Construction Of Heat Exchanger Research Articles

Experimental study on the preparation of superalloy Inconel718 heat exchanger channels by electrochemical etching method

The nuclear energy field requires the construction of heat exchangers that can withstand sufficiently high temperatures. In this paper, the etching technique was utilized to fabricate heat exchange channels on Inconel718 plates, and experiments were carried out in NaCl-ethylene glycol solution, three temperature conditions of 35 °C, 40 °C, and 45 °C, and two concentrations of electrolyte solutions, 0.5 mol/L and 1 mol/L, with the addition of 50 kHz ultrasound for comparison. The experimental results show that the etching rate can be as high as 2.894 mm/h, and the inter-electrode current is as high as 908 mA. The roughness characterization of the etching channel Ra and Rq measured by the aspheric surface measuring instrument can be as low as 2.416 μm and 2.647 μm, respectively. In the images generated by SEM scanning, it is found that uneven distribution of pits and bumps exist in the etching channel, but their diameters are all less than 0.1 μm, which means the etched channel is acceptably smooth.

Sensitivity analysis of fluid flow parameters on the performance of fully dense ZrB2-made micro heat exchangers

Heat exchangers are important in modern technology and are used in various industries such as power plants, automobiles and airplanes. Their main role is to ensure efficient heat transfer tailored to specific system needs. With miniaturized electronics, challenges such as circuit overheating have emerged, increasing the demand for compact yet high-performance heat exchangers. The advent of micro-electromechanical systems has increased the application of micro heat exchangers with their high surface-to-volume ratio promising enhanced efficiency. Although metals such as aluminum are commonly used for fabricating heat exchangers, their susceptibility to corrosion and high temperatures limits their usefulness. This study turns attention to ultrahigh temperature ceramics, specifically fully sintered ZrB2, known for their high temperature durability and oxidation resistance. Utilizing the Taguchi approach, a robust optimization method, this study explores the sensitivity analysis of fluid flow parameters on the performance of fully dense ZrB2-made micro heat exchangers and highlights the potential of ceramics in heat exchanger construction. Based on the results, the mass flow rate with an estimated contribution of 4.4% in the effectiveness is the most influential parameter on the performance, and in the best case, the effectiveness reaches 24.3%.

Методика расчета витых теплообменников, применяемых для термической обработки инструментов горного оборудования

Introduction. In modern conditions (depletion of deposits, complication of development conditions, the application of sanctions on the import of equipment, etc.), a special role is played by increasing the resource of equipment used in the mining industry, including processing drilling impact-rotary tools. One of these methods is cryogenic processing of machining tools, as a result of which the hardness and wear resistance of the cutting tool increase several times. For the production of cryogenic substances such as nitrogen, oxygen, methane, etc. in the liquid state, a method is proposed based on the use of adsorption-cryogenic technology implemented through the use of heat exchangers, the development of calculation methods of which is the subject of this article. The purpose of the research is to develop a methodology for calculating heat exchangers used as cold sources for cryogenic surface treatment of mining equipment tools in order to harden it. Research methods. The analysis of the current state of development of technical and technological solutions in the field of development and construction of heat exchangers was carried out through the use of such informal methods as: expert, morphological and factographic. To optimize the modeling calculations of the a priori selected configuration of the heat exchange surface, the method of uniform (blind) search was used. Research results and discussion: 1. In the course of the conducted research, the results of the analysis of the current state of development of technical and technological solutions in the field of development and construction of heat exchangers were obtained. 2. A method for calculating twisted heat exchangers has been developed. 3. It is determined that the presented method of calculating heat exchangers used as cold sources for cryogenic surface treatment of mining equipment tools in order to harden them allows optimization of modeling calculations a priori of the selected configuration of the heat exchange surface. 4. It is established that: heat exchangers with finned pipes should be used when the ratio of the heat transfer coefficient of the flow inside the pipes to the corresponding coefficient in the inter–tube space is 3 ...5 times greater. 5. The use of finned pipes in heat exchangers makes it possible to increase the area of the outer surface of the pipes due to finning, thereby improving the thermal characteristics of heat exchangers, while reducing its weight and size characteristics. 6. It has been revealed that heat exchangers with dense winding are less efficient compared to devices with sparse winding, and heat exchangers with smooth pipes should be used in cases of proximity of the values of the heat transfer coefficient of flows in the tube and inter-tube space. Resume: 1. The analysis of the current state of development of technical and technological solutions in the field of development and construction of heat exchangers was carried out. 2. A method has been developed for calculating heat exchangers used as cold sources for cryogenic surface treatment of mining equipment tools in order to harden them. 3. The developed method of calculating heat exchangers can be used to design heat exchangers consisting of pipes with different surface geometries that are wound onto the core in a spiral, used both in the extractive industries and in the engineering, chemical, oil and gas, rocket and space industries. The further development of the research topic is the optimization of the operating parameters of the heat exchanger according to the criterion of energy efficiency.

