ANSYS CFD Research Articles

Numerical and experimental investigation of different rib roughness in a solar air heater

A numerical study is aimed at comparing dissimilar types of repeated-rib roughness: arc-shape with gap and V-shape with gap on the absorber plate of the solar air heater having similar shape and size working under identical boundary conditions. Relative gap width (g/e) of 1, relative roughness height of 0.04, the relative roughness pitch of 10, p/P = 0.65, d/W = 0.69, No. of gaps = 1, attack angle α = 600 of the rib, heat flux 1000 W/m2, etc. are kept constant and variation in range of Reynolds number is 3000–15000. Numerical simulations are conducted with the help of ANSYS CFD tool, and results have been validated with the experimental studies. The V-shape ribs have maximum frictional loss penalty of 4.05 and Nusselt number enhancement of 3.4 at Re 3000. The arc-shape ribs have maximum frictional loss penalty of 3.94 and Nusselt number enhancement of 2.4 for Re 15000. The maximum THPP for the V-shape ribs and arc shape ribs are 2.21 and 1.5 respectively at Re 3000.

Characterization of a micro thermal cavity receiver – Experimental and analytical investigation

The objective of this work is to characterize the optical and thermal performance of a micro-scale cylindrical cavity solar receiver for the Brayton gas power cycle at various solar radiation levels through experimental and analytical investigation. A thermal receiver consisting of a 300 mm deep and 200 mm diameter cylindrical cavity equipped with an 8 mm diameter helical copper tube was studied. An advanced ray-tracing technique using OptisWorks software was used to predict the distribution of solar radiation inside the cavity. Also, computational fluid dynamics simulations were carried out using ANSYS CFD software to predict the temperature distributions of the coil surface and the compressed air outlet temperature. Having satisfying conformity between the numerical and the experimental results, the current results demonstrated that a competent flux and temperature distributions were directed on the receiver’s tube. Moreover, an outlet temperature up to 70 °C, based on the available compressed air flow rate. This point leads to the probability of operating a micro-scale dish concentrator for Concentrated Solar Power in a domestic application. The results of a parametric study indicated that a cavity’s receiver depth and width of 180 mm and 240 mm give the best thermal operation.

Air side performance of tube bank of an evaporator in a window air-conditioner by CFD simulation with different circular tubes with uniform transverse pitch variation

Abstract This paper summarises a two dimensional numerical study of the performance of an evaporator of a window type air conditioner. The analysis of the performance of the heat exchanger is done using software ANSYS CFD with finite volume discretization. For the study a couple of commercially available sizes of copper pipes were considered. Six transverse pitch sizes with identical variation between them with an inlet velocity range of 1.5 to 4.0 m/s, the prevalent conditions for Indian window air conditioners were considered as the input data. The objective of the investigation is to understand the effects of transverse pitch variation on Nusselt number, heat transfer, pressure drop and friction factor in a tube bank of an evaporator with seven rows of tubes. The above study provides better understanding of the effect on heat transfer due to variation of transverse tube pitch and velocity of fluid flow under constant surface temperature of the tubes through simulation study. The outcome of the simulation revealed that for lower transverse pitch values heat transfer was lower and as the pitch increased the Nusselt number increased so also was the heat transfer. With the increase in tube size there was corresponding increase in Nusselt number and heat transfer. In the airflow direction, the larger diameter tube performed better as compared to inline smaller diameter tube. For the verification and validation of the outcome from this study were compared with the values derived from existing correlations of the earlier published literature. The simulation values of Nusselt number showed a deviation of 8% with the correlated values which are well within the acceptable range. The information from the study can be used to improve the design and operation of heat exchanger units in window air conditioners.

