Pressure Drop Characteristics Research Articles

Pressure drop characterization on cryogenic multiphase flow in spiral wounded heat exchanger under high mass flow conditions

In order to clarify the influence of dryness, working medium and mass flow rate on pressure drop characteristics in shell side of spiral wound heat exchanger, a simplified test section has been analyzed in this study. The model is with a coiled section under compact design: 1 mm layer spacing of and 2 mm tube spacing in the main structure. The mixed alkane composed of methane, ethane, propane and others are used as working fluid. The current study is focused on the pressure drop behaviors and the effects of multiphase flow in different stages of cooling process in the cryogenic heat exchanger. Systematic numerical model has been established in this study to investigate the pressure behaviors, which are also verified against newly constructed experimental system. Operating conditions range from vapor quality of 0.1–0.9, mass flux of 60–120 kg·(m2·s)−1, under the operation pressure of 0.25 MPa and temperature from −27 °C to −170.6 °C. The absolute error of pressure measurement is less than 1.5 kPa and the absolute error of pressure drop measurement is less than 25 Pa, and the relative error is 0.25 % for the current test. The experimental results show that the friction pressure drop increases with the increase of vapor quality from 0.1 to 0.9 and mass flux from 60 to 120 kg·(m2·s)−1, and the growth gradient of friction pressure drop decreases with the increase of vapor quality. A set of pressure drop correlation has been established to reflect the influence of factors such as vapor quality and mass flow rate, and the deviation between predicted pressure drop and experimental data was within ±20 %.

Development of ceramic-based 3D staggered microchannel catalyst support used in MSR microreactor for hydrogen production

Ceramic materials have good temperature and corrosion resistance, which is one of the ideal materials used in microchannel catalyst support for medium and high temperature catalytic reaction. Three-dimensional (3D) flow field structure is the most potential microchannel structure due to its high efficiency of mass and heat transfer. However, ceramic materials are hard and brittle, and the size of microchannel structures are small. It is a great challenge to construct a ceramic based microchannel catalyst support with a complex 3D flow field by traditional processing methods. In this paper, a 3D staggered flow field microchannel with the width of 450 μm and the depth of 1500 μm was designed and processed by diamond wire sawing. The mass and heat transfer properties of straight microchannel (SM), micro-column array (MA) and 3D staggered microchannel (3DSM) were compared by simulation. The effects of different windward angles (60°, 90° and 120°) on the performance of mass and heat transfer in 3D flow field were analyzed. The simulation results showed that the performance evaluation criteria (PEC) of 3DSM120° was 1.37, which meant better performance of heat and mass transfer than SM and MA. And the PEC of 3DSM structure was increased from 1.25 to 1.37 with the windward angle increasing from 60° to 120°. The pressure drop characteristics and hydrogen production performance of the microchannel catalyst support with different structures (SM, MA, 3DSM) were tested. The experimental results showed that the 3DSM had a good hydrogen production performance of methanol steam reforming (MSR) with the inlet flow rate of 1.5 ml/h at 300 °C. The methanol conversion rate was 99.43%, which was 15.41% and 6.20% higher than that of SM and MA, respectively, due to its better performance of mass and heat transfer.

Numerical study of heat transfer, pressure drop and entropy production characteristics in inclined heat exchangers with uniform heat flux using mango bark/CO2 nanofluid

