Parameters Of Heat Exchanger Research Articles

Heat Transfer through Wire Cloth Micro Heat Exchanger

The main objective of this study is to calculate and determine design parameters for a novel wire cloth micro heat exchanger. Wire cloth micro heat exchangers offer a range of promising applications in the chemical industry, plastics technology, the recycling industry and energy technology. We derived correlations to calculate the heat transfer rate, pressure drop and temperature distributions through the woven structure in order to design wire cloth heat exchangers for different applications. Computational Fluid Dynamics (CFD) simulations have been carried out to determine correlations for the dimensionless Euler and Nusselt numbers. Based on these correlations, we have developed a simplified model in which the correlations can be used to calculate temperature distributions and heat exchanger performance. This allows a wire cloth micro heat exchanger to be virtually designed for different applications.

Solution of conjugate problem in a conical coil heat exchanger

Today, coil heat exchangers are widely used in various industries. A large number of works have been published devoted to the study of the characteristics of helical coil heat exchangers. According to the authors, conical coil heat exchangers have higher efficiency compared to helical ones. The article investigates the influence of the geometric parameters of conical coil heat exchangers on their effectiveness. The object of study is a conical coil heat exchanger with different tube diameters of the inner coil (di = 13, 15, 17 mm) and various number of turns (N = 6, 10, 14). Modeling was carried out in the Ansys Fluent software package. For each combination of the parameters, data were obtained on the temperature and velocity of the coolant at the outlet. It was found that a change in the number of turns by a factor of 2.3 leads to an increase in the temperature of the heated fluid by an average of 9.7 ° C. The effect of changing the diameter of the inner coil is non-linear.

Effects of the Circuit Arrangement on the Thermal Performance of Double U-Tube Ground Heat Exchangers

Given that the issue of variations in geometrical parameters of the borehole heat exchanger (BHE) revolves around the phenomenon of thermal resistance, a thorough understanding of these parameters is beneficial in enhancing thermal performance of BHEs. The present study seeks to identify relative changes in the thermal performance of double U-tube BHEs triggered by alterations in circuit arrangements, as well as the shank spacing and the borehole length. The thermal performance of double U-tube BHEs with different configurations is comprehensively analyzed through a 3D transient numerical code developed by means of the finite element method. The sensitivity of each circuit configuration in terms of the thermal performance to variations of the borehole length and shank spacing is investigated. The impact of the thermal interference between flowing legs, namely thermal short-circuiting, on parameters affecting the borehole thermal resistance is addressed. Furthermore, the energy exchange characteristics for different circuit configurations are quantified by introducing the thermal effectiveness coefficient. The results indicate that the borehole length is more influential than shank spacing in increasing the discrepancy between thermal performances of different circuit configurations. It is shown that deviation of the averaged-over-the-depth mean fluid temperature from the arithmetic mean of the inlet and outlet temperatures is more critical for lower shank spacings and higher borehole lengths.

Optimal design of organic Rankine cycles for exhaust heat recovery from light-duty vehicles in view of various exhaust gas conditions and negative aspects of mobile vehicles

The organic Rankine cycle (ORC) is a promising method of recovering the exhaust heat of the internal combustion engine (ICE). However, the off-design exhaust conditions and the negative effects (such as increased backpressure and added weight) of the ORC installation onto vehicles greatly deterioratetheperformanceof ORC applied on mobile vehicles. In this paper, the ORC thermodynamic model with an integrated plate heat exchanger model is developed to evaluate the effects of sizing the heat exchanger and designing the ORC operating conditions on the thermodynamic performance of the ORC system. Considering various major exhaust conditions and the negative impacts of ORC system installation on vehicles, an optimal ORC system design strategy is proposed to maximize the net output power. The optimum geometric parameters of heat exchangers and ORC operating conditions are simultaneously designed through a mixed integer nonlinear programming problem. The proposed design strategy is compared with the design method without considering negative effects and the design method only based on one major engine operating point. The comparison results indicate that the proposed design strategy increases the weighted net output power and the proposed design strategy can ensure that the ORC works normally in various exhaust conditions. Among all the operating parameters, the size of the heat exchanger (two geometric parameters) is the major factor affecting the performance of ORC. These findings highlight the importance of considering various exhaust conditions and the negative impacts of vehicle-mounted ORC during the design procedure.

