Allowable Pressure Drop Research Articles

Calculation of a cavitation device for industrial water treatment

Relevance. Currently, the issue of preventing pollution of the hydrosphere by industrial wastewater, the use of new effective technologies for industrial water purification and its reuse in production is extremely acute. In this regard, the urgent tasks are the search and implementation of new methods of water treatment: innovative technologies, disinfection and desalination of water, methods of its reuse.Methods. The article proposes a new technology for water treatment – the cavitation effect on the flow is enhanced by the shock effect of a pressure surge, which makes it possible to suppress the vital activity of microorganisms in the water. On the basis of the developed workflow, its mathematical model and the author’s methodology, calculations were made for three hydrodynamic cavitation devices with a pressure jump in order to disintegrate sulfate-reducing bacteria in industrial waters.Results. In accordance with the terms of reference (nominal fluid flow Q, nominal absolute pressure before installation P1, allowable pressure drop on the device ΔP, nominal fluid temperature t, physical properties of the medium) based on the proposed working process of a hydrodynamic cavitation device that forms a supersonic flow with a transition to subsonic through a pressure jump, an appropriate mathematical model and an adequate technique, the regime and geometric parameters of three pilot samples of hydrodynamic cavitation devices designed to destructurize sulfate-reducing bacteria in industrial waters were calculated. In order to form a supersonic flow in the installation under sufficiently strict conditions for ensuring permissible pressure drops, a nozzle was profiled with a minimum drag coefficient along the Vitashinsky curve. Industrial testing of cavitation devices showed good convergence of theoretical and experimental data: the suppression of bacteria was carried out by 80–100%.

Experimental and parametric analysis of exhaust heat exchanger used in thermoelectric generator

A thermoelectric generator system consists of an exhaust heat exchanger, a thermoelectric module, and water heat exchanger. Perfect heat exchangers recover as much heat energy as possible from engine exhaust with an acceptable pressure drop. The capacity and efficiency of the heat exchanger depend on its shape, type, and material of the heat exchanger. The main objective of this research was to perform a parametric analysis of the test section of the exhaust heat exchanger by using simulation tools. The simulation results were validated with the experimental results to ensure the performance of the simulation model. The performance of the test section was measured in relation to geometry, pressure drop, temperature distribution, fluid velocity, and temperature uniformity coefficient. The test section of 60 mm × 60 mm × 180 mm (F-type) shows a higher surface temperature with an allowable pressure drop than the other types of test section without inserts. The inserts played a vital role in enhancing the surface temperature distribution and uniformity coefficient. The cone type (G-type), cone-cylinder type (H-type), and cone-cylinder-cone type (I-type) inserts were used to improve the performance of the F-type test section. The G-type and H-type test sections of the exhaust heat exchanger have a high surface temperature, high-temperature uniformity, and allowable pressure drop.

A design model for spiral wound heat exchangers which accounts for property variation, longitudinal heat conduction, and heat-in-leak

• A combined analytical-numerical design model for cryogenic SWHE is developed. • Analytical sizing module finds the optimum configuration of SWHE. • The effects of property variation, LHC, and heat-in-leak are investigated. • LHC impact is negligible compared to property variation and heat-in-leak. • A sensitivity analysis on the input constraint is performed. Spiral Wound Heat Exchangers (SWHEs) can be a good and reliable choice for serving as the main heat exchanger in the cryogenic gas liquefaction cycles using throttling process such as the Linde-Hampson cycle. In this application, a high pressure hot gas stream has to be cooled down via transferring heat to a low pressure cold gas in a high-effectiveness heat exchanger. Present research has been organized to develop a design model which is able to find the optimum SWHE configuration for gas liquefaction cycles. The model has to be capable of considering the important physical phenomena in the cryogenic temperature ranges, including variation of fluid properties with temperature, longitudinal heat conduction (LHC) through separating walls, and heat-in-leak. Therefore, a combined analytical-numerical design model has been developed in the present study. The design model is essentially composed of two stand-alone modules, i.e. an analytical sizing module and a numerical performance evaluation module. To develop the design model, first, the geometrical characteristics of SWHE are studied and primary geometrical parameters are recognized. Then, the analytical sizing module is developed which is able to determine the optimum values of primary geometrical parameters of SWHE minimizing the heat transfer surface area based on the input design requirements. Afterwards, a 1D finite difference numerical module is presented in which important physical phenomena can be considered in the evaluation of the thermo-hydraulic performance of all types of counter flow or parallel flow heat exchangers as well as SWHEs. Finally, the two modules are combined to construct a design model. Two examples in which the low pressure superheated vapor helium is intended to cool down the high pressure supercritical helium flowing inside the tubes are also provided to demonstrate the applicability of the proposed combined model, and also, to elucidate its sensitivity to the input constraints. It was concluded that while variations of fluid properties and the external heat fluxes due to the radiation and convection have significant influence on the performance of cryogenic SWHE, the LHC is of minor importance and can be neglected. Moreover, decreasing the shell-side allowable pressure drop from 10 kPa to 2 kPa, causes the heat exchanger length and its outside diameter to increase by 79% and 48%, respectively.

