Papers by Keyword: CFD Analysis

Abstract: Heat exchangers are widely recognized as eco-friendly devices that transfer heat between two or more fluids without mixing. Double Pipe Heat Exchangers (DPHE) are used in many industrial applications such as power generation, chemical processing, HVAC, and renewable energy systems. Traditional DPHEs are simple and reliable, however, they often face limitations in heat transfer. Improving the thermal performance of DPHE can significantly enhance the operational efficiency of thermal energy systems. This study presents a novel fin arrangement to the traditional DPHE using different diamond-shaped fins to improve its thermal performance. The thermal and hydraulic properties of DPHE with different diamond-shaped fin configurations are investigated using CFD analysis. The optimization process is carried out using the Response Surface Method (RSM) for optimal diamond-shaped fin design. The results indicate that novel diamond-shaped fins improve thermal performance, particularly at high mass flow rates. The thermal enhancement factor (TEF), overall heat transfer coefficient, and pressure drop are used to evaluate the thermal performance of DPHE. The diamond-shaped fins exhibit a 55% increase in overall heat transfer coefficient compared to conventional DPHE. The TEF for diamond-shaped fin configurations is higher than 1 with a maximum value of 1.63 for DPHE-HF45 depicting a 63% increase in thermal enhancement. The optimization results show that the optimal fin design achieves a desirability of 81.3%, with a pressure drop of 870.726 Pa and an overall heat transfer coefficient of 2199.85 W/m²K at a mass flow rate of 2.711 lit/min.

Abstract: Aiming at the inner flowing characteristics of round tube, the different transient cases of tube with rotating wall boundary are analyzed by CFD, and the six cases are determined according to the different rotating speed respectively. The fluid is water, with the same dimension of tubes, the negative pressure region moves forward in the tube as the increase of rotating speed, and the outflow velocity is high to 31.42 mm/s, being 348.22% more than that of steady case. When the rotating speed is 1 rev./s, there is a lowest temperature band between the wall and center high temperature flow. In the transient temperature analysis, the high temperature cloud changes to cone-like shape, and there is a swirl with lower temperature at the inlet part with a large depth into the tube center. The case with 2 rev./s has the much more uniform temperature distribution than others.

Abstract: This work studies the design of a fixture used in vibration sorting rig which is used for core balancing in turbo charger. The main objective of this paper is to design and optimize the fixture for holding the turbo chargers. To balance the core of turbo charger, turbine wheel and compressor wheel should balance which is turbine wheel is placed into the fixture. This paper analyzes the existing fixture and proposed new design. The fixture runs at higher speeds which is why we have to put the more concentration on the fixture design. The small issue in the fixture design results more problems due to high rotating speed of the turbine wheel of turbo charger. Many of the parts rejects due to poor fixture design. New fixture design is based on several aspects like design of work piece, rotating speed etc. The CFD analysis on the existing and proposed design is carried out. The results obtained were compared with existing fixture design.

Abstract: This works centers on the design of a De Laval (convergent - Divergent) nozzle to accelerate the flow to supersonic or hypersonic speeds and computational analysis of the same. An initial design of the nozzle is made from the method of characteristics. The coding was done in Matlab to obtain the contour of the divergent section for seven different exit Mach numbers viz. 2.5,3,3.5,4,4.5,5 and 5.5.To quantify variation in the minimum length of the nozzle divergent section with respect to the exit mach number, a throat of constant height (0.005m) and width (0.05m) was chosen for all the design. The area exit required for each mach no varying from 1 to 5.5 was plotted using isentropic relations and was also used to verify the exit area of the nozzle for each of those mach numbers. An estimate of the exit pressure ratio is obtained by using isentropic and normal shock relations. With this exit pressure ratio, a more refined verification is done by computational analysis using ANSYS Fluent software for a contour nozzle with exit Mach number 5.5. The spalart Allmaras and k-epsilon model were used for turbulence modeling.

Abstract: This paper deals with a use of CFD modelling for optimization of supply of secondary combustion air in the two-chamber biomass boiler combusting very wet biomass (capacity ca. 200 kW). Objective of the analyse is to observe the impact of diameter of a secondary air supply pipe and air flow velocity on mixing of the secondary air with flue gas in the combustion chamber. The numerical model of the experimental boiler was build up for subsequent utilizing of CFD computation based on finite element method. The commercial code STAR-CD was used for carried out parametrical studies. Series of calculations were carried out for four different diameters of air distribution pipes and for 3 different air velocities in distribution orifice. Quality of air dispersion in flue gas flow was assessed in the vertical cross section lead in the end of the combustion chamber. The results of calculation were verified on the experimental installation of the boiler. Influence of secondary air mixing on emission production was measured and analysed. Emissions of pollutants for recommended air distribution comply with emission limits stipulated in the most stringent class 5 according to ČSN-EN 303-5 as well as with emission limits under Regulation No. 405/2012 Sb.

