Abstract

This paper presents the design, implementation, and experimental validation of a novel canned cycle for CNC milling machines, enabling the precise and efficient cutting of threads with fixed or variable pitch and radius. Conventional canned cycles are limited to fixed pitch threads, restricting the versatility of CNC milling machines in thread machining applications.

The development process involves integrating a sophisticated control algorithm into the CNC milling machine’s software, giving the operator remarkable control over the thread cutting process. This algorithm allows the operator to choose between external or internal threads, set both initial and final radii, determine initial and final pitches, specify the number of turns, and select the left or right-hand thread type. Such flexibility enables the creation of threads with diverse geometries. Furthermore, the proposed canned cycle provides the capability to switch between roughing and finishing passes by adjusting the step motion along the prescribed helical curve.

Simulation tests conducted under various threading cases clearly demonstrate the efficiency of the proposed canned cycle. These results showcase its capability to address a wide range of machining scenarios, offering practical solutions applicable across a spectrum of applications.

Introduction

The evolution of Computer Numerical Control (CNC) machining has brought about a revolution in manufacturing processes, not only enhancing precision and efficiency but also addressing the challenges posed by complex geometries and demanding machining applications. This paper deals with the domain of CNC thread milling, introducing an innovative approach through the development and implementation of a comprehensive canned cycle.

A canned cycle is a predefined machining operation that entails a sequence of machine movements to perform various machining tasks like drilling, pocketing, slotting, boring, and tapping. It aims to simplify programming by consolidating multiple commands into a single block, utilizing G-code to define machining operations that would typically necessitate multiple blocks [1, 2]. Continuous efforts are made by CNC manufacturers to incorporate new canned cycles into their controllers, specifically designed to handle intricate and complex geometries [3, 4]. This is easily concluded by comparing the canned cycles available nowadays with the older ones.

Centered on programming and facilitating the precise and efficient cutting of threads within a user-friendly environment, incorporating both fixed and variable pitch and radius, the presented canned cycle addresses limitations posed by conventional canned cycles, which primarily target fixed pitch threads. In the precise domains of engineering and manufacturing, the use of variable pitch threads is necessitated by diverse potential applications. These applications encompass manufacturing components for automotive vehicle engines, fasteners for aerospace systems, industrial devices, robots manufacturing parts [5,6,7,8] and the creation of medical implants [9,10,11,12]. The mentioned references constitute a sample of recent related research work.

Conclusions

The work presented in this paper built upon the foundations laid in previous mentioned research. As predicted in that earlier work, the present study advanced and extended the capabilities of the thread canned cycle to encompass threads with predefined start and ending radii, start and ending pitches, and the desired number of turns, applicable to both left- or right-hand, internal or external threads. Moreover, the proposed canned cycle seamlessly transitions between roughing and finishing passes, allowing precise regulation of step motion along the prescribed helical curve. The introduced canned cycle surpasses the limitations of conventional cycles, which are confined to fixed pitch threads, by providing a comprehensive solution for diverse threading requirements.

Simulation tests confirm the adaptability of the proposed canned cycle across diverse threading conditions. The graphical outputs, combined with the mathematical formulation of helix equations and CNC milling machine simulations across various threading cases, collectively verify the efficiency, and validation of the proposed canned cycle.

Abstract

Pure waterjet surface treatment without abrasive particles has a promising application in the biomedical field, because it induces compressive residual stresses on a metal surface and never leaves the tiny hard particles. In this work, the influence of operation pressure, standoff distance and the number of paths of the waterjet on the surface topography as well as the hardness was studied using the Taguchi method. The results showed that the most essential parameter is the operation pressure. By tuning the operation pressure from 100 to 300 MPa, the surface of Ti6Al4V specimens can be smoothed, roughened or damaged; when the surface layer is eroded, the new-born surface exhibits a clear stochastic nature accompanied by microvoids. The standoff distance benefits finer controlling the height parameters, whilst the number of paths affects the waviness. The hardening effect generated by the waterjet impingement extends to a few hundred-micron depth of the specimens, and the peak value of microhardness was found at a depth of 70 μm, which is an increase by greater than 20 %. The roughness parameters of Arithmetical mean height (Sa), Skewness (Ssk), Auto-correlation length (Sal), and Developed interfacial area ratio (Sdr) as a set are recommended to characterize the biomaterial’s surface. The present research results promote the application of waterjet treatment in the field of fine-tuning biomaterial surface morphology.

Introduction

The surface topography of the implant significantly influences the bone response [1,2]. There are two stages (short/long) of biological response after implantation [3]. One is the short-term response that a fibrous soft tissue is formed and capsules around the implant, and another response directly relates to bone-implant contact without the connective tissue layer, known as osseointegration [4]. The surface topography plays an important role in the biomechanical fixation between the implant and the soft fibrous tissue at the early stage of implantation. Meanwhile, the rate and quality of osseointegration that determine the long-term success of the clinic implantation are also affected by the surface topography [5]. The demand for specific surface finishes of biomedical devices [6] drives researchers to develop efficient surface modification methods.

