Impact of the Anticorrosion Films on the Condensing Heat Transfer of Flue Gas in Fin-Tube Heat Exchangers
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The forced convective heat transfer with condensing was experimentally investigated when wet flue gas was flowing in the fin-tube heat exchangers with three anticorrosion films respectively, including the nickel-phosphorus amorphous composite eletroless and organic compound (NPACE&OC) surface, the nickel-phosphorus amorphous composite eletroless (NPACE) surface, and the organic compound (OC) surface. The experimental results indicate the convection heat transfer characteristics as following: Among the three heat exchangers, the convection heat transfer for the heat exchanger with NPACE&OC surface is the best, the convection heat transfer coefficient is about 18%∼25% higher than that of the other two heat exchangers. It could be caused by the lower surface energy of the NPACE&OC surface that forms the drop condensate. The experimental results of heat transfer coefficient relative to Reynolds Number and Jakob Number were also presented in this paper. Based on the experimental results and the analysis, the correlation of the measurements was achieved.Keywords:
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In this paper, a three dimensional numerical analysis of turbulent fluid flow and heat transfer on the air-side and water-side of plain fin-and-tube heat exchangers is performed in order to obtain their heat transfer characteristics with non-constant physical properties. Besides convection heat transfer on water and air sides, the heat conduction through pipe walls and fins is also considered in the study. The two types of heat exchangers having cascade and in-line flat tube arrangements are presented.. Heat exchangers have been numerically simulated for different inlet air temperatures and velocities. As crossflow has been taken into account, the heat exchangers have been modeled with all fins considering the temperature changes on both sides. Numerical values are compared to the results obtained by analytical calculations of the heat exchangers, and good agreement of results is derived. The heat transfer characteristics are observed to be better for the heat exchanger with cascade tube arrangement for all of the analyzed conditions.
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Heat exchangers are devices whose primary responsibility is to transfer heat, typically from one fluid to another. In such applications, the heat exchangers can be parallel flow, crossflow, or counter flow. An essential part of any heat exchanger analysis is the determination of the effectiveness of the heat exchanger. In the present work, three different types of heat exchangers are investigated. Numerical and experimental performance analyses are applied. The main objective of the present work is to compare the effectiveness of each heat exchanger at different conditions. Six experimental investigations for Plate, shell & tube, and fluidized bed heat exchangers are executed. All experimental tests are reached to steady-state conditions. The results show that the counter flow plate heat exchanger has an effectiveness of 90% compared with the parallel flow of 60% effectiveness for working experimental conditions. Also, the fouling effect in decreasing heat transfer is cleared. In the present work, fouling decreases effectiveness from about 18% to about 4%. In addition, the effectiveness of the fluidized bed heat exchanger depends on the material used for the bed. Finally, the overall heat transfer coefficient is obtained and compared for all experimental tests, and it is directly proportional to the effectiveness of the heat exchanger. The FEHT program is used to get the temperature distribution in all types of present work heat exchangers.
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Compact heat exchangers are most widely used for heat transfer applications in industries.Plate heat exchanger is one such compact heat exchanger, provides more area for heat transfer between two fluids in comparison with shell and tube heat exchanger.Plate type heat exchangers are widely used for liquid-to-liquid heat transfer applications with high density working fluids.This study is focused on use of plate type heat exchanger for water as a working fluid.This research work deals with experimental investigation of plate type heat exchanger with evaluation of convective heat transfer coefficient, overall heat transfer coefficient, exchanger effectiveness.The heat exchanger used for carrying out this work consists of thin metal welded plates of stainless steel with 1mm thickness, rectangular geometry and distance between two plates is 7mm.This test setup consists of total 16 numbers of plates and it is designed to withstand with 85 0 C temperature, pressure drop is neglected.Tests are conducted by varying operating parameters like mass flow rate, inlet temperatures of hot water.The main objective of this work is to find effects of these parameters on performance of plate heat exchanger with parallel flow arrangement.Results show that, overall heat transfer coefficient and convective heat transfer coefficient increases with increase in mass flow rate and Reynolds number.Also the effectiveness varies slightly with heat capacity ratio.In this study, maximum effectiveness achieved for plate heat exchanger with water as a working fluid is 0.48.Use of plate heat exchanger is more advantageous than the tube type heat exchanger with same effectiveness, as it occupies less space.