Spirally wound tubular heat exchanger optimisation using Genetic Algorithm

• Spirally coiled (Giauque-Hampson) type heat exchanger optimization. • Thermal analysis of optimum tube geometry predicted by Genetic Algorithm. • Design aimed at minimum exchanger weight under pressure drop constraints. • Design aimed at minimum exchanger height under pressure drop constraints. • Effect of different process parameters on the optimum heat exchanger design. A Genetic Algorithm based optimization of spirally wound two-fluid stream exchanger is presented. The proposed method elaborates a design methodology consistent with the user-defined specifications while simultaneously fulfilling a design objective linking optimization of either weight, height or thermo-hydraulic performances, etc., depending on the customer requirement. Optimization variables include tube material, tube size, normalized transverse and longitudinal pitches, number of tubes in the innermost layer, increment in the number of tubes with each successive layer, and the total number of tube layers. The effectiveness-NTU approach is adopted for design calculations, including fluid property variations with temperature. This paper explores the effect of optimization criteria like minimum weight or height and variation in pressure drop constraints on the optimized design. A compromise in exchanger effectiveness can substantially reduce its weight. Among the exchangers of the same effectiveness, the one handling 10 times larger flow could be 35 times heavier (subjected to other constraints). Exchanger designed with the minimum height criterion is nearly two times shorter than the one created on a minimum weight basis, while the shorter unit could be two times heavier. The optimum design is a trade-off between achievable minimum mass and maximum allowable pressure drop.

Shell and tube heat exchanger flexible design strategy for process operability

Traditionally, the shell and tube heat exchanger (STHE) design minimizes the total annual cost subject to allowable pressure drop. However, it is often insufficient when considering equipment limitations and uncertain disturbance factors. Design inefficiency or improper operation of overall process systems could potentially occur. A rigorous design strategy of STHE based on the flexibility index analysis method is proposed to address the above issues. The genetic algorithm with rigorous constraints is considered for the STHE design optimization. Simultaneously, the flexibility index (FI) is incorporated to quantify the uncertain factors of the STHE operation. The STHE load capacity and the corresponding uncertain disturbance factors affecting the STHE operability are evaluated. In addition, design workflows incorporating flexibility index are also discussed. Simultaneous consideration of the flexibility index in the optimization procedure can improve the STHE design operability under the expected range of disturbance factors and lower the total cost.

Adaptive design methodology of segmented non-uniform fin arrangements for trans-critical natural gas in the printed circuit heat exchanger