Waterjet technology that places a sample under the waterjet itself and subjects it to the water pressure in the air or underwater is one of the promising methods [7,8]. As one of the fastest-growing technologies, the waterjet can machine (cut, drill and mill, clean, remove) almost any material [9]. Waterjet is used in a variety of fields from automotive and aerospace to medical and the food industries [10]. Particularly, pure waterjet induces compressive residual stress to enhance fatigue strength [11], and never leaves tiny residues (hard particles) on a metal surface compared to the abrasive waterjet, it holds tremendous promise in the medical industry [7,11].

Conclusion

Using the Taguchi method, nine waterjet experimental cases were designed and conducted. The influence of the operation pressure, standoff distance, and the number of paths on the surface topography and the areal roughness parameters as well as the hardness were analyzed and discussed. The main conclusion is drawn as follows:
• Among the three process parameters of waterjet treatment, the most critical one is the operation pressure. The standoff distance is beneficial for finer control of the height parameters, whilst the number of paths affects the waviness.

• By increasing the operation pressure from 100 to 300 MPa, the surface of Ti6Al4V specimens can be smoothed, roughened, or damaged; when the surface layer is eroded, the new-born surface exhibits a clear stochastic nature accompanied by microvoids.

• The hardening effect generated by the impingement of waterjet spans over a few hundred microns width, with the peak microhardness being found at a depth of 70 μm, which increases by over 20 %.

• After a comprehensive analysis of the 5 categories of 14 areal roughness parameters, the parameters of Sa, Ssk, Sal, and Sdr as a set are recommended to characterize the biomaterial’s surface.

Abstract

Climate change requires transforming the production processes of high-emission industries toward low-carbon technologies. One of the main emitters of greenhouse gases is the steel industry. Therefore, steel manufacturers are planning to substitute the blast furnace-basic oxygen furnace route with hydrogen-based direct reduction and electric arc furnaces. Thus, direct greenhouse gas emissions can be avoided almost entirely. This involves changes in the materials and energies used. Besides hydrogen, natural gas is becoming more important for the direct reduction of iron ores. Therefore, future greenhouse gas emissions associated with low-carbon steelmaking are deeply intertwined with the developments of the system environment. Upon potential transformation pathways of the system environment, future greenhouse gas emissions from natural gas and hydrogen-based direct reduction coupled with electric arc furnaces are investigated. To this end, a prospective cradle-to-gate life cycle assessment approach is used. The results indicate that greenhouse gas emissions highly depend on the electricity mix if hydrogen is produced by electrolysis. Using natural gas for direct reduction is a viable short-term option until the decarbonization of the energy sector is further advanced.

Introduction

Due to climate change, it is required to decarbonize highemission industries such as the steel industry. Approximately 7% of global greenhouse gas (GHG) emissions result from steelmaking processes, especially from primary steelmaking [1]. In most cases, the coal-based blast furnace-basic oxygen furnace (BF-BOF) route is used for the primary production of crude steel [2]. However, alternative technologies for reducing direct GHG emissions of steelmaking already exist. As of today, most steel manufacturers are planning to substitute BFBOF production facilities with direct reduction plants (DRP) and electric arc furnaces (EAF) from 2025 onwards [3–5]. In this process design, sponge iron is produced within the DRP. Afterward, the sponge iron is further processed within the EAF for crude steel production. Existing DRPs are currently solely operated with natural gas (NG/DR) for direct reduction [1]. The NG/DR-EAF process serves as a transitional technology in the transformation process of integrated steel mills toward lowcarbon steelmaking. In the long term, NG/DR can be substituted by hydrogen-based direct reduction (H/DR) of iron ore. If hydrogen is used, direct GHG emissions can be reduced by up to 97% [6]. A framework for designing economically advantageous transformation pathways is developed within [7].

Conclusion

Most European steel manufacturers are planning to transform their integrated steel mills’ production infrastructure toward DR-EAF production to significantly reduce GHG emissions from primary steelmaking. This article consists of a prospective cradle-to-gate LCA approach for DR-EAF steelmaking. For environmental impact assessment, it is differentiated between NG/DR, H/DR with hydrogen from electrolysis using the German electricity mix, and H/DR with hydrogen from electrolysis using electricity from onshore wind turbines. The developed assessment provides an understanding of the environmental impacts of the DR-EAF route considering different future developments of the system environment.

This study finds that direct GHG emissions can be reduced by around 96% if H/DR-EAF production is applied to substitute the BF-BOF route. However, indirect GHG emissions are highly intertwined with future developments of the system environment. Thus, fast decarbonization of the energy sector is highly important to heavily reduce overall GHG emissions. Also, GHG emissions from raw material extraction, processing, and transportation need to be reduced to aim for a low GHG emission steel industry. Process-related, direct GHG emissions are higher when NG/DR is applied. Indirect emissions, however, are less affected by system environment developments. Thus, natural gas provides a viable short-term option for the DR process. Besides decarbonization of the system environment which needs to be driven by policymakers, steel manufacturers need to focus on measures to increase their shares of low-carbon hydrogen in the early phase of the transformation process. To this end, electrolysis capacities need to be installed if sufficient external hydrogen sources for H/DR are not available. Also, increasing the share of low-carbon electricity to operate electrolysis facilities is of high importance.

