Discharge Angle Research Articles

Experimental and numerical study on scroll compressor under different profile correction and discharge ports shapes

The scroll compressor is an essential component in air conditioning and heat pump systems. This study examined an electric scroll compressor using R22 refrigerant, focusing on how modifications in the scroll head profile and discharge structure affect its performance. Initially, a semi-empirical model based on mathematical formulas was developed to predict the performance improvements of the updated scroll compressor. Three-dimensional simulation software was then used to illustrate changes in the internal flow dynamics before and after enhancements. The predictions were validated through experimental testing. Both the semi-empirical model and the three-dimensional unsteady numerical calculation model analyzed the effects of modifications to the tooth head profile and discharge port shape on compressor performance. The adoption of a PMP profile correction delayed the compressor discharge process, shifting the starting discharge angle from 315°to 344°, thereby reducing under-compression occurrences during operation and increasing volumetric efficiency by 1.31%. Additionally, mathematical formulas correlating temperature with compressor performance were developed from fitting data, predicting compressor behavior under various conditions. Moreover, replacing a circular discharge port with a waist-shaped port reduced power consumption by 0.59 kW, resulting in a more uniform temperature distribution and enhanced mass flow rate during compressor operation.

DEVELOPING AND TESTING AN AIR FLOW DISTRIBUTOR OF SOLAR DRYER FOR DRYING MORINGA OLEIFERA IN ARID CLIMATE

This study was aimed to investigate an air-flow distributer of a solar dryer. This study was contained two factors: First, the air outlet throttle (three angles, 30°, 60°, and 90°). Second, the design of the air inlet with three levels (new design (I2), without (I1), and half-opening air inlet gate of the new design (I3)). The results show significant effects on these parameters, where the highest efficiency (51.7%) was obtained at (I1) and (30°) angles. While the temperature changes between the inlet and outlet had a significant effect on the pressure difference, the pressure difference increased, reaching (1.65 Pa). Also, the drying rate was affected by the temperature and the amount of air entering the dryer. The highest drying rate gave (0.165 kg/h) when used the air discharge angle (30°) with the (I3), where this increased the temperatures of the air in the dryer reduced the air entering.

Laboratory study on inclined desalination discharges in perpendicular cross-flow

To mitigate the ecological impact of dense effluents discharged from diffusers, understanding the influence of ambient currents and discharge characteristics on desalination outfall performance is crucial. For this purpose, a series of laser-induced fluorescence (LIF) experimental tests were conducted to address the combined effects of the flowing current strength and nozzle inclination in the discharge region for dense jets issuing into a plane perpendicular to the cross-flows. Various nozzle discharge angles (30°, 45°, and 60°) and cross-flow Froude numbers (urF=uau0×u0g0′D) are studied to assess 3D jet trajectory and concentration distribution. Empirical equations describing the dilution and geometrical characteristics of the jets are also derived. The findings indicate that deploying the 60° jet can achieve dilutions of over 50 % and 20 % compared to the 30° and 45° jets, respectively, due to its longer trajectory and greater expansion. Thus, the previously reported insensitivity of dilution to the nozzle angles in the range of 40°-70° for stationary ambient water is questioned herein when dealing with flowing currents. Moreover, the 60° jet is more sensitive to the changes in urF compared to the two other shallower angles. The presented outcomes provide valuable insights for safeguarding coastal water bodies through the efficient design of inclined dense outfall discharges.

Early Identification of River Blockage Disasters Caused by Debris Flows in the Bailong River Basin, China