АНАЛИЗ РАБОТЫ ВОЗДУШНОГО ТЕПЛООБМЕННИКА, ПРИМЕНЯЕМОГО В ПРОИЗВОДСТВЕ МЕТИЛТРЕТБУТИЛОВОГО ЭФИРА

The operating parameters of the air heat exchanger used at the stage of cooling the butadiene fraction in the production of methyl tert-butyl ether are analyzed. The insufficient efficiency of its operation in the summer period has been revealed. The solution is to make changes to the design of the heat exchanger. Installing an air heat exchanger with a larger heat transfer surface is not economically feasible

АНАЛИЗ РАБОТЫ ВОЗДУШНОГО ТЕПЛООБМЕННИКА

The operating parameters of the air heat exchanger used at the stage of cooling the butadiene fraction in the production of methyl tert-butyl ether are analyzed. The insufficient efficiency of its operation in the summer period has been revealed. The solution is to make changes to the design of the heat exchanger or to install an air heat exchanger with a larger heat transfer surface.

THERMO-HYDRAULIC OPTIMIZATION OF PLATE HEAT EXCHANGER IN ORC FOR A RATED HEAT LOAD

The efficiency of an Organic Rankine Cycle which utilizes low-grade waste heat or heat from renewables like solar depends on the performance of its condenser infinite surface area, the infinitesimal temperature difference is needed for effective heat transfer. Practically, neither are possible in a heat exchanger and therefore designers tend to improve effectiveness at a finite temperature difference of the two fluid streams and finite areas that are practically possible, based on other design constraints like space. The present work aims to optimize geometrical parameters of a plate heat exchanger that meets fixed heat load so as to minimize the area of heat transfer and pressure drop. An evolutionary genetic algorithm is used with a single objective function combining the dual objectives area and pressure drop by giving appropriate weights to these functions. Optimization is carried out to find optimal geometrical parameters width, length, the distance between plates, and enlargement factor for minimizing the area and also the pressure drop. Also, different weights are given to the two objective functions to compare optimal design variables for varying requirements of objective functions and optimal values of geometrical parameters width, length, the distance between plates and enlargement factor are determined.

Modeling of characteristics of heat exchangers of heat supply systems in variable operating modes

Heat exchangers used in heating systems usually operate under conditions of variable flow rates and temperatures of heat carriers. However, the theory for calculating the variable modes of operation of such devices is based on the use of constant parameters of heat exchangers. At the same time it is clear that the parameter of the heat exchanger can be affected by all quantities that determine the change of the heat transfer coefficient. In addition, the groups of heat exchangers with a tied supply of heat, i.e. with redistribution of the heat flow in a variable mode of operation, are used. A new method for calculating the variable modes of operation of heat points with a tied heat supply has been developed. The method of mathematical modeling defines the dependencies that determine the change in the heat exchanger parameters in variable operating modes. The obtained expressions can be used to configure programmable regulators which will allow the correction of inefficient modes of operation of the heating system.

Increasing heat efficiency by changing the section area of the heat transfer pipelines

On the territory of our republic, individual boilers are widely used for heating many social facilities in the winter season. The efficiency (efficiency) of these heating boilers is only 70-75%. Sustainable and efficient use of fossil fuels is now becoming a problem not only in Uzbekistan, but throughout the world. In recent years, the results of expert research on the use of solid, liquid and gaseous fuels in heating boilers show that in many countries there is a shortage of fuel and problems with the supply of natural resources to these countries. Of course, given the fact that the process of burning fossil fuels depends on the cross-sectional area of heating boilers, it is necessary to develop recommendations for creating more energy-efficient use of methods to reduce fuel consumption or resource conservation. In our republic, a number of scientific works are consistently carried out to create resource-saving capacities for heat transfer pipelines. In particular, the main content of the dissertation is the development of the introduction of the latest modern scientific methods to increase the efficiency of heating boilers by improving the method of calculating resource-saving heat transfer pipelines. The article presents methods for determining the heat transfer parameters of heat exchangers in laboratory conditions, as well as methods for analyzing the results.

