Pressure drop and flow pattern of slush nitrogen in a horizontal pipe

Based on the two-fluid model, a three-zone drag model was developed, and the kinetic theory of granular flows and the Schneiderbauer solids wall boundary model were modified to establish a new three-dimensional (3D) unsteady mathematical model for high-pressure dense-phase pneumatic conveying in horizontal pipe. With this mathematical model, the influence of the three frictional stress models, namely Dartevelle frictional stress model, Srivastava and Sundaresan frictional stress model, and the modified Berzi frictional stress model, on the simulation result was explored. The simulation results showed that the three frictional stress models accurately predicted the pressure drop and its variations with supplementary gas in the horizontal pipe, with relative errors ranging from −4.91% to +7.60%. Moreover, the predicted solids volume fraction distribution in the cross-section of the horizontal pipe using these frictional stress models exhibited good agreement with the electrical capacitance tomography (ECT) images. Notably, the influence of the three frictional stress models on the simulation results was predominantly observed in the transition region and deposited region. In the deposited region, stronger frictional stress resulting in lower solids volume fraction and a higher pressure drop in the horizontal pipe were observed. Among the three frictional stress models, the simulation results with the modified Berzi frictional stress model aligned better with the experimental data. Therefore, the modified Berzi frictional stress model is deemed more suitable for simulating high-pressure dense-phase pneumatic conveying in horizontal pipe.

Modification of kinetic theory of granular flow for frictional spheres, part II: Model validation

Does the use of slush nitrogen (SN) for embryo vitrification improve embryo transfer outcomes compared to liquid nitrogen (LN)? SN is a safe method for embryo preservation and significantly improves post-warming survival rates during repeated vitrification-warming cycles; however, after a single freeze-thaw cycle, pregnancy outcomes are not improved when embryos are vitrified with SN compared to LN. SN is a combination of solid and LN, with a temperature lower than regular LN, and it is an alternative to conventional LN in achieving a faster cooling speed. Studies have shown that SN improves survival in non-human embryos and human oocytes. However, it is unknown whether the use of SN reduces blastocyst damage in humans during vitrification-as indicated by increased survival across multiple vitrification-warming cycles-or whether it enhances pregnancy outcomes in a single vitrification-warming cycle. Following the pre-clinical trial assessing embryo survival after repeated freeze-thaw cycles using SN and LN on 50 donated embryos per group, a randomized controlled trial was performed, where 253 patients were enrolled between September 2020 and January 2022, and 245 underwent an IVF stimulation, which resulted in at least one blastocyst for cryopreservation. Of those, 121 were allocated to the SN (study), and 124 were allocated to the LN (control) group. Randomization occurred on the day of blastocyst biopsy using a computer-generated block schema. Groups were assigned via opaque envelopes, opened by the embryologist on vitrification day. The patient, physician, and clinical team were blinded to the intervention. All couples with female aged between 18 and 42 years old undergoing IVF stimulation at one university-affiliated infertility center, with plan for preimplantation genetic testing for aneuploidy and subsequent single, frozen embryo transfer (FET) were eligible for inclusion in this study. The pre-clinical trial demonstrated significant improvements in blastocyst survival, with the SN group achieving a mean of 7.5 survived vitrification-warming cycles (range: 3-22), significantly surpassing the mean of 3.0 cycles (range: 0-10) in the LN group (P < 0.0001). Following the pre-clinical trial, 223 patients randomized to SN or LN underwent single FET. Baseline characteristics were similar between groups, as were embryology outcomes, including the number of oocytes retrieved, mature oocytes, fertilization rate, and total blastocysts biopsied. No significant differences were observed between the two groups in pregnancy rate, clinical pregnancy rate, sustained implantation rate, or miscarriage rate (P = 0.16, 0.80, 0.49, and 0.74, respectively, using Student's t-test). A futility analysis indicated no value in continuing recruitment and therefore the study was closed. Neonatal or birth outcomes were not assessed. Termination of the study based on futility analysis precludes a conclusion of equivalence between SN and LN. This study demonstrates that SN is a safe alternative to traditional LN for vitrification; however, it did not demonstrate improvements in the reproductive potential of vitrified embryos. The project was funded by the Foundation for Embryonic Competence. NCT04496284. 3 August 2020. 5 September 2020.