As the core heat transfer equipment of a floating storage regasification unit (FSRU), the printed circuit plate heat exchanger (PCHE) has a significant impact on the gasification performance of liquefied natural gas (LNG). During LNG regasification process, natural gas undergoes a trans-critical process and its thermal properties such as density, viscosity and specific heat capacity vary considerably especially near the pseudo-critical point, which will probably lead to more volatile flow heat transfer mechanism. The traditional design scheme of uniform finned channel is difficult to give full play to the efficiency and compactness of PCHE because of lacking considering the local fluid thermodynamic variation. Therefore, this paper provides a novel design method for optimizing the flow channel profile of PCHE by applying adaptive segmented non-uniform finned micro-channels. Firstly, the entire flow channels are segmented by qualifying the gradient of density with temperature ∂ρ/∂t of trans-critical natural gas. Subsequently, within the constraints of heat exchange requirements, maximum allowable pressure drop, existing manufacturing techniques and structural strength, a mathematical optimization design model considering non-uniform fin arrangements and interlinked thermal states among these segmented channels is established. Then, to comprehensively improve entropy generation number and volume, Pareto solutions covering local flow channel parameters are obtained based on multi-objective genetic algorithm. Finally, the actual performance differences between two optimization methods respectively derived from the conventional uniform fin channels and the proposed non-uniform fin arrangements are compared based on distributed parameter model. The results show that the deviation of the entropy generation number between the optimized and validated values for the non-uniform design is very small at 6.5%, much less than that of 31.4% in the uniform design. Moreover, under the premise of the similar heat transfer efficiency, the volume for the PCHE by the non-uniform design can be reduced by 9.3%. These indicate that the proposed design methodology of segmented non-uniform fin arrangements indeed makes the PCHE more compact and enables the thermal-hydraulic performance better. The current work will serve as a framework for the design and optimization of PCHEs with drastic changes in fluid physical properties.

Design and thermal-hydraulic analysis of a printed circuit heat exchanger for ADS applications

Printed circuit heat exchanger (PCHE) is considered a promising candidate for accelerator driven systems (ADS) due to its high compactness and efficiency. The preeminent high-temperature, high-pressure and corrosion resistance enables it to withstand the severe conditions of ADS and ensure the safe and efficient operation. In this paper, a PCHE applied to the ADS is proposed, adopting helium as the cold source and lead-bismuth eutectic (LBE) as the heat source. On this basis, a three-dimensional model is established and the flow and heat transfer characteristics of the PCHE are numerically investigated. The thermal performance is further improved by optimizing structural and operating parameters. The results indicate that the high thermal conductivity and superior field synergy degree of LBE ensures a strong heat transfer performance of PCHE. The velocity disturbance and double-vortex secondary flow generated in modified channels, which intensify the fluid mixing and improve the field synergy level, help to further enhance the overall heat transfer coefficient. Structural and operating parameters of the helium side are more critical to the thermal-hydraulic performance, an increase of helium mass flow rate within allowable pressure drop is conducive to the comprehensive performance.

Proton Improvement Plan II Cryogenic Distribution System thermodynamic design

The Proton Improvement Plan – II (PIP-II) is a superconducting linear accelerator being built at Fermilab that will provide 800 MeV proton beams for neutrino production. The Linac requires cooling at 40 K, 5 K, and 2 K temperatures, which will be provided by cryogenic helium produced by a Helium Cryoplant and distributed by a Cryogenic Distribution System (CDS). Based primarily on the Linac heat load requirements at each temperature and the allowable pressure drop, we have made a preliminary thermodynamic design of the CDS. The design also incorporates special requirements such as controlled and/or fast cooldown of the superconducting RF cavities and their dual maximum allowable working pressures. This paper presents the overall features of the PIP-II CDS, sizing of helium process circuits, different operating modes, and calculated mass flow capacities that cater to these operating modes.

Design optimization of an additively manufactured prototype recuperator for supercritical CO2 power cycles

Supercritical CO2 (sCO2) power cycles are being developed due to their potential for high efficiency and reduced capital cost. It is necessary that these recuperators operate at high pressures and temperatures, up to 30 MPa and 900 K, with effectiveness values > 95% and pressure drops <1% to achieve high cycle efficiencies. Moreover, it is also necessary to have reasonable cost recuperators to control the capital costs of the sCO2 power cycles. In this study, a Plate Pin-Fin (PPF) heat exchanger has been proposed as an sCO2 recuperator. This preliminary recuperator design leverages capabilities enabled by additive manufacturing. Although the PPF design has characteristics similar to those of a plate heat exchanger, small diameter and relatively long fins are used to increase surface area, enhance heat transfer, and provide structural support for the partition plates that separate the fluid streams. Existing correlations for heat transfer and pressure drop were adapted for the PPF heat exchanger. These correlations were implemented in a 1D analytical model and used for the optimization of a 5-kWth high temperature recuperator for an indirect sCO2 cycle by varying the design parameters to minimize the quantity of material required. A 3D conjugate heat transfer numerical simulations were conducted to validate the heat transfer and pressure loss correlations. A steepest descent method was used to minimize heat exchanger mass for a 5-kW prototype recuperator subject to a maximum specified pressure drop. The design analysis indicated that an optimum PPF recuperator would be attained for the minimum allowable pin transverse spacing, minimum pin width, minimum pin height and near maximum cell aspect ratio. At a low material requirement of 0.216 kg/kW and a pressure drop, which is almost five times lower than the allowable pressure drop design target, the optimized PPF heat exchanger has the high potential to be an alternative to a printed circuit heat exchanger, which is a conservative design basis for the current state-of-the-art sCO2 recuperators.