The Bailong River Basin is one of the most developed regions for debris flow disasters worldwide, often causing severe secondary disasters by blocking rivers. Therefore, the early identification of potential debris flow disasters that may block the river in this region is of great significance for disaster risk prevention and reduction. However, it is quite challenging to identify potential debris flow disasters that may block rivers at a regional scale, as conducting numerical simulations for each debris flow catchment would require significant time and financial resources. The purpose of this article is to use public resource data and machine learning methods to establish a relationship model between debris flow-induced river blockage and key influencing factors, thereby economically predicting potential areas at risk for debris flow-induced river blockage disasters. Based on the field investigation, data collection, and remote sensing interpretation, this study selected 12 parameters, including the basin area, basin height difference, relief ratio, circularity ratio, landslide density, fault density, lithology index, annual average frequency of daily rainfall exceeding 40 mm, river width, river discharge, river gradient, and confluence angle, as critical factors to determine whether debris flows will cause river blockages. A relationship model between debris flow-induced river blockage and influencing factors was constructed based on machine learning algorithms. Several machine learning algorithms were compared, and the XGB model performed the best, with a prediction accuracy of 0.881 and an area under the ROC curve of 0.926. This study found that the river width is the determining factor for debris flow blocking rivers, followed by the annual average frequency of daily rainfall exceeding 40 mm, basin height difference, circularity ratio, basin area, and river discharge. The early identification method proposed in this study for river blockage disasters caused by debris flows can provide a reference for the quantitative assessment and pre-disaster prevention of debris flow-induced river blockage chain risks in similar high-mountain gorge areas.

Aerodynamic sealing using a segmented recirculating horizontal air curtain for buoyancy-driven flows in doorways

Dealing with buoyancy-driven flow to reduce infiltration heat is challenging for buildings such as cold storages where the indoor-outdoor temperature differences are significant. In this study, a segmented recirculating horizontal air curtain (SRHAC) is proposed to respond to the vertical thermal buoyancy profile in doorways and recover the cold air entrained by the air curtain. Specifically, SRHAC is a planar turbulent impingement jet discharged through a vertically mounted rectangular nozzle. The discharge nozzle is divided into segments and the return vent recirculates the discharged air to the rear of the discharge nozzle. In this study, the aerodynamic sealing performance of the SRHAC is investigated by considering structural, operational, and ambient parameters. Orthogonal analysis reveals the flow rate, nozzle width, and discharge angle as significant factors affecting the thermal separation efficiency of the SRHAC. Increasing the flow rate and decreasing the nozzle width leads to an increase in the jet momentum flux, thereby enhancing the thermal separation efficiency, with a maximum efficiency of 75.9 %. Setting the discharge parameters in the three sections along the height improves the thermal separation efficiency by 16.5% points. The maximum efficiencies of two-, three-, and five-segment air curtains are 83.6 %, 87.3 %, and 90.3 %, respectively. The separation efficiency of the SRHAC remains relatively stable even when the indoor-outdoor temperature difference varies between 32 and 57 K. These results establish that the SRHAC is an efficient energy-saving device, with the ratio of reduced infiltration load to energy consumption as high as 110.9.

Steady‐State Bedrock Channel Width

AbstractThe increase in bedrock channel width and the decline in bedrock channel slope with increasing drainage area are fundamental characteristics of mountainous landscapes. Compared with slope, little is known about controls on steady‐state bedrock channel width. We model steady‐state bedrock channel width by iteratively solving models for bed and bank erosion by impacting bedload, using measurable physical parameters, including uplift rate, water discharge, sediment supply, grain size, rock strength, and bank angle. The results indicate that width is largely controlled by sediment flux, rather than water discharge. The commonly used width‐discharge scaling relation is an artifact of the covariance of sediment flux and water discharge. Scaling up from cross‐section to drainage basin scales, our model reproduces the width‐drainage area scaling relation and suggests that the scaling exponent is largely controlled by the downstream change in the fraction of total sediment supply transported as bedload.

