Printed Circuit Heat Exchanger Research Articles

Technical Characteristics and Development Trend of Printed Circuit Heat Exchanger Applied in Floating Liquefied Natural Gas

The printed circuit heat exchanger with high efficiency and good compactness and reliability presents potential application in the floating liquefied natural gas platform. This paper offers a review on technical characteristics and development trend of the printed circuit heat exchanger applied in floating liquefied natural gas, including the development state of printed circuit heat exchangers, the application state of printed circuit heat exchangers in floating liquefied natural gas, and the key issues for potential application of printed circuit heat exchangers in floating liquefied natural gas. Firstly, the existing research results of heat transfer and pressure drop characteristics of printed circuit heat exchangers with various flow channels are analyzed, and the correlations of the heat transfer coefficients and the pressure drop of these flow channels are summarized. Then, the application state of printed circuit heat exchangers in floating liquefied natural gas is introduced, and the functions of printed circuit heat exchangers used in the existing floating liquefied natural gas facilities are analyzed. Finally, the key issues for applying printed circuit heat exchangers in floating liquefied natural gas, including the structure design criteria, influence mechanism of sloshing conditions on performance, and methods of suppressing the adverse effects of sloshing conditions, are proposed. It is indicated that the present studies focus on the effect of single sloshing motion on the thermal–hydraulic performances of printed circuit heat exchangers, but few attention has been paid onto the coupling effects of multiple sloshing motions which conform more closely to the actual operation conditions of printed circuit heat exchangers in floating liquefied natural gas. Thus, the future work should aim at the influence mechanisms and structure optimizations in terms of thermal–hydraulic performance under multiple sloshing conditions.

Numerical Improvement Using Flow and Heat Transfer Calculations of the Zigzag Geometry for Carbon Dioxide PCHEs

A printed circuit heat exchanger (PCHE) is an efficient and compact heat exchanger that can work under high temperature and high pressure. For Z-shaped channel PCHEs, the corner structure could enhance heat transfer at the expense of increasing the flow resistance. In order to optimize the structural design and control the pressure loss caused by the corner, a three-dimensional numerical simulation using ICEM and Fluent is conducted to study the flow and heat transfer characteristics of carbon dioxide in a PCHE by inserting straight sections (offset distance 0.5–4 mm) or arc segments (radius of curvature 0.5–4 mm) at the zigzag corners of conventional Z-shaped channels. The overall performance of the PCHEs with different structures was compared based on the comprehensive evaluation factor. The results show that the pressure loss of the PCHE can be significantly reduced by inserting straight sections and arc segments at the zigzag corners, with the mass flow rate varying from 100 to 400 kg/(m2 s). The greater the offset distance of the straight sections or curvature radius of the arc segments are, the more significant the effect is, but the heat transfer performance will be weakened at the same time. The comprehensive performance of the PCHE was the best when the curvature radius of the arc segment inserted at the zigzag corner was 4 mm.

Comprehensive Numerical Analysis on Flow and Heat Transfer Characteristics of Printed Circuit Heat Exchanger With Fins

Abstract Printed circuit heat exchanger (PCHE), as a high-efficiency and compact heat exchanger, shows a high potential in high temperature, high pressure, and some extreme environments, thus, it is widely used in nuclear power generation, refrigeration, aerospace, etc. In this paper, the flow and heat transfer characteristics of heat transfer channels with different fins were numerically analyzed, by changing helium inlet temperature and mass flowrate. The results indicate that, with the increase of helium mass flowrate, Nusselt number and pressure loss grow, while Colburn factor and Fanning friction factor drop. As helium inlet temperature rises, Nusselt number, Colburn factor, and pressure loss grow, whereas Fanning friction factor decreases. In addition, the heat transfer characteristics of the channels with different fins are higher than that of the finless channel, among which the circular finned channel has the best heat transfer performance. In spite of a slightly degraded flow performance, the comprehensive performance of the finned channels is superior to that of the finless channel, and the elliptical finned channel has the best performance, followed by airfoil finned channel and circular finned channel.