Abstract

Over 766 million people have been infected by coronavirus disease 2019 (COVID-19) in the past 3 years, resulting in 7 million deaths. The virus is primarily transmitted through droplets or aerosols produced by coughing, sneezing, and talking. A full-scale isolation ward in Wuhan Pulmonary Hospital is modeled in this work, and water droplet diffusion is simulated using computational fluid dynamics (CFD). In an isolation ward, a local exhaust ventilation system is intended to avoid cross-infection. The existence of a local exhaust system increases turbulent movement, leading to a complete breakup of the droplet cluster and improved droplet dispersion inside the ward. When the outlet negative pressure is 4.5 Pa, the number of moving droplets in the ward decreases by approximately 30% compared to the original ward. The local exhaust system could minimize the number of droplets evaporated in the ward; however, the formation of aerosols cannot be avoided. Furthermore, 60.83%, 62.04%, 61.03%, 60.22%, 62.97%, and 61.52% of droplets produced through coughing reached patients in six different scenarios. However, the local exhaust ventilation system has no apparent influence on the control of surface contamination. In this study, several suggestions with regards to the optimization of ventilation in wards and scientific evidence are provided to ensure the air quality of hospital isolation wards.

Introduction

The study of airborne diseases has recently become increasingly significant with the emergence of severe acute respiratory syndrome, Ebola virus, tuberculosis, coronavirus disease 2019 (COVID-19), and other infectious diseases (Hathway et al. 2011). With the worldwide outbreak of COVID-19 (as of May 10, 2023), there have been 765,903,278 people diagnosed with COVID-19, including 6,927,378 deaths globally (WTO 2023). Some countries or regions succeeded in preventing the spread of the epidemic by managing quarantines and closures, which seriously affected economic growth and the normal operation of whole cities. Over the last 3 years, countries have prioritized preventing and controlling the epidemic. At the beginning of the outbreak, 100,000 people died every day worldwide as a result of COVID-19. It can affect anyone anywhere, especially healthcare workers exposed to environmental existing virus droplets. Therefore, the study of airborne virus diffusion in hospital isolation rooms is significant.

Viral respiratory infections are diffused by contact and droplet transmission, fomite transmission, and other types of transmission (WTO 2020). Contact transmission occurs when a healthy man is in close contact with an infected person (direct contact) or when an infected individual exhausts fomites containing viral droplets (indirect contact) (Morawska and Cao 2020). Viruses spread through the air via droplets or aerosols produced during coughing, sneezing, and talking (Jones and Brosseau 2015). Coughing, which is an intense process of droplet generation over transient time, has recently been the focus of many studies. Small virus droplets expelled into the air can exist as airborne droplets for a long time (Chartier et al. 2009) and can fill the whole room under the effect of an air conditioner (Liu et al. 2020b). Li et al. 2020a, b) investigated the spread of droplets in a tropical outdoor environment and found that at wind speeds of 2 m/s, 100 μm droplets can move up to 6.6 m. Wei and Li (2015) modeled the coughing process as a turbulence jet to investigate the diffusion of droplets and obtained travel distances with different droplet sizes. Lindsley et al. (2016) compared aerosol droplet samples of 61 adult volunteer outpatients through experiments and found that more aerosol droplets containing viruses were released through coughing. Nicas et al.

Conclusion

In this study, the full-scale geometry of the isolation ward in Wuhan Pulmonary Hospital is modeled, and the droplet diffusion process from a coughing event in the ward is simulated. An experiment is conducted to validate the CFD model, and a local exhaust ventilation system is designed to ensure indoor air quality.

(1) Although the local exhaust ventilation system reduces the number of airborne contaminants, a substantial increase in turbulent air motions may occur. The results show that a negative outlet pressure of 2.5 and 3.5 Pa led to a decrease in evaporated droplets and airborne contaminants remaining indoors, and the negative outlet pressure of 3.0 Pa increases the number of droplets tracked in the ward of the excessively turbulent flow. It is found that the number of droplets remaining indoors on the outlet negative pressure is not linear. The exhaust system can effectively extract contaminants when the negative pressure value is small. However, the negative pressure is increased, and the local exhaust system promotes turbulent transport, leading to a complete breakup of the droplet cluster and enhancing the dispersion of droplets indoors. The mass of the droplets is light, and when the outlet negative pressure value reaches a certain value, droplets can also be effectively removed.

Abstract

     Management 4.0 assists businesses in evolving, surviving and performing in the competitive and dynamic world. This fourth revolution uses advanced technologies like Artificial Intelligence (AI), Virtual Reality (VR), Internet of Things (IoT), Robotics, Holography, Additive Manufacturing etc., for the proper management systems. These technologies facilitate working personnel and make it more appealing to complete their duties efficiently and accurately. The main aim of this paper is to understand the concept of Management 4.0, its technologies and applications for proper management systems. As Management 4.0 enhances process control, the chance of human error is reduced, leading to increased efficiency. It enables rapid and intelligent decision-making, reduces costs, accelerates growth, and raises profitability. Management 4.0 technologies and advanced data analytics are helpful to make smart supply chain management well suited to fulfil industry 4.0. Thus, to overcome various obstacles and effectively deploy Management 4.0 technologies in manufacturing industries, top management must establish a clear asset performance management plan with the help of process engineers familiar with industrial system failure occurrences and what operators need to improve. Management 4.0 involves advanced technologies, system connectivity, data collection & analysis at the organisation level. Management 4.0 is expected to be a critical component in the long-term survival of any business, either manufacturing or service-providing organisations.

