Pipe Length Research Articles

Pulse and pulsating supercharging phenomena in a semi-enclosed pipe

Considering the discontinuous square pulse wave and continuous sine pulsating wave, we report a distinctive supercharging phenomenon of fluid in a water-filled semi-enclosed pipe and reveal the supercharging regularity. We demonstrate that there can be significant supercharging phenomena at the pipe end-face if the water is periodically injected at the pipe inlet with certain frequency. Compared to the traditional pulsating injection method, the present injection strategy can remarkably enhance the peak pressure of the water at the end face of the pipe. We explained this phenomenon by numerical simulations based on the computational fluid dynamic method. It’s found that there is a quantitative relationship between the optimal pulse frequency, pipe length and wave speed. The proposed frequency model is suitable for the multi-waveform, such as sine wave, square wave and arcuate wave. The fluid pressure at the pipe end-face intermittently increases and the end-face peak pressure is largest when the inlet injection frequency equals to the optimal frequency.

Parametric Study of the Ground-Air Heat Exchanger (GAHE): Effect of Burial Depth and Insulation Length

A parametric study of a ground-to-air heat exchanger (GAHE) using numerical models based on computational fluid dynamics with the finite volume method to evaluate the thermal potential of GAHE is presented. After the validation of the numerical code developed with published experimental data, it is proceeded to the study of the geometric parameters to define those that have the greatest impact on the application potential of GAHE. Climatological variables such as relative humidity, air flow velocity, and inlet air temperature are analyzed, as well as the increase in the thermal conductivity of the soil due to its humidity content. In addition, a study of the optimal installation depth as well as the length of the thermal insulation in the outlet pipe of the GAHE is presented. The results reveal that there is a higher heat exchange potential in the GAHE for an optimal burial depth of 4 m and a length of pipe of 15 m, 30% soil moisture content for heating and 32% for cooling, and a pipe diameter of 0.15 m. The use of thermal insulating is recommended only for the last 2 m of length in the outlet pipe of the GAHE.

Dynamic stability of cantilevered piping system conveying slug flow

In this paper, the dynamics and stability of a cantilevered piping system conveying slug flow are examined using the stable slug flow model and hysteretic model. The truncation technique of Galerkin and eigenvalue analysis are used to discrete and solve the model equations. The Argand diagrams and stability maps are employed to investigate the effects of superficial gas and liquid velocities and structural damping on the dynamics and stability of the system. The results showed that the increase of superficial gas velocities have a negative influence on the stability under the condition that the dimensionless liquid velocity is caused by the pipe length. In the process of the increase of the superficial gas velocity, the critical flutter velocity reduced and the system underwent several phenomena such as instability-restabilization-instability and mode exchange. However, the superficial liquid velocities have a positive effect on the stability, and the critical flutter velocities increased with it, which resulted in the stability boundary moving upward. It should be pointed out that its increase made the stability of the 4th mode worse and the vibration became more complex. Additionally, the structural damping could improve the stability of the high superficial gas velocity system. This work is helpful to design operating parameters to ensure the safety of the piping system.

FLUID BEHAVIOR INVESTIGATION ON A SINGLE-PHASE EJECTOR USING NUMERICAL APPROACH

This study aims to determine fluid flow behaviors and its property inside of an ejector for a single-phase system. Numerical simulation has been employed to investigate the efficiency of the ejector. The numerical process begins with model creation, mesh sensitivity study, turbulent model selection and validation study. Seven parts of ejector that can be optimized to achieve the objectives namely nozzle diameter, venturi tube neck diameter, nozzle distance, venturi tube neck length, straight pipe length, mixing chamber diameter, and mixing chamber length. Through these seven aspects, a total of 82 design points has been generated by CFD software and have obtained a candidate that provides optimized parameters that are 2.12mm, 18.93mm, 3.12mm, 80.71mm, 195.9mm, 138.63mm and 165.64mm. These parameters that contribute to the optimized output have contributed 0.0462% efficiency than before. This also shows that this ejector model does not require significant changes because this model is said to be close to the optimized ejector. Through these seven modifiable parameters, a total of 82 design points has been generated by MOGA algorithm and have obtained a candidate that provides optimized parameters that are 2.12mm, 18.93mm, 3.12mm, 80.71mm, 195.9mm, 138.63mm and 165.64mm. These parameters that contribute to the optimized output have contributed 0.0462% efficiency.