For sustainable low-carbon cities, using sustainable urban energy system solutions is imperative. CO2-based bionanofluid is one proposed energy system solution that is sustainable and environmentally friendly. This paper examines the thermal-hydraulic and entropy production properties of mango bark/CO2 nanofluid for industrial-inclined gas cooling applications. The influence of gravitational force (in terms of tube inclination angle), volume fraction, and Reynolds number on the heat transfer, pressure drop, and entropy production of CO2-based mango bark nanofluids in laminar flow through a circular aluminum tube are numerically studied. The bionanofluid flows through a tube with an inner radius of 2.25 mm, a length of 970.0 mm, and an initial temperature of 320.0 K. A constant heat flux of −10.0 W/m2 is applied to the flow at its walls. The laminar flow regime with Reynolds numbers of 100, 400, 700, and 1000 are subjected to flow inclinations of ±90°, ±60°, ±45°, ±30°, and 0° and bionanofluid volume fractions of 0.5%, 1.0%, and 2.0%. Results show that ±45° tube inclination angle offers the optimal heat transfer coefficient, maximum pressure drop, and minimum total entropy production rates for Re > 100; however, for Re = 100, these occur at the inclination angle of −30° and +60°. The pressure drop shows less sensitivity to the inclination angle; however, it offers peak values at the same inclination angles as the heat transfer coefficient for the respective Reynolds number values. The maximum thermal enhancements due to gravitational effect are 42%, 93.98%, 121.28%, and 150% for Reynolds numbers of 100, 400, 700, and 1000, respectively, while that due to nanofluid volume fraction are less than 16%.

Heat transfer and pressure drop characteristics of the silicone-based plate heat exchanger

The paper presents an experimental investigation of a silicone based heat exchanger, with passive heat transfer intensification by means of surface enhancement. The main objective of this paper was to experimentally investigate the performance of a heat exchanger module with the enhanced surface. Heat transfer in the test section has been examined and described with precise measurements of thermal and flow conditions. Reported tests were conducted under steady-state conditions for single-phase liquid cooling. Proposed surface modification increases heat flux by over 60%. Gathered data presented, along with analytical solutions and numerical simulation allow the rational design of heat transfer devices.

Heat transfer enhancement for outlet part of the bionic microchannel by various concise rib configurations

In this study, to solve the problems of high temperature in the region near the outlet of microchannel and the difficulty in manufacturing complex ribs, three concise rib configurations were proposed, i.e. semicircle rib (SE-MCHS), triangular rib (TR-MCHS) and square rib (SQ-MCHS), respectively. The flow, heat transfer and pressure drop characteristics, and the comprehensive performance for the designed MCHS were analyzed numerically. The results showed that for the case of SQ-MCHS, the heat transfer can be enhanced by a maximum of 273.22% compared to the regular straight channel at Re is 1000. However, SQ-MCHS also exhibited a maximum pressure drop. Therefore, the comprehensive heat transfer performance index was put forward to consider both heat transfer and pressure drop. Our analysis indicated that when Re is 400, the MCHS with square ribs had a better comprehensive performance, while when Re is more than 600, the MCHS with semicircle ribs has a better comprehensive performance. Our work should be of practical value for the design of high efficiency microscale heat sink.

Flow characteristics of moist-mixed materials for shotcrete: From experiment to CFD-DEM simulation

Moist-mixed materials for shotcrete is an effective way to solve the volume control of shotcrete equipment in small and medium cross-section tunnels. The material of moist-mixed materials for shotcrete is characterized by cross-scale particle composition, and the problems of difficult dust control and short conveying distance remain unsolved. The pneumatic conveying simulation of the moist-mixed materials for shotcrete is studied using the CFD-DEM method. At the same time, a pipeline test system is designed, and the effectiveness of the CFD-DEM coupling model is verified by comparing the pressure drop and flow pattern with the field experiment. The model is used to study the pressure drop characteristics under different tilt angles, lifting angles, bend diameter ratio, and bend angle, involving three aspects: pressure drop in acceleration section (PDAS), unit pressure drop in stable section (PDSS), and energy loss caused by the elbow (ELE). The pressure drop model of pneumatic conveying of moist-mixed materials for shotcrete is established, and the relationship between the PDAS, PDSS, and ELE is obtained. The relationship between the Froude number and solid-gas ratio is clarified, and the calculation formula of maximum feed rate or minimum air flow rate is deduced. The velocity and spatial position distribution of particles at different tilt and lifting angles are revealed, and the elbow's main wear areas and wear rates at different bend angles and bend diameter ratios are obtained. The fundamental research has realized the unification of experiments and numerical simulation. The pressure drop law brought can guide further research on long-distance pneumatic conveying of moist-mixed materials for shotcrete.