Introduction

     Implementing Management 4.0 technologies provides firms with increased efficiency by connecting automation with data collecting and exchange protocols. Streamlining the procedures and boosting access to valuable data can optimise production with optimal resource utilisation. Advanced technologies are integral to Management 4.0, and their effective use could lead to better production and management. For instance, robots are an essential part of flexible automation and have many services in industrial manufacturing, including welding, assembling, plasma cutting, and finishing [1], [2], [3]. Manufacturers of all sizes may profit from robots in a variety of ways. Proper integration of Robots contributes to improved quality control, a safer work environment, decreased bottlenecks, higher output, enhanced worker satisfaction, and many more. Like this, a new factory is planned, and another powerful digital twin technology could be utilised for new products or processes. It allows for faster and more reliable innovation development with fewer physical prototypes. When a product is manufactured, or a factory is implemented, more data is generated to improve the Management 4.0 environment [4,5].

Conclusion

     Management 4.0 technologies help connect machines to the cloud and construct customised versions of their industrial IoT. These technologies are laying the groundwork for future development and scalability. The ultimate objective of Management 4.0 is to enhance and advance industrial processes. In recent years, the manufacturing business has undergone many changes. Management 4.0 is a comprehensive and unified set of technologies that can transform the entire management system. It has also become a reality in which factory automation is commonplace, and factories are more intelligent than ever before. Technologies aim to collect massive volumes of data from various sources. These provide intelligent production scheduling software, the foundation for smart autonomous decision-making. In this Management 4.0 scenario, supply chain analytics will reach new heights. Manufacturing as a service allows firms to bid on manufacturing a product or a single production step. This specialisation can improve manufacturing efficiency while lowering costs and fine-tuning the supply chain. Production and logistics operations are smartly connected, resulting in a more efficient and adaptable real-time lean manufacturing environment. This will make it easier to build smart value-creation chains that span the whole product life cycle, from conception to manufacture, usage, and maintenance to recycling. These characteristics of the Management 4.0 facilitates the managers to make data-driven decisions and set their strategic goal in that direction. Management 4.0 enabled culture to help the employee develop their own skill set that might help make the process and operations more efficient. The primary role of Management 4.0 is to motivate the managers to develop the Management 4.0 culture. In addition, Management 4.0 technologies will become extremely useful in the manufacturing process and assist with various logistics, including manufacturing, production, and shipping. This study might be helpful for proper management systems in the industries and provide proper information systems.

Abstract

Temperature is known to greatly affect the efficiency, security, and cycle life of lithium-ion battery (LiB) cells. LiB cells are delicate to changes in temperature by using a variety of nanofluids. This study uses a novel cooling system with a Re between 15 × 103 and 30 × 103 to lower the cells’ temperature. Al2O3, CuO, SiO2, and ZnO with nanoparticles concentrations of 5% and nanoparticle diameters of 20 nm dispersed in a base liquid (water) are used to produce the effects. The findings demonstrate that as the Re rises, so does the Nusselt number. An innovative cooling system is designed and numerically tested to show how different kinds of nanofluids affect the increment in heat transmission and distribution of temperature in LiB cells. The temperature of LiB cells drops by flowing the water between the 52 batteries inside the cooling pack. For each spacing value, the Reynolds numbers are increased, which results in an increase in the average Nusselt numbers. According to the computational fluids dynamics results, the Nusselt number rises with increasing spacing. The results show that Re of 18000, 22000, 25000, 27500, and >30000 are needed for SiO2 nanofluids, Al2O3 nanofluids, ZnO nanofluids, CuO nanofluids, and pure water, respectively, to get battery pack temperature of <40 °C (the typical operating conditions). Higher Re values improve the heat transfer slightly with the expense of pumping power; therefore, Re of 18000 with SiO2 nanofluids is preferred. The utilization of nanofluids also shows that SiO2 exhibits the best thermal cooling for battery packs among all investigated nanofluids. Al2O3 nanofluid is also an excellent option, followed by ZnO nanofluid. For example, the temperature reduction of the hottest battery cell reaches >47, 44, 43, 42, and 42 °C for SiO2 nanofluids, Al2O3 nanofluids, ZnO nanofluids, CuO nanofluids, and pure water, respectively.

Introduction

The Greater demands for battery thermal management systems (BTMS) have been made as lithium-ion batteries are increasingly used in solar systems, power electric cars, and any engineering applications People are most concerned with the temperature at which batteries operate, their reliability, their safety, and their cycle life. The fluid cooling system can manage the peak battery temperature and the temperature differential among batteries within a tolerable range, therefore increasing the cycle battery’s lifespan [[1], [2], [3]]. However, the operating temperature has a significant effect on the efficiency and life of lithium-ion batteries. Too high or too low an operating temperature can damage the battery’s cycle life, efficiency, dependability, and safety, as well as cause substantial degradation of its charge and discharge performance [4,5]; Sheng, Su, Zhang, Li et al., 2019; Z [6]. When a lithium-ion battery’s working temperature is raised from 25 to 50° Celsius, the capacity loss increases by 100% after 300 cycles. Lithium-ion (Li-ion) batteries, as a vital element of electric automobiles (EVs), have drawn considerable interest in recent years [7]. Due to their high energy and power density, long cycle life, and low self-discharge, Li-ion batteries are considered the best energy storage technology for electric vehicles in comparison to other types of rechargeable batteries.

