Simulation Of Heat Exchanger Research Articles

Experimental Research and Simulation of Fin and Tube Heat Exchanger

The paper provides the results of experimental and theoretical test of a wavy fin and tube heat exchanger used to cool air in a ventilation system when the wavy fin of the heat exchanger is dry and wet. The experimental tests, performed in the range of 1000<Re<4500 of the Reynolds number applying LMTD-LMED methodology, determined the dependency of the heat transfer coefficient on the supplied air flow rate with the varying geometry of the heat exchanger (the number of tube rows, the distance between fins, the thickness of the fin and the diameter of the tube). The experimental tests were performed on 9 heat exchangers in heating and 6 heat exchangers in cooling mode. After processing the results of the experimental tests, empirical equation defining the characteristics of the heat transfer coefficient of all heat exchangers were derived. The maximum heat transfer coefficient deviation is 11.6 percent. The correction factor of the wet fin (Lewis number) depending on the number of Reynolds, which ranges from 0.75 to 1.1 also is determined. Maximum capacity deviation equals 3.7 percent. The obtained equations can only be applied to a certain group of heat exchangers (with the same shape of fins or the distance between the tubes). The results of the experimental test and simulation with ANSYS program are compared and the heat transfer coefficients vary from 6.5 to 11.4 percent.

Численное моделирование теплообмена при охлаждении высокотемпературной металлической заготовки из стали 30ХГСН2А

The results of the numerical simulation of heat exchange at the cooling metal blank made of steel 30ChGSN2A are shown. The velocities of blank cooling with the flow of gas-liquid medium are defined. Cooling intensity changes depending on the blank motion speed opposite the flow of cooling medium are analyzed.

Influence of Joule Dissipation on Heat Exchange and Magnetic Hydrodynamics of Liquid in a Spherical Layer. Part I

Results of numerical simulation of the convective heat exchange in the electrically conducting liquid flowing between two concentric isothermal spheres are presented. The influence of Joule heating of this liquid and the thickness of the spherical liquid layer on the structure of the liquid flow, the temperature and magnetic-induction fields, and the distribution of Nusselt numbers in it was investigated. Equations for simulation of the heat exchange in the spherical liquid layer in the case where the gravitational acceleration is directed to its center were derived.

Design and Simulation of Condensing Heat Exchanger

The conventional heat recovery techniques recover only sensible component of the flue gas heat and a significant portion of the flue gas heat is lost to the atmosphere. Condensing heat exchangers are designed to retrieve both sensible and latent heat components of the heat present in flue gas by promoting condensation of water vapour present in the flue gas. It has several challenges due to non-availability of the low-temperature heat sink. The paper explains numerical simulations based on analytical modeling of the heat and mass transfer processes involved in condensation of moisture in the flue gas in a cross-counter flow tubular heat exchanger- of size 1.752 m × 1.274 m × 2.230 m which comprises of 78 tube passes and 6 tubes with cooling water flowing inside and flue gas over the tubes. The performance of the system is exhibited as a function of different parameters. A mathematical model using MS-Excel and VB Macros as a tool is developed to study the effect of operating parameters on the performance. The governing equations and correlations based on mass and energy balances for the system are used to compute variables such as flue gas exit temperature, cooling water outlet temperature, mole fraction and condensation rates of moisture. The equations are solved using an iterative solution technique with calculations of heat and mass transfer coefficients and physical properties. The paper focuses on the maximization of heat recovery and the various parameters affecting the heat and moisture recovery and condensation. The effect of operating parameters like inlet temperatures of both the fluid streams and flow ratio is studied in order to achieve the maximum heat and moisture recovery. The condensation and heat transfer rates increase significantly by increasing the flow ratio and decreasing the inlet cooling water temperature.

Parametric analysis of domestic refrigerators using PCM heat exchanger

In the present study, numerical simulation of refrigeration cycle incorporated with a PCM heat exchanger is carried out. To this end, the refrigeration cycle without PCM has been simulated and then, the performance coefficients of the refrigerator in either with and without PCM are evaluated. The PCM heat exchanger is located in the refrigeration cycle, at a location after the condenser and before the expansion valve. The utilised PCM is N-Octadecane with fusion temperature of 27.5 °C. The simulation of heat exchanger is based on computational fluid dynamics (CFD) in which the flow inside the pipe is considered one-dimensional in the axial extension and PCM surrounding it, is considered two dimensional. Numerical simulation is carried out using MATLAB software. Simulation results show that utilizing PCM in refrigeration cycle of a refrigerator causes an improvement in the convection procedure and results a 9.58% increase in performance coefficient of refrigerator.

