Allowable Pressure Drop Research Articles

Numerical simulation and experimental research on heat transfer and flow resistance characteristics of asymmetric plate heat exchangers

The asymmetric plate heat exchanger (APHE) has the possibility of achieving balanced pressure drops on both hot and cold sides for situations with unbalanced flow, which may in turn enhance the heat transfer. In this paper, the single-phase water flow and heat transfer of an APHE consisted of two types of plates are numerically (400⩽Re⩽ 12000) and experimentally (400⩽Re⩽ 3400) investigated. The numerical model is verified by the experimental results. Simulations are conducted to study the effects of N, an asymmetric index proposed to describe the geometry of APHEs. The correlations of the Nusselt number and friction factor in the APHEs are determined by taking N and working fluids into account. It is found that an optimal Nexists where the pressure drops are balanced and the heat transfer area reaches the minimum. The comparison between heat transfer and flow characteristics of the APHEs and the conventional plate heat exchanger (CPHE) is made under various flow rate ratios of the hot side and the cold side and different allowable pressure drops. The situations under which APHE may perform better are identified based on a comprehensive index Nu/f1/3.

Test and Modeling of the Hydraulic Performance of High-Efficiency Cooling Configurations for Gyrotron Resonance Cavities

The design and manufacturing of different full-size mock-ups of the resonance cavity of gyrotrons, relevant for fusion applications, were performed according to two different cooling strategies. The first one relies on mini-channels, which are very promising in the direction of increasing the heat transfer in the heavily loaded cavity, but which could face an excessively large pressure drop, while the second one adopts the solution of Raschig rings, already successfully used in European operating gyrotrons. The mock-ups, manufactured with conventional techniques, were hydraulically characterized at the Thales premises, using water at room temperature. The measured pressure drop data were used to validate the corresponding numerical computational fluid dynamics (CFD) models, developed with the commercial software STAR-CCM+ (Siemens PLM Software, Plano TX, U.S.A.) and resulting in excellent agreement with the test results. When the validated models were used to compare the two optimized cooling configurations, it resulted that, for the same water flow, the mini-channel strategy gave a pressure drop was two-fold greater than that of the Raschig rings strategy, allowing a maximum flow rate of 1 × 10−3 m3/s to meet a maximum allowable pressure drop of 0.5 MPa.

Application of compact thermoelectric generator to hybrid electric vehicle engine operating under real vehicle operating conditions

A compact thermoelectric generator is developed for waste-heat recovery in a sedan-type hybrid electric vehicle. The shape and dimensions of the thermoelectric generator are precisely determined by performing a series of theoretical analyses to meet spatial and maximum allowable pressure drop restrictions. The waste-heat recovery performance of the thermoelectric generator is experimentally evaluated using a hybrid electric vehicle engine under the nine most commonly experienced driving conditions. One surface of the thermoelectric modules is heated by the exhaust gas flow, whereas the other surface is cooled by the engine coolant flowing at 10 L/min and 353 K. A maximum power output of ~118 W and an energy conversion efficiency of ~2.1% are obtained using 12 thermoelectric modules under the engine operating conditions that led to the highest exhaust gas flow rate and temperature. The waste-heat recovery characteristics of the present thermoelectric generator are systematically analyzed, and the results corresponding to thermal energy flow and heat recovery efficiency, as well as the voltage output–current output and power output–load resistance curves, are presented.

셸 앤 관 열교환기에서 셸 측의 압력강하 특성

Shell and tube heat exchangers are the most common type of heat exchangers which are widely used in industrial applications. The pressure drop prediction on the shell side of a shell and tube heat exchanger is quite complicated due to taking into account of the presence of bypass and leakage streams. The Bell-Delaware method reflects the effects associated with leakage and bypass streams on the shell side pressure drop. The simulation results show that the shell side pressure drop for tube layout of 90o is lower than that of the other cases. In addition, The lower allowable pressure drop for tube side is obtained from tube layout of 90o. Finally, it is found that the overall heat transfer coefficient and surface area for tube layout of 90o are higher than the other cases.

Concept Design of 1 GW LH2-LNG-Superconducting Energy Pipeline

A 1 GW LH2-LNG-superconducting energy pipeline has been designed, and the design parameters under the consideration of the maximum allowable temperature difference and pressure drop are verified to achieve high efficiency.