Review of the State-of-the-Art Uses of Minimal Surfaces in Heat Transfer

The design of heat exchangers may change dramatically through the use of additive manufacturing (AM). Additive manufacturing, colloquially known as 3D printing, enables the production of monolithic metal bodies, devoid of contact resistance. The small volume of the exchanger, its lightness of weight, and the reduction of its production costs, compared to conventional methods, make the production of heat exchangers by AM methods conventional technologies. The review study presents a new look at the TPMS as a promising type of developed surface that can be used in the area of heat transfer. (Thus far, the only attractive option. The most important feature of additive manufacturing is the ability to print the geometry of theoretically any topography. Such a topography can be a minimal surface or its extended version—triply periodic minimal surface (TPMS). It was practically impossible to manufacture a TPMS-based heat exchanger with the method of producing a TPMS.) The issues related to the methods of additive manufacturing of metal products and the cycle of object preparation for printing were discussed, and the available publications presenting the results of CFD simulations and experimental tests of heat exchangers containing a TPMS in their construction were widely discussed. It has been noticed that the study of thermal-flow heat transfer with the use of TPMSs is a new area of research, and the number of publications in this field is very limited. The few data (mainly CFD simulations) show that the use of TPMSs causes, on the one hand, a several-fold increase in the number of Nu, and on the other hand, an increase in flow resistance. The use of TPMSs in heat exchangers can reduce their size by 60%. It is concluded that research should be carried out in order to optimize the size of the TPMS structure and its porosity so that the gains from the improved heat transfer compensate for the energy expenditure on the transport of the working fluid. It has been noticed that among the numerous types of TPMSs available for the construction of heat exchangers, practically, four types have been used thus far: primitive, gyroid, I-WP, and diamond. At the moment, the diamond structure seems to be the most promising in terms of its use in the construction of heat exchangers and heat sinks. It is required to conduct experimental research to verify the results of the CFD simulation.

Construction and Performance Evaluation of a Triple-Stage Latent Heat Exchanger Packed with Three Latent Heat Storage Materials for Recovering Low-Grade Thermal Energy

Construction and Performance Evaluation of a Triple-Stage Latent Heat Exchanger Packed with Three Latent Heat Storage Materials for Recovering Low-Grade Thermal Energy

Numerical analysis of high temperature minichannel heat exchanger for recuperative microturbine system

Considering the development of energy sector, distributed small-scale power generation, e.g., gas micro-CHP, is attracting considerable interest. In such installations, the heat exchanger is one of the key components possessing a significant influence on overall performance. Most studies concentrate on units operating below 900 °C, which do not fulfil the requirements of gas micro-CHP. Therefore, there remains a challenge to design a compact heat exchanger with passive technologies of heat transfer enhancement. This work describes the implementation of the own construction of a plate minichannel heat exchanger for high-efficiency gas microturbine engines with an external combustion chamber, supplied with air at a temperature of about 1000 °C. The results of this study will greatly contribute to the increase of system efficiency. To understand transport phenomena occurring inside it, a numerical model of the entire heat exchanger was developed in OpenFOAM. Defined boundary conditions were based on experimental data used also to validate the numerical model. The pressure drop experimental and numerical results agreed within the 2%–14% range, while the heat rate ones – within the 1%–8% of the range. In addition, numerical analysis exhibited the limits of thermal and exergetic efficiency values possible to be obtained, when the boundary conditions are strongly controlled.

