Search Results (10)

The operational condition of fire water supply aims to ensure the continuous and reliable supply of high-pressure water in emergency situations. Assuming a fire breaks out in a mountain village located far from the city center, due to the significantly higher flow rate and velocity of the water supply pipeline compared to normal operating conditions, any malfunction or shutdown of the pump caused by improper operation could result in catastrophic damage to the pipeline system. In response to the call for sustainable development, addressing this urgent academic challenge means finding a way to safely and economically maintain a continuous water supply to the target water demand point, even under extreme accident conditions. In this paper, drawing on engineering examples, we considered air tanks with varying process parameters installed at multiple locations within a water conveyance system to prevent water hammer and ensure water supply safety. To ensure that air tanks are of high quality and cost-effective after procurement and use, a multi-objective optimization design model comprising fitting, optimization, and evaluation plates was constructed, aimed at selecting certain process parameters. In the multi-objective optimization design model, Latin hypercube sampling improved by simulated annealing (LHS-SA), stepwise regression analysis (SRA), the Multi-Objective Whale Optimization Algorithm (MOWOA), and the Multi-Criteria Decision Analysis (MCDA) method with various weight biases are used to ensure the rationality of the optimization process. By comparing the optimization results obtained using these different MCDA methods, it is evident that the results output after AHP-EWM evaluation tend to be economic indicators, whereas the results output after FN-MABAC evaluation tend to be safety indicators. In addition, according to the sensitivity analysis of weight distribution, it can be inferred that the changes in maximum transient pressure head caused by water hammer have the most significant impact on final decision-making. Full article

Stringent sustainability goals are set for the next generation of aircraft. A promising novel airframe concept is the ultra-high aspect ratio Strut-Braced Wing (SBW) aircraft. Hydrogen-based concepts are active contenders for sustainable propulsion. The study compares a medium-range Liquid Hydrogen (LH2) to a kerosene-based SBW aircraft designed with the same top-level requirements. For both concepts, overall design, operating costs, and emissions are evaluated using the tool SUAVE. Furthermore, aerostructural optimizations are performed for the wing mass of SBW aircraft with and without wing-based fuel tanks. Results show that the main difference in the design point definition results from a higher zero-lift drag due to an extended fuselage housing the LH2 tanks, with a small reduction in the required wing loading. Structural mass increases of the LH2 aircraft due to additional tanks and fuselage structure are mostly offset by fuel mass savings. While the fuel mass accounts for nearly 25% of the kerosene design’s Maximum Take-Off Mass (MTOM), this reduces to 10% for the LH2 design. The LH2 aircraft has 16% higher operating costs with emission levels reduced to 57–82% of the kerosene aircraft, depending on the LH2 production method. For static loads, the absence of fuel acting as bending moment relief in the wing results in an increase in wing structural mass. However, the inclusion of roll rate requirements causes large wing mass increases for both concepts, significantly outweighing dry wing penalties. Full article

The growing interest in hydrogen (H₂) has motivated process engineers and industrialists to investigate the potential of liquid hydrogen (LH₂) storage. LH₂ is an essential component in the H₂ supply chain. Many researchers have studied LH₂ storage from the perspective of tank structure, boil-off losses, insulation schemes, and storage conditions. A few review studies have also been published considering LH₂ storage; however, most are simply collections of previous articles. None of these review articles have critically evaluated the research articles. In this review study, recent reports, conceptual studies, and patents have been included and critically discussed. Further, challenges and recommendations have been listed based on the literature review. Our results suggest that the multi-layer insulation scheme and integrated refrigeration system can effectively reduce boil-off losses. However, boil-off losses from storage tanks during transportation are the least discussed and must be addressed. The cost of an LH₂ storage tank is high, but it can be reduced with advancements in materials and the utilization of latest technologies. The present challenges and future directions for LH₂ storage include minimizing and utilizing boil-off losses, improving insulation schemes, and ensuring cost-effective large-scale LH₂ storage. This review study can be fundamental for process engineers and new academic researchers to design energy-efficient and cost-effective LH₂ storage systems. Full article

