Exchanger Design Research Articles

Finite Time Analysis of Endoreversible Combined Cycle Based on the Stefan-boltzmann Heat Transfer Law

This work examines endoreversible combined cycle based on finite time thermodynamic concepts. In this study, the proposed system is cascade combined cycle have three heat sources. Effects of irreversibility due to the heat transfer at the system boundaries are considered. The study is based on Stephen Boltzmann's heat transfer laws. Based on finite size, this research analyzes the system based on first and second law thermodynamics. Dimensionless power, efficiency, and entropy generation are calculated based on the dimensionless variables. Dimensionless variables are primary and secondary temperature ratios, common temperature ratio, and the ratio of thermal conductance of each heat exchanger. The effects of dimensionless variables on thermodynamic criteria are examined. Also, optimization is performed base on different criteria such as dimensionless power, energy efficiency and entropy generation by genetic algorithm. The optimization results show that the maximum dimensionless power, the maximum energy efficiency and minimum entropy generation are 0.035092393, 61.09% and 8.132 E-07, respectively. The results of this study are very close to the actual results. New thermodynamic criteria bring systems closer to better conditions. Furthermore, the heat transfer mechanism and heat transfer law greatly affect performance and thermodynamic criteria another. These results are used in the design of radiant heat exchangers.

Design and simulation of a new PCM heat exchanger for domestic hot water and air temperature control

Based on previous experiences which have proven the efficiency of PCM heat exchangers for air temperature control, we designed and simulated new PCM heat exchanger structures made of multiple PCM layers sandwiched between loading and discharge layers. By circulating air or water in the discharge circuit, these heat exchangers can be used for heating air or water, respectively. For both use cases, a three-dimensional analysis of the phase change and calculations of the charge/discharge powers were performed for the fusion and solidification processes. We obtained heating discharge powers ≥ 2.6 kW/m3 for 8 hours for air and ≥ 65 kW/m3 for 13 minutes for water with a respective total storage capacity of 28 kWh/m3 and 37 kWh/m3. The heat extraction of air and water flows and their time dependence are discussed according to the percentage of liquid PCM and the temperature profile of the discharge flow inside the heat exchanger.

АНАЛИЗ МЕТОДОВ ПРОЕКТИРОВАНИЯ ОХЛАДИТЕЛЕЙ СИСТЕМ ОБЕСПЕЧЕНИЯ ТЕПЛОВОГО РЕЖИМА СУДОВЫХ ЭНЕРГОУСТАНОВОК

The design methods for shipboard shell-and-tube oil and water coolers are presented. As a result of the review, it was revealed that currently there is no systematic and complete methodological support for the integrated computer-aided design of ship heat exchangers (CAD SHE), which in turn would be integrated into the CAD / CAM / CAE system and later on into the production preparation. From the analysis it follows that not all operating conditions of ship power plants are provided with an oil cooler. This is due to the fact that the surface of the cooler and its flow characteristics were calculated only on the nominal mode, and other operating characteristics were not evaluated. The complexity of the work of ship oil and water coolers lies in the fact that the parameters of the heat load on these devices change, the temperature and salinity of the outboard water change depending on the navigation area. Determining the effect of the oil cooler on changing the power of the power plant when the characteristics of the cooling coolant (seawater) change, such as initial temperature, flow rate, salinity, without additional testing in each mode is difficult. It is also difficult to change the salinity and temperature of the seawater during the tests. Thus, the designer of the power plant does not know how the mode of its operation will change when the ship (ship) in the World Ocean is different. This indicates the need to improve the methods of thermal and hydrodynamic calculations of SHE with their integration into the overall design system. Under these conditions, the problem of using integrated CAD SHE is of particular relevance.