Heat Enhancement Effectiveness Using Multiple Twisted Tape in Rectangular Channels

Heat enhancement and heat removal have been the subject of considerable research in the energy system field. Flow-through channels and pipes have received much attention from engineers involved in heat exchanger design and construction. The use of insert tape is one of many ways to mix fluids, even in a laminar flow regime. The present study focused on the use of different twisted tapes with different pitch-to-pitch distances and lengths to determine the optimum design for the best possible performance energy coefficient. The results revealed that twisted tape of one revolution represented the optimal design configuration and provided the largest Nusselt number. The length of the tape played a major role in the pressure drop. The results revealed that the insertion of a shorter twisted tape can create mixing while minimizing the changes in the pressure drop. In particular, the best performance evaluation criterion is found for a short tape located towards the exit of the channel. The highest performance energy coefficient was obtained for the half-twisted tape for a Reynolds number varying between 200 and 600.

Correlation for Predicting Heat Transfer Characteristics of A Helical Oscillating Heat Pipe (HOHP) at Normal Operating Conditions

The helical oscillating heat pipe (HOHP) is a high heat transfer heat exchanger with high flexibility in its installation and can therefore be used in a wide variety of applications. In this study, the effect of various parameters on the heat transfer rates of HOHP were used to establish a correlation equation for use in the heat flux prediction, the dimensionless parameters studied were rv/rl, Bo, Nu, We, Ja, Pr, Fr, Co, Ga, Bi, Wo, Oh, and Ku. Experiments were conducted to find out their effects on the heat transfer rates of copper HOHP with internal diameters were 2.03, 3.5, and 4.5 mm. The lengths of evaporator and condenser sections were equal at 1500, 2000, and 2500 mm. The pitch coils were 10, 15, and 20 mm. The working fluids used were R134a, ethanol, and water with the filling ratios were 30%, 50%, and 80% of the total internal volume. The temperature of evaporator section were varied between 60, 70, and 80°C within normal operating conditions in a vertical position. The results of the experiment showed that the internal diameter, lengths of evaporator/condenser sections, pitch coil, type of working fluid, filling ratio and temperature of evaporator section affected the heat transfer rates of the HOHP. The results of dimensionless parameters can establish the correlation equation to predict the heat flux for the HOHP as shown in this paper. In addition, the results of this research can be applied in the designing and construction of HOHP heat exchangers.

The optimal parameters technique for the vertical ground heat exchangers of the geothermal heat pump systems

A scientifically substantiated methodology for determination the optimal parameters of vertical heat exchangers of a underground circuit of the geothermal heat pump systems (GHPS) by the condition of reaching the maximum integral effect or Net Present Value (NPV) is presented. The calculations have confirmed the maximum economic efficiency of the vertical ground heat exchangers can be achieved when observing the optimal values of two defining parameters: the total length of U-shaped heat-receiving pipe and the consumption of the heat carrier passing on it. The optimal values of these parameters are calculated depending on the type and temperature of the ground, the diameter and grade of polyethylene pipes, the initial temperature of the heat carrier at the inlet, tariffs for heat and electricity, specific capital investments in all elements of the ground exchangers, including earthworks, taking into account the real discount rate and a number of additional initial data. The technique allows, to determine the optimal construction and operating parameters of vertical ground heat exchangers under various climatic conditions and types of ground. Also, this technique makes it possible to quantitatively evaluate the maximum achievable economic efficiency of using underground circuit with vertical U-shaped exchangers for the extraction of low-potential ground heat. The use of given technique is necessary for a real assessment of the feasibility of using GHPS as alternative sources of thermal energy in each case.