Conclusion

This paper investigates an effective cooling process for a battery pack having 52 batteries in a staggered arrangement (5 rows and 21 columns) using four nanofluids (i.e., SiO2, Al2O3, ZnO, CuO) and pure water. The flow and energy equation is modeled using ANSYS Fluent, which is validated against reported experimental data. The nanofluids are taken at the same concentration (5 vol%) and particle size (20 nm). Based on the applied conditions, the following remarks are concluded:

– Higher Re values result in a better cooling process and reduce battery cells’ temperature. To get a typical battery pack temperature of <40 °C, Re = 18000, 22000, 25000, and 27500 for SiO2, Al2O3, ZnO, and CuO nanofluids, respectively, should be used compared to Re > 30000 for pure water.

– The hottest battery cell temperature could be dropped by 47, 44, 43, 42, and 42 °C for SiO2, Al2O3, ZnO, CuO, and pure water, respectively.

– SiO2 is preferred since it cools all battery temperatures by < 40 °C with lower Re (i.e., 18000).

Abstract

The heat transfer performance (HTP) of an improved elastic tube bundle (IETB) was analyzed using a bi-directional fluid-structure interaction calculation method. The vibration-enhanced HTP of heat exchangers with different inlet velocities (Uin) and row number N were studied. The results show that the amplitude gradually increases as the Uin increase with a maximum increase of 309.98%. The amplitude with fixed shell side length (FL-heat exchanger) is generally higher than that with variable shell side length (VL-heat exchanger) under different row numbers. The average amplitude of the three directions increased by 4.55%, 11.54%, and 7.41%, respectively. The heat transfer coefficient (h) is directly proportional to Uin, and the comprehensive HTP gradually decreases with the increase of Uin. With the increase in the row numbers, h generally showed a downward trend. For the VL-heat exchanger, h decreases as the row number increases, which increases from N=6 to N=9, and h decreases by 13.85%. For the FL-heat exchanger, h first increases and then gradually decreases. The comprehensive HTP also maintained the same trend. Compared VL-heat exchanger and FL-heat exchanger, reducing the spacing between tube rows increases heat transfer per unit volume, leading to improved comprehensive HTP of the IETB heat exchanger.

Introduction

Heat exchangers [1–3] are commonly used devices for exchanging energy in industries such as aerospace, chemical, and refrigeration production. When the traditional tubular heat exchanger works, its internal rigid heat transfer elements begin to vibrate under the impact of fluid, which can result in fatigue damage and decreased heat exchanger service life [4,5]. Shell and tube heat exchangers [6,7] are currently the most widely used in industrial production. The study of enhanced heat transfer in heat exchangers has become a hot topic of current research [8]. To reduce the influence of fluid shock, utilizing the vibration-enhanced heat transfer principle, an elastic tube bundle heat exchanger is proposed [9,10]. The material of the heat transfer element was replaced from steel to copper to achieve small amplitude vibration of the internal tube bundle at the low frequency, this improvement not only improves the heat transfer coefficient (h), but also uses the vibration deformation to remove the scale on the heat transfer surface, reduce the thermal resistance, and finally realize the composite heat transfer enhancement. However, due to the disadvantages such as poor comprehensive heat transfer performance (HTP) of elastic tube bundles, it is essential to improve the structure to obtain better comprehensive HTP.

Conclusion

Based on the bi-directional fluid-structure interaction calculation method, the effect of Uin and row number N on vibration and HTP of the IETB heat exchanger are studied. According to the results above, the key conclusions follow.

(1) The average amplitude of IETBs in different row numbers gradually increases with the rising of Uin. The vibration uniformity of the IETBs is better at low Uin. Besides, the difference in amplitude among different IETBs becomes larger and larger. And the amplitude in the FL-heat exchanger is generally higher than the VL-heat exchanger. For the VL-heat exchanger, when the row number is increased, the average amplitude decreases gradually. For the FL-heat exchanger, it decreases first and then increases.

(2) The average heat transfer coefficient ha/hva of IETBs is directly proportional to Uin and comprehensive HTP decreases gradually with the rising of Uin. With the increase of tube number i, the ha/hva presents a general trend of decline. And ha/hav in the FL-heat exchanger is generally greater than that VL-heat exchanger. In addition, the hva is always greater than h, which indicates that vibration facilitates the achievement of heat transfer enhancement.

Abstract

Reducing manufacturing cost is the main goal of machine tool precision allocation under the condition of meeting precision design requirements. The previous studies generally took “ensuring machining errors completely within the allowable range of design precision” as constraint. Due to the strict constraint, the cost reduction effect is limited. This paper proposes a new method of precision allocation based on precision reliability. The probability that the machining errors are within the design precision allowable range is taken as the measurement index of precision reliability, and the optimization model constraint is relaxed to “that the machining errors are within the allowable range of design precision with predefined precision reliability”, so as to obtain lower manufacturing cost under tolerable precision loss risk. The case study of a large-scale gear hobbing machine shows that this method can effectively reduce the manufacturing cost, and the precision allocation is more economical and reasonable.