A composite superconducting energy pipeline and its characteristics

A superconducting energy pipeline cooled during its clean energy transferring becomes attractive recently to be a promising alternative way for combined green energy transmission to meet the ever-rising energy demand across the world. Though, study on superconducting energy pipelines gets into the conceptual design of single energy integration, the critical multi-composite structure and its characteristics have not yet been systematical. A novel high-temperature superconducting (HTS) energy pipeline integrated with power cable and liquid hydrogen (LH2) and liquefied natural gas (LNG) is proposed in this paper. The maximum allowable temperature difference and pressure drop methods are adopted to design the pipeline. A two-dimensional axisymmetric electromagnetic thermal coupling model has been established using the finite element method. The interface magnetic field formulation, heat transfer modeling, and multiphysics interface has been applied to conduct a detailed analysis of the designed superconducting energy pipeline (LH2-LNG-HTSEP). The results show that the designed LH2-LNG-HTSEP is feasible for practical operation and has more favorite characteristics to suit the HTS cable for the composite pipeline operation. The model and analysis method provide a theoretical base for the composite superconducting energy pipeline design and structural optimization.

Cooling Effect of Water Channel with Vortex Generators on In-Wheel Driving Motors in Electric Vehicles

Designing an effective cooling system for high-power-density in-wheel motors of electric vehicles is required to avoid the irreversible demagnetization of the permanent magnet due to a rise in its temperature. In this study, a water-cooling channel was used between the stator and housing to evaluate the cooling performance of a 25 kW in-wheel motor utilizing the commercially available software Ansys Fluent 19.2. Initially, cooling channels with a single or pair of vortex generators have been used with varying heights for pressure drop evaluation considering the allowable pressure drop of 0.7 bar for a water pump. The results indicates that both a single and a pair of vortex generators satisfy the limit of a pressure drop at the height of 4 and 3 mm, respectively, and the cooling performances of two vortex generators were evaluated at these heights. It has been found that the cooling performance of a permanent magnet is enhanced by 4.1% and 6.5% using a single and a pair of vortex generators, respectively, compared to the cooling channel without a vortex generator. Furthermore, considering the ram air effect on water-cooling channels of in-wheel motors under high-speed conditions, the temperature of the permanent magnet is decreased by about 2.1 °C and was found to be 148.8 °C under the temperature limit of demagnetization of the permanent magnet.

Size optimization of heat exchanger and thermoeconomic assessment for supercritical CO2 recompression Brayton cycle applied in marine

When the state-of-the-art supercritical CO2 cycle is applied to the marines, priority should be given to the feasibility of its component size. In this study, a thermodynamic model of the marine supercritical CO2 recompression cycle was developed. To evaluate the thermoeconomic and component size of the system, the recuperator and precooler with a microtube structure were designed. After quantitatively discussing the impact of the two-stage compression mode on the component scale, the sizes of the heat exchangers were optimized based on the maximum allowable pressure drop. The parameter analysis demonstrates that increasing the speed of the power turbine is beneficial to the system thermoeconomic. Not only can an efficiency improvement of 1.73% and a cost saving of 1.77 $/MWh be achieved, but also the implementation of two-stage compression reduces the volume of the high-temperature recuperator, low-temperature recuperator, and precooler by 4.62%, 6.33%, and 37.4%, respectively. The size optimization analysis suggests that the direction with the longest distance should be regarded as the length constraint of the heat exchanger design in the absence of multi-objective optimization. Moreover, this study has guiding significance for the size optimization of the supercritical CO2 cycle used in a limited space.