МОДЕЛІ РОЗРАХУНКУ ТЕПЛООБМІНУ ПІД ЧАС ПЛІВКОВОЇ КОНДЕНСАЦІЇ У СЕРЕДИНІ ГОРИЗОНТАЛЬНИХ ТРУБ

The study of heat transfer during condensation in the middle of the pipes is relevant due to the constant need to improve the design of various heat exchangers (condensers of refrigeration and air conditioning systems, reactor safety systems, and power plant heaters). It is important to know the exact values of heat transfer coefficients in the case of condensation when their value is close to the heat transfer from the cooling side. Well-known theoretical, semi-empirical and experimental models and correlations for heat transfer calculation during condensation of working fluids inside smooth horizontal pipes have been described in the article. Selected models are widely used in various scien-tific publications for heat transfer prediction and construction of various heat exchangers with in-tube condensation. All correlations allow determining the average by tube perimeter, but local by the length of the tube, heat transfer coefficients in the case of annular and intermediate regimes of two-phase flow. All used dependences take into account current modes of phase flow. For choosing the best correlations, a comparison between selected models and experimental values of heat transfer coefficients obtained by different authors for condensation of ten working fluids inside smooth hori-zontal tubes with internal diameters more than 3 mm have been performed. Experimental values were selected from well-known works, in which heat transfer was studied during condensation of such fluids as fluorocarbons, immersion refrigerants, hydrocarbons and steam in the case of intermediate and annular phase flows with a detailed description of research conditions (geometrical parameters of investigated tubes and regimes parameters of condensation process, such as heat flux, mass velocity, vapour quality, and condensation temperature). Comparison of various models with experimental data of different authors allowed identifying the models that show the best convergence with experi-ments among all correlations. Recommendations (range of application) for use of models in engineer-ing practice are given.

Design and Construction of a Double Pipe Heat Exchanger for Laboratory Application

Engineering education is incomplete without laboratory practices. One of such laboratory equipment necessary for all engineering students to have hands-on in the course of their undergraduate studies is the heat exchanger. This work presents the detailed design and construction of a laboratory type double pipe heat exchanger that can be used both in the parallel and counter flow configuration. The heat exchanger was constructed using galvanized steel for both the tube and shell. Experiments were designed and carried out to test the performance of the heat exchangers. The heat exchanger performance characteristics (logarithm mean temperature difference (LMTD), heat transfer rate, effectiveness, and overall heat transfer coefficient) were obtained and compared for the two configurations. The LMTD tends to be relatively constant as the flow rate was increased for both the parallel and counter-flow configuration but with a higher value for the parallel flow configuration. The heat exchanger has a higher heat transfer rate, effectiveness, and overall heat transfer coefficient and therefore has more performance capability for the counter-flow configuration. The overall heat transfer coefficient increased as the flow rate increased for both configurations. Importantly, as a result of this project, Mechanical Engineering students can now have hands-on laboratory experience on how the double pipe heat exchanger works.

Design and Construction of a Double Pipe Heat Exchanger for Laboratory Application

Engineering education is incomplete without laboratory practices. One of such laboratory equipment necessary for all engineering students to have hands-on in the course of their undergraduate studies is the heat exchanger. This work presents the detailed design and construction of a laboratory type double pipe heat exchanger that can be used both in the parallel and counter flow configuration. The heat exchanger was constructed using galvanized steel for both the tube and shell. Experiments were designed and carried out to test the performance of the heat exchangers. The heat exchanger performance characteristics (logarithm mean temperature difference (LMTD), heat transfer rate, effectiveness, and overall heat transfer coefficient) were obtained and compared for the two configurations. The LMTD tends to be relatively constant as the flow rate was increased for both the parallel and counter-flow configuration but with a higher value for the parallel flow configuration. The heat exchanger has a higher heat transfer rate, effectiveness, and overall heat transfer coefficient and therefore has more performance capability for the counter-flow configuration. The overall heat transfer coefficient increased as the flow rate increased for both configurations. Importantly, as a result of this project, Mechanical Engineering students can now have hands-on laboratory experience on how the double pipe heat exchanger works.