Simulation of the Hydraulic Performance of Parallel Pivot Weirs with Different Angles

Pivot weirs are one of the most important structures for regulating the water level in rivers and canals. These weirs are constructed with one or more gates in a row in the waterways. Changing the angle of each gate is done individually with an independent system. Based on available information, the hydraulic performance of this type of weirs (especially in several gates and different angles) in different operational conditions has not been investigated. In present study, pivot weirs with two gates are simulated using Ansys CFX software with the angles of 27.8 to 90 degree and the discharges between 40 to 130 L/s. Further, the importance of the open space between the two adjacent weirs with different angles (lack of retail wall) and its hydraulic behavior have been studied. The model was calibrated based on valid laboratory data and using the K-ϵ turbulence model. Therefore, the weirs with equal angles were studied in the first step. In this case, the effective discharge angle coefficient was studied and its maximum value compared to the vertical angle was obtained 1.076 for the angle of 52°. Furthermore, relationships for discharge coefficient versus upstream water depth were developed. In the next step, the effective length of the crest was found to be increases by 30% under unequal angles operation and the discharge coefficient raised by 1.3 to 2.4 times. Also, it was recognized that, in case of two weirs with unequal angles, about 26% to 69% of the flow passes through the distance between the two weirs. Therefore, the performance of unequal angles operation seems to be more effective in controlling the water level and discharge in different conditions and especially in flood events.

Estimation of airborne infection risk in a school classroom according to operation of a floor-standing type ventilation system

Horizontal airflow, typically from floor-standing type ventilation systems used in school classrooms in some countries including Korea, may increase the risk of airborne infection. To estimate such risk, we conducted experiments in a classroom using simulated particles (DEHS) following the ventilation system discharge angles [upward (+45°), straight (0°), and downward (−45°)] and airflow rate (200 and 400 m3/h), along with desk partitions and simulated human heat release in a classroom. Calculations using the revised Wells–Riley equation showed that horizontal air supply potentially increases the infection risk by transporting particles [coarse (3.0–5.0 μm) and fine (0.5–3.0 μm)] over extended distances, from the air inlet to the back of the classroom. In comparison, downward air supply reduced the overall average infection risk by 30.1% compared with horizontal direction. Desk partitions yielded inconsistent effects, with short-term (5 min) and long-term (20 min) reductions in infection risk. However, when the internal heat gain increased, the average estimated infection risk decreased by 24.0%. Therefore, the risk of airborne infection could be reduced by changing the discharge angle of ventilation systems. Our findings could be useful in developing operating guidelines for existing ventilation systems or designing ventilation systems that reduce infection risk in classrooms.

Jet Flame Risk Analysis for Safe Response to Hydrogen Vehicle Accidents

With an increase in the use of eco-friendly vehicles such as hybrid, electric, and hydrogen vehicles in response to the global climate crisis, accidents related to these vehicles have also increased. Numerical analysis was performed to optimize the safety of first responders responding to hydrogen vehicle accidents wherein hydrogen jet flames occur. The influence range of the jet flame generated through a 1.8-mm-diameter nozzle was analyzed based on five discharge angles (90, 75, 60, 45, and 30°) between the road surface and the downward vertical. As the discharge angle decreases toward the road surface, the risk area that could cause damage moves from the center of the vehicle to the rear; at a discharge angle of 90°, the range above 9.5 kW/m2 was 1.59 m and 4.09 m to the front and rear of the vehicle, respectively. However, at a discharge angle of 30°, it was not generated at the front but was 10.39 m to the rear. In response to a hydrogen vehicle accident, first responders should perform rescue activities approaching from a diagonal direction to the vehicle front to minimize injury risk. This study can be used in future hydrogen vehicle design to develop the response strategy of the first responders.

Effects of discharge angle of jet from a slot orifice on cooling performance for a perforated air ducting system in dairy cattle barn