Thermal Design Optimization of No Phase Change Shell-and-Tube Heat Exchanger using Particle Swarm Algorithm

Shell-and-tube heat exchanger is designed to satisfy certain requirements such as heat transfer capability, allowable pressure drop and limitation of size. Beside such requirements, it is important to consider economical point of view to get lowest total cost. In this study, computational program and optimization for thermal design shell-and-tube heat exchanger were built for liquid to liquid with no phase change process in four variables design parameters using Bell-Delaware method. The design variables were tube size, tube length, baffle cut to shell inside diameter ratio and central baffle spacing to shell inside diameter ratio. Particle swarm algorithm was used as optimization method to get lower solution for economical point of view shell-and-tube heat exchanger. The results from two study cases show that particle swarm algorithm got lower total cost from the original design. The total cost decreased 28.84 % in first study case and 52.57 % in second study case from the original design.

A comprehensive sensitivity analysis on the performance of pseudo‐steady propane thermal cracking process

AbstractThe propane thermal cracking reactor process is investigated in an industrial furnace with an alternative wall burner arrangement. Temperature and heat distribution of the furnace is obtained by three‐dimensional computational fluid dynamics (CFD) simulation technique using Ansys Fluent software. Ten calculation domains are adopted to decrease calculation costs. Different fuel rate ratios are selected as the main effective parameter on reactor performance. Different ratios of base fuel rate (0.0695 kg/s) have been considered. The obtained reactor tube wall temperature profile is used for a one‐dimensional pseudo‐steady reactor operation. By the proposed new arrangement, the created coke layer thickness is lower about 3 mm compared with the base case after 700 h. Meanwhile, Propane conversion is increased by 4%. Besides, reactor feed flow rate variations are considered one of the essential parameter on reactor operation. Despite surging in propylene yield after coke formation, ethylene yield decreases during the process. By increasing the fuel rate in each reactor flow rate, ethylene increased while propylene yield descended. The maximum allowable pressure drop is 2.7 bar. At 0.5ṁ fuel rate and 0.85 kg/s reactor flow rate, pressure drop, reactor lifetime, and ethylene yield are 1.23 bar, 1444 h, and 28%; respectively. In the reactor flow of 0.85 kg/s, by raising fuel rate 0.5–2ṁ ethylene yield is increased from 28% to 46.83%, while process operating time is reduced to 780 h. According to the results, 0.8–0.85 kg/s could be considered as an appropriate range for reactor feed flow rate.

Influence of inlet configuration and distributor geometry on the performance of cryogenic plate-fin heat exchangers

• A three-dimensional simulation model is used to evaluate flow patterns in plate-fin heat exchangers. • Performance of different distributor geometries is evaluated in terms of pressure drop and heat transfer. • Different feasible inlet configurations of a 6-stream heat exchanger are compared to an idealized geometry. • Inlet configurations can significantly affect the performance of plate-fin heat exchangers. The influence of inlet placement and distributor geometry on the steady-state efficiency and pressure drop of cryogenic plate-fin heat exchangers (PFHEs) is studied using a three-dimensional simulation model. The simulation model employs a porous media approach to combine computational fluid dynamics with well-established correlations for heat transfer and pressure drop in fin materials. An isothermal study is conducted for comparison of six different distributor geometries. The selection of a favorable design depends on a trade-off between heat transfer and allowable pressure drop of a specific task but the presented results can serve as a guideline. Furthermore, two different configurations of a 6-stream PFHE are compared to an idealized, pseudo one-dimensional design. Both feasible designs lead to a significant increase in pressure drop and the thermal efficiency of the feasible designs differs by 5 percentage points. This highlights the necessity of considering the inlet- and distributor configuration in the design of a cryogenic PFHE.

Multi-scale modeling and simulation of low-pressure methane bi-reforming using structured catalytic reactors

Methane bi-reforming has gained interest recently for its potential of converting CH4 and CO2 into chemicals while avoiding catalyst deactivation by coke formation. Recycling CO2 produced can be considered, but introduces constraints on the allowable pressure drop over the reactor. The latter is particularly the case in low-pressure processes, such as those encountered in the steel industry. The paper reports on a multi-scale modeling approach for a structured catalytic reactor that offers lower pressure drop than classical pellets while improving heat transfer. The use of a thin catalytic coating furthermore improves the catalyst effectiveness. The coupled CFD-reaction model accounts for the details of the reaction mechanism and kinetics, intra-catalyst transport and the details of the flow pattern. Radiative heat transfer and thermal conduction in the reactor tube walls and in the reactor internals coated with catalyst are also taken into account. Several scale-bridging strategies have to be introduced and combined to allow a computationally tractable solution. This requires a variety of detailed experimental data, an aspect that is also discussed. The coupled CFD-reaction model was first validated using data from a bi-reforming pilot plant and then used to evaluate the performance of a structured reactor under typical commercial process conditions and to study optimization of the reactor design and potential increase in capacity.