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Heat exchanger analysis tools such as F correction factor charts and e-NTU relations assume that the overall heat transfer coefficient is constant across the heat exchanger. The short lengths and the comparatively thick walls in microchannel heat exchangers preclude the existence of thermally fully developed flow over a large portion of the heat exchanger and increase the significance of heat conduction in the wall. In this study, a parallel flow heat exchanger is simulated numerically to determine the impact of entrance effects and conduction heat transfer through the walls on the performance of the heat exchanger, including the number of transfer units and the effectiveness. The impact of wall conduction on the heat transfer is studied for different wall thickness and thermal conductivity. It is shown that entrance and wall effects can be incorporated in the longitudinally averaged number of transfer units and accounting for them significantly changes the heat exchanger size for to a given effectiveness.
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the corrugated plate heat exchangers were more efficient in both heat transfer and efficiency when compared to standard smooth tube heat exchangers. In the present experiment, three different angles (300, 400, 500) of corrugated plate heat exchangers with a channel spacing of 15 mm, length of 30 cm and width of 10 cm were considered to investigate the heat transfer studies. As a heat transfer medium, an oil was taken as hot fluid and water were taken as cold fluid. The heat transfer analysis was conducted on the corrugated plate heat exchangers to find the behaviour of a heat exchanger using oil and water. This was done by comparing the results of the Nusselt number. The outcome of this study will give the overview of corrugated plate heat exchanger for oil.
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Heat exchanger made of heat pipes with round cross section (Known as round heat pipe heat exchanger) has been widely used in China. But some further improvements are greatly desired both in design and in operation. The two main performance parameters of heat exchanger are its heat transfer coefficient and flow resistance, which often affect each other. For example, the maximum permissible pressure drop which is propotional to the flow resistance limits heat transfer coefficient, especially for the round heat pipe heat exchangers. The self-clean ability of the exchanger is also affected negatively when heat transfer ability is too low.
These problems are well solved by a newly developed heat exchanger made of heat pipes with elliptic cross section (Known as elliptic heat exchanger). It is shown that the performances of elliptic heat pipe heat exchanger are much higher than those of round one. The details will are presented and discussed in the following sections. It is believed that the use of elliptic heat pipe heat exchangers indicates a way for further application of heat pipe heat exchangers.
These problems are well solved by a newly developed heat exchanger made of heat pipes with elliptic cross section (Known as elliptic heat exchanger). It is shown that the performances of elliptic heat pipe heat exchanger are much higher than those of round one. The details will are presented and discussed in the following sections. It is believed that the use of elliptic heat pipe heat exchangers indicates a way for further application of heat pipe heat exchangers.
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A high-performance heat exchanger was developed. This heat exchanger has a form of double tube type, and the inner tube spins around its axis. Additionally, fixed blades are settled to touch the surfaces of the heat transfer tube. With this mechanism, the boundary layers on the heat transfer tube are scraped and the heat transfer rate is drastically improved. The heat transfer characteristics of this heat exchanger were experimentally measured in the previous study and it was suggested that the fluid flow in the heat exchanger contributes to improve the characteristics. In this study, the thermal fluid flow in the heat exchanger is numerically analyzed and its characteristics are discussed.
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A compact heat exchanger performs better under the same conditions as a traditional heat exchanger with less size, weight, and cost. In this study, a compact heat exchanger is prepared by coiling a copper spring of 19 gauge on a circular copper tube. Due to this wounding of spring the inner wire of the spring will touch the tubes of heat exchanger which will disturb the viscous sub layer of the fluid flow and hence resistance to heat transfer will decrease. The outer wire of the spring will act as fins and hence surface area of compact heat exchanger will increase which results in increase in heat transfer. The entire assembly of copper spring attached to copper tube is inserted in a PVC pipe. The temperatures at the inlet and outlet of heat exchanger are measured with calibrated thermocouple. The pressure drop at the inlet outlet is also measured. It is observed that the effectiveness of compact heat exchanger is increased by 2.1 times while the overall heat transfer coefficient is increased by 2.69 times of regular heat exchanger.
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Based on cold-hot-medium type three-fluid heat exchanger, the characteristics of the three-fluid plate heat exchangers composed of 6 channels and 9 channels have been investigated theoretically. The heat transfer effectiveness of the three-fluid plate heat exchangers was defined by considering the maximum heat transfer rate. It was found that the performance of the three-fluid plate heat exchangers depended on the arrangements of three-fluid heat exchanger and the initial temperature ratio.
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