Introduction

Due to the fierce competition in the machinery industry, higher requirements are put forward for the design of machine tools. The traditional empirical design method cannot meet the design requirements of balancing the precision, cost and reliability of machine tools. Optimization design is a kind of modern design method, which is to optimize the design parameters under various specified constraints to obtain the optimal value of one or more design indicators. It aims at improving product quality and reducing product cost.

The machine tool design mainly includes the structural design, electrical design, precision design, and thermal design. Precision design, also known as precision allocation, is to reasonably allocate the precision of each part of the machine tool according to the machining performance requirements of the machine tool. Due to the complex impact on product quality and cost, the precision allocation is a highly responsible task [1]. Precision allocation generally includes three steps: precision prediction, precision allocation optimization modeling and model solving.

Conclusions

Precision allocation is an important work in machine tool design, which is of great significance to ensure the machining precision, improve product quality and reduce manufacturing cost. The precision allocation method mainly includes the basic principle method, the method with the optimization objective of minimizing manufacturing cost, and the method with the optimization objective of minimizing quality loss. The precision allocation of motion parts is mostly based on the sensitivity (or contribution) of their errors to the manufacturing cost.

According to the modern mechanical precision design theory, the overall precision of machine tool transmission chain is a random variable with normal distribution. Taking the normal distribution random variables properties into consideration, the probability is very low with variable reaching the maximum. Obviously, it is too harsh for the overall precision to fully meet the requirements of design precision, and the precision allocation scheme based on this constraint is not economical and reasonable. In the design of precision allocation, it does not seek meeting 100 % design requirements. Based on the characteristics of normal distribution of the comprehensive machining precision, it takes the probability of the machining precision meeting the design requirements to reach a certain threshold as the constraint condition for precision allocation, which can ensure the machining precision of the CNC-LGHM and effectively reduce the manufacturing cost.

Abstract

The importance of cutting hardened materials without influencing their structural properties makes abrasive waterjet machining a favorable choice in certain applications in comparison with other manufacturing technologies. Using this technology, faulty surface structures and errors caused by high thermal loads such as burrs, burns and cracks, can be avoided. In this paper, the results of applying the abrasive waterjet technology for cutting of hardened steel and its advantageous properties in comparison with cut-off grinding will be presented. The influence of process parameters on surface properties and burr formation has been determined by experimental analysis.

Introduction

Separating bars with small diameters made of hardened steel is usually conducted by applying the cut-off grinding technology [1]. This approach results in high temperatures within the cutting process, which leads to thermally influenced structural and surface errors on the workpiece, such as grinding burns, burrs and residual stress within the material [2]. These negative effects can be lowered by optimizing the machining strategy and process parameters in addition to using a CBN grinding wheel, which exhibits a high thermal conductivity and reduces the temperature transferred in the workpiece [3]. However, such an approach increases tooling costs and the overall processing time per one workpiece, which makes the application of these strategies applicable only when these factors are not of high importance. In this paper, a different approach for separating bars made of hardened steel using the abrasive waterjet technology is investigated.

Conclusion

In this research work, the influence of common abrasive waterjet process parameters and different cutting strategies on the surface quality and kerf properties were presented. Based on the study of the results gathered within the conducted experimental analysis of the abrasive waterjet cutting of the hardened high-strength steel 1.7102, following statements can be concluded:

Abstract

Molten salt is one of the most promising heat transfer and thermal energy storage medium for the third-generation solar thermal power generation, and the spiral-wound tube heat exchanger can improve the heat transfer performance of molten salt. In this paper, the flow and heat transfer characteristics of molten salt nanofluids in spiral-wound tubes are experimentally and numerically studied. Molten salt nanofluids and synthetic oil as the heat transfer fluids, the heat transfer performance of them in the spiral-wound tube heat exchanger were studied. The Wilson separation method was used to process the experimental data, and the heat transfer correlation of molten salt nanofluids is obtained through experiments. The heat transfer correlation can be in good agreement with the experimental data, the heat transfer correlation on the molten salt nanofluids side is  , Re = 4296–8348, Pr = 13–23, and the maximum error is 17.9%. A three-dimensional model of the spiral-wound tube heat exchanger is used to explore the distribution of the pressure, temperature and velocity fields of the molten salt nanofluids. The friction factor correlation on the molten salt nanofluids side is  , Re = 3536–17684, Pr = 13–23 and the maximum error is 12.65%. The heat transfer correlation and resistance correlation of molten salt nanofluids obtained in this paper can contribute to the design of heat exchanger for the third-generation solar thermal power.

Introduction

Solar thermal power generation technology has received extensive attention due to high efficiency and sustainability. Energy storage technology is an effective measure to solve the problem of intermittent solar power generation [[1], [2], [3]]. Molten salt can be used in the field of energy storage because of its large heat capacity, low viscosity, low vapor pressure, scholars around the world have paid extensive attention and carried out related research [[4], [5], [6]].