Thermal resistance capacity model for short-term borehole heat exchanger simulation with non-stiff ordinary differential equations

In the present study, a new thermal resistance capacity circuit for the heat transfer modeling in borehole heat exchanger with low computation time is developed. Generally, the thermal circuit models result in sets of ordinary differential equations which are solved numerically. The system of equations derived from the traditional thermal resistance capacity model (TRCM) are usually stiff and lead to unstable results unless for a very small time steps which can increase the computation time significantly. Meanwhile, the system of ordinary differential equations derived from the present model is non-stiff and there is no time step limitation for the stability of the results. It is shown that the present model yields accurate and stable results even for large time steps. Finally, the two-dimensional model is extended to the three-dimensional model. The results of the three-dimensional solution of the present model are in good agreement with the numerical results and experimental measurements reported in the literature.

Simulation of Heat Exchange in the Liquid Core of the Earth

Simulation of Heat Exchange in the Liquid Core of the Earth

Application of a modified algebraic heat-flux model and second-moment-closure to high blowing-ratio film-cooling and corrugated heat-exchanger simulations

The present paper outlines the application of the recently proposed heat-flux model (Mazaheri et al., 2017) to high blowing-ratio film-cooling and corrugated heat-exchanger simulations. Here, the focus is mainly on the accuracy of the predicted thermal fields, while to find out the sources of inaccuracy detailed analysis of the adopted second-moment-closure hydrodynamic model is provided. To do so, fundamental benchmarks which contain the dominant phenomena in the main cases are thoroughly analyzed to identify the anomalies. Then, the main cases including leading-edge film-cooling, antivortex film-cooling and corrugated heat-exchanger are investigated. The numerical predictions indicate that the erroneous evaluation of the surface temperature near the leading-edge stagnation-line, caused by constant Prandtl assumption, is markedly improved through a more accurate prediction of heat-fluxes within the impinging region. In this regards, for a high blowing ratio case, i.e. BR=2, the error in prediction of average adiabatic cooling effectiveness (η‾) is reduced more than 30% and 75% near the first and second row of cooling holes, respectively. In the antivortex film-cooling, the lateral diffusion of the coolant jet, which is essentially depending on heat-transfer between kidney vortices and surface, is reasonably predicted which results in more than 90% error reduction in prediction of η‾ in vicinity of the holes with respect to constant Parndtl assumption case. Also, more than 50% improvement can be observed in predicting the average surface temperature in the corrugated heat-exchanger case, which contains numerous recirculation zones, with respect to constant Prandtl simulations. The results demonstrate that the anisotropic hydrodynamic model may offer potentially improved predictions, however, in order to achieve high level of accuracy, adopting a proper heat-flux model is essential for the high blowing-ratio film-cooling cases which contain highly non-equilibrium flow characteristics.

A CFD-based simulation of fluid flow and heat transfer in the Intermediate Heat Exchanger of sodium-cooled fast reactor

A three-dimensional computational fluid dynamics (CFD)-based simulation for the Intermediate Heat Exchanger (IHX) of a pool-type sodium-cooled fast neutron reactor has been performed in this paper, which investigates the flow-field and temperature distributions of liquid sodium on both primary and secondary sides at full power conditions. Typically, some simplifications are applied to reduce the difficulty of computation and render the problem more tractable. A proposed method is that treat a number of tubes as porous media that replicates the pressure loss and heat transfer characteristics of the detailed model. The heat exchanger model of the ANSYS FLUENT code is used to analyze the heat transfer phenomena inside of the IHX and the resistance coefficients of porous media have been predicted by empirical relationships which vary with height and flow directions. Two separate models, with different size of inlet and outlet area for shell-side sodium, have been developed in this paper. By comparing the results from the different simulations, the model with larger inlet area for primary and non-uniform inlet velocity distribution of secondary sodium satisfies the design requirements with respect to the permissible upper limit of temperature difference and local radial velocity.

Efficiency analysis of borehole heat exchangers as grout varies via thermal response test simulations

Grout is normally used in borehole heat exchangers, in part for separating different water layers. Grout can also enhance heat transfer with the ground when it has high thermal conductivity. In this article, thermal response test results from simulations of borehole heat exchangers are presented. The work is undertaken to enhance understanding and predictions of the heat transfer effectiveness and energy efficiency of borehole heat exchangers as grout varies. The following borehole heat exchanger types are considered: coaxial, single U-tube and double U-tube. The results quantitatively describe the effect of grout on energy efficiency and indicate if it is reasonable to incur the higher costs of using grouts of high thermal conductivity to enhance borehole heat exchanger performance.