Experimental and numerical study on cooling performance of a novel earth-to-air heat exchanger system with an inlet plenum chamber

Previous studies have focused on the horizontal buried pipe section regarding the performance improvement of the earth-to-air heat exchanger, showing limited attention paid to the vertical air inlet section. In this study, we proposed a novel earth-to-air heat exchange system utilising an inlet plenum chamber (IPC-EAHE) to pre-treat the outdoor air in the inlet section. To evaluate its cooling performance, a numerical model was developed and validated based on a field experiment. The results showed a good agreement between simulated and experimental data, with a maximum absolute relative error of 4.43 % for the outlet air temperature. Then comparative studies between the IPC-EAHE and traditional EAHE are conducted under three airflow rates. Results indicated that the IPC-EAHE has a lower and more stable outlet air temperature than traditional EAHE. Compared to the traditional EAHE, the IPC-EAHE reduces the fluctuation of outlet air temperature by 53.13 %, 29.84 %, and 26.60 % under the airflow rates of 190 m3/h, 380 m3/h, and 570 m3/h, respectively. This improves the free cooling potential of EAHE for buildings. Moreover, the IPC-EAHE can reduce the buried pipe length by around 60.30 %, 53.0 %, and 50.0 % for three airflow rates, respectively. The friction resistance loss of the IPC section is at least 20 % less than that of the traditional EAHE vertical inlet section. The above results demonstrate that the IPC-EAHE offers greater renewable energy utilization efficiency and less buried pipe length than the traditional EAHE.

Earth-to-air Heat Exchanger for Cooling Applications in a Hot and Dry Climate: Numerical and Experimental Study

Shallow geothermal energy, by an earth-to-air heat exchanger (EAHE), is utilized to cool buildings with minimal energy usage. Significant parameters affecting the heat exchanger's performance must be investigated to obtain a suitable design. Shallow geothermal energy, by an earth-to-air heat exchanger (EAHE), is utilized to cool buildings with minimal energy usage. Significant parameters affecting the heat exchanger's performance must be investigated to obtain a suitable design. This article numerically and experimentally investigates the effect of pipe diameter, pipe length, inlet air temperature, soil temperature, airflow velocity, and soil thermal conductivity on the performance of the heat exchanger under hot and dry climate conditions. The soil temperature distribution was measured from the surface to a depth of 7 m in the city of Karbala (center of Iraq) in the summer season. The experimental test for EAHE was carried out in water-saturated soil and ambient air temperatures of 41 ºC, 45 ºC, and 49.5 ºC at four different velocities. The percentage drop in the EAHE outlet air temperature at 9 m/s was 28.3%, 25.5%, and 19.5%, respectively. Also, the three-dimensional model was created, and the simulation results were compared with the experimental results, which were in good agreement. An equation for the outlet air temperature was found as a function of pipe diameter and length, ambient air temperature, soil temperature around the pipe, and soil thermal conductivity. The resulted equation were compared with the current experimental results and experimental results of reported data inliterature. As a result, a very good agreement was observed. The results showed that the parameter L (length of the pipe) causes the strongest nonlinear behavior in the equation. For the cases considered, at diameters 75 and 100 mm, an approximate linear behavior for the length required to achieve a specific outlet temperature was observed. It can be concluded from the results that changing the soil type from dry one (k=0.5 W/m K) to saturated one (case of Karbala city, k=1.5 W/m K) resulted about 25% reduction in the length of the pipe. Also, the results showed that at an air velocity of 7m/s, the length required to obtain 26 ºC at the outlet of EAHE is 62.1 m which is 55% higher than the case of 29 ºC (39.9m).

Nonlinear Frequency Analysis of FGM Pipes Based on the Homotopy Method

Based on the homotopy analysis method, this paper studies the nonlinear vibration of FGM pipeline with pores under generalized boundary conditions. Based on the power-law distribution of FGM, the physical properties of the material are distributed along the radial direction of the pipe. For the mathematical model of the pores of the pipe, we choose Voigt model to describe the material properties of FGM pipes with pores. Based on Euler Bernoulli beam theory and the influence of von-Kármán nonlinearity, using Hamilton variational principle, the dynamic control equations and generalized boundary conditions of functionally graded fluid transmission pipelines with pores are established. The homotopy analysis method is used to solve the nonlinear vibration characteristics of functionally graded flow pipelines under generalized boundary conditions. The numerical results show that the translation spring has little effect on the critical velocity of instability, while the rotation spring can increase the critical velocity of instability, making the system more stable;In the nonlinear system, the viscoelastic coefficient does not change the critical velocity; pipe length, power-law exponent and porosity all affect the nonlinear free vibration of FGM porous flow pipeline.

