| The heat exchanger is the common equipment to transfer heat between diffirent media, it can work as process device and also heat recovery equipment. Heat exchangers are widely utilized in Power, Metallurgy, Chemical, Food and other industrical sectors, as well as the urban central heating system. Usually, the level of the heat exchangers industry is closely related to the economy development level of the country or region, and directly affects the energy utilization efiiciency. China is in a sustained and rapid economic development stage, with the rapid urbanization, and the large number of energy consumption, which will undoubtedly bring great opportunities and challenges to the heat exchanger industrys.Compared with developed countries, Chian’s energy utilization efficiency is still relative low now(about33%).One of the main reasons is a large amount of industrial waste heat in the industrial sector which used up about70%of Chian’s total energy consumption, in particular, a large number of lower-grade waste heat resources are not effectively recovered and utilized. At the same time, China’s energy demand and consumption are increasing. Where, the urban civilian energy needs related with people’s daily life are increasing significently with the urbanization. Over the past decade, China has been in the peak period of the constructions, the growth rate of the construction area is about12.8%～26.6%per year, so many related issues with the unban construction are caused. For example, China’s vast regions, especially in the northern cities, it is an enormous distress to ensure the residents heating in winter, to develop the central heating is an inevitable choice. Moreover, residential comfort requirements are significantly improving as the same time. Heating in winter is no the noly heat demand, hot water supply of residential homes is gradually becming the daily necessary energy consumption, which propose the new requirements undoubtedly for the energy supply, as well as the existing heat transfer equipments and technologies.In fact, with the deep understanding for the heat transfer process research and application, it is founded that the heat exchange processes with the different grade exist in the industrial areas or civilian areas. Where, involve cooling, heating precess, or thermal control with one working medium with multi-media. In a sense, the development of multi-media heat transfer equipment is in line with the point of view of scientific utilization of energy, and has its positive significance in terms of the aspects of the effective recycling low-grade heat, or in the reasonable distributiong of higher grade heat. At the same time, the multi-media heat exchanger equipments also have many advantages, such as the high compactness, small footprint, less investment in equipment, as well as flexible use.The plate heat exchangers are the important common equipment, having the high heat transfer coefficient, and the compact structure, possible to meet the heat transfer process for low temperature difference. In China, the production of plate heat exchanger began in the1960s, and had been widely used in many areas. Where, the detachable plate heat exchangers annually for urban central heating accounte for about70%of the total number of related products.The heat exchanger plate is key components, its structure and arrangement, the wave form and parameters directly determine the heat transfer media flowing form, affect the heat transfer and resistance properties of the plate heat exchanger, are the study emphasis and difficulty at the same time. The thin metal corrugated plate were occured in1930, and then generated the plate heat exchangers’ leaps and bounds development, and now has developed straight corrugation, vertical corrugation, chevron corrugation, cross corrugation commonly used. At present, the chevron corrugated paltes are the most widely used and most in-depth study. Chevron plate heat exchanger in the application shows the significant performance advantages of high efficience and compact, and also the lack of high flow resistance, many domestic and abroad scholars focus the research on this area, developing the new type of plate become one of the important research direction.At present, the production of plate heat exchangers in China has been extremely common, but compared with the international advanced level, gaps are exist, most appear a kind of low-level redundant, or simple imitation. The gap is mainly reflected differences in the plate thickness, wave form, and the design, as well as the gap caused on the heat exchanger performance due to the above reasons. For example, heat transfer coefficient of China’s chemical heat transfer equipments just reaches20%to50%of the developed countries generally similar equipment. A major reason is that the research data has been monopolized by foreign companies, lacking innovation of independent research and development, lacking advanced design methods and the appropriate selection software. At the same time, the enhanced heat transfer technologies and some specific ways (3D rib, vortex generators, etc.) have been accepted, understand and applicated, but the evaluation of the heat transfer enhancement and theoretical analysis of the heat transfer effect have no an appropriate expression. Therefore, the heat transfer enhancement research, high efficiency, low consumption energy-saving heat transfer equipment research are also relatively scattered, without an unified standard, high efficient heat transfer equipment design and optimization lacked an unified theoretical guidance, and also constrained the development of plate heat exchangers.Based on the above review, firstly the commonly used heat exchanger performance evaluation criterias were this analyzed in this paper. The common characteristics of the traditional evaluation of the heat exchanger to evaluate the advantages and disadvantages of the convective heat transfer process with the heat transfer rate, the pressure drop coefficient, or the composite index, but lack of a clear expression of the heat transfer process, so it is difficult to optimize heat transfer equipment design. And the enhanced heat transfer technologies are mostly developed according to the experience, the flow resistance often increases more obviously when the heat exchangers have been strengthened at the same time, which is not energy-efficient. In addition, the second law of thermodynamics is considered as an important evaluation criteria, considering the irreversible dissipation caused by the flow and heat transfer processes as the objective function, forming the entropy generation minimization method, providing a theoretical possibility for the optimization of heat transfer equipmenton, but application in the heat exchanger optimization process, the so-called "entropy production paradox" and some contradictions exist. Therefore, there are still imperfect for the minimum entropy generation as the objective function for the optimization of the heat exchangers and heat exchanger performance evaluation.In view