De-dusting in biomass gasification process using a coated bag filter

The gasification process of solid refuse fuel (SRF) releases tar and particulate pollutants in addition to many gaseous pollutants. This study investigated the effectiveness of pre-coating on a fabric filter for dust collection instead of a combined control process involving a wet scrubber and a bag filter. The powder layer composed of hydrated lime, wood char, or activated carbon contributed to reduce the blocking of the open pores of the fabric filter by tar and particulate matter. Among the three materials, hydrated lime was accumulated the most, resulting in a 0.7-mm coating thickness. The filter made of polyphenylene sulfide was the most effective in collection efficiency (86%) for the allowable pressure drop (60 mmH2O). Since a single filter with pre-coating is highly efficient, an oil scrubber with a removal efficiency of 2% to 3% is not essential.

Thermal Design Optimization of Shell-and-Tube Heat Exchanger Liquid to Liquid to Minimize Cost using Combination Bell-Delaware Method and Genetic Algorithm

Shell-and-tube heat exchanger is designed to satisfy certain requirements such as heat transfer capability, allowable pressure drop and limitation of size. Beside such requirements, it is important to consider economical point of view to get the lowest total cost. In this study, computational program and optimization for thermal design shell-and-tube heat exchanger were built for liquid to liquid with no phase change process in four variables design parameters using Bell-Delaware method. The design variables were tube size, tube length, baffle cut to shell inside diameter ratio and central baffle spacing to shell inside diameter ratio. The genetic algorithm was used as optimization method to get lower solution for economical point of view. The results from two study cases show that the genetic algorithm got lower total cost from the original design. The total cost decreased 28.83% in first study case and 52.56% in second study case from the original design.

Optimization of Heat Transfer and Pressure Drop in Axially Finned Staggered Tube Banks

Numerical optimization of heat and fluid flow over staggered tube banks are investigated for both unfinned and axially finned tube banks. Ansys Fluent software is utilized for numerical computations. To find maximum total heat transfer and minimum volume of tube bank for the given mass flow rate, allowable pressure drop and tube bank effectiveness; A Multi-objective Genetic Algorithm II is used. Optimum designs are given on tabular forms and variations of total heat transfer with total volume are presented. Moreover, effects of transversal and longitudinal pitches on objective functions are graphically demonstrated. In order to confirm reliability of the numerical studies, unfinned staggered tube bank configuration is compared with experimental studies in literature. As a result of optimization studies, axial fin usage results in 42.7% decrement in volume of staggered tube bank with respect to unfinned case, while heat transfer values are equal with maximum obtainable heat transfer rate for the given optimization problem.

3D printed compact heat exchangers with mathematically defined core structures

Abstract This paper describes a new design method for generating a compact heat exchanger (CHX) computational model consisting of triply periodic minimal surface (TPMS) core structures. These TPMS-based core structures are not easy to design using existing CAD systems, especially in the case of CHXs with complex 3D geometries. In this paper, we introduce a novel CHXs design strategy based on the calculation of volumetric distance fields (VDFs). All geometric components, including TPMS-based core structure, heat exchanger exterior shape, and a set of parts for inlet and outlet, are expressed as VDFs in a given design domain. This VDF-based geometric components description allows for the computationally efficient design of a complex-shaped CHX computational model with high levels of geometric complexity. In conjunction with several TPMS-based CHX prototypes built with additive manufacturing (AM) technologies, we describe and discuss the design and manufacturing results for a wide range of CHXs with various geometries to validate the effectiveness of the newly proposed design method. Besides, by examining the heat transfer performance experimental data, we show that the innovative CHX production method using the combination of VDF-based Boolean operations, TPMS-based core structures, and AM technologies proposed in this paper can create an ultra-efficient CHX while maintaining an allowable pressure drop.