Flow and heat transfer characteristics of nano-organic working fluid during evaporation for organic Rankine cycle

Nanoparticle can enhance the heat transfer coefficient of organic working fluids, and thus reduce the heat exchanger area, resulting in the decrease in organic Rankine cycle (ORC) investment. This study presents an experimental investigation on the physical properties and heat transfer characteristics of R123/ZnO with the mass fraction of ZnO of 0.1 %. The stability, viscosity and thermal conductivity of R123/ZnO are analyzed, while the comparison of heat transfer coefficient and pressure drop between nano-organic working fluid and pure R123 are examined. The mass flow rate is in range of 250–500 kg/m2 s. The inlet temperature is in range of 50-70℃, while the inlet pressure is ranging from 0.2 to 0.4 MPa. Results demonstrated that R123/ZnO yields a 111 %-481 % higher thermal conductivity than R123. When the mass flux is 247 kg/m−2·s, the heat transfer coefficients of ZnO/R123 increase from 1274 to 2242 W/m2·K, which is 10.11–27.60 % higher than that of R123 ranging of 1130–2035 W/m2·K with the pipe length, indicating that nano-organic working fluids obtain a relatively higher heat transfer coefficient than the pure working fluids. However, R123/ZnO yields a 1.65 %-79.36 % higher pressure drop than R123. Meanwhile, this study provides a potential of applying nano-organic working fluid on thermodynamic cycle.

NOVEL MODEL FOR ESTIMATING GAS-SOLID TWO-PHASE FLOW RATE IN A HORIZONTAL PIPE

Dilute and dense conveying systems through pipelines are a common practice in our everyday life. It is used in many industries to convey a mixture of gas and solids from one location to another through pipes. Gas-solid transport is desirable in some industries but unwanted in others. Depending on the density, size, and shape, these solid particles may result in erosion and subsequent damage to piping and other equipment. Understanding the gas-solid two-phase flow dynamics can help develop efficient and cost-effective pipe transport systems, thereby mitigating the problems associated with the gas-solid two-phase flow. Models for estimating volumetric flow rates and other gas-solid two-phase flow properties are scarce as most are very complex, expensive, and unavailable proprietary commercial software. This study, therefore, developed a simple model using the general energy balance equation and relevant mixing theories for estimating the volumetric flow rate of natural gas-solid two-phase flow in horizontal pipes. The results from the model showed that the gas-solid flow rate is a function of pipe diameter, pressure drop, pipe length, solid volumetric concentration, solid-to-gas density ratio, and solid-to-gas friction factor ratio.

Methods of acoustic control of reservoir liquid level for portable measuring devices

The paper is devoted to developing methods of acoustic control for multifunctional device for measuring the level of liquid in tanks, as well as the length and diameter of pipes. To measure the level of the liquid filling in the tank a wave guide is installed, where additional sound reflectors are placed inside at known distances, which reflect part of the acoustic wave back to the receiver. When analyzing the data on the amplitude and time of propagation, it becomes possible to determine the speed of sound in the interval between adjacent reflectors, which significantly increases the accuracy of level measurement. The method of tube length measurement is based on mathematical processing of the acoustic signal reflected from the open end of the tube and allows obtaining information about the length, diameter of the tube simultaneously. During practical tests a prototype of the device was created, which showed an error of liquid level measurement of 0.1%. In a tube length measuring mode an error on the tube length of 5 m made no more than 0.12%, an error of measurement of tube diameter equal to 110 mm made no more than 7%.

Computational Studies of Earth Air Heat Exchanger using CFD: Parametric Analysis

Parametric studies of earth air tunnel heat exchanger (EATHE) using FLUENT 6.3 Computational fluid dynamics (CFD) software have been carried out in this paper. From the parametric analysis it is found that economic analysis of the system is required for the optimization of length, diameter, and depth of buried pipe. For a long earth air tunnel more than 60 m, soil thermal conductivity doesn’t give any significant effect. The higher mass flow rate also increases the overall energy conservation potential of the system, but it reduces thermal comfort. So, the mass flow rate also takes to optimize according to the requirement. This study is beneficial to the design and energy researchers of this field.