By employing a type of ventilation system that relies on perforated air ducting (PAD) and slot orifices, dairy farmers can help their cows avoid heat stress and in so doing increase milk production. However, the air jets from the orifices would be delivered at an angle, namely the discharge angle, which is the angle between the outflowing jet direction and the axis of the air duct. The discharge angle can affect the system’s efficiency and the jet will fail to deliver a sufficient amount of air if the angle is such that the jet does not properly target the cow. Consequently, by means of computational fluid dynamic simulation, this study sought to optimize the discharge angle on the cooling efficiency of PAD system, first by examining the factors (such as airflow rate and duct diameter) that affect the discharge angle and then by evaluating two types of air jet deflector (rectangular duct and rectangular plate) and also the effects produced by varying the spacing between the slot orifices. Results showed that the first orifice (counting from the inlet to the end of the duct) was mostly affected by the two investigated factors. Increasing the airflow rate from 376.3 to 564.5 m3 h−1 and the duct diameter from 0.8 m to 1.0 m had a limited effect on the discharge angle (around a 2° difference in the discharge angle). Also, as the number of sequential orifices increased, the discharge angle increased gradually, and the discharge angle of the last orifice remained at a constant 90°. Of all the discharge-angle mitigation tested, the rectangular-duct deflector produced the highest mean-convection heat transfer rate of the skin surface (98.37 W m−2) and the lowest standard deviation (±1.25 W m−2). The convection heat transfer rate registered by the cow positioned under the first orifice would increase by as much as 27.5% after the spacing between the orifices was modified (in comparison with the original case), while both an increase and a decrease in the convective heat transfer rate were observed to occur among the other cows. Given these findings, it was concluded that the PAD system’s performance could best be improved by adding a deflector with a rectangular duct to adjust the discharge angle.

Deposition behaviour of inclined momentum sediment-laden jet

As wastewater is commonly disposed of in the form of sediment-laden jet from a submarine outfall, the sediment movement when the jet evolves in the ambient water and its final deposition are of great importance to marine engineers. This study aims to investigate the settling mechanism of the sediment from an inclined discharge nozzle and quantify the deposition profile for various jet conditions in the hydrostatic environment through physical experiments and dimensional analysis. In the experimental tests, separate flow visualizations for the fluid and sediment phases are achieved to enable the simultaneous observation of sediment particles and jet fluid movement, through which the analysis of the relationship between the fluid and the sediment movement is carried out. The results show that at locations close to the nozzle (s/D = 5), sediment mean velocity has an inverse relationship with the turbulence intensity while positively correlated with the initial jet momentum. The discharge angle is found to have dominant effect on alternating the sediment velocity profile from symmetrical to asymmetrical. With the newly defined momentum settling length scale lmi, the non-dimensional formulations for deposition rate and accumulated deposition profile involving the nozzle inclination have been validated by the experimental data and are potential to be applied to the prediction of depositional rate and final deposition distribution near the outfall for the full-scale wastewater discharge events.

Conceptual thermal design for 40 ft container type 3.8 MW energy storage system by using computational simulation

Since the application of wind guide and flow circulators makes the flow inside the energy storage system complicated and difficult to predict, research to numerically predict the flow and heat transfer characteristics inside the energy storage system is important. In this study, the cooling performance according to the heat pump discharge angle and wind guide angle was numerically investigated. Three cases were considered to evaluate the cooling performance of the wind guide and flow circulator. The angle of the wind guide and the discharge angle of the heat pump are 5° and 45° in Case 1 and 15° and 30° in Case 2, respectively. Case 3 is a structure in which a flow circulator is applied. In this regard, three-dimensional and computational fluid dynamics simulations have been conducted. As a result, the maximum and average temperatures of the battery rack can be reduced by 11.9 % and 11.17 %, respectively. The cooling performance according to the cooling conditions of the energy storage system was analyzed by analyzing the maximum, average, and minimum temperatures of the battery rack according to the change in the flow rate of the heat pump and the flow circulator.

