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In this study numerical analysis is carried out for four different types of fins for top and bottom fin arrangement. The obtained results are compared with each other and the design with best heat transfer and minimum pressure drop is selected. The working fluids used in the model are sulfur trioxide, sulfur dioxide, oxygen and water vapor. The operating pressure is 1.5 MPa and the operating temperature ranges from 973 K to 1223 K. From the results it was found that the ripsaw fin design with thickness of 0.00005 m gives a good heat transfer rate with minimum pressure drop. The inverted bolt fins also gives a good heat transfer rate but due to the fin arrangement and the flow disturbances caused by the arrangement the pressure drop is the highest compared to other fins. The pressure drop and the heat transfer obtained for the rectangular and triangular fins are similar to each other. Friction factor, Colburn j- factor and dimensionless numbers like Nusselt number, Schmidt number are calculated for all the models. The average Nusselt number obtained for the ripsaw fin design with thickness of 0.00005 m for the top and bottom arrangement is 3.023. The friction factor for the ripsaw fins for the top and bottom arrangement is 0.589. [ABSTRACT FROM AUTHOR]

In this study numerical analysis was carried out for four different types of fins namely rectangular, triangular, inverted bolt fins and ripsaw fins and three different types of arrangements namely straight, staggered and top and bottom arrangement. The obtained results were compared with each other and the design with the highest decomposition percentage of sulfur trioxide was selected. The working fluids used in the model were sulfur trioxide, sulfur dioxide, oxygen and water vapor. The operating pressure was 1.5 MPa and the operating temperature ranges from 973 K to 1223 K. From the results it was found that the ripsaw fin design with thickness of 0.05 mm gives the highest decomposition percentage of sulfur trioxide. The inverted bolt fins gives a good heat transfer rate but due to the fin arrangement and the flow disturbances caused by the arrangement the pressure drop was the highest compared to the other fins. The pressure drop and heat transfer obtained for the rectangular and triangular fins were similar to each other. The obtained decomposition percentage of sulfur trioxide for straight, staggered and top and bottom arrangement were 17.60%, 16.74% and 20.55%. The obtained decomposition percentage increased from 16.74% to 85.15% when the channel length of the heat exchanger was increased ten times. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rip saw fin design (case 9) was considered to be the best because it has thin fins and has higher heat transfer coefficient. [•] Due to higher surface area density the heat transfer coefficient and Nusselt number obtained for case 7 is lower than other fin types. [•] The values of the average Nusselt number obtained for all the cases vary in small order of magnitude. [•] The maximum Nusselt number was obtained for the ripsaw fin design (case 9). [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the effects of inlet temperature and rib height on the fluid flow and heat transfer performances of the ribbed channel inside the high temperature heat exchanger are presented. The inlet temperature varies from 850K to 1250K and the ratio of rib height to channel height varies from 0.083 to 0.333. The results indicate that increasing the rib height can enhance the flow disturbance and hence improve the heat transfer performance. The inlet temperature has little effect on the basic structure of fluid flow and the heat transfer is enhanced due to the increased velocity. Compared to increasing the rib height, more heat can be transferred by increasing the inlet temperature with less pressure drop. The high pressure drop is more serious as the inlet temperature increases. It is proposed to use the compact heat transfer structure at the low temperature region and replace it by loose heat transfer structure at the high temperature region. It also demonstrates that the Nusselt number and friction factor are unsuitable to compare the heat transfer and pressure drop performances among different temperature conditions because the physical properties of fluid change with temperature variation. [Copyright &y& Elsevier]