Novel operation strategy for a gas turbine and high-temperature KCS combined cycle

This paper designs a high-temperature Kalina cycle system (KCS) to recover a gas turbine (GT) waste heat. A novel methodology of predicting off-design performance of GT-KCS combined cycle is presented by introducing geometric parameters of heat exchangers. The inlet guide vane of GT compressor operation strategy is applied in GT. Novel operation strategies named modified sliding pressure operation (MSPO) and novel modified sliding pressure operation (NMSPO) are proposed for KCS. The MSPO uses a fixed KCS turbine inlet temperature and an optimized ammonia concentration at KCS separator inlet under GT part-load conditions, while the NMSPO adopts an optimized ammonia concentration at KCS separator inlet and a fixed temperature difference between KCS turbine inlet and GT exhaust. The results show that the optimal ammonia concentrations at KCS separator inlet under the MSPO and NMSPO decrease with declining GT load. The MSPO has the highest bottoming KCS thermal efficiency among the sliding pressure operation (SPO), MSPO and NMSPO. The NMSPO recovers the most heat from GT exhaust, resulting in the highest KCS net power and GT-KCS thermal efficiency. The NMSPO recommended as the optimal operation strategy could produce 20.72 kW and 25.75 kW more net power than the MSPO and SPO, respectively.

Research on the feasibility of compressed carbon dioxide energy storage system with underground sequestration in antiquated mine goaf

Energy storage has recently attracted a great attention as a promising way to utilize the fluctuating renewable energy. This paper proposes a novel carbon dioxide energy storage system, where the energy is stored and released in antiquated mine goaf with a simultaneous benefit of carbon dioxide storage. Different system configurations and their performances are evaluated based on solving steady-state thermodynamic models. Meanwhile, a parametric analysis considering the seepage process is carried out to examine the effect of key factors including heat exchange parameters, device efficiencies, design pressures, reservoir parameters and gas purities. Besides, a detailed assessment of the system performance in different energy storage cases is conducted to investigate the effects of economic factors. The results show that the system performance can be improved with less compression stage and more expansion stage. The Round Trip Efficiency can be decreased with high Green Energy Index with the increase in reservoir permeability and ambient temperature. The economic analysis suggests that system operates with energy storage can make profit in most step tariff existing cases. The standalone energy storage system shows economic advantage only when the carbon taxes are lower than 47 USD/t and 68 USD/t compared to the integrated system and standalone carbon dioxide storage system, respectively.

Parametric Analysis of a Plain-Fin Compact Heat Exchanger for a Small-Scale Gas Turbine

The influence of the thermal parameters of a Plain-Fin Compact Heat Exchanger on its performance is examined in this paper. The objective of this work is to analyse the effect of the different flow and geometric parameters on the output performance of a plain fin compact heat exchanger (PFCHE) designed to be used on a small-scale gas turbine and how these parameters can be used for the optimisation of PFCHEs.In this work, we examined the effects of the variation of input parameters of a plain-fin compact heat exchanger (fin length, fin height, fin thickness, mass flow rate of air and turbine exhaust gas) on the output performance of the heat exchanger (Overall heat exchanger efficiency, fin heat transfer efficiency and the outlet temperatures). The analytical expressions for the outlet temperatures and heat exchanger efficiencies were derived and analysed. Then the derived model was designed and simulated using CFD codes. Also, from the derived expressions, the performance model of the heat exchanger was programmed for analysis. From the results, it shows that the effectiveness (e-value), fin length, fin height and mass flow rates of the gases influence performance of a plain-fin compact heat exchanger. A 50% reduction in fin height can cause as much as an 18% increase in the fin efficiency of the heat exchanger. While a 50% increase in the effectiveness value can cause as much as a 40% increase in the outlet temperature.