Sensitivity analysis of thermoacoustic oscillation in cryogenics system based on response surface method

In the practical application of cryogenic systems, the presence of thermoacoustic oscillation can cause a series of adverse consequences such as pressure fluctua-tions, thermal leakage, structural damage, and so on. To ensure stable operation of the system, variable cross-section control pipe fittings are introduced, and re-sponse surface analysis method is used to optimize the parameter design of the control pipe fittings. A series of simulations have been conducted and the response surface method is introduced to conduct variance analysis on the simulation re-sults, and obtain the regression model of the system pressure ratio, then analyze the interaction between parameters. The analysis of variance shows that the cor-relation coefficient and adjustment coefficient are both close to 1.0, the signal to noise ratio is high, and the fitting degree of the regression model is good. The prediction error of the regression model for the pressure ratio is within ?10, and the distribution of the residual meets the random normal distribution, which can predict the system performance within the parameter design range. The interaction between pipe diameter and length has no significant impact on the oscillation state, so in design, priority should be given to the impact of location and pipe diameter. This work will provide the basis for determining the optimal control structure size of oscillation-free piping system.

Understanding district metered area level leakage using explainable machine learning

Understanding the various interrelated effects that result in leakage is vital to the effort to reduce it. This paper aims to understand, at the district metered area (DMA) level, the relationship between leakage and static characteristics of a DMA, i.e. without considering pressure or flow. The characteristics used include the number of pipes and connections, total DMA volume and network density, as well as pipe diameter, length, age, and material statistics. Leakage, especially background and unreported leakage, can be difficult to accurately quantify. Here, the Average Weekly Minimum Night Flow (AWM) over the last 5 years is used as a proxy for leakage. While this may include some legitimate demand, it is generally assumed that minimum night flow, strongly correlates with leakage. A data-driven case study on over 800 real DMAs from UK networks is conducted. Two regression models, a decision tree model and an elastic net linear regression model, are created to predict the AWM of unseen DMAs. Reasonable accuracy was achieved, considering pressure is not an included feature, and the models are investigated for the most prominent features related to leakage.

Effects of drill pipe length and weight on bit on lateral and longitudinal vibrations

The vibration of a drill string is the topic under study in drilling and mining engineering. Drill string vibrations cause early failure of bits due to fatigue, drill pipe fracture and bearings damage. A modal and harmonic vibrational analysis of a drill string up to 60-65m long was done in a vertical water well by carrying out parametric studies. This paper investigates vibration of a drill string under longitudinal and mainly lateral which is the most dominant under the action of parameters such as drill pipe lengths and weight on bit. Finite element modelling of a drill string was made in Ansys workbench 2020, mechanical. Modal and harmonic frequencies were determined to obtain optimal drill pipe length and possible weight on bits. The drilling environment was assumed by using different weights on bit.

Development of Measuring Device for Torque and Pipe Length of Hydraulic Torque Tongs

Development of Measuring Device for Torque and Pipe Length of Hydraulic Torque Tongs

Impact source identification on pipes using acoustic emission energy

Impact is a common source of damage in pipes and pipeline systems and detecting the location and nature of damage is vital for reliability and safety of these systems. The main difficulty in the use of AE technology for such applications is being able to investigate the extent to which the temporal structure of such a non-impulsive event can be reconstructed using sensors located on the external surface of a pipe at some distance from the source. There is currently no reliable way of relating the temporal structure of the generating event to the temporal structure of an AE source. This work uses a set of matching AE experiments and finite element simulations to study the relationship between the generating AE event (dropped ball on a steel surface) and the resulting stress-time history recorded at a given point on the surface of the pipe. Two test objects were used; a solid cylindrical steel block of diameter 307mm and length 166mm and a 2m pipe length of diameter 100mm and wall thickness 10mm. The AE resulting from the surface impacts was recorded over a period of 2 seconds for both experiments and simulations. The work builds on an earlier study with the same test objects using impulsive sources. The results confirmed that a mechanical disturbance which is extended in time can be identified from its energy-time imprint carried on the stress wave.

荞麦旋风分离清选的参数分析与试验研究

Based on the material characteristics of buckwheat, the cyclone separation and cleaning test bench were designed. The cleaning rate and loss rate of the buckwheat separation and cleaning by the influencing factors of the investigation were studied through single factor and orthogonal tests. The single-factor test results show that the cyclone separation and cleaning performance is better when the speed range of the suction fan is 800~1200 r/min, the speed range of the feeding fan is 600~1200 r/min, and the length range of the suction pipe is 100~250 mm. The regression equation model of the cleaning rate and loss rate was constructed, and the response surface analysis of the test influencing factors and their interaction was carried out. The results show that the speed of the suction fan has the most significant influence on the cleaning rate and loss rate, followed by the speed of the feeding fan and the length of the suction pipe in the separation cylinder has the least effect. By optimizing and solving multi-objective parameters of the regression equation model, reasonable experimental parameters are obtained. The appropriate speed of the suction fan is 1055 r/min, the appropriate speed of the feeding fan is 600 r/min, and the proper length of the suction pipe in the separation cylinder is 175 mm. The cleaning rate and the loss rate of the cyclone separation and cleaning system were 94.78% and 1.67%, respectively.