Investigation of modes and conditions for superimposing ultrasonic vibration on heat exchangers

The article presents investigations results of ice destruction on heat exchange surfaces (radiators) using intense ultrasonic vibrations for subsequent research of cavitation resistance of heat exchangers. Possible locations and methods of mounting the ultrasonic vibratory system were identified for the typical construction of heat exchanger. Several constructions of ultrasonic vibratory systems have been studied for use in further researches.

Design optimization of a high-temperature fin-and-tube heat exchanger manifold – A case study

High-temperature fin-and-tube heat exchangers are widely used in many industries such as petrochemical industry, automotive, energy, and many others. The major advantage of those heat exchanger is a large heat transfer area within a compact shape. However, it is necessary to ensure uniform distribution of velocity in all the tubes. Failing that, it leads to large differences in mean temperature in the tubes. Consequently, excessive thermal stress occurs, that may cause the heat exchanger to break down. The small volume of collectors of the heat exchangers implicates possibility of improper flow condition inside the tubes, causing an unsuitable inner distribution of thermal and mechanical loads. This case study presents a design optimization of high temperature fin and tube heat exchanger manifold. The modified design of heat exchanger manifold is proposed. To optimize the manifold shape, the Particle Swarm Optimization and Continuous Genetic Algorithms are used. The design consists of tube used for a typical manifold, welded to the wedge, that enlarges the volume of the fluid and improves the flow distribution to tubular space of heat exchanger. The ANSYS CFX based CFD simulations are performed in order to determine the flow distribution in the tubes of fin-and-tube heat exchanger. The structural analysis is performed with ANSYS to determine the occurring thermal stresses. The new design of heat exchanger manifolds allowed one to reduce the tube wall temperature from 185 °C to 134 °C and compressible stresses in the construction of heat exchanger by nearly five times (from 105 MPa to 23 MPa), compared to the traditional fin-and-tube heat exchanger manifold.

ASPECTS OF COMPLEXITY OF METAL-FIBROUS MICROSTRUCTURE FOR THE CONSTRUCTION OF HIGH-PERFORMANCE HEAT EXCHANGERS: ESTIMATION OF ADHESIVE STRENGTH

The paper deals with aspects of the complexity of mechanical properties of porous structures made from copper fibers and fibers reinforced with copper meshes to assess the adhesive strength of the fibrous structure and the cohesion between the components of the tested elements used for the construction of heat exchangers. All of the tested samples were characterized by macroscopic open porosity. The internal structure of the obtained connections was analyzed by metallographic techniques. Statistical relations of the connections made between the layers have been provided. The side effects of the production technology related to the “hydrogen disease” of copper have been discussed.

Application of porous materials in heat exchangers of heat supply system

Heat exchange capacity increase is one of the main concerns in the process of manufacturing modern heat exchange equipment. Constructing heat exchangers with porous metals is an advanced technique of heat exchange increase. A construction of heat exchangers with porous aluminum is described in this paper. The first heat transfer agent (hot water) flows through thin copper tubes installed within the porous aluminum. The second heat transfer agent (freon) flows through the pores of aluminum. Laboratory facility was created to study such a heat exchanger. Series of experiments were carried out. The purpose of the research presented here is to create a mathematical model of heat exchangers with porous metals, to perform analytical calculation of the heat exchangers and to confirm the results with the experimental data. In this case, one can`t use the standard methods of heat exchangers calculation because the pores inner surface area is indeterminate. The developed mathematical model is based on the equation describing the process of cooling the porous plate. A special mathematical technique is used to take into account the effect of tubes with water. The model is approximate but its solution is analytic. It is convenient. One can differentiate it or integrate it, which is very important. Comparison of calculated and experimental data is performed. Divergence of results is within the limits of experimental error. If freon volatilizes inside the heat exchanger, the heat of phase transition has to be taken into account alongside with heat capacity. The structure of the mathematical model makes it possible. The results presented in this paper prove the practicability of using porous materials in heat exchange equipment.