Pressure drop reduction of the impeller spiral static mixer design enabled by additive manufacturing

A new spiral static mixer (SSM) design, also known as helical or twisted tape mixers, called the Impeller SSM, inspired by centrifugal pump impeller blades and fabricated by additive manufacturing (AM), is presented. The pressure drop and mixing efficiency of an Impeller SSM are compared to the standard SSM. Both the pressure drop and mixing characteristics are measured experimentally and validated by computational fluid dynamics (CFD) analyses. Five Impeller SSM designs of different taper, release, and attack angles were studied. Compared to a standard SSM of the same size, the Impeller SSM demonstrated a pressure drop (and power) reduction up to 18.2%. Such reductions could lead to significant energy saving and size reduction in static mixer industrial applications. Experimental results also show the ability of AM to fabricate the custom Impeller SSM without using costly machining and joining techniques.

Analysis of Flow and Pressure Drop on Tube Side of Spiral Tube Heat Exchanger under Sloshing Conditions

The utilization of the spiral tube heat exchanger (SHE) has become increasingly prevalent in large-scale liquefaction processes. However, the flow pattern and frictional pressure drop of two-phase flow in the spiral tube have been scarcely studied, particularly under offshore sloshing conditions. An experimental system had been developed to explore the flow pattern and frictional pressure drop characteristics of mixed hydrocarbon fluid in a spiral tube. Moreover, these have been developed in order to examine the effects of sloshing style (roll, pitch, heave), sloshing period (5–15 s), sloshing amplitude (5–15° or 50–150 mm), mass flux (200–800 kg/(m2·s)), vapor quality (0–1), and saturation pressure (2–4 MPa) on the frictional pressure drop of methane/ethane mixture in the spiral tube. The results indicated that sloshing conditions reduce the frictional pressure drop, thereby enhancing fluid flow. A correlation was established to predict the sloshing factor of frictional pressure drop, and the MARD under verification conditions was 6.04%. Furthermore, three flow pattern boundaries were proposed based on We* as an indicator.

Numerical Investigation of Heat Transfer and Pressure Drop Characteristics in a Double Pipe Heat Exchanger with Corrugated Tubes and Rod Baffles at Various Reynolds Numbers

Numerical Investigation of Heat Transfer and Pressure Drop Characteristics in a Double Pipe Heat Exchanger with Corrugated Tubes and Rod Baffles at Various Reynolds Numbers

Machine learning-assisted correlations of heat/mass transfer and pressure drop of microchannel membrane-based desorber/absorber for compact absorption cycles

Microchannel membrane-based desorbers and absorbers are key components in efficient and compact absorption refrigeration systems. To improve the accuracy of current empirical correlations for describing the heat/mass transfer and solution pressure drop characteristics, more advanced correlation models are urgently needed. This study applies three machine learning algorithms, namely Random Forest (RF), Least-Squares Support Vector Machine (LS-SVM), and Genetic Algorithm-optimized Back Propagation Artificial Neural Network (GABPNN), to develop new models for Nusselt number (Nu), Sherwood number (Sh), and friction factor (Fr) of microchannel membrane-based desorber and absorber, respectively, based on experimental results. These machine learning-assisted models effectively improve the prediction accuracy for both the desorber and absorber. Among them, the Random Forest model performs best, improving the prediction accuracy by 12.37% (Nu), 21.49% (Sh), and 14.24% (Fr) for the desorber and 24.28% (Nu), 27.82% (Sh), and 30.47% (Fr) for the absorber, compared to the conventional empirical correlations. Moreover, in relative to the correlations obtained from the literature, the Random Forest model predicts the overall heat transfer coefficient (U), sorption rate (J), and solution pressure drop (DP) with accuracies higher by 44.75%, 64.66%, and 83.52% for the desorber, and 79.66%, 81.52%, and 69.53% for the absorber. This study is expected to facilitate the simulation, design, and optimization of microchannel membrane-based desorbers/absorbers towards more efficient and compact absorption cycles.