Optimal design of plate-fin heat exchanger for improving core volume and heat transfer performance

Optimal design of plate-fin heat exchanger for improving core volume and heat transfer performance

A novel 2-D ring-tubes model and numerical investigation of heat and moisture transfer around helix ground heat exchanger

As for the helix ground heat exchanger, a novel 2-D ring-tubes heat and moisture transfer model was built in this paper for the sake of efficiency and convenience. And a miniature model experiment was conducted to verify the correctness of the model. Four different soil initial water content conditions were simulated with the established model. In addition, the novel model was compared with the pure heat transfer model of which there is no moisture migration. The results indicate that increasing the initial soil water content can increase heat transfer capacity of the exchanger effectively. Three different heat transfer stages can be divided for the helix ground heat exchanger in the water flow direction. And during the design of exchanger, the proportion of entrance and exit stages should be increased for the sake of larger heat exchange capacity. Moreover, some effective measures can be conducted to increase soil water content near the entrance stage in order to avoid excessive reduction of soil water content in this area. There is a critical initial water content θcr for heat release condition to determine the applicability of the pure heat transfer model, and it’s 0.111 m3/m3 for the typical mudstone soil in Chongqing.

Characterisation of the heat transfer in displaced enhancement devices by means of inverse problem approach applied to IR images

ABSTRACT Displaced enhancement devices are inserts positioned inside pipes that increase the heat transfer rate. This study presents an original application of an inverse analysis technique to experimental infrared temperature data to estimate the local convective heat flux for forced convection flow in a pipe in which this kind of device is present. Butterfly-shaped inserts have been investigated to determine their local and global thermal performance. The insert produces a distortion in the velocity profile that causes an irregular distribution of the wall heat flux along the circumferential coordinate. Several studies have investigated displaced enhancement devices, but they generally considered only the overall heat transfer performance. The present work aims to fill this gap by presenting and testing an experimental procedure for estimating the local convective heat flux in pipes equipped with this type of insert. The experimental results obtained in the present investigation are useful for the design of heat exchangers for processes in which product temperature must be carefully controlled (e.g. pharmaceutical and food industries). These types of devices induce significant spatial variation of the heat flux, and quantitative data of this aspect is of primary importance.

Peripheral Heat Transfer Coefficient during Flow Boiling: Comparison between 2-D and 1-D Data Reduction and Discussion about Their Applicability

This paper presents a critical analysis of possible data reduction procedures for the evaluation of local heat transfer coefficient during flow boiling experiments. The benchmark method using one-dimensional (1-D) heat transfer in a heated tube was compared to a new data reduction method in which both radial and circumferential contributions to the conductive heat transfer inside a metal tube are considered. Using published experimental flow boiling data, the circumferential profiles of the wall superheat, inner wall heat flux, and heat transfer coefficients were independently calculated with the two data reduction procedures. The differences between the two methods were then examined according to the different heat transfer behavior observed (symmetric or asymmetric), which in turn was related to the two-phase flow regimes occurring in a channel during evaporation. A statistical analysis using the mean absolute percentage error (MAPE) index was then performed for a database of 417 collected flow boiling data taken under different operating conditions in terms of working fluid, saturation temperature, mass velocity, vapor quality, and imposed heat flux. Results showed that the maximum deviations between the two methods could reach up to 130% in the case of asymmetric heat transfer. Finally, the possible uses of the two data reduction methods are discussed, pointing out that the two-dimensional (2-D) model is the most reliable method to be employed in the case of high-level modeling of two-phase flow or advanced design of heat exchangers and heat spreader systems.

Multiphysics field coupling simulation for shell-and-tube heat exchangers with different baffles

Baffles are important components to control shell-side flow distribution and enhance heat transfer for shell-and-tube heat exchangers (STHXs). Based on multiphysics field coupling simulation, thermal–structural performance was studied for three types of STHXs with different baffles including segmental baffles, plain helical baffles and fold helical baffles. The results show that zigzag flow appears in STHXs with segmental baffles, and flow behavior is helical pattern in STHXs with helical baffles. Especially, much vortex and high velocity are generated in STHXs with fold helical baffles, where the shell-side pressure drop and Nussult number are the highest, and thermal enhancement factor (TEF) to evaluate thermal–hydraulic performance is also the largest. Although higher von-Mises stress distributes on the tube bundle, results of stress linearization at dangerous location in elastic stage show that membrane stress and sum of primary stress and secondary stress are both within range of corresponding stress intensity. Therefore, the comprehensive thermal–structural performance of STHXs with fold helical baffles is the best. The research can have a degree of theoretical guidance for design and choice of heat exchangers.