Technical background on design of DS recombiner for fusion facility

Detritiation system of a nuclear fusion facility should maintain its detritiation performance even in an event of accident of the facility such as fire. The major technical background on design of recombiner for tritium oxidation are detailed kinetics data including the impact of possible gaseous impurities on kinetics, characteristics on pressure drop, impact of heat of reaction and effect of flow rate on kinetics. The volume of catalyst is evaluated by the overall reaction rate constant, required conversion efficiency and gas flow rate for processing. Our demonstration showed that the overall reaction rate constant has the effect of hydrogen concentration. Among possible impurity gases, water vapor, ammonia and halogenated acids affect tritium oxidation. Experimental demonstration revealed that the scale of recombiner have little effect on the overall reaction rate constant. The height of the catalyst layer is determined first from the allowable pressure drop considering the upstream line of the recombiner not to be pressurized. Then, the inner diameter of the recombiner is determined from the volume of catalyst. The concept of adiabatic recombiner with a vacuum jacket can be applied to avoid tritium permeation. The rate of tritiated methane produced by side reactions on the catalyst between methane and tritium was negligibly small.

A Comprehensive Investigation of Depth Filter Functionality for a Colloidal Silica Slurry Used for Semiconductor Manufacturing Process

We report a comprehensive study on depth filter functionality by using a slurry, colloidal silica, used for chemical mechanical polishing process in semiconductor manufacturing. We show that the depth filters with nominal pore size ranging from 0.1 $\mu \text{m}$ to 0.5 $\mu \text{m}$ selectively reduces the concentration of ‘large’ particles up to 80%, and maintains other critical properties of slurry including solid content ratio, mean diameter of particles, pH, zeta potential, and conductivity. Furthermore, we find the particle size-dependent filter efficiency, and the stable and allowable pressure drop across the filters. The depth filtration efficiently reduces the large particle concentration in slurry, and thus could be useful for suppressing the associated manufacturing defects such as micro-scratches and pits on the polished wafers.

Strategy and consequence of intermittent segmented pulse-jet cleaning for long-box-shaped filter dust collector

This study investigated the influence of the intermittent segmented pulse-jet cleaning strategy for dust collectors on their filtration pressure drop, dust emission concentration, and detached dust migration. An experimental pulse-jet cleaning dust collector with 6 filter cartridges in line was designed. The intermittent segmented pulse-jet cleaning was simulated. The air volume, filtration pressure drop, and dust emission concentration were tested, and the resistance to airflow through the cartridge was calculated. The pulse-jet cleaning parameters, including positive and reverse cleaning orders, online and offline conditions, single-row and dual-row pulse-jet modes, and maximum allowable pressure drop, were analyzed. Re-capture (captured again by the just cleaned filter) and sec-capture (secondary captured by other filters) rates of the detached dust from the cleaned filter cartridge were defined and calculated. This study has demonstrated that the cleaning order has remarkable influence on the operation performance. The positive cleaning order leads to lower residual pressure drop, more uniform residual dust on the cartridges, and higher dust emission concentration during the cleaning affected stage. More obvious re-capture and sec-capture phenomena are found in the reverse cleaning order, with re-capture and sec-capture rates of 17.86% and 10.00%, respectively. This study is useful for optimizing the design of dust collector cleaning.

An approach for pillow plate heat exchangers design for single-phase applications

Pillow-plate heat exchangers (PPHEs) represent a novel equipment type. For their application in industry, reliable preliminary design techniques are required. In this article, the existing methods for heat exchangers design are analysed and the approach for selecting the PPHE design with minimal heat transfer area is proposed. It is based on the mathematical model of thermal and hydraulic PPHE behaviour, in which the overall heat transfer coefficient and pressure drop in PPHEs are expressed through the fluid velocity. The estimation of fluid velocities in PPHE channels is based on the condition that the predefined allowable pressure drop is fully exploited. Two case studies for water heating and crude oil preheat train operating conditions are discussed, in which the flowrates of the fluids on the hot and cold sides differ significantly. The PPHE design with minimal heat transfer area for the considered case studies is presented, with specified pillow-plate geometry parameters and distance between pillow-plate panels. The resulting pressure drops and velocities in PPHEs channels as well as the obtained heat transfer surface areas are compared with existing data for chevron-type plate heat exchangers (PHEs) designed for the same operating conditions. This comparison shows that PPHEs have higher velocities in channels, longer plates and lower heat transfer area. It can be concluded that PPHEs can be successfully used for operating conditions, under which the flow rates for hot and cold fluid are significantly different and the application of chevron-type PHEs with single-pass arrangement is complicated.