Conveying characteristics of shrimp feed pellets in pneumatic conveying system and minimum power consumption dissipation factor

Based on the CFD-DEM coupling method, this paper explores the dilute phase pneumatic conveying characteristics of shrimp feed particles. Furthermore, an experimental platform is established to verify the accuracy of the model. The simulated pipeline structure consists of a long horizontal pipe with horizontal bends and long vertical pipe with vertical bends. The results demonstrate a non-linear relationship between the pressure drop of the vertical pipeline and the inlet wind speed. Initially, the pressure drop decreases as the inlet wind speed increases, but it eventually starts to increase. When the inlet wind speed is not less than 18 m/s, the pressure drop of the horizontal pipeline increases with an accelerated inlet wind speed. The optimal inlet wind speed for adult shrimp farming is 24 m/s, while that for juvenile shrimp farming is 21 m/s. A correlation between system energy consumption and solid-gas ratio has been constructed. The ideal solid-gas ratio for adult shrimp farming is 3.69, while that for juvenile shrimp farming is 1.9–2.75. The solid-gas ratio and particle distribution at the inlet section of the straight pipe have a significant impact on the pressure drop characteristics. Their variation with the conveying wind speed directly influences the pressure drop patterns observed in the initial section of the straight pipe. This paper’s findings offer valuable scientific and practical insights for the dilute phase pneumatic conveying of shrimp feed particles, providing guidance for effective and efficient processes in this domain.

스크러버 내 충진층에서의 압력강하 특성에 관한 실험적 연구

According to the regulation on the pollution of the marine environment, SOx emission from ships has to be reduced. A SOx scrubbing system installed in a funnel of a ship is considered in order to reduce SOx emission. A scrubbing layer with a porous material is present in the funnel to increase the contact area between exhaust gas and water. In this study, experiments on the pressure drop characteristics in the scrubbing layer are conducted to investigate the effect of the scrubber on the engine load. The pressure drop according to flow rate of air instead of exhaust gas was measured for fillers such as sphere, pall ring and saddle in the scrubbing layer. First of all, porosity is experimentally measured for the three types of filler and it is confirmed that the porosity of the saddle-type filler was the largest. The pressure drop according to the change in air flow rate was measured for the three types of fillers in the scrubbing layer. As a result, the pressure drop was the smallest in the scrubbing layer with the saddle-type filler which has the largest porosity. In addition, the effect of spraying water flowing counter flow against air flow is experimentally examined. It is known that the pressure drop is increased because the air flow space is reduced when water is sprayed. In the case of the saddle, the pressure drop is about 1.5 to 2 times greater than that when only air flows at the optimum exhaust gas-water injection ratio.

Condensation heat transfer and pressure drop characteristics inside smooth and enhanced tubes with R410A and R32

An experimental investigation was performed to evaluate the condensation heat transfer characteristics for R32 and R410A inside four horizontal round tubes with 12.7 mm outer diameter. The saturation temperatures were 35 °C and 45 °C, the vapor qualities ranged from 0.2 to 0.8, and the mass flux ranged from 50 kg m−2 s−1 to 200 kg m−2 s−1. Different inside surface structures of the four tubes were smooth (ST), hydrophobic (HYD), herringbone (HB) and hydrophobic/herringbone (HYD/HB), respectively. Effects of mass flux, vapor quality, refrigerant and saturation temperature on condensation heat transfer in different tubes were discussed with the aid of flow pattern visualizations. Experimental results show that the heat transfer coefficient of R32 was higher than that of R410A due to different physical properties of the refrigerant. HB tube had the highest heat transfer coefficient at low vapor quality and HYD tube was the best at high vapor quality. The performance enhancement factors (PEF) of HB tube and HYD tube were better, ranging from 1.07 to 1.4 and from 1.02 to 1.31, respectively. However, as the composite of HB and HYD, the HYD/HB tube had the lowest overall performance, with the PEF ranged from 0.94 to 1.12. Additionally, the specific sensitivity factor (SSF) was used to evaluate the influence of various parameters on heat transfer and pressure drop.

