Fabrication Of Heat Exchangers Research Articles

Numerical assessment of ceramic micro heat exchangers working with nanofluids by Taguchi optimization approach

The rapid advancements in microsystems technology have necessitated the exploration of innovative materials for efficient thermal management in micro heat exchangers. This research delves into the performance evaluation of three ultra-high temperature ceramics (UHTCs): ZrB2, BeO, and Si3N4 as alternative micro heat exchanger fabrication materials. The study systematically assessed the ceramics' interaction with Al2O3-nanofluids across diverse volume percentages and mass flow rates using the Taguchi optimization method. Beryllium oxide (BeO) emerged as the superior material, registering warm outlet temperatures as low as 64.86°C and cold outlet peaks at 31.68°C. Sensitivity analyses further underscored the critical role of inlet temperature on outlet dynamics, with warm and cold outlets showing significances of ~72% and ~99%, respectively. Additionally, the research pinpointed 0.75 vol% as the optimal Al2O3-nanofluid concentration, yielding the most favorable performance metrics across the ceramics.

The application of additive manufacturing to heat exchangers for oscillatory flow: A case study

Additive manufacturing is an option for the fabrication of heat exchangers for thermoacoustic applications. In thermoacoustic devices, heat exchangers are placed in oscillatory flow. A careful consideration of heat exchanger geometries examines the application of methodologies to optimise heat transfer and the temperature gradient. Additive manufacturing is proposed as an alternative fabrication technique that can overcome the current limitations of conventional fabrication machining. Six identical crossflow heat exchangers were made and tested, three from stainless steel and three from aluminium. The oscillatory flow moves back and forth through circular cross-section channels, and water flows in channels perpendicular to them. Heat transfer and temperature gradients were investigated at different drive ratios and mean pressures.

Development of palmitic acid-lauryl alcohol as binary eutectic for cold thermal energy storage in buildings indoor thermal comfort application - Thermophysical studies and discharging characteristics

There has been a steep increase in cooling energy requirements in recent years owing to the growing demand for thermal comfort in buildings. Electric peak demand required to meet thermal comfort could be curtailed by integrating the Latent Heat Thermal Energy Storage (LHTES) system with conventional systems, resulting in lower greenhouse gas emissions and savings of precious fossil fuels. This paper focuses on the development of binary eutectic Phase Change Material (PCM) and property analysis to determine its compactness for indoor thermal comfort building applications. The investigated eutectic PCM comprises Palmitic acid (PA) –Lauryl alcohol (LA) in the composition 10:90 and the material is a viable system fitting the intended application. By DSC analysis, the phase transition temperature and latent heat of the eutectic PCM are discovered to be 20.25°C and 155.59 Jg−1, respectively. The present study involves various thermophysical studies including corrosion test, thermogravimetric test, thermal conductivity, FTIR analysis, and automated thermal cycling test to evaluate the long-term feasibility of the TES system. The study pays special attention to the corrosiveness of the developed PA-LA eutectic PCM confirming that stainless steel-316 and aluminium are recommended as ideal materials for the fabrication of heat exchangers with longer life. Further, the experimental discharging characteristic of the developed PCM carried out in a high-performance Vapour Absorption Refrigeration (VAR) chamber highlights the robustness of the developed material in terms of prolonged cooling retrieval duration. The developed system will elevate energy efficiency and curb the cooling energy demand when it is coupled with a conventional cooling system.

Enhanced refrigerant flow boiling heat transfer in microstructured finned surfaces

Flow boiling is used in air-conditioning and refrigeration, thermal management of electronics, distillation, chemical synthesis, desalination, power generation, and cryogenics. To enhance the flow boiling heat transfer, internally finned tubing has been widely used. In this work, we demonstrate a fabrication method to generate interal microstructures in 5.2 mm internal diameter finned aluminum tubing through crystallographic chemical etching to further increase heat transfer coefficients of low-GWP refrigerant R-515B. Enhancements in heat transfer coefficients are demonstrated across the range of vapor qualities with peak enhancements up to 172% observed at high vapor qualities with similar levels of enhancements demonstrated with R-134a. The effects of varying operating parameters such as heat flux, mass flux and saturation pressure, on performance improvement were also examined. Flow visualization studies performed through an adiabatic glass visualization section at the test-section exit allowed quantiification of film thickness and showcased lower conduction resistance for microstructured finned surfaces. The advantages of this structuring technique are further highlighted by the relatively minor increase in pressure drop (∼20%). We demostrate that etching of plain aluminum tubes exceeds the performance of finned tubing under high heat flux condtions, with enhancements being more pronounced at low mass fluxes, indicating potential replacement of current extrusion methods used for the manufacture of finned tubing. Surface characterization results after mechanical expansion of the etched finned tubing demonstrated the remenance of microstructures in fin valleys, thus proving potential compatibility with heat exchanger fabrication methods.