Efficient calculation of constraint back-offs for optimization under uncertainty: A case study on maleic anhydride synthesis

In the present work we propose an efficient and general algorithm for optimization under uncertainty based on the work of Srinivasan et al. (2003). We use specialized cubature rules to speed up the uncertainty propagation step which results in a significant reduction of the overall computational effort. The approach is illustrated by studying the optimal design of a fixed bed reactor for the synthesis of maleic anhydride from raffinate II feedstock, where the amount of n-butane and n-butenes in the feed is assumed to be uncertain. Applying the algorithm results in a robustified reactor design which shows significantly less temperature constraint violations and runaway conditions while still satisfying reactor performance criteria such as minimally required conversion and maximum allowable pressure drop.

Deriving guidelines for the design of plate evaporators in heat pumps using zeotropic mixtures

This paper presents a derivation of design guidelines for plate heat exchangers used for evaporation of zeotropic mixtures in heat pumps. A mapping of combined heat exchanger and cycle calculations for different combinations of geometrical parameters and working fluids allowed estimating the trade-off between heat transfer area and pressure drops on the thermodynamic and economic performance indicators of the cycle. Compressor running costs constituted the largest cost share, and increased due to a steep decrease of the heat pump coefficient of performance at high refrigerant pressure drops. It was found that the pressure drop limit leading to infeasible designs was dependent on the working fluid, thereby making it impossible to define a guideline based on maximum allowable pressure drops. It was found that economically feasible designs could be obtained by correlating the vapour Reynolds number and the Bond number at the evaporator inlet as ReV−0.42Bd0.26≈0.040. The use of the proposed guideline was illustrated for the mixture Propane/Iso-Pentane (0.5/0.5), leading to evaporator designs with net present values deviating maximum −4.4% from the best value found in the mapping. The presented methodology can be applied in different scenarios to develop similar guidelines, thereby decreasing the cost of combined cycle and component optimizations.

Optimal design of microtube recuperators for an indirect supercritical carbon dioxide recompression closed Brayton cycle

This paper presents a baseline design and optimization approach developed in Aspen Custom Modeler (ACM) for microtube shell-and-tube exchangers (MSTEs) used for high- and low-temperature recuperation in a 10 MWe indirect supercritical carbon dioxide (sCO2) recompression closed Brayton cycle (RCBC). The MSTE-type recuperators are designed using one-dimensional models with thermal-hydraulic correlations appropriate for sCO2 and properties models that capture considerable nonlinear changes in CO2 properties near the critical and pseudo-critical points. Using the successive quadratic programming (SQP) algorithm in ACM, optimal recuperator designs are obtained for either custom or industry-standard microtubes considering constraints based on current advanced manufacturing techniques. The three decision variables are the number of tubes, tube pitch-to-diameter ratio, and tube diameter. Five different objective functions based on different key design measures are considered: minimization of total heat transfer area, heat exchanger volume, metal weight, thermal residence time, and maximization of compactness. Sensitivities studies indicate the constraint on the maximum number of tubes per shell does affect the number of parallel heat exchanger trains but not the tube selection, total number of tubes, tube length and other key design measures in the final optimal design when considering industry-standard tubes. In this study, the optimally designed high- and low-temperature recuperators have 47,000 3/32 in. tubes and 63,000 1/16 in. tubes, respectively. In addition, sensitivities to the design temperature approach and maximum allowable pressure drop are studied, since these specifications significantly impact the optimal design of the recuperators as well as the thermal efficiency and the economic performance of the entire sCO2 Brayton cycle.