Proposed Material Properties, Allowable Stresses, and Design Curves of Diffusion Bonded Alloy 800H for the ASME Code Section III Division 5

AbstractIncreased interest in compact heat exchangers (CHXs) to serve as intermediate heat exchangers of very high temperature reactors resulted in significant research and development on their design, analysis, and construction. Printed circuit heat exchangers are a type of CHXs with high thermal efficiency and compactness achieved through diffusion bonding a stack of etched plates with millimeter scaled channels. The diffusion bonding process changes the microstructural and mechanical properties of the wrought metal plates. The current nonnuclear design code ASME section VIII, division 1 captures the material property change through a “joint efficiency factor.” However, the current nuclear design code ASME section III, division 5 does not address or support the diffusion bonded material properties. Hence, there is a need to develop allowable stresses, isochronous curves, and fatigue life curves for various diffusion bonded alloys. In this study, Alloy 800H material was selected to establish the diffusion bonded material properties under tension, creep, fatigue, and creep-fatigue loads at elevated temperatures in the range 550–760 °C. A set of tests on diffusion bonded Alloy 800H (DB 800H) were performed and the acquired data are used in developing allowable stresses Sy, Su, Sr, Sm, St, Smt, So, isochronous curves and fatigue life curves according to the ASME section III, division 5 requirements. This paper also presents detailed procedures used in developing the ASME code section III division 5 design provisions for diffusion bonded Alloy 800H.

Investigation on flow distribution of supercritical natural gas in a printed circuit heat exchanger

Printed circuit heat exchanger is considered as an promising candidate for floating storage and regasification unit of liquefied natural gas due to its high compactness and efficiency. The flow maldistribution is an essential issue in practical applications of the printed circuit heat exchanger, which leads to the performance degradation. In this study, the flow distribution of supercritical natural gas in a printed circuit heat exchanger plate is three-dimensionally simulated, and the thermal-hydraulic performance of the channels is investigated. To save the computational cost, a simplified two-dimensional model is proposed. The comparisons of results between the two- and three-dimensional models show that the effects of backflows, vortex, interaction between properties and flow distribution are the reasons that result in the differences between the two models. The findings suggest that the simplified two-dimensional model is capable for engineering demands with the satisfaction of computational accuracy and efficiency. It helps to overcome numerical difficulties and save computational resources in engineering applications such as the PCHE design.

Topology optimization of an airfoil fin microchannel heat exchanger using artificial intelligence

High-performance microchannel heat exchangers are needed to supply heat for power conversion for nuclear microreactors. An airfoil fin microchannel design, constructed of Alloy 617 with helium as the working fluid, is analyzed and optimized using a design of experiments with artificial intelligence techniques. The use of airfoil fins offers the potential to reduce pressure drop across the heat exchanger, as compared to other types of channel configurations. A framework for topology optimization of airfoil fin printed circuit heat exchangers (PCHEs) has been developed that can be readily extended to different fin sizes and shapes, as well as different inlet and operating conditions, materials of construction, and working fluids. An optimization procedure is developed that employs computational fluid dynamics for a set of design points identified using Latin hypercube sampling. Computational fluid dynamics is used to analyze a simplified two-channel configuration where five design parameters are varied – inlet angle, fin scale, extent of staggering, transverse and longitudinal pitches. Two methods (a 5D polynomial and a regression neural network) are compared for generating surrogate models and the resulting response surface approximation is input to a genetic algorithm that is used to identify a set of optimal parameters. The optimal geometries are found across six channel Reynolds numbers ranging from 1000 to 5000, since inlet conditions affect flow through the heat exchanger. A set of optimal designs that maximizes heat transfer and minimizes pressure drop is identified, and a thermal stress analysis is performed on the optimal design. Correlations for the Nusselt number and Darcy friction factor are developed that can be useful for thermal hydraulic analyses using system codes. Thermal stresses are analyzed and a brief discussion of the status of code cases of PCHEs for nuclear applications is given. Testing and thermomechanical modeling is needed to facilitate future code compliance of PCHEs for high pressure and high temperature applications.

Experimental Study on Prototype of Printed Circuit Heat Exchanger

The printed circuit heat exchanger (PCHE) is the key equipment of the supercritical carbon dioxide Brayton cycle applied to sodium cooled fast reactor. It is required that the equipment not only can operate in high temperature and high pressure environment but also has high efficiency and compact structure. The China Institute of Atomic Energy has carried out the research on a sodium-supercritical carbon dioxide PCHE and has designed and manufactured a heat exchanger prototype with the heat transfer power of 50 kW. In addition, the supercritical carbon dioxide test loop and sodium test loop have been built to test the performance of the heat exchanger prototype. The conclusions are as follows: 1) The heat exchange power of the heat exchanger under rated working condition is 54.2 kW, and the deviation is around 8%, which meets the design requirements; 2) With the increase of the flow ratio of sodium to carbon dioxide, the temperature difference at the high temperature end decreases, and the temperature difference at the low temperature end increases; 3) The change of flow rate of the carbon dioxide has a great influence on heat transfer power; 4) The total heat transfer coefficient of the heat exchanger increases with the increase of the pressure of carbon dioxide; when the pressure increases from 15.5 to 20 MPa, the total heat transfer coefficient increases by 12.8%.