Abstract: The currently applied structure and fatigue assessment of support structure for offshore wind energy converter was based on common design rules. The accurate evaluation for environments of sea floor as to installation of support structure, loads of generator, dynamic loads in operation, and offshore environmental loads might be an essential requirement to acquire a safety design for the substructure. This study aims at dedicating to offshore-relevant technology fields by suggesting design methods of structures and estimating their safety in relation to the structural analysis of the substructure requiring high safety to various environment conditions. Especially, with respect to 5MW Offshore Wind Power System, this study will provide information about major wind directions and duration in combination with the developing wave climate at the test field. In this study in the dynamic analysis for 5MW offshore wind power substructure which is considered to be proper in Korea, it is expected that reliability of domestic technology is confirmed with respect to its structural stability.

Abstract: The applications of heat exchangers are vast and the enhancement of heat transfer and compact size are the key factors for designing the heat exchangers in order to achieve energy savings. In the field of tubular heat exchangers one of the possible ways for reducing the space occupied by the exchanger is by bending tube axis in helical shape. This option is particularly suitable when construction simplicity is needed and the geometry of the place in which the exchanger has to be housed is the cylindrical one. In this paper, an attempt is made to enhance the heat transfer rate without application of any external power. This is achieved by providing the helical tube in tubes. The parameters influencing the nature of flow in a helical coil heat exchanger are the tube geometry namely pitch coil diameter, pitch and tube diameter. CFD analysis is carried out to study these geometry effects on heat transfer and hydraulic characteristics by varying Reynolds number (hot fluid). The CFD results of velocity and temperature distribution in the heat exchanger are used to estimate the Nusselt number and heat transfer coefficient. This helps to arrive at an optimum value of Reynolds number and Nusselt number for the corresponding tube-to-coil diameter ratios.

Abstract: The human powered vehicle market is not only a larger market per unit than the automotive market, but it is one in growth. The main product of this market is the classical bicycle, which is familiar around the globe, but mainly in the urban environment. The bicycle, which in this paper will be considered a human powered vehicle, is slowly gaining ground in the field of urban transportation solutions. This paper analyzes the possibility of optimizing the body of a human powered vehicle recumbent tricycle through continuous fluid dynamics. The vehicle is already designed and built, and is fully functional. The body of the vehicle comes as a necessity to give the operator protection from the elements, but the main reason is, to give the vehicle less air resistance. This would be a great benefit to the operator and the perceived comfort. Usually the aerodynamics analysis comprise of a wind tunnel test that confirms the theoretical results. This paper shows the evolution of the body of a human powered vehicle as it is optimized after identifying the turbulent areas in its shapes. After optimization, a body is obtained which will be proposed for implementing over the built vehicle.

Abstract: For the intake restrictors which are designed in line with FSAE race stipulations, this paper carries out compute simulation on the convergent section and divergent section of the intake restrictors via CFD software; the paper systemically analyzes the distribution characters of its flow field, thus obtaining optimal design scheme. It finds through simulation that: when the converging half angle of the restrictor is less than 45°, the outlet flow of the restrictor will decrease as the converging half angle increases; meanwhile, the divergence half angle will affect the outlet flow of the restrictor as the pressure difference between the restrictor inlet and outlet varies. According to the simulation results, the optimal scheme finally designed is: the intake restrictor has the best effect when the converging half angle of the restrictor is 10°, while the divergence half angle is 11°.

Abstract: The aim of study is to develop highly reliable and less time consuming steam dryness fraction measuring experimental setup. This method of dryness fraction measurement is based on throttling process which is obtained by using orifice plate. Calculation of orifice diameter was done by using ISO 5167 for given pressure drop. This paper deals with the conceptual design of orifice in a steam pipe line. The objective of the conceptual design is to obtain throttling process. Three parameters are chosen for the conceptual design: the diameter of the orifice, the aspect ratio between length and diameter and the entrance angle to the orifice. This work also deals with validation of calculated orifice diameter through CFD simulation for pressure drop in pipe line. To simulate the throttling process, the inlet condition of the orifice upstream flow is fixed at 10 bar and 180°C. The temperature and pressure is measured at the outlet of the orifice while steam is flowing through the pipe. An orifice diameter of 11.00mm is selected as the optimal value to keep throttling process. The resulting optimal orifice design will be used in steam pipe line.