Optimization of circuitry arrangements for heat exchangers using derivative-free optimization

Optimization of the refrigerant circuitry can improve a heat exchanger's performance. Design engineers currently choose the refrigerant circuitry according to their experience and heat exchanger simulations. However, the design of an optimized refrigerant circuitry is difficult. The number of refrigerant circuitry candidates is enormous. Therefore, exhaustive search algorithms cannot be used and intelligent techniques must be developed to explore the solution space efficiently. In this paper, we formulate refrigerant circuitry design as a binary constrained optimization problem. We use CoilDesigner, a simulation and design tool of air to refrigerant heat exchangers, in order to simulate the performance of different refrigerant circuitry designs. We treat CoilDesigner as a black-box system since the exact relationship of the objective function with the decision variables is not explicit. Derivative-free optimization (DFO) algorithms are suitable for solving this black-box model since they do not require explicit functional representations of the objective function and the constraints. The aim of this paper is twofold. First, we compare four mixed-integer constrained DFO solvers and one box-bounded DFO solver and evaluate their ability to solve a difficult industrially relevant problem. Second, we demonstrate that the proposed formulation is suitable for optimizing the circuitry configuration of heat exchangers. We apply the DFO solvers to 17 heat exchanger design problems. Results show that TOMLAB/glcDirect and TOMLAB/glcSolve can find optimal or near-optimal refrigerant circuitry designs after a relatively small number of circuit simulations.

Simulation of Heat Exchange in Vessels with Helical Coils and Influence of Stirrer Position

AbstractAgitated vessels are used for a wide range of applications, especially in chemical industry. This work is a pilot study on the influence of the stirrer installation height on the local as well as on the total heat flux with an immersed helical coil in an agitated vessel. A simplified geometrical model is used for observation of fundamental effects in contrast to a full mathematical model. The local heat flux, however, was observed to demonstrate the heat flux disparity along the coil. An optimum is proposed with the aim to maximize total heat flux and minimize tempering time.

Measurement and simulation of heat exchange in fractured bedrock using inert and thermally degrading tracers

AbstractMulticomponent groundwater tracer tests were conducted in a well‐characterized field site in Altona, NY using inert carbon‐cored nanoparticles and a thermally degrading phenolic compound. Experiments were conducted in a mesoscale reservoir consisting of a single subhorizontal bedding plane fracture located 7.6 m below ground surface contained between two wells separated by 14.1 m. The reservoir rock, initially at 11.7°C, was heated using 74°C water. During the heating process, a series of tracer tests using thermally degrading tracers were used to characterize the progressive in situ heating of the fracture. Fiber‐Optic Distributed Temperature Sensing (FODTS) was used to measure temperature rise orthogonal to the fracture surface at 10 locations. Recovery of the thermally degrading tracer's product was increased as the reservoir was progressively heated indicating that the advancement of the thermal front was proportional to the mass fraction of the thermally degrading tracer recovered. Both GPR imaging and FODTS measurements reveal that flow was reduced to a narrow channel which directly connected the two wells and led to rapid thermal breakthrough. Computational modeling of inert tracer and heat transport in a two‐dimensional discrete fracture demonstrate that subsurface characterization using inert tracers alone could not uniquely characterize the Altona field site. However, the inclusion of a thermally degrading tracer may permit accurate subsurface temperature monitoring. At the Altona field site, however, fluid‐rock interactions appear to have increased reaction rates relative to laboratory‐based measurements made in the absence of rock surfaces.

Computational simulation of thermal hydraulic processes in the core and fuel assembly in the liquid-metal fast-breader reactor in the porous medium approximation

The results of numerical simulation of the sodium coolant flow in the fuel assembly with partial blocking of its cross section are presented. A comparison of the results obtained with experimental data confirmed the operability of the APMod module intended for simulating heat exchange processes in cores and heat exchange equipment of promising nuclear reactors.

A novel optimization framework for designing multi-stream compact heat exchangers and associated network

Despite the performance gains of heat exchangers by thermal-hydraulic optimization, many design approaches suffer from a long process of trial-and-error, limited practical problem formulation and poor robustness. This paper addresses those challenges and develops an optimization framework for designing multi-stream compact heat exchangers. The optimization framework consists of a multi-stream matching organization design with Pinch analysis principles on the heat exchanger network, fin selection and relevant layer pattern using multi-objective algorithm for the thermal-hydraulic modeling, and a field synergy optimization analysis for the temperature field of exchanger. There are compatible with each other by the mutual restriction of design parameters and the process requirements. Finally, by means of a segmented differential calculation, the designed temperature field of all the streams and layers can be obtained. Design capabilities of this optimization framework are investigated on two multi-stream heat exchangers for cryogenic air separation processes. The optimization results are compared with traditional design methods, proving that this framework not only satisfies the specific energy requirement, but also to some extent improves the heat transfer efficiency and reduces the fluid resistance. The developed optimization framework provides a flexible and robust method for numerical simulation and optimization design of multi-stream heat exchangers.

