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Heat transfer and pressure drop of a fin-and-tube heat exchanger are studied by taking into account the conjugated heat transfer between the flow and the fin. The temperature distribution of the fin is calculated in respect to the convective heat transfer of the air flowing through the tube bank channel. Contemporary enhancement methods emphasize the importance of local turbulence augmentation which effects the convective heat transfer. In this paper, the importance of conjugated heat transfer, where the temperature of the flow and fin are coupled together is emphasized and compared with a constant surface temperature boundary condition simulation and experiment, which are found in the literature. 相似文献
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Xin Gu Zhiyang Zheng Xiaochao Xiong Tongtong Wang Yuankun Luo Ke Wang 《热科学学报(英文版)》2018,27(6):602-610
Periodic whole cross-section computation models are established for segmental baffle heat exchanger, shutter baffle heat exchanger, and trapezoid-like tilted baffle heat exchanger. The reliability of models is verified by comparing the simulated results to the results obtained from the Bell-Delaware method. Due to the orthogonal assembly of the baffles, the shell side fluid shows the twisty flow of trapezoid-like tilted baffle heat exchanger. The essential mechanism on disturbing flow and heat transfer enhancement is revealed by defining the non-dimensional factor η of the shell side fluid flow direction of heat exchanger and the field synergy principle. The results show that at the same Reynolds number, the shell side fluid convection heat transfer coefficient of trapezoid-like tilted baffle heat exchanger is 12.43%-24.33% and 6.71%-11.51% higher than those of segmental baffle heat exchanger and shutter baffle heat exchanger, respectively. The shell side fluid flow velocity field and the pressure gradient field of trapezoid-like tilted baffle heat exchanger and shutter baffle heat exchanger decreases compared with that of segmental baffle heat exchanger, so the shell side fluid flow resistance and pressure drop is increased; the shell side comprehensive performance of trapezoid-like tilted baffle heat exchanger is 5.85%-9.06% higher than that of segmental baffle heat exchanger, and 15.27%-23.28% higher than that of shutter baffle heat exchanger. In this study, a baffle structure with higher efficiency of the energy utilization for the heat exchanger is provided. 相似文献
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一种监测换热器污垢的新方法 总被引:2,自引:1,他引:2
在考虑污垢对换热器传热性能影响的基础上,提出换热器当量总污垢热阻和污垢函数的概念,并给出换热器当量总污垢热阻的监测方法,讨论了换热流型、传热有效度ε和冷热流体热容量率比R对换热器当量总污垢热阻的影响。 相似文献