Design and Development of a Trapezoidal Plate Fin Heat Exchanger for the Prediction of Heat Exchanger Effectiveness

A trapezoidal plate-fin exchanger has been designed and developed, and an experimental test rig fabricated to test the plate fin heat exchanger. The heat exchanger was constructed in a 5 layer cross-flow arrangement. The length of the trapezoidal fins between the layers were 380mm and its height, thickness, top width and bottom width were 40mm, 0.5mm, 20mm, and 80mm respectively. A hot fluid test has been conducted to determine the thermo- hydraulic performance of the given heat exchanger at different mass flow rates (4.975 kg/s to 9.751 kg/s) at a hot inlet temperature of 369K. The values of the effectiveness obtained were plotted against the corresponding values mass flow rate to compare and evaluate the variation of the results. Thus, the performance of a heat exchanger with trapezoidal fins has been studied experimentally and it has been determined that: the mass flow rate of the fluids is proportional to the temperature drop of the fluids after passing through the exchanger. Also Increase in mass flow rate, increases the effectiveness of the heat exchanger. Improper insulation influenced heat transfers in heat exchanger cores and caused energy imbalance in the heat exchanger. This study suggests that the calculated effectiveness of 0.98 using trapezoidal plate fin heat exchanger result provides benchmark data to evaluate and predicts the performance of a plate-fin heat exchanger with trapezoidal fins for energy recovery application. Keywords: Heat exchanger development; trapezoidal fin, effectiveness, heat exchanger analysis; hot and cold fluids DOI : 10.7176/JETP/9-8-03 Publication date: November 30 th 2019

Calculation of the Geometrical Parameters of the Heat Exchanger Type “Pipe in Pipe” with a Spiral-Coiled Channel

The designs of the modern type of twisting devices include spring-twisted channels, which to use as innovative heat exchange elements of tubular apparatuses. The paper presents a method for determining the equivalent diameter of the tube and intertubular space in a heat exchanger apparatus of the type “tube-in-tube” with a spring-twisted channel which composed of tori closely adjacent to each other. Based on the integral calculus, formulas are obtained for calculating the equivalent diameters of the tube and annular space in a tube-in-tube apparatus with a spring-twisted channel. The results of experiments on heat transfer are generalized by criterial equations, in which the equivalent diameter is used as the characteristic size. It is shown that the equivalent diameters of the examined channels differ from each other by no more than 5%. The results of this work can be used in the design and calculations of promising heat exchangers with intensified heat transfer.

The Optimal Design of Welded Plate Heat Exchanger with Intensified Heat Transfer for Ammonia Synthesis Column

The modification of heat exchanger networks of industrial enterprises targeting energy saving solutions requires proper heat transfer equipment. The estimation of the optimal design parameters for heat exchangers requires reliable mathematical models for the description of the thermo-hydraulic processes inside the channels, and adequate optimisation methods. This work proposes the novel mathematical model and optimisation algorithm for the selection of welded plate heat exchanger (WPHE) operating in ammonia synthesis column. It enables finding the optimal design with the specified shape of the corrugated plates, distribution of flows and number of plates and passes. The developed algorithm is implemented in Mathcad software. The application of the proposed approach is illustrated by example in which the resulted WPHE with the cross flow in one pass and overall symmetric counterflow of streams has shown a reduction of heat transfer area 25 % compared to previously tested in industry WPHE with unsymmetric passes arrangement.