Experimental study on friction pressure drop and circumferential heat transfer characteristics in helical tubes

Helical tubes are widely used in nuclear plants, heat recovery process, and refrigeration technology. The fluid is influenced by centrifugal force flow through the helical tube, accompanied by secondary flow which is conducive to the enhancement of heat transfer. However, the uneven circumferential heat transfer caused by the secondary flow was seldom reported, while the pressure drops and heat transfer characteristics of helical tubes under single-phase and two-phase flow conditions need to be supplemented. This paper investigated the friction pressure drop and circumferential heat transfer characteristics based on the experiments on helical tubes with the coil diameter to the tube diameter varying from 28.5 to 128.5 and lift angle varying from 3° to 10°. The results showed that the coil diameter was the key parameter affecting the pressure drop and non-uniform circumferential heat transfer, compared with the lift angle. At the same cross section, the heat transfer coefficient at the outside tube wall was the highest, which was more obvious under small coil diameter conditions. Correlations of flow resistance and heat transfer were proposed for the single-phase and saturated boiling two-phase flow, respectively, and the predicted values were improved compared with the prediction results of correlations in the existing literature.

An Experimental Investigation of Two-Phase Frictional Pressure Drop in Straight-Tube Steam Generator Used in SFR

Due to the presence of sodium, it is a challenging task to achieve the reliable and safe operation of steam generators in a sodium-cooled fast reactor (SFR). Water flow oscillations in a two-phase flow system worsen the tube integrity. An accurate prediction of two-phase pressure drop is essential in designing steam generators to operate in a stable regime. Toward this, experiments have been carried out on an industrial-size 19-tube model sodium-heated steam generator of 5.5-MW capacity to understand two-phase pressure drop characteristics at various operating conditions. The measured data are used to estimate the two-phase frictional pressure drop. The concept of a two-phase friction multiplier has been used in the present study. A significant variation in the two-phase frictional multiplier is seen with steam quality, whereas the variation of the two-phase friction multiplier is insignificant at saturated steam condition. Based on the experiments, complemented by computational model, a correlation has been developed for the two-phase frictional multiplier as a function of steam quality for sodium-heated once-through straight-tube steam generators.

Effect of flue gas condensing waste heat recovery and its pressure drop on energy saving and carbon reduction for refinery heating furnace

The refinery heating furnace has high energy consuming and high carbon emission, and the flue gas condensing waste heat recovery can achieve prominent results in saving energy and reducing emissions of petrochemical industry. Based on adding a flue gas condensing heat exchanger (FGCHE) at the rail of heating furnace, this paper investigates the effects of flue gas waste heat recovery and pressure drop on the energy saving and carbon reduction through theoretical and on-site testing methods. Flue gas heat recovery and pressure-drop characteristics of the FGCHE are analyzed to achieve maximum energy saving and emissions reduction under the normal operating conditions of heating furnace. Meanwhile, the effects of flue gas temperature and pressure drop on the energy saving and carbon reduction are derived under different combustion air temperature, humidity and excess air coefficient after fuel gas complete combustion. The results show that when the flue gas temperature is reduced from 180 °C to 20–40 °C, the energy saving efficiency, utilization ratio of flue gas waste heat, condensate recovery efficiency and carbon emission reduction ratio reach 12.5–16.9%, 74.4–98.1%, 58∼89.3% and 13.7–18.3%, respectively. Reducing the flue gas pressure drop can significantly improve the flue gas waste heat utilization ratio and carbon reduction.