Оценка интенсивности орошения для пожарных лафетных стволов

Purpose. The paper considers methods for determining discharge density when extinguishing agents are discharged via monitors. The work is aimed at developing methods for objective and practically relevant discharge density assessment when extinguishing agents are discharged via monitors. To achieve the purpose the following tasks have been solved: – analysis of monitor discharge density assessment approaches has been carried out, their advantages and disadvantages as well as limited scope of application for monitors have been established; – scientifically based approach has been developed for discharge density practical assessment when extinguishing agents are discharged via monitors under various conditions, aimed at optimizing labour and time costs during testing. Methods. Empirical observation and calculation-based method has been used. Findings. Scientifically based method has been developed for discharge density assessment when extinguishing agents are discharged via monitors under various conditions, which requires practical testing. Research application field. Assessment method of discharge density when extinguishing agents are discharged via monitors can be used to assess discharge density both under standard monitor test conditions (monitor axis slope angle equals 30°, solid jet) (in accordance with GOST R 51115–97) and with other different variations of monitor slope angle and spray discharge angle. This method has practical significance in technical decisions justification when designing monitor-based fire safety systems at the facility. Conclusions. The proposed method will allow assessing monitor discharge density. It is worth noting that it can be used to assess discharge density both under standard monitor test conditions (monitor axis slope angle equals 30°, solid jet) (in accordance with GOST R 51115–97) and with other different variations of monitor slope angle and spray discharge angle. The proposed method’s main advantages include reducing investigators labour costs, test time optimization and full-scale tests partial transferring into calculation. The proposed method requires practical testing, introducing correction factors if necessary and further implementation when updating regulations in the field of monitor requirements rationing and designing monitor-based fire safety systems.

Modelling the final discharge angle in flighted rotary drums

Rotary drums equipped with longitudinal flights are mainly used to dry granular solids and handle high throughputs. The design of the flights is a crucial task because they decisively influence the distribution of the particles over the dryer cross section. In a previous work, the authors derived a mathematical model for the particle flow in rotary drums with rectangular flights. In this model, the final discharge angle was underpredicted resulting in errors when calculating the contact area of the particles in the air-borne phase. Therefore, a new model was developed in this study to predict the final discharge angle based on a forces balance approach on a single particle. This approach includes the Coriolis force acting on the last discharging particles sliding down the inclined flight sheet. The model was solved by using the vector analysis method. Experiments were performed at rotary drums with 0.5 m and 1.0 m in diameter, respectively, and 0.15/0.3 m in length using glass beads and quartz sand as bed materials. Each drum was equipped with 12 flights around the shell. The model validation was performed by varying the bed material, drum diameter, flight length ratio, and the rotating speed. The model predictions have shown that as the flight length ratio and the Froude number increased, the final discharge angle attained higher values. The model predictions agree well with the measurements.Graphic abstract

Comparison of Indoor Air Quality in Summer and Winter According to Four-Way Cassette Fan Coil Unit Operation in a Four-Bed Ward.

This study targeted a four-bed ward with a ventilation system and a four-way cassette fan coil unit (4-way FCU) installed on the ceiling. The indoor air quality under summer and winter conditions was comparatively analyzed. The age of air was calculated by conducting tests and simulations under diverse conditions, assuming that the ventilation system and 4-way FCU were continuously operating. The use of an air cleaner and ward curtain was investigated for its impact on the air quality in the breathing zone of a patient lying on the bed, and effects of the airflow and discharge angle of the 4-way FCU were considered. Because the 4-way FCU was installed in the central part of the ceiling, where indoor air is sucked in and subsequently discharged in four directions, the age of air at each bed was found to vary depending on the airflow and discharge angle of the 4-way FCU. When the airflow and discharge angle of the 4-way FCU was fixed, the age of air at each bed appeared to be lower during winter heating than in summer cooling mode. The age of air was significantly lowered at each bed, depending on the use of the curtain and the air cleaner along with the ventilation system and 4-way FCU, and appropriate seasonal operating conditions were identified to maintain a lower age of air at each bed.

Effect of alumina particulate and E-glass fiber reinforced epoxy composite on erosion wear behavior using Taguchi orthogonal array

This article includes the erosion wear behavior of alumina (Al2O3) and E-glass fiber reinforced epoxy composites. The erosion wear was conducted on air jet erosion tester. Alumina was reinforced with a variation of 0–20 wt%. Five formulations were made: L1, L2, L3, L4, and L5. The reinforcement content, impact velocity, discharge, and impingement angle as machine control factors were employed for the erosion wear. Taguchi (L25) orthogonal array was used to determine erosion wear. From the Taguchi analysis, the minimum erosion rate was recorded at 10 wt% of reinforcement content, 30 m/s of impact velocity, 1 gm/min of discharge, and 45°of impingement angle. The impact velocity was found the most influential parameter affecting the erosion rate from the ANOVA analysis, with a percentage contribution of 41 %. From the investigation of the scanning electron microscope, the result shows that Al2O3 particles have more interaction with polymer matrix and good stress transfer properties.