Sınırlı Deneysel Verilerle Yapay Sinir Ağı Kullanılarak Chevron Tipi Isı Değiştirici için Termal Modelleme ve Performans Analizi

The problem of heat exchange between two or more fluids at different temperatures is one of the most important and most common problems of engineering applications. In order to solve this problem efficiently, the transfer of energy between two liquids at different temperatures is carried out by heat exchangers. Heat exchangers increase the energy efficiency as they can transfer the energy contained in the system to another part of the process instead of just pumping and wasting. A plate heat exchanger, a variant of heat exchanger, use a series of thin plates to transfer heat between two liquids. Thermal modelling of the heat exchanger is important due to determination of the outlet temperature of fluids depending on the system parameters. In this paper, an artificial neural network (ANN) model is used to simulate the thermal performance of a chevron type plate heat exchanger using water as working fluid. The ANN algorithms have a widely usage in thermal analysis studies of heat exchangers such as modelling of heat exchangers, estimation of heat exchanger parameters, estimation of phase change characteristics in heat exchangers and control of heat exchangers. The outer temperatures of the water are estimated depending on the cold water mass flow rate, inlet hot water temperature and inlet cold water temperature by using limited experimental data. Then the experimental results and the estimated results are compared for testing the accuracy and reliability of the developed algorithm. The results show that the experimental and estimated results have a good agreement. The developed network structure estimates the outlet temperatures with 2.58 % and 1.80 % for hot and cold water, respectively. In addition, the predicted performance of the network developed by applying untested input parameters was examined. Estimation accuracy was compared with theoretically calculated output temperatures by thermal analysis using the same inputs. According to the obtained results, it is seen that the theoretical results and prediction results are compatible with each other in determining the output for new inputs and the reliability of the developed network is proved in different inputs according to this result. After that, experimentally not obtained variations of the heat transfer rate, overall heat transfer coefficient and energy efficiency are determined depending on the inlet temperatures and mass flow rate of cold water.

Study on Estimating Heat Exchanger Parameters and Internal State of an Adsorption Chiller

Study on Estimating Heat Exchanger Parameters and Internal State of an Adsorption Chiller

Simulation, equipment performance evaluation and sensitivity analysis as a comprehensive parametric study of sulfur recovery unit

AbstractThe sulfur recovery unit based on modified Claus process with split flow was simulated, so that the validation results showed satisfactory agreement with the refinery data. In this study, comprehensive investigation was carried out on various parameters of the unit. Concentration changes of compounds were investigated as the process stream passes along various equipment. Composite curves were generated, and the minimum approach temperature was calculated as one of the operational parameters of heat exchangers. Fluid condensation probability was investigated in catalytic reactors. The recovery of sulfur and the amount of sulfur production were calculated by process streams passing along catalytic reactors and condensers respectively. The most influential performance parameters including the fuel flow rate, combustion air flow rate, and bypasses fraction were considered as sensitivity analysis parameters, and their variation influences were investigated on the recovery of sulfur, the ratio of hydrogen sulfide to sulfur dioxide, the amount of produced steam, and the furnace outlet stream temperature. The optimal amounts for fuel flow rate and inlet air flow rate were calculated with the values of 0 and 202 mol/s, respectively, and according to the results, 15% of the mainstream flow rate gives the optimum amount of bypass fraction.

Numercial analysis on the thermal performance of capillary heat exchange system in metro running tunnel

Abstract During the operation of the capillary heat exchange system in the metro tunnel, the pipe length, pipe spacing and air velocity have different effects on the heat transfer effect and show certain rules. Taking Kunming as an example, a single-factor analysis method was used to establish multiple-capillary model, and the variation of different influencing factors in the heat transfer process was obtained. On this basis, a single-capillary model was established to analyze the thermal interference variation of the pipe spacing between the two models. Under the condition of ensuring the capillary outlet water temperature and heat flux, the relevant parameters of the capillary heat exchanger were optimized. The results show that the pipe length of the capillary heat exchanger should be kept within 3–5 m, the pipe spacing is maintained at 20–30 mm, and the capillary heat exchanger of each set can be operated in parallel to ensure that heat exchanger have better heat transfer performance. During the system stop running, the air velocity in winter and summer has different effects on the recovery of surrounding rock.