A Numerical Investigation into the Impact of Icing on the Aerodynamic Performance of Aerofoils

Aircraft wings and wind turbine blades are often subjected to harsh and cold climatic conditions. Icing is often observed on wing and blade surfaces in these cold climatic conditions. Wind turbine blades, in particular, are severely impacted by ice accretion which greatly hampers their performance and energy generation efficiency. Ice-accretion patterns are observed to vary with changes in temperature. As the temperature changes, the thickness of the ice accretion, the shape and location of ice-accretion vary greatly. In this paper, three different ice accretion patterns and their impact on the aerofoil efficiency have been investigated using the SST k – ω model in ANSYS CFD. An analysis of the impact of ice-accretion through a comparison of lift and drag coefficients for all three ice accretion patterns indicate that the accretion of ice on an aerofoil can reduce lift generation by 75.3% and increase drag by 280% thereby severely impacting the performance of the aerofoil. The loss in aerodynamic performance is greatly dependent on the ridge height, the extent of ice accretion and the thickness of this ice. The loss in aerodynamic performance has no fixed correlation to the drop in temperature.

Effect of leakage on refrigerant distribution in an air conditioned room using propane as working fluid

Propane R-290 as hydrocarbon refrigerant has more benefits from the aspect of thermophysical properties, but the only weakness from this refrigerant is flammable. The distribution prediction of R-290 leakage to an air-conditioned room. The study using numerical simulation of CFD ANSYS FLUENT V.13. The distribution of R-290 with a leakage rate of 0,001kg/s and an airflow of 0,1m/s will run out after 600s, with 0,002kg/s will run out after 300s and with 0,005kg/s and 0,5m/s will run out after 120s. The mass flow rate can influence the refrigerant distribution of leakage effect flowrate. Airflow can increase the dispersion of refrigerant gas and decrease the level of the refrigerant amount at any certain point in the room after the refrigerant charge is empty. This momentum effect was due to the impact of supply air initial velocity. The buoyancy effect was due to R-290 density is greater than the air makes the refrigerant flows downward, accumulated, and stagnant. Make sure that the contactor relays and other electrical tools have the position, x=0 m ≤ x ≤ 1 m on y=0 m ≤ x ≤ 26 m and then y=1 m, x=0 m ≤ x ≤ 4 m.

Fluid Structure Interaction Analysis of Horizontal Axis Wind Turbine

Wind power is a clean energy source that we can rely on for long term use. A wind turbine creates reliable, cost effective pollution free energy. A Horizontal axis wind turbine (HAWT) with three blades having aerofoil profile NACA 2421 is modelled in CAD software and the performance of the turbine is investigated numerically using 3D CFD Ansys 18.1 software at rotor speeds varying from 1 to 7.5 Rad/sec at wind speeds ranging from 8 to 24 m/s. In order to ensure the turbine blades do not fail due to pressure loads and rotational forces, Fluid structure interaction is carried out by importing the surface pressure loads from CFD output on to static structural module, the rotational velocities are also imparted on the blades and FE analysis is carried out to estimate the equivalent von-Mises stress for structural steel as well as aluminium alloy. It is found that aluminium alloy blades are preferable than the structural steel blades. At high rotor speeds, stresses in the structural steel exceeding the yield strength limit. For aluminium alloy the stresses are below the yield strength limit.

Computation of 3D Water Flows by the Double Potential Method for the Simulation of Electromagnetic Water Purification

In this paper, we discuss the modeling of the electromagnetic water purification. This model requires a velocity distribution in a study domain. For that purpose, the double potential method for simulating incompressible viscous fluid flows was used. The system of equations was discretized with the help of the finite volume method using an exponential transformation for the vortex calculation. As a result, a software implementation of the developed numerical scheme was obtained. The simulation of the three-dimensional flow was carried out in a study domain. The results were compared with Ansys CFD. The comparison showed a good degree of consistency between the two distributions. Using the obtained velocity field, we simulated the process of water purification using the induction of the electromagnetic field.