Liu et al. [7] conducted an experimental study on the turbulent heat transfer of molten salt in a circular tube, and obtained the heat transfer correlation of molten salt in the circular tube. Chen et al. [8] conducted an experimental study on the convective heat transfer of Hitec salt in three kinds of transversely corrugated tubes. He et al. [9] explored the convective heat transfer characteristics of ternary salts in shell and tube heat exchangers through experiments. Yang et al. [10] studied the flow and heat transfer characteristics of molten salt in trough solar collectors by numerical simulation. Chen et al. [11] carried out numerical simulation on the convective heat transfer of molten salt mixed in a unilaterally heated horizontal square tube. The results show that under the condition of non-uniform heating, the buoyancy force causes the core area of molten salt flow to be close to the heating surface to form eddy currents, which can enhance the heat transfer effect. Yang et al. [12] studied the heat transfer and flow performance of molten salt in the annular channel with helical coils by numerical simulation. The results show that adding helical coils can effectively enhance the heat transfer of molten salt in the annular channel, but the flow resistance also increased. Du et al. [13] designed a U-shaped tube for the experimental test of the heat transfer characteristics of molten salt in a shell-and-tube heat exchanger in transition flow, and fitted the heat transfer correlation of molten salt. Qiu et al. [14] proposed a baffle rod shell-and-tube heat exchanger configuration applied in the field of concentrated solar thermal power generation, using ternary salt and heat transfer oil as shell-side working fluids for experimental research. He et al. [15] studied the turbulent heat transfer characteristics of molten salt in shell-and-tube heat exchangers with Reynolds numbers ranging from 10,000 to 91,000 and 11,000 to 27,000 on the tube side and shell side, respectively. The comparison of available correlations for molten salt is in Table 1.

Conclusions

In this paper, the spiral-wound tube heat exchanger is taken as the research object, and the molten salt nanofluids and synthetic oil are used as heat transfer fluid to carry out experiments and numerical simulation studies respectively. The experiment was carried out with the salt-side temperature ranging from 573 K to 613 K, mass flow rate ranging from 0.6 to 1 kg/s. The corresponding Reynold’s number range is Re = 4296–8348. The flow heat transfer characteristics inside the heat exchanger, the following results are obtained:

Abstract

Introduction

Methodology

PV efficienc

Data collectio

Experimental setup

Results and discussion

Effect of temperature on the power output of PV panels and TEGs

Conclusions

Nomenclature

References

Abstract

     Many factors affect the efficiency of photovoltaic panels (PV), which convert solar energy directly into electrical energy. Among these factors, temperature is one of the most important one. While some of the radiation from the sun is converted into electrical energy, part of it emerges as heat energy. This causes the photovoltaic cells to heat up and reduce their electrical efficiency. Different methods are used in the literature to reduce the temperature in PV panels. In this study, in order to reduce the adverse effects caused by the high temperature in the PV panels, 30 Thermoelectric Generators (TEG) were applied to the back surface of the PV panel to increase the PV panel output power and to produce additional electrical energy. Energy and exergy analysis made on the data obtained from both PV panels in the climatic conditions of the installation site showed that the temperature of the PV panel is reduced, and the energy and exergy efficiency is increased with the TEG application. At the end of July, August, and September, when the experiments were carried out, an average of 8.4% more electrical energy was obtained from a single PV panel with TEG, compared to the standard PV panel. Our results suggests that combination of TEG with PV panels could significantly increase the electrical energy, especially when a series of PV panels are used together.

Introduction

     Recently, investments in electricity generation from renewable energy sources, especially solar and wind energy, have been increasing. However, when the performance of photovoltaic cells in the natural field environment is compared with the version of the standard test conditions, the efficiency of the PV panels decreases with the increase in temperature due to radiation (Bel Hadj Brahim Kechiche, Hamza, and Sammouda 2016). Since the energy that cannot be converted into electricity increases the photovoltaic surface temperature, it causes damage to the PV panel module cells and leads to reduced service life of the PV panels (Enescu and Spertino 2017). When the studies in the literature about reducing the heat losses in photovoltaic panels (PV) are examined; A water-cooled nozzle spray system has been developed that significantly reduces the module cell temperature (Benato and Stoppato 2019). The factors affecting the performance of PV panels and the applications that can be made to increase the panel power are explained in detail (Fouad, Shihata, and Morgan 2017).To obtain higher efficiency by cooling the PV panel surface, the panel output power and the cell’s lifetime are increased with different cooling methods (Siecker, Kusakana, and Numbi 2017). To prevent the decrease in PV panel power output with temperature increase, new models are proposed on the bottom surface. In experiments carried out under natural conditions, it has been determined that the panel temperature can be reduced by 10°C with the evaporative cooling model and the power improvement is 5% (Haidar, Orfi, and Kaneesamkand 2021).

Conclusions

     In this study, the losses in energy production due to the increase in temperature in the PV panels, especially in the summer months, were reduced by TEG application. An increase in the PV Panel output power was achieved. According to the results obtained;

● More electrical energy was produced in the PV panel with a thermoelectric generator in July, August, and September when the experiments were carried out.

● With the application of a thermoelectric generator in the PV panel, an average of 8.4% more electrical energy was obtained per month. This indicates that when the number of PV panels combined with TEG is increased, the total energy could increase significantly

● The output power of TEGs also increases depending on the rise in air temperature and PV panel surface temperature

● Since the average temperature was higher in July, maximum energy was produced in the thermoelectric generator panel. Compared to the standard panel, the PV panel, in which a thermoelectric generator is applied, had 10.29% more electricity in July, 7.15% in August, and 7.09% more in September, respectively.