Double diffusive effect on geometrical characteristics of inclined thermal-saline negatively buoyant jets

In this paper the turbulent reversible thermal-saline buoyant jets discharged upwards at angles 300, 450 and 600, into a stagnant ambient are experimentally studied. In all cases, the flow finally behaves as a negatively buoyant jet, even in cases where the flow has positive buoyancy at the source. In reversible thermal-saline jets, there is a nonlinear relationship of the geometric characteristics of negatively thermal-saline buoyant jets with the relative density. The highest values of centerline peak and terminal rise height of jets were observed in the discharge angle of 600, and the lowest values were observed in the discharge angle of 300. Also, the value of horizontal distance to the centerline peak and return point for the discharge angle of 300 shows a higher value than the angle of 450 and 600.

Life prediction of lithium thionyl chloride batteries based on the pulse load test and accelerated degradation test

AbstractThe lithium thionyl chloride (Li/SOCl2) battery is widely used as an important long‐life backup power source. Accurate battery life prediction is essential to ensure the reliability of equipment and systems. In this paper, a novel method was proposed for the life prediction of Li/SOCl2 batteries based on the pulse load test and accelerated degradation test (ADT). The proposed pulse load test method can estimate the primary battery capacity accurately and nondestructively, which solves the challenge of quantifying degradation due to unknown initial values. Furthermore, we noticed a new phenomenon that capacity loss was affected by electrolyte fluidity, and unexpected capacity loss was observed for batteries at different discharge angles. By analyzing the mechanism of this phenomenon, we avoided serious capacity measurement errors in the 24‐week ADT. A life prediction model with a satisfactory ability to approximate the measured data was established depending on the exponential influence of time and temperature on capacity degradation.

Laboratory study to quantify lower boundary influences on desalination discharges

Brine discharges from desalination facilities represent an important environmental consideration surrounding the use of desalination technologies. These discharges are typically released through a series of subsurface discharge ports, and the ability to quantify their flow behaviour is critical to mitigating adverse environmental effects. Previous experimental studies on desalination discharges or Inclined Negatively Buoyant Jets have highlighted discrepancies in the dilution measurements reported in the literature. These discrepancies are potentially due to the inconsistent treatment of the lower boundary in the experimental setup, which in practice represents the seabed. This issue is investigated through a series of experiments using the Laser Induced Fluorescence method. Three discharge angles (300, 450 and 600) are tested and the non-dimensional source height above the boundary (H/F0d) is varied between 0.06 and 1.84 (termed the bed proximity parameter). The results illustrate a relationship between dilutions measured at common reference points near the boundary and the bed proximity parameter. Dilutions are also shown to decrease by up to 30% compared to experiments without lower boundary influence. The outcomes from this study provide valuable insight into the previously reported discrepancies and enable the lower boundary to be incorporated into the design of desalination discharge systems.

On the Computational Modeling of Inclined Brine Discharges

In this paper, five computational approaches are used to model bulk flow parameters of inclined round negatively buoyant jets. More specifically, an integral model employing Gaussian distributions for velocity and apparent acceleration of gravity, proposed in earlier study, is implemented with two different entrainment formulae. The remaining three computational approaches include an integral model known as EMA, which takes into consideration the fluid detachment occurring in the inner side of the flow near the terminal height, the widely known commercial model Corjet and analytical solutions that were proposed in a previous study. Predictions are provided for the maximum centerline height and its horizontal position, the terminal height of the upper jet boundary, the horizontal distance to the points where the jet centerline and the upper jet boundary return to the source level, the centerline dilution at the maximum height and the centerline dilution at the return point. Detailed comparisons are made in dimensionless form between the estimations provided by the models and a wide range of experimental data for discharge angles between 15° and 90°. Conclusions are drawn regarding the performance of the five computational approaches.