MELTING CHARACTERISTICS OF CAPSULATED PHASE CHANGE MATERIALS

An experimental and computational investigation studied phase change material melting in a cylindrical capsule with PCM. The capsule is placed horizontally in a rectangular test section, where it is insulated from all sides’ wall except the front one. The PCM capsule is heated by passing hot water from downward to upward with different inlet mean water temperatures (327.9, 333.7, 338 and 343) K, different velocities, varied thermal conductivities of capsule material wall (copper, iron, pyrex-glass, and polyethylene), and PCM. Experiment during melting inside a pyrex-glass capsule was performed and compared with prediction analysis by using CFD ANSYS 2019 R2. Image processing of melting photographs along with melted time were used in comparison. The comparison between the liquid fraction and energy stored with time for lauric acid and paraffin wax was analyzed. PCM liquid fraction, temperature and energy stored measurements for lauric acid were assessed numerically. The results reveal for lauric acid that the total melting time was enhanced 43% for 4.6% increase in water mean inlet temperature, 18% for 500% increase in inlet water mean velocity, and 7% when used copper capsule wall. The results proved that the lauric acid charged with energy stored were 47% more than paraffin wax during the total melting time of it, and the effect of different water mean inlet temperatures was the main factor for the charging process to improve the PCM melting time.

Analysis of Convergent - Divergent Nozzle with and without Macro - Extends using ANSYS CFD

Analysis of Convergent - Divergent Nozzle with and without Macro - Extends using ANSYS CFD

Fluid structure interaction simulations and experimental validation of a pipeline immersed in liquid

In launch vehicles, there are number of fluid systems to cater to various requirements like propellant filling, draining to/from tanks, venting of ullage gases, pressurization of the tanks, feed systems to convey propellants to engine from tanks, lines to convey command gas to actuate various valves etc. These pipe lines are subjected to environmental loads i.e. vibration loads when the launch vehicle starts its course to place the satellite into its designated orbit. It is essential to study the dynamic characteristics of these pipe lines for the design of them for vibration loads. The response of these pipelines depends on fluid environment in which they are immersed. If a pipe line is immersed in liquid, its dynamic characteristics vary largely from that of a pipeline vibrating in ambient environment (air). If the pipe line immersed in fluid, natural frequency reduces and damping increases due to the added mass and fluid viscosity respectively. In order to study these effects, FSI studies are carried out on a pipe line immersed in water using ANSYS CFD and Mechanical software. Convergence studies with respect to time scale are carried out to benchmark the simulation procedure. This simulation procedure is validated by conducting the experiments.

Numerical Simulation of Turboexpander on Organic Rankine Cycle with Different Working Fluids

Renewable energy is an alternative to overcome the energy crisis and dependence on fossil-fuel energy that has an environmental impact due to the greenhouse effect. Meanwhile, disadvantage of EBT is depend on weather periodically. Geothermal is a source of EBT that is independent with weather. Geothermal resources dominated by water (brine) can’t be directly utilized as a power generated, but it has to separated into water and steam phase. The high enthalpy owned by brine can still be utilized due to development of Organic Rankine Cycle. ORC uses organic refrigerant fluids or hydrocarbons as a working fluid because it has low boiling temperatures. The numerical simulation was analyzed using a CFD ANSYS CFX with turbulence model K-epsilon and Pentane, R245fa, and butane as a working fluids with expansion ratio 5:1 and rotational speed variation at 2000 until 14000 rpm.

MODELING THE WET CONDITION OF TUNNELS KP «KIEV METRO» IN THE CALENDAR YEAR

The analysis of the experimental values of the relative humidity of the tunnel air of the service interconnect lines (SIL) of the Kyiv Metro KP under the existing tunnel ventilation operating modes during 2018. It has been established that during the summer period the value of the relative humidity of the tunnel air exceeds the standard value of 75 % under the current operating modes of tunnel ventilation, when the air is pumped in from the stations and removed from the tunnels into the environment.To solve the problem, a computer model of the heat and humidity state of the tunnels was built, which includes geometric, physical and mathematical sub models. The geometric model on a 1: 1 scale reflects the length of the 2.5 km tunnels and their spatial orientation and consists of 1.5 million cells. The physical model is a set of physical processes that take place in SIL tunnels: the processes of movement and mixing of external and wet tunnel air, heat transfer between the tunnel air and the rim of the tunnel wall, the processes of evaporation and condensation of water. These physical processes are described by differential equations of heat conduction, motion, energy, heat transfer, which are used to calculate the temperature, velocity fields for three components along the directions of x, y, z coordinates, pressure and humidity. The thermogasdynamic and humidity model was developed using the Ansys CFD software. Verification of the computer model was carried out using experimental data for 2018. Unknown tunnel air flow rates were determined by the computer model parameters identification. When modeling the heat and humidity state of the tunnels, the thermal inertia of the soil layer around the tunnels was taken into account.Simulation of the heat and humidity state of the SIL tunnels during the calendar year showed that a change in the operating modes of ventilation units during the summer period, when air from the environment is pumped into the tunnel and removed from the tunnels by station fans, will reduce the relative humidity below 75 %. The simulation results were confirmed by experimental tests in the Kiev metro and introduced for use throughout the calendar year in the future.