Heat transfer and flow characteristics of straight-type PCHEs with rectangular channels of different widths

Printed circuit heat exchanger (PCHE) is considered to be the most promising heat exchangers in the supercritical CO2 Brayton cycle. The heat transfer and flow characteristics in straight-type PCHEs with rectangular channels of different widths were numerically investigated in this paper. With the increase of rectangular channel width, the average heat transfer coefficients in the cold side decrease first and then increase, while the average heat transfer coefficients in the hot side always increase. The increase of rectangular channel width can effectively increase the heat transfer rate per unit volume and reduce the pressure drop at the same mass flux. However, the changes of heat transfer rate per unit volume and pressure drop tend to be gentle with the width increase. Furthermore, the overall performance evaluation of PCHEs with rectangular channels of different widths was performed. The overall performance evaluations of rectangular channels in the hot side of PCHEs are enhanced compared with the semicircular channel, and the enhancement becomes more and more significant with the increase of mass flux. While the overall performance evaluations of the rectangular channels in the cold side are not as good as that of the semicircular channel. The channel width should be appropriately increased in the hot channel design of straight-type PCHEs to reduce flow resistance and improve overall performance evaluation. The sharp corners of the PCHE channel cross-sections should be eliminated to reduce the heat transfer deterioration zone.

Numerical Study on Flow and Heat Transfer Characteristics of Supercritical CO2 in Zigzag Microchannels

The zigzag channel is the uppermost channel type of an industrial printed circuit heat exchanger (PCHE). The effect of geometric properties on the flow and heat transfer performance of the channel is significant to the PCHE design and optimization. Numerical investigations were conducted on the flow and heat transfer characteristics of supercritical CO2 (sCO2) in semicircular zigzag channels by computational fluid dynamics method. The shear stress transfer (SST) k–ω model was used as turbulence model and the National Institute of Standards and Technology (NIST) real gas model with REFPROP database was used to evaluate the thermophysical parameters of sCO2 in this numerical method. The effectiveness of the simulation method is verified by experimental data. Thermal hydraulic performance for zigzag channels with different pitch lengths, bending angles, and hydraulic diameters are studied comparatively based on this numerical method, with the boundary conditions which cover the pseudocritical point. The comparison results show that reducing the bending angle and pitch length will strengthen the effect of boundary layer separation on the leeward side of the wall and enhance the heat transfer performance, but the pressure drop of the channel will also increase, and the decrease of channel hydraulic diameter is beneficial to the heat transfer enhancement, but it is not as significant as that of the straight channel.

Numerical analysis of the Sodium–Water Reaction in a minichannel to evaluate the safety of a Printed Circuit Steam Generator

ABSTRACT A printed circuit heat exchanger is expected to improve the safety of a sodium-cooled Fast reactor when it is used as the steam generator. To use such a Printed Circuit Steam Generator (PCSG), the Sodium–Water Reaction (SWR) should be evaluated first. Because the diameter and length of a sodium channel in the PCSG are 4 mm and 2 m, respectively, a numerical approach is useful to understand the SWR characteristics in a minichannel. CFD modeling is conducted using commercial code and the SWR in a single sodium channel is analyzed under operating conditions. H2O at 16.8 MPa and 683 K is injected into the sodium channel through the cracks of different sizes (0.1–1.0 mm). Although the SWR is extreme in the early stage, most of the Na(l) is pushed towards the inlet and outlet of the channel within 15.3–35.3 ms as H2O inflowed. The peak temperature is around 1200–1600 K in the early stage of the SWR and the temperature reaches around 683 K. Moreover, the calculated depth of target wastage is around 0.62–3.34 μm. Therefore, the effect of the SWR is negligible in the PCSG core under operating conditions.

Analysis of printed circuit heat exchanger (PCHE) potential in exhaust waste heat recovery

Exhaust waste heat recovery technology based on power cycles requires high efficiency, low flow resistance, and a compact structure for exhaust gas heat exchangers. It is a huge challenge for traditional heat exchangers, such as double tube or shell and tube heat exchangers. A printed circuit heat exchanger (PCHE), which is a compact heat exchanger, has not been used in the heat exchange process between the exhaust gas and supercritical CO2. Focusing on this application, a novel design concept of PCHE based on a comprehensive performance index is proposed, which fully considers the differences in physical properties and working conditions between the exhaust gas side and the CO2 side. A series of experiments were carried out in a CO2-based transcritical power cycle system. The experimental test results show that the PCHE with a novel structure is stable and feasible. To further optimise the PCHE, a numerical analysis of different structures was conducted. The calculation results show that the comprehensive performance of the PCHE with an optimised structure was improved by 11.92%. This research shows that PCHE has great potential for achieving a compact design with excellent performance, especially for use in engine waste heat recovery.