Finding a criterion for the pressure loss of energy recovery exchangers in HVAC systems from thermodynamic and economic points of view

Heat recovery devices can help ventilation systems conserve energy; However, they cause a pressure drop in the system, and hence the system incurs an electricity consumption. In the present paper, the maximum allowable pressure drop of the recovery units is achieved from thermodynamic and economic points of view. The novelty of the research is that, unlike the existing criterion which does not differ for different cities, the introduced criteria can be calculated for each city with individual weather, economic, power plants, and energy conditions. Although the methods presented to calculate the criteria consider a broad range of effective parameters, there is no need to use complex energy simulation methods. Moreover, for each city, four types of criteria are introduced, which allows the city authorities to choose the best ones according to their city conditions, and then calculate the chosen criteria by the data of the city. In order to gain the criteria, modified enthalpy-hours and bin method variables are introduced to calculate sensible and latent energy consumption due to ventilation. The criteria are numerically calculated for Kerman city in Iran, and the results show that the recovery type and the chosen viewpoint has a considerable effect on the allowable pressure drop. The sensitivity of the results to different variables is analyzed in the end.

Optimal design of the first stage of the plate-fin heat exchanger for the EAST cryogenic system

The size of the heat exchanger is an important factor determining the dimensions of the cold box in helium cryogenic systems. In this paper, a counter-flow multi-stream plate-fin heat exchanger is optimized by means of a spatial interpolation method coupled with a hybrid genetic algorithm. Compared with empirical correlations, this spatial interpolation algorithm based on a kriging model can be adopted to more precisely predict the Colburn heat transfer factors and Fanning friction factors of offset-strip fins. Moreover, strict computational fluid dynamics simulations can be carried out to predict the heat transfer and friction performance in the absence of reliable experimental data. Within the constraints of heat exchange requirements, maximum allowable pressure drop, existing manufacturing techniques and structural strength, a mathematical model of an optimized design with discrete and continuous variables based on a hybrid genetic algorithm is established in order to minimize the volume. The results show that for the first-stage heat exchanger in the EAST refrigerator, the structural size could be decreased from the original 2.200 × 0.600 × 0.627 (m3) to the optimized 1.854 × 0.420 × 0.340 (m3), with a large reduction in volume. The current work demonstrates that the proposed method could be a useful tool to achieve optimization in an actual engineering project during the practical design process.

Laboratory measurements of slippage and inertial factors in carbonate porous media: A case study

Two important issues for accurate modeling of gas reservoir performance are the gas slippage and the inertia flow within porous media. Depending on the flow condition, these factors can make the gas permeability differ from the true (liquid) permeability. Nevertheless, since the gas flow tests are cheaper and less time consuming than the liquid flow tests, a reservoir engineer may choose to estimate the true (liquid) absolute permeability from the results of a single gas permeability test utilizing a valid empirical correlation. Although many such correlations exist in the literature, most of them have been developed for unconsolidated porous media or sandstone core samples. Therefore, using them for a specific formation will result in erroneous predictions.This paper is presented in three parts. In the first part, an empirical equation is developed to estimate the gas slippage factor using the results of laboratory measurements on 49 samples of Iranian carbonate reservoirs of Kangan and Dalan. In the second part, a correlation is developed to estimate the inertia factor for the samples. In the last part of the paper, an equation is derived to estimate maximum allowable pressure drop per length to maintain the laminar (Darcy) flow regime in the samples.The developed models in the first and the second parts of the current paper match the experimental data more accurately than the popular existing correlations. The derived equation in the last part is applicable in proper design of gas flow tests, where a laminar flow must be maintained in porous media.

Heat Exchanger Design By Using Software Program

This paper is intended to assist anyone with some general technical experience, but perhaps limited specific knowledge of heat transfer equipment. A characteristic of heat exchanger design is the procedure of specifying a design, heat transfer area and pressure drops and checking whether the assumed design satisfies all requirements or not. The purpose of this paper is how to design the oil cooler (heat exchanger) especially for shell-and-tube heat exchanger, which is the majority type of liquid-to-liquid heat exchanger. General design considerations and design procedure are also illustrated in this paper. In design calculation, the Mat/LAB and Auto/CAD software are used. Fundamental heat transfer concepts and complex relationships involved in such exchanger are also presented in this paper. The primary aim of this design is to obtain a high heat transfer rate without exceeding the allowable pressure drop. This computer program is highly useful to design the shell-and-tube type heat exchanger and to modify existing deign.