The Stress Behaviour of Powered Vehicle Body

The stream around body (powered vehicle, transports, trucks) under typical working condition is basically fierce. It is regularly portrayed by substantial scale division and distribution areas, a mind boggling wake stream, long trailing vortices and cooperation of limit layer stream on vehicle and ground. In growing new street vehicle basic for planner for see completely its assembly of stream around to the vehicle. It will have impact on such important element as the state of vehicle, streamlined drag, fuel utilization, clamor generation and street dealing with. Generally, vehicle planner have picked up their comprehension of the wind current around a vehicle through broad breeze burrow testing. Body-on-outline is a vehicle development strategy a different body is fixed on a generally inflexible casing or body conveying in the motor & drivetrain. The first strategy for structure cars, body-on-outline development is currently utilized for the most part for fueled vehicle. Car streamlined features includes the investigation of optimal design of street vehicles. Its fundamental objectives are diminishing drag, limiting clamor outflow, improving efficiency, averting undesired lift powers and limiting different reasons for streamlined insecurity at high speeds. In the current project cfd analysis of powered vehicle’s outer body is done at 30kmph. Design of frame done using NX-CAD software and CFD analysis runs through Ansys CFD package.

Technology of computational analysis of the working process parameters of low-thrust rocket engines running on gaseous oxygen-hydrogen fuel with the use of ANSYS CFD

The paper presents the description of a mathematical model of the working process of a low-thrust rocket engine operating on gaseous oxygen-hydrogen fuel and some fragments of the technology of computational analysis of distribution of gas-dynamic parameters in the engine duct. We present the results of calculating the stream line distribution, the distribution of total temperature profile along the flow path of the engine chamber and at its characteristic cross sections, the axial component of (total) speed of combustion products in the Laval nozzle output section. The results of calculating the temperature in the area of the rocket engines inner wall are presented. It is shown that the distribution of the combustion products stagnation temperature has a significant impact on the efficiency of fuel conversion in the engine chamber, its thermal state and makes it possible to identify the ways of improving the workflow of the low-thrust rocket engine.

Determination of kinetic parameters for pressed tetranitropentaerytrite according to results of <i>ODTX </i>experiments

The paper introduces a method for determining kinetic parameters for the pressed explosive tetranitropentaerytrite. This method includes analytical dependence for the period of induction, which is used to process the experimental data, and the ANSYS CFD finite element analysis software package. The found values of the kinetic parameters made it possible to obtain a satisfactory agreement between the calculated and experimental ignition distances for pressed tetranitropentaerytrite

Computational fluid dynamics analysis of heat transfer in a greenhouse solar dryer “chapel‐type” coupled to an air solar heating system