High energy consumption in fluidized bed dryers (FBDs) remains a critical challenge for tea processing, largely due to poor fluidization quality of sticky, irregular, and non-uniform tea particles. To address this issue, this study investigated the potential of horizontal-axis rotary agitators to improve the hydrodynamics of a gas-solid FBD and reduce energy losses. Computational fluid dynamics (CFD) simulations were performed using the two-fluid model combined with the kinetic theory of granular flow (TFM-KTGF), focusing on key parameters including pressure drop, standard deviation of pressure drop, solid volume fraction distribution, and granular temperature. Some configurations were analyzed: a bed without an agitator, and beds equipped with rotary agitators of varying blade numbers (three and five) and diameters (200 mm and 300 mm) at different rotational speeds. The results demonstrated that introducing a horizontal-axis rotary agitator significantly improves fluidization. The largest rotary domain (five blades, 300 mm diameter) achieved the lowest pressure drop of 315,135 Pa at 6.28 rad/s, while also promoting more uniform solid distribution and increasing granular temperature up to 2.5 × 10⁻ 3 J/kg. The agitator enhanced particle circulation, expanded lean regions within the bed, and reduced dense packing, leading to improved gas-solid contact and reduced resistance to airflow. Furthermore, increasing the agitator speed decreased pressure drop and its standard deviation, while increasing the granular temperature, confirming the beneficial effect of enhanced stirring energy. This study highlights the effectiveness of horizontal-axis rotary agitators in enhancing the hydrodynamic performance of FBDs, offering a promising approach to improve energy efficiency and drying uniformity in tea production. The insights presented here can guide future design and optimization of industrial-scale dryers handling cohesive, irregular particles.

Parametric study of particles homogenization in cold-flow riser reactors

Effects of fluidization velocity on solid stack volume in a bubbling fluidized-bed with nozzle-type distributor

CFD modeling of heat transfer and hydrodynamics in a draft tube conical spouted bed reactor under pyrolysis conditions: Impact of wall boundary condition

Horizontal wells can have very complex flow geometries, in part due to interaction between the main flow stream and the influxes along the wellbore, and also due to completion type. In this study, the flow behavior in horizontal wells with a single perforation and with multiple perforations of perforation densities equivalent to 1, 2 and 4 shots per foot were investigated. A new test facility was designed and constructed to simulate single phase liquid flow in horizontal wells. Experiments were conducted with Reynolds numbers ranging from 5,000 to 60,000 and influx to main flow rate ratios ranging from 1/5 to 1/100 for the single injection case and from 1/100 to 1/2000 for the multiple injection case and for the no influx case. A general horizontal well friction factor expression was developed using the principles of conservation of mass and momentum. Horizontal well friction factor correlations were developed by applying experimental data to the general friction factor expressions. It was observed that the friction factor for a perforated pipe with fluid injection can be either smaller or greater than that for a smooth pipe, depending on influx to main flow rate ratios. The proposed friction factor correlation can be used in any horizontal well model which considers pressure variation along the wellbore. Introduction The most commonly used assumptions in studying horizontal well production behavior are: infinite conductivity, and uniform influx. Infinite conductivity assumes no pressure drop along a horizontal well, and uniform influx assumes that the influx from the reservoir is constant along a horizontal well. It has been argued in the literature that the infinite conductivity wellbore assumption is adequate for describing flow behavior in horizontal wells. Although this may be a good assumption in situations where the pressure drop along the horizontal section of the wellbore is negligible compared to that in the reservoir, it is also reasonable to expect the friction and acceleration effects to cause noticeable pressure drops in long horizontal wellbores. In a horizontal well, depending upon the completion method, fluid may enter the wellbore at various locations along the well length. The distance between perforations may not be sufficient to achieve a stabilized velocity profile, and this may lead to different pressure behavior than for fully developed flow. The pressure distribution in a horizontal well can influence the well completion and well profile design, as well as having an impact on the production behavior of the well. Therefore, both the pressure drop vs. flow behavior along the well and the relationship between the pressure drop along the well and the influx from the reservoir need to be understood. Flow behavior in porous wall pipes or plates has been studied by several investigators in other disciplines. Although they provide useful information to the study of horizontal well flow behavior, the results can not readily be applied in the petroleum industry. The petroleum industry started to investigate horizontal wellbore hydraulics in the late 1980's. Investigators conducted analytical or experimental studies to investigate different aspects of horizontal well flow behavior. A friction factor correlation for horizontal wellbores was proposed by Asheim et al. which includes accelerational pressure losses due to continuous fluid influx along the wellbore. However, the literature survey reveals that experimental data are limited and theoretical studies are inconclusive for predicting frictional pressure loss in horizontal wells. In this study, an experimental and theoretical investigation of the flow behavior in a horizontal pipe with fluid injection from a single injection point in the pipe wall and from multiple injection points in the pipe wall with perforation densities equivalent to 1, 2 and 4 shots per foot has been conducted. New correlations based on acquired experimental data were developed for the prediction of friction factors in a horizontal wellbore. Model Development A general model was developed to predict horizontal well friction factors. P. 603