Thermal-Hydraulic Studies on the Shell-and-Tube Heat Exchanger with Minijets

In this paper a patented design of a heat exchanger with minijets, with a cylindrical construction is presented. It is followed by the results of its systematic experimental investigations in the single-phase convection heat transfer mode. Based on these results, validation of selected correlations (coming from the literature) describing the Nusselt number was carried out. An assessment of the heat exchange intensification level in the described heat exchanger was done through the comparison with a shell-and-tube exchanger of a classical design. The thermal-hydraulic characteristics of both units were the subjects of comparison. They were constructed for the identical thermal conditions, i.e., volumetric flow rates of the working media and the media temperatures at the inlets to the heat exchanger. The experimental studies of both heat exchangers were conducted on the same test facility. An increase in the heat transfer coefficients values for the minijets heat exchanger was observed in comparison with the reference one, whereas the generated minijets caused greater hydraulic resistance. Experimentally confirmed intensification of heat transfer on the air side, makes the proposed minijets heat exchanger application more attractive, for the waste heat utilization systems from gas sources.

The Effect of Compressible Flow on Heat Transfer Performance of Heat Exchanger by Computational Fluid Dynamics (CFD) Simulation

As a part of vehicle thermal management, water-cooled intercoolers play an important role in engine efficiency. The incompressible simulation model was usually applied to estimate the performance of water-cooled intercoolers. In this paper, the computational fluid dynamics (CFD) compressible model is taken to analyze more accurate prediction models. The rate of section change, heat exchange, and the surface friction coefficient are used as the comparison basis of the compressible flow model and incompressible model on the pressurized air side of the water-cooled intercooler. By comparing the simulation results of the air side, it was found that the compressible simulation is closer to the experimental value than the incompressible simulation. Compared with the experiment, the compressible model heat transfer maximum value of deviation is 6.5%, and the pressure loss maximum deviation is 7.5%. This provides guidance to optimize the design of heat exchangers, in order to save on costs and shorten development times.

Material of High Temperature Heat Exchanger in Fuel Cell System

Solid Oxide Fuel Cell (SOFC) systems are considered to be the most competitive green energy technology in the future because of their high energy conversion rates, low emissions and multiple fuels available. High temperature heat exchanger plays an important role in the system. The process system requires the design of heat exchangers to achieve operating temperature (700-800 °C), cross-temperature (>500°C) and low pressure drop in the smallest space, which is a challenge to the choice of materials. In this paper, the performances (Tensile strength, yield strength, linear expansion coefficient, and thermal conductivity coefficient) and price of high temperature alloy materials (304H, 310S, incoloy800H and Incoloy625) in the current application environment are compared. The applicable material (310S) of heat exchanger is determined. It provides a material basis for research and development of high temperature heat exchangers in SOFC system and commercialization.

Study on heat transfer performance of geothermal pile-foundation heat exchanger in GSHP system

In order to study the heat transfer performance of geothermal pile-foundation heat exchanger in ground source heat pump system (GSHP), the physical models of pile-foundation heat exchanger and heat exchanger group were established. The heat transfer processes of pile-foundation heat exchanger and heat transfer performance was analyzed both in cooling and heating mode. To carry out the simulation of heat transfer process for 3×3 energy piles, an office building located in Nanjing was introduced. The all-year dynamic building load was calculated with DeST, including the cooling period from June to September, the heating period from December to March and two recovery periods. After ten year’s running, the average soil temperature increases in non-equilibrium condition. Study results are approximate to the actual situation and can be used as theoretical basis for the design and application of pile-foundation heat exchanger in GSHP system.

Heat transfer from the collective finning of pipes in heat exchangers under asymmetric boundary conditions

The solution of the problem of the heat flux from the surface of collective finning at various temperatures of its ends is given. The obtained analytical formulas allow giving a quantitative estimate of the influence of the asymmetry of the boundary conditions on the heat transfer through the finned heat exchange surface. Calculated dependencies can be used in the design of high-efficiency heat exchangers for air conditioning, ventilation, and heating systems. The presented results can be especially useful under real operating conditions of heat exchange surfaces. This, in turn, ensures the safe and reliable operation of the building’s engineering systems as a whole.