Comparative assessments of mixing and pressure drop characteristics in spiral, serpentine and straight micromixers

Comparative assessments of mixing and pressure drop characteristics in spiral, serpentine and straight micromixers

CFD analysis of heat transfer enhancement by wall mounted flexible flow modulators in a channel with pulsatile flow

The aim of the present study is to explore heat transfer and pressure drop characteristics in a pulsating channel flow due to wall-mounted flexible flow modulators (FFM). Cold air in pulsating fashion is forced to enter through the channel having isothermally heated top and bottom walls with one/multiple FFMs mounted on them. The dynamic conditions of pulsating inflow are characterized by Reynolds number, non-dimensional pulsation frequency and amplitude. Applying the Galerkin finite element method in an Arbitrary Lagrangian-Eulerian (ALE) framework, the present unsteady problem has been solved. Flexibility (10−4 ≤ Ca ≤ 10−7), orientation angle (60° ≤ θ ≤ 120°), and location of FFM(s) have been considered in this study to find out the best-case scenario for heat transfer enhancement. The system characteristics have been analyzed by vorticity contours and isotherms. Heat transfer performance has been evaluated in terms of Nusselt number variations and pressure drop across the channel. Besides, power spectrum analysis of thermal field oscillation along with that of the FFM’s motion induced by pulsating inflow has been performed. The present study reveals that single FFM having flexibility of Ca = 10−5 and an orientation angle of θ = 90° offers the best-case scenario for heat transfer enhancement.

Experimental Research on a New Mini-Channel Transcritical CO2 Heat Pump Gas Cooler.

This paper presents the results of an experimental study on the heat transfer and pressure drop characteristics of a novel spiral plate mini-channel gas cooler designed for use with supercritical CO2. The CO2 channel of the mini-channel spiral plate gas cooler has a circular spiral cross-section with a radius of 1 mm, while the water channel has an elliptical cross-section spiral channel with a long axis of 2.5 mm and a short axis of 1.3 mm. The results show that increasing the mass flux of CO2 can effectively enhance the overall heat transfer coefficient when the water side mass flow rate is 0.175 kg·s-1 and the CO2 side pressure is 7.9 MPa. Increasing the inlet water temperature can also improve the overall heat transfer coefficient. The overall heat transfer coefficient is higher when the gas cooler is vertically oriented compared to horizontally oriented. A Matlab program was developed to verify that the correlation based on Zhang's method has the highest accuracy. The study found a suitable heat transfer correlation for the new spiral plate mini-channel gas cooler through experimental research, which can provide a reference for future designs.

Comparative investigation of convective heat transfer and pressure drop characteristics of MWCNT, Fe3O4, and MWCNT/Fe3O4 nanofluids

The present work discusses the experimental investigation of the convective heat transfer (CHT) and pressure drop characteristics of a hybrid nanofluid (HNF). The multi-walled carbon nanotube (MWCNT) NF, Fe3O4 NF, and MWCNT/Fe3O4 HNFs with 0.025 wt% to 0.2 wt% concentrations were prepared through ultrasonic dispersion. The CHT coefficient of the three NFs was investigated in a cylindrical test section at different Reynolds numbers (Re) and compared. As an outcome, the CHT coefficients of the MWCNT/Fe3O4 HNFs ranged from 1823.2 to 2030.5 W/m2·K, which is 6%–15.9% more than the base fluid. Furthermore, the MWCNT/Fe3O4 HNFs outperformed the MWCNT and Fe3O4 NFs individually during the CHT coefficient enhancement. At Re of 1000–1600, the increase in pressure drop of the MWCNT NF, Fe3O4 NF, and MWCNT/Fe3O4 HNFs varied from 62.4% to 91.7% as compared to water. Therefore, it is expected that the MWCNT/Fe3O4 HNF could be an effective heat transport medium.