Modeling of the alloy solidification modified by refractory nano-size particles

The authors propose a mathematical model of non-equilibrium crystallization of a binary alloy with modifying refractory nano-sized particles. The model describes heat transfer processes, as well as heterogeneous nucleation and crystallization of two components of the melt. The nucleation of the crystalline phase occurs on the surface of the nanoparticles during the supercooling of the melt. The liquidus temperature in the melt depends on the concentration of the dissolved alloying component, which is determined by the non-equilibrium lever equation. When the metal is cooled down to the eutectic temperature, the solidification of the alloy α-phase takes place, followed by solidification of β-phase if the cooling continues. The growth rate of the crystal phase is proportional to the supercooling value. The volume of the solid phase formed around the nucleus determines the size of the grain structure in the solidified alloy. The article depicts numerical simulation of aluminum melt solidification in cylindrical ingot mold, carried out by the authors. The parameters of heat exchange of the melt-mold system with the environment are available from experiments. The conditions of nucleation, crystallization rate, supercooling and solidification time prove to significantly differ within the cast. The area with the finest structure of the solidified metal is located near the wall of the mold. The calculated size of the grain structure in the casting is consistent with the experimental results. Comparing the results of numerical calculation with the data of a physical experiment on measuring the temperature during solidification of the melt and studying the properties of the cast confirm reliability of the proposed model.

The influence of main parameters of regenerative heat exchanger on its energy efficiency

The influence of various parameters of stationary switching regenerative heat exchangers used for ventilation on its thermal efficiency was studied. Considered are the geometric (length, diameter and wall thickness of a single equivalent nozzle channel), thermophysical (density and heat capacity of the nozzle material) and operation (air flow through the regenerator and the time of one stage of accumulation/regeneration of thermal energy) parameters.

Effectiveness evaluation for geothermal heat recovery in closed mines of Donbas

The study aims to develop a method of effectiveness evaluation for geothermal heat recovery in closed mines of Donbas using relations of heat transfer theory in rocks and fluids. Geothermal heat is proposed to recover using coaxial geothermal probes to be installed in flooded closed mines. As a result of evaluation and ranking, five top promising sites with the highest expected performance indicators among 27 closed mines located in Donbas have been identified. The evaluation method takes into account geological settings, mine condition, and heat exchange parameters of the probe with mine water. The locations of the most promising sites were found to correlate with the areas of higher geothermal flux and the deeper mines. The results obtained can be used in feasibility studies on installation and operation of geothermal probes in closed mines.

Simulation of the effectiveness of longitudinal rectangular fins on the efficiency of the double pipe heat exchanger

In this article, a mathematical simulation of a double pipe heat exchanger is carried out, having the longitudinal rectangular fins with the dimension of (2*3*1000) mm, mounted on the outer surface of the inner tube of the heat exchanger. In this paper, the advantage of using of that type of fins and its effect on the effectiveness of the heat exchanger are studied with the help of the computer program. The carried out research allowsmaking the calculation to find the optimum design parameters of heat exchangers. The outer tube diameter is (34.1mm) while the inner tube diameter is (16.05mm). The tubes wall thickness is (1.5mm) and the model length was (1 m). The hot water is flowing through the inner tube in parallel with the cold water that passing the outer tube. The hot and cold water temperature at the inlet is (75°C & 30°C) respectively. The mass flow rate inside the central pipe is (0.1 kg/s) while the annular pipe carrying (0.3 kg/s). In the present work, the program ANSYS Workbench 15.0 was used to find out the results of heat transfer as well as the behavior of liquids inside the heat exchangers.