Multifactor optimization of medium and deep U-type borehole heat exchanger design using Taguchi method

The medium and deep U-type borehole heat exchanger (MDUBHE) coupled with ground source heat pump systems has recently received extensive attention as a novel closed-loop geothermal energy utilization system. The heat extraction performance of MDUBHE is impacted by multiple factors, while previous studies mainly concentrate on the impacts of single short-term factors. Therefore, long-term multifactor optimization is a great need to improve the heat extraction performance of MDUBHE. In this paper, six impact factors of buried depth, horizontal pipe length, flow rate, inlet temperature, geothermal gradient, and ground thermal conductivity are selected through sensitivity analyses. The Taguchi method is creatively applied to optimize the multiple impact factors of MDUBHE. The percentage contribution of each impact factor on the evaluation parameters QL-a, COP-a, and Rd-15 is quantified using Analysis of Variance. The results indicate that the geothermal gradient has the highest impact on the average per meter heat transfer rate QL-a, with a percentage contribution of 39.21%. The inlet temperature has the highest percentage contribution of 29.77% for COP-a. The ground thermal conductivity is the main impact factor for the average heat loss rate Rd-15 with a percentage contribution of 80.75%. Comprehensively considering the evaluation parameters with same weights, the ground thermal conductivity has the most significant influence on the heat extraction performance of MDUBHE, with a percentage contribution of 46.15%. This study could provide theoretical guidance and technical support for the design and promotion of MDUBHE.

Numerical simulation of stand-alone photovoltaic integrated with earth to air heat exchanger for space heating/cooling of a residential building

Earth-to-air heat exchanger is one of the efficient energy-saving approaches to meet the heating/cooling requirement of residential buildings/greenhouses. In this work, a comprehensive numerical and statistical approach using the response surface method aiming at the integration of stand-alone photovoltaics with earth-to-air heat exchangers is discussed for the coordinates of Delhi. For parametric optimization of the earth-to-air heat exchanger, statistical tool, and response surface methodology is used by taking ground temperature profile and weather data into account. Among the primary parameters, the diameter of the pipe is found to be the most significant parameter. Optimized pipe diameter of 0.2 m, pipe length of 70 m, and air velocity of 7 m/s have yielded a total energy gain of 8116.7 kWh/year. Evaluation of herein designed hybrid system has estimated CO2 mitigation of 16.18 tons/year which in turn has evinced the carbon credit value to US$ 336.86/year. Calculations exhibit a simple payback period of approx. 5 and 10 years for one day and 2 days autonomy respectively when compared with the electricity cost of diesel generators for rural areas. With 24 h grid availability, the simple payback period with a photovoltaic system gets reduced to 4–5 years in urban areas as it doesn't require any battery bank. This kind of self-sufficient hybrid system is an eco-friendly and sustainable energy solution for altogether rural and urban areas. This work provides an effective blueprint of commercially viable photovoltaic integrated with earth-to-air heat exchanger systems for households.

Evaluation of Resources and Environment Carrying Capacity Based on Support Pressure Coupling Mechanism: A Case Study of the Yangtze River Economic Belt.

Resource and environmental carrying capacity (RECC) is an important basis for achieving sustainable urban development, and analysis of the relationship between regional resources and human activities is of great significance for sustainable regional development. Taking the Yangtze River Economic Belt (YREB) as the study area, this study establishes a framework for analyzing RECC based on the resource and environmental support capacity (RES) and the pressure on the resource and environment (REP), calculates the RES and REP of 110 cities in the YREB from 2009 to 2018, and analyzes the main constraints on RECC. The results show that (1) there are inter-regional imbalances in RECC within the study area, with cities that are more economically developed or at a higher administrative level usually having more severe problems with RECC. (2) The RES and REP indices of cities in the YREB show an overall increasing trend, but the relative growth rates of the RES and REP indices of cities at different levels differ. (3) The built-up area, green space in built-up areas, total gas supply, and length of sewage pipes are hindering factors for most cities to improve their RES. This study contributes to a comprehensive understanding of the current situation and changing trends of RECC in the YREB and can provide a reference for decision-making on sustainable development of the region's large river basin.