Correlation between pressure loss and heat transfer coefficient in boiling flows in printed circuit heat exchangers with semicircular and circular mini-channels

• Boiling flow heat transfer coefficient and pressure drop were evaluated. • Printed circuit heat exchangers with semicircular and circular channels were employed. • Nucleate boiling in corners affected the heat transfer and flow resistance. • Heat transfer coefficient in semicircular channel was twice as high at low quality. • Increase in pressure drop was suppressed by effect of corners at a low quality. In this study, we investigated the correlation between the pressure loss and heat transfer coefficient for boiling flows in printed circuit heat exchangers. The effect of channel cross-sectional shapes—semicircle and circle—was evaluated. The hydraulic diameters of the semicircular and circular channels were 1.04 mm and 1.0 mm, respectively. A subcooled liquid with a subcooling temperature of 10 K was heated with hot water, and the saturation temperature was 30 °C. The refrigerant mass flux was set in a range of 100–400 kg/m 2 ·s. Consequently, despite the lower pressure drop, for low outlet quality, the heat transfer coefficient was higher for the semicircular channel than for the circular channel. The heat transfer was enhanced by the promotion of bubble nucleation in the thick liquid film at the corners, and the flow resistance was suppressed by the decrease in the vapor shear stress. However, for high outlet quality, the difference in the heat transfer coefficient decreased with an increase in the outlet quality. The experimental results were compared with the results obtained by correlation equations. The lowest mean absolute error of heat transfer coefficient and pressure drop for the semicircular mini-channel were 15.1 % and 26.7 %, respectively.

Multi-objective optimal design of NACA airfoil fin PCHE recuperator for micro-gas turbine systems

• An AF-PCHE was first employed as a micro gas turbine recuperator. • Heat transfer, pressure drop and compactness are multi-objective studied. • A comprehensive optimal solution is obtained for recuperator design. In this study, an airfoil fin printed circuit heat exchanger (PCHE) was first employed as a micro gas turbine recuperator for extended-range electric vehicles. Optimal heat transfer rate, pressure drop, and compactness are important requirements for a PCHE to serve as a recuperator; therefore, in this study, a multi-objective optimal design was proposed using the aforementioned three targets. The considered factors included three airfoil fin structure parameters (arc height, maximum arc height position, and airfoil thickness), two airfoil fin arrangement parameters (horizontal and vertical spacings), and the velocity inlet condition, for both cold and hot sides. A series of 53 numerical tests were designed using the central composite surface method. And the numerical work was performed by the realizable k - ε model with the maximum validation error is less than ± 5%. Moreover, regression formulas for the three targets were established based on the results of the 53 numerical tests, using the high-determine factors. The maximum arc height position was found to be an insignificant factor; thus, it was neglected in the regression formulas. The Pareto fronts for the cold and hot sides were obtained based on nondominated sorting genetic algorithm II; decision-making could be achieved on the Pareto front, according to the design requirements. A comprehensive optimal solution was recommended for the recuperator PCHE with an overall heat transfer rate of 181.29 W/m 2 /K, a total pressure drop of 26.63 kPa/m, and compactness of 8.5 kw/m 2 .

Corrigendum to “Correlation between pressure loss and heat transfer coefficient in boiling flows in printed circuit heat exchangers with semicircular and circular mini-channels” [Appl. Therm. Eng. 204 (2022) 117963

Corrigendum to “Correlation between pressure loss and heat transfer coefficient in boiling flows in printed circuit heat exchangers with semicircular and circular mini-channels” [Appl. Therm. Eng. 204 (2022) 117963

A performance recovery coefficient for thermal-hydraulic evaluation of recuperator in supercritical carbon dioxide Brayton cycle

Recuperator is an important component in supercritical carbon dioxide Brayton cycle. However, open literature mainly focused on the performance of recuperator in component scale but the effect of its thermal–hydraulic performance on the cycle efficiency was seldom concerned. Besides, to be more convenient in practical applications, a criterion for thermal–hydraulic evaluation of recuperators in supercritical carbon dioxide Brayton cycle is needed to avoid the coupling analysis of recuperator design and cycle design. In the present study, an integrated model is developed by combining the supercritical carbon dioxide Brayton cycle with the recuperator of a printed circuit heat exchanger. Based on the integrated model, the effects of design parameters of recuperator on the cycle performance are discussed. It is shown that ultra-large Reynolds number and effectiveness fail to improve the cycle efficiency and are not recommended due to the caused large pressure drop. The effects of conventional performance evaluation criteria and the ratio of heat transfer rate to pressure drop on cycle efficiency are also examined. It is indicated that the existing criteria are not sufficient to evaluate the effect of recuperator channel configuration on cycle efficiency. The performance recovery coefficient with value between 0 and 1 is finally proposed and validated to be an effective and convenient criterion as well as straightforward to various cycle layouts with other types of recuperators.