Analyzing the response of submerged arc welding process parameters on Form factor and dilution

Stainless steel (316) possesses higher strength to weight ratio, high toughness and high tensile strength. It has wide range of applications in fabrication of heat exchangers, boat fittings as wire rope clips, in making of tanks, springs and screws, Medical implants, Sinks and splash backs. Welding of these materials has always been a challenging task. Submerged arc welding due to its various properties and specification has been found suitable for this type of work. In this research work, weld bead geometry parameters; Dilution, Form Factor were optimized by using Response Surface Methodology (RSM). Welding current has been found to be the most crucial parameter among all the selected parameters.

Feasibility of Molten Salt Reactor Heat Exchanger Online Monitoring

Abstract Online structural health corrosion monitoring in advanced molten salt reactor heat exchangers is desirable for detecting tube degradation prior to leaks that would either cause mixing of heat exchanger fluids or release of radiologically contaminated fluids beyond the design containment boundary. This program seeks to demonstrate the feasibility for a torsional wave mode sensor to attach to the outside of a long (30-m) heat exchanger tube in the stagnant flow area where the tube joins the heat exchanger plenum and where it is possible to protect a sensor cable from high-force flow connecting through a heat exchanger shell to a monitoring instrument. The envisioned sensor and cable management approach will be impractical to implement on existing heat exchangers; rather, sensors must be installed in conjunction with the heat exchanger fabrication. Initially, flaw surrogates of interest (50% notch and 50% flat-bottom hole) have been detected in a 3-m tube using low-temperature PZT piezoelectric crystals. The transducer consisted of multiple shear elements placed circumferentially around a tube. The program will continue to investigate higher temperature piezoelectric ceramics, long-term performance of high-temperature adhesives, and flaw sensitivity on long (30-m +) tubes.

Experimental analysis of temperature field and distortions in multi-pass welding of stainless cladded steel

The stainless clad steel materials (particularly A283-Gr-C hot-rolled to austenitic stainless steel plate SA240 TP 316L) have become widely used in the fabrication of heat exchangers, pressure vessels, and other components owing to their very interesting properties and low production cost. These cladded materials are mostly joined using multi-pass welding techniques. The temperature distribution that supervenes during welding affects the microstructures and the mechanical properties and may generate residual stresses in the heat-affected zone of the welded plates. Since limited experimental data are available in the literature regarding the complex cases of multi-pass welding of cladded steel materials, a thorough experimental study was performed in order to evaluate the temperature distribution on the welded plates. In fact, eight K-type thermocouples were fixed at different distances from the weld centerline in order to record the temperature evolution along longitudinal, transversal, and thickness directions during the welding process. Due to the unavoidable effects of the generated heat fluxes that always follow the welding, several dimensional changes were occurred on the welded plates. In this study, the longitudinal shrinkage and the angular distortion generated during the welding process by the effect of the heat fluxes were investigated. Then, tensile and bending tests were performed in order to check the welded plate reliability. It was found that (i) the welded joint presents a higher mechanical tensile strength than the parent metal and (ii) no separations, fractures, or tearing appear on the weld joint surface after the bending test.

Evaluation of the residual stress in stainless steel 304L hydraulically expanded joints

Stainless steel 304 L tubes are commonly used in the fabrication of heat exchangers for nuclear power stations. The stress corrosion cracking (SCC) of 304 L tubes in hydraulically expanded tube-to-tubesheet joints is the main reason for the failure of heat exchangers. In this study, 304 L hydraulically expanded joint specimens were prepared and the residual stresses of a tube were evaluated with both an experimental method and the finite element method (FEM). The residual stresses in the outer and inner surfaces of the tube were measured by strain gauges. The expanding and unloading processes of the tube-to-tubesheet joints were simulated by the FEM. Furthermore, an SCC test was carried out to verify the results of the experimental measurement and the FEM. There was good agreement between the FEM and the experimental results. The distribution of the residual stress of the tube in the expanded joint was revealed by the FEM. The effects of the expansion pressure, initial tube-to-hole clearance, and yield strength of the tube on the residual stress in the transition zone that lay between the expanded and unexpanded region of the tube were investigated. The results showed that the residual stress of the expanded joint reached the maximum value when the initial clearance was eliminated. The residual stress level decreased with the decrease of the initial tube-to-hole clearance and yield strength. Finally, an effective method that would reduce the residual stress without losing tightness was proposed.