High-performance strategy of a simulated moving bed chromatography by simultaneous control of product and feed streams under maximum allowable pressure drop

In this study, a novel operating strategy was developed to improve the separation performance of simulated moving bed (SMB) chromatography by the simultaneous control of product outlet streams and feed inlet stream (SimCon). The SimCon operation can achieve a high separation performance without exceeding the maximum allowable pressure drop in an SMB system. The SimCon operation consisted of three steps within a single switching period: the initial, middle, and last steps. The extract port and feed-inlet port were closed at the initial step, but the raffinate port was closed at the last step. Therefore, in the SimCon strategy, we introduce two additional operating variables in a switching period, namely the middle time and middle length. In the SimCon operation, the middle step is a key factor to achieving a good separation performance because concentration profiles can be well controlled by two new middle-step variables. The SimCon operation showed outstanding results compared with those of the corresponding conventional SMB and other stream-control strategies in terms of purity, recovery, productivity, and eluent consumption. Because the SimCon operation can be operated with smaller flow and pressure fluctuations than other flow-rate-control strategies and improves the column efficiency, it is expected that the strategy can be practically adapted to real SMB processes with a good separation performance.

A new optimization approach for shell and tube heat exchangers by using electromagnetism-like algorithm (EM)

This study proposes a new procedure for optimal design of shell and tube heat exchangers. The electromagnetism-like algorithm is applied to save on heat exchanger capital cost and designing a compact, high performance heat exchanger with effective use of the allowable pressure drop (cost of the pump). An optimization algorithm is then utilized to determine the optimal values of both geometric design parameters and maximum allowable pressure drop by pursuing the minimization of a total cost function. A computer code is developed for the optimal shell and tube heat exchangers. Different test cases are solved to demonstrate the effectiveness and ability of the proposed algorithm. Results are also compared with those obtained by other approaches available in the literature. The comparisons indicate that a proposed design procedure can be successfully applied in the optimal design of shell and tube heat exchangers. In particular, in the examined cases a reduction of total costs up to 30, 29, and 56.15 % compared with the original design and up to 18, 5.5 and 7.4 % compared with other approaches for case study 1, 2 and 3 respectively, are observed. In this work, economic optimization resulting from the proposed design procedure are relevant especially when the size/volume is critical for high performance and compact unit, moderate volume and cost are needed.

Distillation in special chemistry

In the final product, special chemicals are minor ingredients by volume, but essential for performance and function. Distillation is the separations workhorse. Specific challenges arise from the nature of special chemicals. High product purity or tight control of trace impurities have to be achieved in non-ideal, often aqueous systems. Foaming, fouling and three-phase systems are often encountered. This paper addresses two typical challenges in special chemicals distillation and practical solution methods.One example is distillation in deep vacuum in order to minimize thermal degradation of temperature-sensitive components. Enlarging column diameter to meet a maximum allowable pressure drop specification instead of a certain flooding factor entails designs with low liquid loads well below the limits given in literature. Special care should be given to distributor design to ensure acceptable efficiency.In multi-step special chemicals synthesis, reactive distillation is an elegant operation to increase conversion and selectivity or to reduce recycle rate. However, additional design interactions arise, which increase the sensitivity to parameter uncertainty. Sensitivity analysis is a powerful tool to assess the process risk arising from incomplete design information and to devise fallback options.In both examples, plant data from similar processes is invaluable to validate designs.

Extension of the Rapid Design Algorithm for Twisted‐Tube Evaporative Fluid Coolers

AbstractThe thermal analysis performance of evaporative fluid coolers (EFCs) is improved by replacing plain tubes by twisted oblong tubes. Results of the system are assessed by a rapid design algorithm (RDA) and compared to conventional plain‐tube EFCs and other traditional algorithms including the effectiveness number of transfer units (ϵ‐NTU). Based on the RDA, a relationship between heat transfer coefficients, pressure drops, heat transfer area, and mass transfer coefficient is derived. Using the maximum allowable pressure drops in this algorithm, the minimum required heat transfer area can be determined. The algorithm is validated by comparing the plain‐tube EFC design with twisted‐tube design. The RDA‐designed EFCs with twisted tubes provide higher efficiency compared with the traditional designs with plain tubes in such that the new design needs a lower heat transfer area for a given heat load.