AbstractThe distribution of turbulent kinetic energy (TKE), temperature, and velocity of humid air inside the greenhouse solar dryer (GHSD) was numerically investigated using 3D CFD ANSYS FLUENT code. The effect of solar radiation was coupled with the energy equations using the discrete ordinate model. Numerical simulations were based on two geometric models: Real model and model with reduced height, the solution was in good agreement with experimental data of temperature. The results of the real model showed that the TKE is ranged between 1.27 m2/s2 and 6 m2/s2 with an average of about 1.6 m2/s2 for the entire greenhouse dryer (GHD) volume. The greatest TKE magnitude is in the paths of the diffusers, which caused a temperature drop of about 2 K in the areas near the walls. Consequently, almost homogeneous temperature distribution was obtained in the entire volume of the GHD, although the average temperature was 315 K, and a gradient with respect to ambient temperature was of 14 K, that is, suitable for drying. Also, the average air velocity at 1 m height was 0.71 m/s, which is a value near the lowest limit (0.6 m/s) of forced convection drying. The improvement in the GHD by 36.5% volume reduction allowed an increase in the average TKE of 3.8 m2/s2 (2.4 times more than the previous one) located in the middle of the greenhouse; the average temperature reached 316.5 K with a gradient of 15.5 K, which represents an increase of 1.5 K (11%) compared to the real geometric model. The air velocity at 1 m height increased to 0.9 m/s in the improved geometric model (a growth of 35.7% compared with the previous geometry). More than 95% of the improved GHD volume has a uniform temperature, which is very suitable for a good quality drying process with higher speed.

Simulation on Heat and Mass Transfer of an Evaporator as Evaporation Chamber In Natural Vacuum Solar Desalination System

Natural Vacuum Solar Desalination technology was designed and built for one of solutions for water scarcity issues right now. An evaporator as the main part of this system should be analyzed to achieve a good result (fresh water productivity). The evaporator is used as an evaporation chamber to evaporate seawater which will be condensed to water storage. The commercial code CFD ANSYS Fluent 16.1 has been used to simulated and analyzed of heat and mass transfer inside the evaporator. There is no laminar model was used in this work with the temperature of heating coil was 70°C and the operation pressure was under atmospherical pressure. In this work, the results of simulation and experimental will be compared to be a validation. The highest temperature 72°C was in heating coil and the lowest temperature 38°C was in a body of evaporator based on the simulation result. The temperature of heating coil was increasing during evaporation processes. From these comparisons, shows there’s a little discrepancy with a magnitude of error between 0,02% to 33%. It also shows the method has been used is right for analyzed and simulated about evaporation-condensation processes.

A new form of equation for force determination based on Navier-Stokes equations

This work is focused on calculating the force effects of an incompressible homogeneous liquid on a surface of a rigid or a flexible tube. An unsteady flow induced by differential pressure at the beginning and at the end of the tube is assumed. The pressure difference for the unsteady flow is determined experimentally. The mathematical model is based on modified Navier-Stokes equations. The unsteady term is modified in order to be able to use the Gauss-Ostrogradsky theorem to calculate the force. This method of solution will allow the calculation of the force by integration of the Navier-Stokes equations, which will help to refine and simplify the calculations. In the article, both methods of force calculation will be presented and compared both through the ANSYS FEA and CFD ANSYS Fluent solvers and by the integration of the Navier-Stokes equation. The calculation will not only respect the compliance of the tube but also its movement status.

Numerical simulation of a phase change material melting process

Storage processes are usually integrated in solar energy systems applications due to daily variation of this energy source availability. Among different thermal storage solutions, phase change materials (PCM) lately became more extensively used covering a wide range of operating temperatures. In this regard, a numerical simulation of a PCM melting process is performed under ANSYS CFD environment. A particular configuration is considered consisting in a 2m length annular tube having a 5.48 cm external diameter. The tube is filled with paraffin chosen as PCM. A concentric interior tube of 2.54 cm diameter is used for transporting the heat transfer fluid (HTF) from the solar collector. Heat is transferred through the 1 mm thick pipe wall to the PCM placed all around the HTF tube. The numerical results reveal the melting process of the PCM at different instances and tube sections. The time variation of the PCM liquid fraction is emphasized. The results describe the dynamic behavior of a PCM melting process and might be further integrated in any solar power plant storage charging process simulation.

Mathematical simulation of temperature influence on pressure drop at pump suction line

The article is focused on mathematical simulation of the temperature influence on the pressure drop at the pump suction line. It is evaluated pressure drop depending on mineral oil flow rate. The courses of individual dependencies are determined by mathematical simulation using the ANSYS CFD computing software. The temperature affects significantly physical properties of the flowing mineral oil. In a paper is also described the experimental measurement of a mineral oil sample and determination of its physical properties depending on temperature.