Numerical Simulation of Shell and Tube Heat Exchanger by using CFD

Numerical Simulation of Shell and Tube Heat Exchanger by using CFD

Mathematical modeling of unsteady response of plate and fin heat exchanger to sudden change in liquid flow rate

A mathematical simulation of plate fin and tube heat exchanger will be presented. The transient operation of the heat exchanger was carried out using general numerical model developed in [1]. Reynolds number of the water flowing inside the tubes varied in the range from 4000 to 12000. A detailed analysis of transient response was modeled for growth in the water volume flow in time.At first, heat transfer correlations for air and water were determined based on the experimental data. Unknown parameters appearing in the relationships for the Nusselt numbers on the air and water-sides were estimated using the least squares method. The power-type form of the relationship for the air-side Nusselt number was used while two correlations of different form were chosen for the water-side Nusselt number. The first is the exponential correlation, and the second form is similar to the relationships of Petukhov-Kirillov and Gnielinski. These correlations were used in the mathematical model of the heat exchanger for the simulation of its transient operation.The results of the numerical simulations of a heat exchanger using experimentally determined air and water-side heat transfer formulas for calculation of heat transfer coefficient were compared with the experimental data. Very good agreement of computation results (i.e. air and water temperature at the outlet of the heat exchanger) with the experimental data was obtained.

Numerical Simulation of Different Models of Heat Pipe Heat Exchanger Using AcuSolve

In this paper, a numerical simulation of heat pipe heat exchanger (HPHE) is computed by using CFD solver program i.e. AcuSolve. Two idealized model of HPHE are created with different variant of entry’s dimension set to be case 1 and case 2. The geometry of HPHE is designed in SolidWorks and imported to AcuSolve to simulate the fluid flow numerically. The design of HPHE is the key to provide a heat exchanger system to work proficient as expected. Finally, the result is used to optimize and improving heat recovery systems of the increasing demand for energy efficiency in industry.

Optimization of Heat Recovery for Shell & Tube Exchangers in Sulphur Granulation Unit of South Pars Fifth Refinery by Software, ASPEN B-JAC

Shell and tube heat exchangers are the most important tools in heat transfer process. Optimization efficiency of these tools is always the goal of designers. Now a day there are a lot of efficient methods for selecting the best heat exchanger, such as analytic and numerical methods that everyone has advantages and defects. For example, confront of jamming in calculations by receiving to the local minimums and errors during interruption quantities. Today by entering of simulation and design softwares in industries, the simulation of process tools is so simple. the procedure of studies in this thesis is in these steps: first simulation of sulfur solidification heat exchangers in ASPEN B-JAC software same as operation conditions and then evaluation the effects of changing the design parameters in tube bundle section such as number of passes, arrangement of tubes, number of baffles,…. the sulfur solidification package’ heat exchanger that it’s active fluid is demine water for cooling of package will be optimized till the rate of exchanged heat increases to 15 percent and pressure drop will not affect the operation conditions. The most important note in the correction of tube bundle is that the heat exchanger should be out of service and stopping of production, on the other hand changing in shell of heat exchanger needs to change the piping system and redesign of supports that will spend a lot of time for shut down of plant, so it is out of order for this thesis and optimization of tube bundle will be done.

A numerical model for transient simulation of borehole heat exchangers

A numerical model is developed to simulate the borehole heat exchanger both in the short and long time. In this regard, the computational domain is divided into the inside and outside borehole regions. A two-dimensional finite volume method is implemented in a cylindrical coordinate system for modeling of the outside borehole. Also, a thermal resistance-capacity model is presented for the borehole cross section. This model is extended to take into account the fluid transport through the U-tube and the temperature variation of the borehole components with depth. The governing equations of the two regions are solved iteratively in each time step. The proposed model is verified with the previously reported numerical, experimental and analytical results. Furthermore, the ability of the model in predicting the short-time response is evaluated in comparison with a three-dimensional computational fluid dynamics (CFD) model with a fine grid. The results show that the proposed model has a good performance in the prediction of the thermal response of the borehole in a wide time interval from 1 min to over 10 years. Moreover, the effects of time step size and number of capacity nodes on the results are investigated.