Entropy generation and thermoeconomic analysis of printed circuit heat exchanger using different materials for supercritical CO2 based waste heat recovery

Abstract This article presents the entropy generation and thermoeconomic performance analysis of printed circuit heat exchanger (PCHE) using different materials of construction-based heat recovery heat exchanger (HRHE) for emerging waste heat recovery system (WHRS) utilising the marine gas turbine exhaust as the heat source and supercritical CO2 as working fluid. The mathematical model for the efficient yet compact PCHE based HRHE has been developed keeping in mind severe footprint, volume and weight restrictions for waste heat recovery in shipboard. The parametric and thermoeconomic analyses of the proposed HRHE using the second law performance parameters such as entropy generation number, rational efficiency, thermoeconomic cost and heat exchanger fabrication materials properties has been presented. The influence of variations in topping engine load on geometrical parameters of HRHE is carried out considering hastealloy-N and stainless-steel materials and the optimized values are presented that lowers the heat transfer and pressure drop irreversibilities. It is found that, at low load operations, the thermoeconomic cost, which is combination of capital cost and the irreversibility penalty costs decreases and the second law efficiency increases. Although using hastealloy-N as heat exchanger fabrication material is costlier compared to stainless steel, but its second law efficiency value increases.

Feasibility of manufacturing combustion chambers for aeronautical use in Mexico

The aeronautical sector is strategically important for the economic development of Mexico and has grown steadily over the last 10 years. Furthermore, it generates high added value for its products. In Mexico, the aircraft manufacturing sector mainly focuses on the fabrication of heat exchangers, seals, fuel ducts, and engine support rings. Currently, this sector is not involved in the manufacture of engine hot section components such as combustion chambers and turbine blades. Estimation of the associated costs enables assessment of the feasibility of fabricating such components. This study investigates the feasibility of establishing production lines for aeronautical combustion chamber fabrication in factories dedicated to the manufacture of aeronautical gas turbine engines.

Effect of filler materials on the performance of gas tungsten arc welded AISI 304 and Monel 400

Dissimilar metal welding involving AISI 304 and Monel 400 finds widespread use in marine and offshore environments for the fabrication of heat exchangers, evaporators, piping and vessels in petrochemical and power generation industries. However studies on the performance of such weldments are scantly found in the literature even though the individual metals have higher corrosion resistance and strength. This paper reports the work carried out on welding of AISI 304 and Monel 400 using Gas Tungsten Arc Welding (GTAW) technique to examine the weldability, mechanical and metallurgical properties. Investigations have been carried out on the hot corrosion behavior of these joints subjected to cyclic air oxidation and K2SO4+NaCl (60%) molten salt environment at 600°C. A comparative analysis was carried out on these weldments for two different filler metals such as E309L and ENiCu-7. The oxide scales formed on the various zones of the weldment have been characterized systematically using surface analytical techniques. Weld zone was found to be more susceptible to degradation than base metals used. The effect of filler materials on the hot corrosion is discussed. The studies reported in this paper would be beneficial for fabricators embracing this type of dissimilar weldments in the petrochemical and power generation industries.

Hot Corrosion Studies on Bimetallic Combinations of Monel 400 and AISI 304 Subjected to Molten Salt Environment

Dissimilar joints of Monel 400 and AISI 304 are used widely in marine and offshore environments for the fabrication of heat exchangers, evaporators, piping and vessels as well as in the chemical, petrochemical, and power generation industries. An attempt was made to weld Monel 400 and AISI 304 by gas tungsten arc welding using ENiCu-7 and E309L filler wires. A comparative analysis was carried out on these weldments so as to examine the weldability, mechanical and metallurgical properties of the weldment. In addition, corrosion behavior of these weldments has been carried out on the dissimilar weldments in K2SO4 + NaCl (60%) molten salt environment at 600°C under cyclic conditions. The oxide scales formed on the various zones of the weldment have been characterized systematically using surface analytical techniques. Weld zone was found to be more susceptible to degradation than in base metals.

균일압력 유도에 의한 꺾임 구조를 가진 미세주름 박판구조물 성형을 위한 고무성형 공정연구

주름구조를 가지는 박판구조물은 비행기, 자동차, 전자제품 등의 다양한 용도의 열교환기로 사용 된다. 이러한 주름구조를 가지는 박판구조물의 경우 대량생산을 위하여 박판소성가공 공정으로 제작하게 되는데 꺾임 각을 가지는 주름구조를 형성하는 것은 매우 어렵다. 이 문제를 해결하기 위해 본 연구 에서는 정확한 주름구조를 형성하기 위하여 일정한 압력을 박판의 전면에 효과적으로 미칠 수 있도록 새로운 고무성형공정을 제안한다. 본 연구에서 제안한 공정을 검증하기 위하여 우선 유한요소해석을 통해 고무성형공정 변수를 최적화하였다. 그리고 최적화한 고무성형공정을 이용하여 꺾임구조와 미세주름 구조를 가지는 박판을 제작함으로써 본 연구에서 제안한 공정이 목표로 하는 박판의 성형에 효과적인 공정임을 검증하였다.