Optimal Design of Welded Plate Heat Exchanger for Ammonia Synthesis Column: An Experimental Study with Mathematical Optimisation

The production of ammonia, consuming up to 5% of natural gas global production, accounts for about 2% of world energy. Worldwide, the Haber–Bosch process is the mainly used method of ammonia catalytic synthesis, involving temperatures up to 600 °C and pressures up to 32 MPa. In this paper, the results of the development and study of the special welded construction of plate heat exchanger (WPHE) for a column of ammonia synthesis are presented. The heat transfer and hydraulic performance of developed WPHE are investigated on a one-pass model in laboratory conditions. An equation for the relation between heat transfer effectiveness and the number of heat transfer units is proposed. A mathematical model of multi-pass WPHE is developed using these results. The validity of this model is confirmed by results of industrial tests performed with the prototype WPHE installed in operating column of ammonia synthesis at temperatures about 500 °C and pressure about 32 MPa. The tests confirmed the reliability of WPHE and its efficiency compared to a tubular heat exchanger. A method of optimal design of WPHE that allows finding the optimal height of corrugations and the number of passes in WPHE for specified conditions of operation is developed.

Thermo‐physical investigation of butyl stearate as potential phase change material for thermal energy storage in cooling application

AbstractPhase change material (PCM) based energy storage technology is a promising solution to conserve thermal energy. This work involves studies on thermophysical properties of butyl stearate as PCM for thermal comfort application and its corrosion compatibility with commonly used heat exchanger construction materials. The thermophysical properties of butyl stearate is studied using differential scanning calorimetry and the result shows that the peak melting and freezing temperatures are 18.64°C and 13.28°C, respectively. The latent heat of melting and freezing are 120.59 Jg−1 and 120.70 Jg−1, respectively. The accelerated thermal cycling test reveals that butyl stearate is stable upto 1000 repeated thermal cycles. The thermogravimetric studies and Fourier transform infrared spectroscopy confirm that butyl stearate is thermally and chemically stable. The results of corrosion test provide information about selection of construction materials for heat exchanger and encapsulation in real‐time application. Butyl stearate is a potential PCM which can be used in thermal energy storage system for thermal comfort application.

RESEARCH OF HEAT DISPOSAL EFFICIENCY IN RECUPERATIVE HEAT EXCHANGERS OF AUTONOMOUS VENTILATION UNITS

Full-scale tests of recuperative heat exchangers of autonomous ventilation units of a new design were carried out in order to determine the efficiency of heat recovery in them. As a result of the tests, it was found that the efficiency of heat recovery in such recuperative heat exchangers varies from 40 to 70 %, depending on the initial parameters of the supply and exhaust air. It was also found that in order to achieve the same heat recovery effect, it is advisable to use the construction of heat exchangers with corrugated mesh than the construction with corrugated plates because the first construction with a comparable heat recovery effect provides up to one and a half times lower aerodynamic drag. During the tests was also made an approbation of a new protection scheme for recuperative heat exchangers against freezing.

The amplitude influence on the thermal and hydraulic performances for a wavy air fin in a compact heat exchanger used in agriculture applications

Wavy air fins are used in the construction of aluminum compact heat exchangers which are used in thermal equipment for agriculture, construction, and industrial applications. Since atmospheric air convective heat transfer coefficient is among the lowest of all fluids, there is a special interest in the optimizing of the geometry for this type of heat exchangers. One of the biggest challenges in designing cooling solutions for agriculture applications is the clogging effect on the performances of the heat exchangers. Clogging leads to a critical performance reduction of the compact heat exchanger used for these types of applications. This specific study, which was conducted in RAAL S.A company in collaboration with the University “Politehnica” of Timisoara”, checks the influence of the wavy air fin amplitude on the thermal and hydraulic performances and tries to find an optimum solution suitable for these specific projects. So, starting from the standard existing amplitude, different amplitude values were studied analytically. The analytical studies were further confirmed by real life measurements. The scope of the study was to find an optimal value for the amplitude that can further improve the overall performance of the aluminum compact heat exchangers and reduce the clogging effect.