Numerical simulation of gas–solid flow with two fluid model in a spouted-fluid bed

Comparison of heat transfer in liquid and slush nitrogen by numerical simulation of cooling rates for French straws used for sperm cryopreservation

A study on the flow characteristics of refrigerant and oil mixture in compressor suction line

Slush nitrogen is a cryogenic two-phase fluid with solid nitrogen particles suspended in liquid nitrogen, which can be a potential coolant for high temperature superconductor thanks to its high density and large heat capacity. The present work focuses on the pool boiling heat transfer characteristics of slush nitrogen. The freeze-thaw method was used to produce slush nitrogen and the capacitance-type density meter was adopted to determine the solid volumetric fraction of slush nitrogen. The experimental results show that the heat transfer characteristics of slush nitrogen matches with typical nucleate boiling heat transfer. The heat transfer of slush nitrogen can be enhanced by increasing the solid fraction. The applicability of Rohsenow equation to the nucleate pool boiling heat transfer of slush nitrogen was analyzed, and then a heat transfer correlation for nucleate pool boiling heat transfer of liquid nitrogen and slush nitrogen, considering the effect of solid volumetric fraction, was summarized.

Ocean floor mining : Pearson,J.S. Noyes Data Corporation, Publicity Department, Mill Road at Grand Avenue, Park Ridge, New Jersey 07656, USA (March 1975) 201 pp, $24

The fundamental two‐phase flow characteristics of slush nitrogen in a pipe are numerically and experimentally investigated to develop effective cooling performance for long distance superconducting cables. First, the governing equations of the two‐phase slush nitrogen flow based on the unsteady thermal nonequilibrium two‐fluid model are presented and several flow characteristics are numerically calculated taking into account the effects of slush volume fraction, particle diameter, and duct shape. Furthermore, in experimental study, minute slush is generated by the slush atomization nozzle and the unsteady pressure and temperature distributions of two‐phase slush nitrogen flow along the longitudinal direction of pipe are measured. According to the numerical and experimental results, it is found that the reduction of the pressure loss by using slush is possible in the case of long distance pipe lengths. Also, optimized thermal flow conditions for cryogenic two‐phase slush nitrogen with practical use of latent heat of slush melting are predicted for the development of new type superconducting cooling systems.

Determination of pressure drop correlation using experimental techniques has been a central topic of research in the area of pneumotransport. However, the objective of the present investigation is to apply the mathematical model (SK model) developed by the author [1,2] along with other correlations [3–5] to estimate pressure drops for conveying varieties of grains through horizontal pipe and compare the values with the experimental results of Siegel [6]. The SK model has also been utilized to calculate pressure drops for conveying mustard seeds pneumatically through horizontal, inclined and vertical pipes and compare the values with the experimental results of Rose and Barnacle [7]. It is evident from various comparisons shown in this paper that the SK model predicts the values of pressure drop accurately as compared to the experimental results in all the cases of grains transport through horizontal, inclined, and vertical pipes, whereas, other correlations do not predict accurate results consistently in all cases.