ВИХРЕВАЯ РАЦИОНАЛЬНАЯ (ЭНЕРГОСБЕРЕГАЮЩАЯ) ИНТЕНСИФИКАЦИЯ ТЕПЛООБМЕНА В НЕКРУГЛЫХ КАНАЛАХ СУДОВЫХ ТЕПЛООБМЕННЫХ АППАРАТОВ

High demands placed to the quality of ship heat exchangers are determined by their outer dimensions and weight, power consumption for heat-transfer agents circulating, size of heat loading, operational availability, processability and manufacturing profitability. Lamellar-ribbed heat exchangers most successfully meet the listed requirements. Two methods of generating vortices (in the case of flow around poorly streamlined bodies and at divergent-convergent segments) in the wall layer of currents in rectangular ducts are realized in 10 plate-fin interrupted (PFTsm) heat transfer surfaces and in 31 tub-plate (TPsm) heat transfer surfaces (HTS) with cross ridges and grooves in order to determine the regularities of rational enhancement of convective heat transfer. The results of experimental studies of the thermo-aerodynamic characteristics of 19 groups from a limited number (4-6) of PFTsm or TP sm heat transfer surfaces and one of 5 tested smooth channeled HTS ( L / d = 19,43 - PFTsm and L / d = 10,50-15,62 - TP sm ) confirmed the realization of rational enhancement of convective heat transfer ( RECHT ) processes and the high level of their estimates (Nu/Nusm)¢max for the value of the complex (Nu/Nusm)Re=idem/(ζ/ζsm)Re=idem = 1, showed the contribution of changed values of geometric parameters δ/ d (0,0580-0,1138), l / d (0,65-3,24) of PFTint and d */ d (0,748-0,953), l / d (0,183-2,003) of TP int HTS in the value of RECHT estimates. There has been proposed and realized (for the studied HTS groups) a technique for determining the ranges of changing values of geometric and regime parameters that proves the realization of the RECHT process, which simplifies the search for rational solutions in the design of heat exchangers. Special conditions of the preparation for the experiments made it possible to exclude the negative effect of side factors on the results.

Stabilizing Nitrous Oxide in Strong Nitric Acid for Industrial Purposes

The nitrous oxide is determined by the content of (NOx) in the strong nitric acid, the increase of nitrous oxide by the way of either acid decomposition or temperature modification[1], [2] influence the safe production of military products and environmental pollutions[3]. The required specifications of the acids should meet the requirement of desired industry and safety during the transportations from site to site and storage. If the specifications (nitrous oxide) changed rapidly during transportation, decomposition takes place. It is believed that the Sudanese ambient temperature plays the main role. The strong nitric acid that has been stored for long time and transferred away will thermally and catalytically decompose and specifications will change. This study aims to develop a set of preliminary guide lines and recommendations for stabilizing the nitrous oxide (HNO2) in strong nitric acid. The equilibrium relations between acids systems (Nitrous oxide NOx expressed by "nitrous acid HNO2 concentration" and strong nitric acid HNO3) were reviewed and explained. The effects of Sudan ambient temperatures on acceleration of nitrous oxide (HNO2) in strong nitric acid, determine the optimum cooling temperature to slow the decomposition and to stabilize the nitrous oxide were investigated. This is done through incubation of three samples of strong nitric acid (97.5%) at the temperatures 20°C, 25°C and 30°C. Laboratory analysis was done to observe the nitrous oxide exit rate as function of temperatures, concentration of strong nitric acid within four days, Table I, II, III and Fig. 2, 4, 6 show the obtained experimental data. A noticeable increase of nitrous oxide at respective temperatures (20 0C, 25 0C, 30 0C) at the beginning was observed then the curve levels after three days’ incubation. It is concluded that (200C) is the higher temperature at which the strong nitric acid is either stored or transported. Hence it is the optimum temperature to slow the decomposition and stabilize the nitrous oxide. Recommendations for checking Strong Nitric Acid storage tank, transportation system design and design of a conventional jacket heat exchanger to cool nitric acid from (40 0C to 20 0C) were made.

Design and Thermal Analysis of Shell and Tube Heat Exchanger

Design and Thermal Analysis of Shell and Tube Heat Exchanger

Characterizing Long-Term Groundwater Conditions And Lithology For The Design Of Large-Scale Borehole Heat Exchangers

Characterizing Long-Term Groundwater Conditions And Lithology For The Design Of Large-Scale Borehole Heat Exchangers