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Heat Transfer
Published in C. Anandharamakrishnan, S. Padma Ishwarya, Essentials and Applications of Food Engineering, 2019
C. Anandharamakrishnan, S. Padma Ishwarya
Baffle spacing is an important parameter which influences the rate of heat transfer. While larger baffle spacing reduces the shell-side pressure drop in conjunction with a decrease in the turbulence and heat transfer coefficient; smaller baffle spacing increases the turbulence and heat transfer coefficient. Nevertheless, the significant increase in pressure drop outweighs the advantage of increased heat transfer coefficient obtained with the smaller baffle spacing and thus nullifies it. Thus, the baffle spacing is chosen after careful consideration of the allowable shell-side pressure drop and the required heat transfer coefficient. As recommended by the TEMA standards, the minimum space between the baffles should be one-fifth (1/5th) of the shell diameter.
Heat Exchangers
Published in Mohammed M. Farid, Mathematical Modeling of Food Processing, 2010
One of the recent developments in heat exchangers has been to reduce the size (length and/or area) by enhancing the rate of heat transfer. This has been achieved by using a grooved surface or electro-hydrodynamic (EHD) enhancement. A grooved surface induces turbulence and increases the surface area available for heat transfer. EHD enhancement involves placing conductive plates around the heat exchanger and applying a voltage across the plates. The electric field generated between the EHD plates induces secondary flow and increases the rate of heat transfer in the heat exchanger. Improvement in PHEs has included the use of different types of fins and plates. Traditionally, segmented baffles have been used in shell and tube heat exchangers. However, segmented baffles result in low local heat transfer coefficients and excessive pressure drop. New geometries of baffles such as rods, grids, twisted tubes, and helical and angled baffles have been developed which allow longitudinal flow on the shell side. Another recent development in the area of heat exchangers has been to minimize fouling by better understanding fouling and integrating it as a part of heat exchanger design.
Shell-and-Tube Heat Exchangers
Published in Sadık Kakaç, Hongtan Liu, Anchasa Pramuanjaroenkij, Heat Exchangers, 2020
Sadık Kakaç, Hongtan Liu, Anchasa Pramuanjaroenkij
Baffles serve two functions: most importantly to support the tubes for structural rigidity, preventing tube vibration and sagging, and second, to divert the flow across the bundle to obtain a higher heat transfer coefficient. Baffles may be classified as transverse and longitudinal types (e.g., the F-shell has a longitudinal baffle). The transverse baffles may be classified as plate baffles and rod baffles. The most commonly used plate baffle types are shown in Figure 9.8 and are briefly described below.4
Thermal-Hydraulic Characteristics of Helical Baffle Shell-and-Tube Heat Exchangers
Published in Heat Transfer Engineering, 2020
Bassel A. Abdelkader, Muhammad Ahmad Jamil, Syed M. Zubair
Beside analyzing the conventional configurations (refer to Figure 1(a)), some efforts have also been made to enhance the performance of HB-STHX (see Figure 1(b)) by changing the geometry. In this regard, Yang et al. [26] proposed a combined multiple shell-pass HB-STHX with continuous helical baffles. They observed that for the same mass flow rate and heat transfer, the proposed HX shows a 13% decrease in and a 5.6% increase in the heat transfer rate compared to the conventional SG-STHX. Likewise, Chen et al. [27, 28] investigated the effect of baffle structure in an HB-STHX on the heat transfer rate, and fouling propensity and compared the results to the conventional one. The results showed that the baffle structure has an impact on the heat transfer rate and fouling. Wen et al. [29, 30] introduced a ladder-type fold baffle to block the triangular leakage zones in a conventional HB-STHX. Their experimentation revealed that the newly presented configuration has higher shell-side and overall heat transfer coefficient by 22–33% and 18–23%, respectively. In another study [31], they used particle image velocimetry to explore the shell-side flow pattern and compared it with the conventional one.
Multiphysics field coupling simulation for shell-and-tube heat exchangers with different baffles
Published in Numerical Heat Transfer, Part A: Applications, 2020
Juan Xiao, Simin Wang, Shupei Ye, Jian Wen, Zaoxiao Zhang
Heat exchangers, as the essential equipment for heat and mass transfer between hot fluid and cold mediums, are widely used in various industrial processes, for example, oil refining, electric power production, food industry, environment engineering, refrigeration and so on [1]. In addition, shell-and-tube heat exchangers (STHXs) play an important role among different types of heat exchangers, whose quantity is more than 35–40% of heat exchangers in the world. The reasons are that STHXs have many advantages including simple manufacture, robust mechanical construction, easy maintenance and wide operation conditions [2–4]. Baffle is one of key components to support tubes and improve shell-side heat transfer efficiency, which has an important effect on shell-side flow distribution as well as heat transfer enhancement.
Numerical Analysis of Baffle Cut on Shell Side Heat Exchanger Performance with Inclined Baffles
Published in Heat Transfer Engineering, 2018
Govindaraj Kumaresan, Ravichandran Santosh, Ponnukutti Duraisamy, Ramar Venkatesan, Nathamani Satheesh Kumar
On the tube side of STHX, numerous efforts have been successfully made to increase the performance [4–8]. For shell side, the baffle elements greatly contribute to the thermal hydraulic performance and introduction of baffle into the flow increases the average Nusselt number by 190%. Heat transfer characteristics and flow conditions are strong functions of baffle spacing [9]. However, baffles improve the heat transfer at the expense of increased total pressure drop. Further, the velocity and temperature fields are relatively complicated due to leakage paths and bypass streams between different flow zones. Round cut plates are used in a traditional STHX with segmental baffles for the support of tubes. These baffles also intensify the fluid flow thus leading to shell side heat transfer enhancement [10–12]. But the flow resistance and harmful vibration level is higher with created large-scale dead flow regions at the corners that results in reduction of effective heat transfer area and help in fouling of tubes. Various new types of baffles have been developed and investigated to solve these problems [13–19]. A new type of fold baffle to block the triangle leakage zones in shell side of STHX was proposed by Wang et al. [20]. With the usage of these fold baffles, it was reported that shell side heat transfer co-efficient and overall heat transfer co-efficient improved by 17.7–34.2% and 7.9–9.7%, respectively. Further, they concluded that optimization of baffle configuration would lead to better heat transfer rate and less pressure drop.