Abstract

Keywords

1. Introduction

2. Literature review

3. Research methodology

4. Case study

5. Results and discussions

6. Conclusions

7. Compliance with ethical standards

Declaration of Competing Interest

References

Abstract

Lean manufacturing is a profound system designed to enhance every manufacturing industry’s efficiency by reducing waste through internationally recognized tools and techniques. Manufacturing industries strive to adopt lean concepts to maximize their resources like staff, facilities, materials, and schedules to be economically effective. However, managers face difficulty selecting the appropriate lean tools out of the many available LM tools for successful lean implementation. This study suggests an innovative approach to choose suitable lean tools to maximize these essential resources. Herein the Value Stream Mapping and plant layout are considered for waste identification. Fuzzy QFD and FMEA prioritize the crucial resources concerning the defined wastes and determine the risk associated with each failure mode’s sub-element for lean application. It saves time by analyzing only the most critical resources for a successful lean implementation since its focus only on the most important resources. The applicability of the proposed approach is demonstrated through a case study of an Ethiopian shoe manufacturing firm. With the aid of future state plant layout and value stream map, total cycle time is reduced by 56.3%, lead-time is reduced by 69.7%, materials transportation distance and transportation activities are reduced by more than 75%, and workers required are reduced from 202 to 200.

1. Introduction

Companies adopt lean manufacturing (LM) principles and tools for various reasons, including global competition, an uncertain market environment, and rising customers’ expectations. The concepts of LM can make it possible to use their resources effectively and increase their competitiveness. According to Deif and ElMaraghy (2014) and Goshime, Kitaw, and Jilcha (2018), LM is characterized by doing more with less. It focuses on reducing/eliminating waste in order to increase productivity and maximize customer values (Belekoukias et al., 2014).

With the origin of the Toyota Production System, several LM techniques and tools were developed and used to achieve lean. Some of them are TPM, JIT, TQM, kaizen, kanban, production smoothing, cellular manufacturing, one-piece flow, Value Stream Mapping (VSM), and standardized work. Most of them are adopted in discrete manufacturers (Kumar & Parameshwaran, 2018). LM techniques and tools where effectively implemented in Automotive (Vamsi Krishna Jasti & Sharma, 2014), chemical (Jilcha & Kitaw, 2015), textile industry (Hodge, Goforth Ross, Joines, & Thoney, 2011), construction (Ko, 2010; Aka, Danladi Isah, Eze, & Timileyin, 2020), and healthcare industries (Barberato, Freitas, Godinho, & Francisco, 2016).

Abstract

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Abstract

In this paper, based on the Li-Peterson pumping consumption-thermal resistance optimization model, a single-phase structure-optimized large-scale microchannel heat sink with each channel having 0.2 mm width and 0.8 mm height for extremely high heat flux cooling was proposed and investigated. Employing deionized water as coolant, two different heat source areas were designed and the results were compared under different pumping power from 0.1 W to 6.5 W. The experimental and simulation results indicates that the proposed copper-based microchannel thermal management system can dissipate heat flux of 1000 W/cm2 over 1cm2 and 500 W/cm2 over 5cm2, respectively, adding critical data support to the database of single-phase microchannel heat sink with heat removal capacity exceeding 1000 W/cm2. Moreover, the possible minimum thermal resistance over a broad pumping power range of 0.1 W to 6.5 W was explored. Extremely low thermal resistance of 0.065 K/W and 0.019 K/W were obtained for these two heating area scenarios. Overall, the proposed copper-based optimized microchannel heat sink is an ideal solution to cool high heat flux devices.

Introduction

The heat fuxes of devices such as high-performance computer chips, lasers and nuclear reactor are rapidly increasing, and the problem of heat accumulation and overheating is getting deteriorate [1]. In recent decades, the heat fux of the chip has reached 500 W/cm2 in the feld of Micro-ElectroMechanical Systems (MEMS), and the local hot spot can exceed 1000 W/cm2 [2–5]. For instance, the thermal fux of the next generation of IGBT modules will gradually increase from 100 W/cm2 to 500 W/cm2 [6]. For high-power laser devices, each diode laser needs to dissipate 500 W/cm2 of heat fux while keeping the operating temperature as low as possible [7]. In the nuclear power engineering, the heat fux generated by components included in fusion reactors and defense applications can be up to 104 W/cm2 [8].

Generally, the operating temperature of electronic devices should be less than 85 °C, and the reliability of products will be decreased by 50% if over-heated temperature exceeding 10 °C [9–11]. Since the demand of miniaturized design also limits the heat dissipation space, the uneven internal temperature distribution and poor heat dissipation have a series of negative efects, which will ultimately afect the performance and reliability of electronic devices. Therefore, reasonable thermal management is critical to electronic products [12, 13].

Current cooling technologies mainly include air cooling, liquid cooling, heat pipe, micro structure and spray cooling. As proposed by previous works, the traditional cooling method has relatively limited heat dissipation capacity, while the microchannel liquid cooling can handle a heat dissipation load of more than 1000 W/cm2 [14–16], which is expected to meet the urgently demand for high heat fux cooling in the near future.