of the above heat transfer equipment performance evaluation and optimization theory, the field synergy principle for heat transfer enhancement by Professor GUO Zengyuan and the application on the design optimization were analysised in this paper. According to the comprehensive introduction and analysis of the single phase convective heat transfer mechanism amd the application of the convective heat transfer field synergy theory for the heat exchangers optimize design, and that the field synergy theory can not only strengthen the existing traditional heat transfer theory a unified interpretation, the field synergy theory is proved that it can not only give one unified explanation for the existing traditional theory of transfer enhancement, but also provide new ideas for the study of convective heat transfer enhancement, a theoretical basis for the research of high-efficient and energy saving heat transfer enhancement trchnologies. It can be achieved under the guidance of the field synergy theory, to research and develop some enhanced heat transfer technologies, in which the heat transfer increase rate is greater than the resistance increase rate under some certain conditions. The same time, actually the field synergy theory leaves some space for the following study, for the more complex and more important heat transfer equipment and system, the further expansion is needed. Field synergy theory pointed out the direction for the development of new energy-saving technologies of heat transfer equipment, but it still can not provide a quantifiable target target function and design guidelines for the optimization of heat transfer components and equipments. For this reason, the further discussion and analysis for the entransy dissipation theory provided by Professor GUO Zengyuan carried on, the entransy dissipation theory not only can proved field synergy theory correctness within a certain range, but also the important value in the evaluation of heat exchangers performance and optimization design. Application analysis for the multi-media plate heat exchangers was performanced in this paper, which build the foundation for the guidance of such heat exchanger design optimization.Based on a kind of novel multi-media heat exchanger invented and applied in the international large project Alpha Magnetic Spectrometer (AMS), accounting for utilization for this novel heat exchanger in the civil areas, analyzed the heat transfer efficiency and resistance characteristic for the spherical wave, and some design was performed. In addition, numerical analysis carried on for the single couple convex sphere wave and concave sphere wave in the rectangular channel, verify the windward side of the sphere wave form reduces the local field synergy angle, and play the role of reducing the local field synergy angle in the tail region alternately. The nolve plate with discontinuous structure wave combined with convex sphere and concave sphere sepatately. In the channels, convex sphere and concave sphere between adjacent plates are in pairs separately to form the flow channel and the vertexes of convex sphere between adjacent plates contact with the pairs, which become effective support points evenly distributed to meet the demand for pressure, and the plate is regular hexagon, three pairs of import and export were arranged at the six top corner of the plate, to meet the two or three media heat exchanger at the same time. For the design of entrance diversion area, convex sphere and concave sphere were evenly arranged at six import and export port, so uneven distribution of the flow field due to the port design could be avoided as possible.Applying the CFD software, the numerical simulation for the new regular hexagon with spherical discontinuous corrugated plate heat exchanger was performed in this paper, consisting of two-fluid and three-fluid heat exchanger. The performance of the novel heat exchanger plate in the state of parallel flow and counter flow was discussed. Compared with60°chevron-type plate heat exchanger, the regular hexagonal plate heat exchanger is better in the aspect of comprehensive performance with the criterion of the overall heat transfer coefficient per unit pressure drop. Correlations on heat reansfer and friction factor were also summaried based on the numerical simulation. According to the analysis with the Graphices of the flow field, temperature field, pressure field, it is certified that the flow in the channel has the uniform morphology without flow dead zone, and the port flow field distribution is reasonable. The spherical wave played the role to strengthen the heat transfer, but also has better resistance properties. The heat transfer is enhanced on the windward sides of convex sphere and concave sphere, and their roles are complementary in the adjacent flow channels.For the multi-media heat transfer equipments, arrangement of flow channels is more relative complex than the heat transfer between two media; furthermore, the heat transfer performance has larger difference for different arrangement of flow channels. According to the concept of entransy dissipation number, for two media heat exchanger process, the entransy dissipative number for multi-media heat exchanger process was analyzed, and the study for flow channels arrangement was performance. For the multi-media heat transfer process, the analysis shows that the arrangement of the flow channels has biger impact on the performance of the heat exchanger. Under the same initial conditions, the entransy dissipation number and the total loss resistance of the heat exchanger reduce with the number of flow channels increasing; for the same number of flow channels, the fluid resistance is little difference in the quantity for the different arrangement, but the entransy dissipation number has big difference. The ways to get a better arrangement of flow channels was analyzed in this paper.The heat transfer and pressure drop performance comprehensive experimental platform was built on the basis of numerical simulation, and the water-water heat exchanger experimental research and analysis were perfoumanced for this novel plate heat exchanger. Equal velocity method was applyed, the regression of the experimental data was performance, and the correlations on heat reansfer and friction factor were also summaried. Analyzing the experimental data, that show that the novel plate with discontinuous structure consisting of convex sphere and concave sphere has the better heat transfer performance than that of the BR1chevron plate heat exchanger, and its resistance characteristics are superior to those of the normally used60-degree plate heat exchanger. The mechanism analysis of heat transfer enhancement shows that the spherical wave structure can reduce the local field synergy angle, so as to improve the field synergy degree of velocity vector and temperature gradient vector.The above analysis for this novel plate heat exchanger provided some useful data and ideas for the engineering application. |
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