Influence of Nanoparticle Shapes of Boehmite Alumina on the Thermal Performance of a Straight Microchannel Printed Circuit Heat Exchanger

The efficiency and irreversibility defined based on the second law ofthermodynamics provide a new path for heat exchangers design and makeperformance analysis more straightforward and elegant. The second lawof thermodynamics is applied in a Straight Microchannel Printed Circuitheat exchanger to determine the thermal performance of different shapes ofBoehmite Alumina compared to Al2O3 aluminum oxide. The various formsof non-spherical Boehmite Alumina are characterized dynamically andthermodynamically through dynamic viscosity and thermal conductivity,using empirical coefficients. The non-spherical shape includes platelet,cylindrical, blades, and bricks forms. Graphical results are presented forthermal efficiency, thermal irreversibility, heat transfer rate, and nanofluidexit temperature. The non-spherical shapes of Boehmite Alumina showdifferent thermal characteristics concerning the spherical shape whenthere are variations in fluid flow rates and the nanoparticles fraction.Furthermore, it was theoretically demonstrated that non-spherical particleshave higher heat transfer rates than spherical particles, emphasizingplatelets and cylindrical shapes for the low volume fraction of nanoparticlesand bricks and blades for high volume fraction.

Chemical Cleaning of Magnetite Deposits on the Flow Mini-Channels of a Printed Circuit Heat Exchanger in an EDTA-Based Solution.

The dissolution behavior of magnetite deposited on flow mini-channel surfaces within a printed circuit heat exchanger (PCHE) and the corrosion behavior of a STS 316L PCHE material were investigated in an ethylendiaminetetraacetic acid (EDTA)-based chemical cleaning solution at 93 °C. The fouling in the PCHE was simulated using a water-steam circulation loop system. Most of the magnetite deposits were rapidly dissolved in the early stage of the circulation chemical cleaning. An empirical equation for estimating the dissolution percentage was derived as a function of cleaning time. The PCHE material showed excellent corrosion resistance during the chemical cleaning tests. These results indicate the fouling layers in the PCHEs can be removed efficiently by the chemical cleaning process without concern about base metal corrosion.

Structural Assessment of Printed Circuit Heat Exchangers in Supercritical CO2 Waste Heat Recovery Systems for Ship Applications

Structural Assessment of Printed Circuit Heat Exchangers in Supercritical CO2 Waste Heat Recovery Systems for Ship Applications

Numerical investigation on flow and heat transfer characteristics of supercritical methane–ethane mixture in a straight channel

Printed Circuit Heat Exchanger (PCHE) is considered as a promising heat exchanger for offshore Liquefied Natural Gas (LNG) production due to its compactness and high efficiency. To reveal the flow and heat transfer performance of real component nature gas mixture in PCHE, numerical study was conducted to obtain flow and heat transfer characteristics of supercritical methane–ethane mixture in a straight channel of PCHE. The influence of operating parameters including inlet temperature, mass flux and outlet pressure are investigated. The simulation results show that heat transfer coefficient and pressure drop increase with the increase of inlet temperature and mass flux, and decrease with the increase of outlet pressure. The overall variation tendency of heat transfer coefficient and pressure drop in supercritical methane–ethane mixture flow was similar to those in supercritical methane flow, but there still exists some difference due to their different physical properties. For the value of heat transfer coefficient, supercritical methane flow is about 7% larger than that of supercritical methane–ethane mixture flow. And for frictional pressure drop, supercritical methane flow is much larger by about 12%. Finally, new correlations were proposed for supercritical methane–ethane mixture flow, which are helpful for a more accurate flow and heat transfer calculation in PCHE designing for natural gas.

Novel Adaptive Design Methodology of Segmented Non-Uniform Fin Arrangements for Trans-Critical Natural Gas in the Printed Circuit Heat Exchanger

Novel Adaptive Design Methodology of Segmented Non-Uniform Fin Arrangements for Trans-Critical Natural Gas in the Printed Circuit Heat Exchanger