During liquid hydrogen bunkering into a cryogenic tank, boil-off losses occur due to the high thermal gradient between liquid hydrogen and the warm surface of the tank. This leads to gaseous hydrogen release. Such losses constitute a significant drawback in using hydrogen as a fuel for maritime applications where bunkering operations are regularly carried out, thereby constituting a significant loss along the liquid hydrogen pathway. Due to the inherently low temperature of liquid hydrogen, boil-off losses are always present. Some boil-off losses cannot be eliminated because they are thermodynamically constrained or intrinsic to the system’s design. Boil-off recovery methods can be implemented to capture the boil-off; however, those solutions come with an additional cost and system complexities. Hence, this paper investigates the feasibility of minimizing boil-off losses during the first bunkering of liquid hydrogen or refilling of liquid hydrogen in an empty cryogenic tank by first precooling the cryogenic tank surface to decrease the thermal gradient between the liquid hydrogen and the tank surface/wall. In this paper, different media for precooling a cryogenic tank are evaluated to assess the boil-off reduction potential and the associated costs in order to identify the most suitable solution. The assessment has been carried out based on analytical formulation. Full article

This paper proposes a performance analysis of a medium-range airliner powered by liquid hydrogen (LH₂) propulsion. The focus is on operating performance in terms of achievable payload and range. A non-conventional box-wing architecture was selected to maximize operating performance. An optimization-based multidisciplinary design framework was developed to retrofit a baseline medium-range box-wing aircraft by designing and integrating the fuel tanks needed to store the LH₂; several solutions were investigated for tank arrangement and layout by means of sensitivity analyses. As a main outcome, a performance analysis of the proposed LH₂-powered box-wing aircraft is provided, highlighting the impact of the introduction of this energy carrier (and the integration of the related tank systems) on aircraft operating performance; a comparative study with respect to a competitor LH₂-retrofitted tube-and-wing aircraft is also provided, to highlight the main possible operating differences between the two architectures. The findings reveal that the retrofitted box-wing can achieve long-range flights at the cost of a substantially reduced payload, mainly due to the volume limitations imposed by the installation of LH₂ tanks, or it can preserve payload capacity at the expense of a significant reduction in range, as the trade-off implies a reduction in on-board LH₂ mass. Specifically, the studied box-wing configuration can achieve a range of 7100 km transporting 150 passengers, or shorter ranges of 2300 km transporting 230 passengers. The competitor LH₂-retrofitted tube-and-wing aircraft, operating in the same category and compatible with the same airport apron constraints, could achieve a distance of 1500 km transporting 110 passengers. Full article

A four-node model is proposed to investigate the no-vent filling performance of liquid hydrogen (LH₂) at microgravity. The no-vent filling method can directly prevent the influence of random gas–liquid distributions at microgravity, making it a good choice for cryogenic propellants to achieve orbital refueling. The typical phase distribution of the centrally located ullage was assumed and, in particular, the correlations for the boiling heat transfer of LH₂ at microgravity were corrected in this model. After the accuracy of this model was effectively verified, the effects of different filling conditions, including the initial tank pressure, the initial temperature, and the temperature of the inlet liquid, were studied. The results showed that the initial pressure had a major influence on the initial pressure rise but only a slight influence on the final pressure development. A higher initial temperature would have led to an obvious increase in the tank pressure and an obvious decrease in the final filling level when reaching the upper pressure limit. Reducing the temperature of the inlet liquid has certain effects on the pressure control and the improvement of the final filling level. In conclusion, to achieve a higher filling level under a lower pressure level during the no-vent filling of LH₂ at microgravity, sufficient pre-cooling of the filling system is required. Furthermore, appropriate evacuation of the receiver tank before filling and subcooling of the inlet liquid within an acceptable range of costs are both suggested. While the proposed model is less accurate than full-resolution CFD for the detailed evolution of physical fields, it offers much greater computational speed for quick parametric studies of key input conditions. Full article

The technology for storing thermal energy as sensible heat, latent heat, or thermochemical energy has greatly evolved in recent years, and it is expected to grow up to about 10.1 billion US dollars by 2027. A thermal energy storage (TES) system can significantly improve industrial energy efficiency and eliminate the need for additional energy supply in commercial and residential applications. This study is a first-of-its-kind specific review of the current projected performance and costs of thermal energy storage. This paper presents an overview of the main typologies of sensible heat (SH-TES), latent heat (LH-TES), and thermochemical energy (TCS) as well as their application in European countries. With regard to future challenges, the installation of TES systems in buildings is being implemented at a rate of 5%; cogeneration application with TES is attested to 10.2%; TES installation in the industry sector accounts for 5% of the final energy consumption. From the market perspective, the share of TES is expected to be dominated by SH-TES technologies due to their residential and industrial applications. With regard to the cost, the SH-TES system is typically more affordable than the LH-TES system or the TCS system because it consists of a simple tank containing the medium and the charging/discharging equipment. Full article