Heat exchanger fabrication with arrays of sensors and heaters with its micro-scale impingement cooling process analysis and measurements

The design and fabrication for the thermal chip of a heat exchanger with arrays of temperature sensors and heaters for study of micro-jet impingement cooling heat transfer process is presented. This thermal chip can minimize the heat loss from the system to the ambient and provide a uniform heat flux along the wall, thus, local heat transfer processes along the wall can be measured and obtained. The fabrication procedure presented can reach a chip yield of 100%. With fabrication of a micro-slot nozzle of B=200 μm, therefore, micro-jet impingement cooling experiments can be performed to obtain the local micro-scale heat transfer Nusselt numbers along the wall. The experimental results indicate and the heat transfer process along the wall is significantly different from the case of large-scale jet impingement cooling process. Correlations for the micro-scale heat transfer cooling process have been successfully obtained.

The Application of the Brazing Process in Selective Laser Sintering Fabricated Parts

Selective Laser Sintering is one of the rapid prototyping technologies in today's market. It has attracted much attention and interest since the introduction of metal object fabrication by metal layer sintering. The success of this technology mainly lies in its ability to fabricate objects of complicated shape in a shorter time and at lower cost. However the complexity of new metal object design has reached a level where some special-shaped objects cannot be fabricated without post-infiltration joining due to process limitations. This paper studies the feasibility of using the brazing process to join sintered parts fabricated by the selective laser sintering method. Suitable brazing metals were chosen by the wettability test and an application example of the fabrication of a new model heat exchanger fabrication is discussed.

APPLICATION OF TITANIUM IN SHIPBOARD SEAWATER COOLING SYSTEMS

ABSTRACTTitanium alloys are evaluated as an alternative to the current copper‐nickel components now employee in U.S. Navy surface ship seawater cooling systems. Titanium offers a solution to the accelerated seawater corrosion and erosion related attack being experienced in seawater systems aboard CG‐47 class cruisers as well as other ship classes and can provide a means for extending service life and substantially improving reliability. Both the positive and potentially negative aspects of utilizing titanium in piping and heat exchangers are reviewed. Titanium's excellent resistance to corrosion and erosion attack, good yield strength and relatively low density permit use of thinner‐walled, reduced diameter piping and heat exchanger tubing (relative to copper‐nickel) and thus offer reduced system weight and volume. System design strategies are discussed for eliminating or greatly mitigating the adverse effects of galvanic corrosion and marine biofouling, the two major concerns when applying titanium in seawater piping and heat exchanger systems.An overall assessment of titanium versus copper‐nickel alloys is provided with regard to piping and heat exchanger fabrication, cost, performance, design criteria, piping component (valves, pumps, etc.) selection criteria, and operational limitations. Specific topics addressed as part of that assessment include: (1) shipyard fabricability of titanium piping systems and onboard repair; (2) biofouling experience and biofouling control techniques with titanium in seawater; (3) galvanic corrosion effects when titanium is coupled to active (less noble) metals and the strategies for eliminating the risk of galvanic attack. The viability of titanium for surface ship seawater systems is summarized, and areas of future work are discussed with the intent of providing guidance for successful application of titanium in shipboard seawater systems.

Superphénix 1 Intermediate Heat Exchanger Fabrication

The eight Superphenix 375-MW(thermal) intermediate heat exchangers (IHXs) are similar in overall design to the Phenix components. Detailed design changes had to be made during fabrication on the fo...

3-KW concentric tubular resistojet performance.

The design and fabrication are described for a resistojet, the performance of which, during a 25-hr test using hydrogen as a propellant, was a vacuum specific impulse of 840 sec and a thrust of 66.5 g force for 3.0 kw of electric power input. The thruster stagnation conditions were a pressure of 8.8 atm and a gas temperature of 2420°K. The over-all efficiency, which includes the input power of the gas, was 79%. Through a first-law power balance, the performances of the heater and nozzle are separately identified. The nozzle power efficiency based on expansion to space vacuum was 88%. The heater efficiency was found to be 90%. Temperatures throughout the engine are given. The tungsten heat-exchanger fabrication method using vapor-deposition techniques is completely new, allowing almost any shape desired. A large, effective, heat-exchanger surface results in a maximum temperature of the heating element only slightly above the maximum gas temperature. Tungsten sublimation and electrical-insulator temperature, both life-deter mining factors, were minimized in this type design.