The current interest in thermal energy storage is connected with increasing the efficiency of conventional fuel-dependent systems by storing the waste heat in low consumption periods, as well as with harvesting renewable energy sources with intermittent character. Many of the studies are directed towards compact solutions requiring less space than the commonly used hot water tanks. This is especially important for small capacity thermal systems in buildings, in family houses or small communities. There are many examples of thermal energy storage (TES) in the literature using the latent heat of phase change, but only a few are commercially available. There are no distinct generally accepted requirements for such TES systems. The present work fills that gap on the basis of the state of the art in the field. It reviews the most prospective designs among the available compact latent heat storage (LHS) systems in residential applications for hot water, heating and cooling and the methods for their investigation and optimization. It indicates the important characteristics of the most cost- and energy-efficient compact design of an LHS for waste heat utilization. The proper design provides the chosen targets at a reasonable cost, with a high heat transfer rate and effective insulation. It allows connection to multiple heat sources, coupling with a heat pump and integration into existing technologies and expected future scenarios for residential heating and cooling. Compact shell-tube type is distinguished for its advantages and commercial application. Full article

Green liquid hydrogen (LH2) could play an essential role as a zero-carbon aircraft fuel to reach long-term sustainable aviation. Excluding challenges such as electrolysis, transportation and use of renewable energy in setting up hydrogen (H₂) fuel infrastructure, this paper investigates the interface between refueling systems and aircraft, and the impacts on fuel distribution at the airport. Furthermore, it provides an overview of key technology design decisions for LH2 refueling procedures and their effects on the turnaround times as well as on aircraft design. Based on a comparison to Jet A-1 refueling, new LH2 refueling procedures are described and evaluated. Process steps under consideration are connecting/disconnecting, purging, chill-down, and refueling. The actual refueling flow of LH2 is limited to a simplified Reynolds term of v · d = 2.35 m²/s. A mass flow rate of 20 kg/s is reached with an inner hose diameter of 152.4 mm. The previous and subsequent processes (without refueling) require 9 min with purging and 6 min without purging. For the assessment of impacts on LH2 aircraft operation, process changes on the level of ground support equipment are compared to current procedures with Jet A-1. The technical challenges at the airport for refueling trucks as well as pipeline systems and dispensers are presented. In addition to the technological solutions, explosion protection as applicable safety regulations are analyzed, and the overall refueling process is validated. The thermodynamic properties of LH2 as a real, compressible fluid are considered to derive implications for airport-side infrastructure. The advantages and disadvantages of a subcooled liquid are evaluated, and cost impacts are elaborated. Behind the airport storage tank, LH2 must be cooled to at least 19K to prevent two-phase phenomena and a mass flow reduction during distribution. Implications on LH2 aircraft design are investigated by understanding the thermodynamic properties, including calculation methods for the aircraft tank volume, and problems such as cavitation and two-phase flows. In conclusion, the work presented shows that LH2 refueling procedure is feasible, compliant with the applicable explosion protection standards and hence does not impact the turnaround procedure. A turnaround time comparison shows that refueling with LH2 in most cases takes less time than with Jet A-1. The turnaround at the airport can be performed by a fuel truck or a pipeline dispenser system without generating direct losses, i.e., venting to the atmosphere. Full article

The provision of clean water to remote communities is a major goal of both the World Health Organization and the United Nations. We report on the long-term sustainability of filter-sterilizing polluted water in remote villages in Ghana that lack electricity. Contaminated water pumped several times a week via a gasoline pump into a 1000 L elevated tank is filtered through polysulfone hemodialyzers on demand. The 3 nm fiber pore size rejects all bacteria, parasites, and viruses. Villagers flush organic matter from the dialyzers thrice daily to maintain a flow of up to 250 L/h. Having previously reported a 73% reduction in diarrheal episodes, we now address system sustainability. After passing through the hemodialyzer filters, a fecally polluted water source remains consistently free of pathogens even after the system has been in place for >1 year in most villages. Filters are easily replaced when needed. Daily cost for unlimited clean water is less than USD 2.22 per village over five years. Villagers have continued to independently fill the tank and flush the system, because they appreciate the clean water and health benefits. We demonstrate that over 2–6 years this system providing pathogen-free drinking water can be maintained independently by villagers for long-term sustainability. It does not require electricity nor disinfectants to be added to the product water and is ready for far broader application in similarly remote settings. Full article