The cross-sectional area of a surge tank (CAST) is a key factor for protecting pipelines from harm by hydraulic transients. However, for long-distance pipeline systems (LDPS), the water level ...fluctuations in the surge tank and valve closure water hammer normally share a coupling relationship. Traditionally, this coupling relationship renders difficulty in determining the CAST. This study focused on the influence of water level fluctuation and water hammer, and proposed a simplified approach for sizing surge tanks. First, a water hammer formula that considers the coupling effect was derived. Subsequently, formulae for sizing the CAST were deduced. Finally, a case study of an actual LDPS was conducted to verify the accuracy of the presented formulae. In addition, the calculation errors caused by the theoretical assumptions are discussed. The results indicate that the theoretical calculation values and time-domain simulation results match well, thereby demonstrating the great convenience of designing surge tanks.
•Solar assisted heat pump system with buffer tank as source for heat pump.•Uncovered photovoltaic-thermal collector used to charge buffer tank in periods without irradiance.•Transient simulation ...model validated with experimental measurements.•Yearly performance of system including parameter variation.•Modulating heat pump with thermal mass modelled via scale factor and extra pipes.
Solar thermal energy systems combined with heat pumps are becoming popular solutions for covering space heating and domestic hot water demand in European Union households. There is a great potential for developing high performing systems by combining components in systems in new ways. This study focuses on the performance of a system consisting of heat pump, photovoltaic-thermal solar collector and two storage tanks. This system is proposed to potentially have better performance compared to air-to-liquid heat pump system while being less costly compared to a liquid-to-liquid heat pump system with ground sourced heat exchanger. The system was set up at the Technical University of Denmark in 2017, for providing domestic hot water. A simulation model of the system was created in the transient simulation software TRNSYS and the data from the experiment were used for its validation. The modulating heat pump was modelled via a function applied to the scale factor and the thermal mass of the heat pump was taken into account by including additional pipes around the heat pump. The performance of the system was assessed using selected key performance indicators. A parametric analysis was performed identifying component sizes that improved the system’s performance. The improved system produced 55% more electricity, had 23% lower electric consumption and wasted 11% less heat by minimizing heat losses compared to the demonstration system. The improved system had a solar thermal fraction of 0.58, a solar electrical fraction of 1.51 and a renewable energy fraction of 0.75. The system was however oversized compared to the load applied to the system as it was built to cover only domestic hot water demand. For the system to be economically attractive it must cover a larger load.
The immense pressure to decarbonise the maritime industry has led to the Liquefied Natural Gas (LNG) uptake as a marine fuel and the LNG fuelled ships design. As LNG is stored in cryogenic ...conditions, the heat ingress from the ambient causes the boil-off gas (BOG) production, which, if not controlled, results in the tank overpressure with implications on the fuel storage system safe operation. This study aims at investigating an LNG storage tank behaviour for realistic operating conditions of an LNG fuelled ocean-going ship, targeting to identify the recommended control actions for avoiding tank overpressure. A dynamic model is developed by considering the mass and energy conservation in the liquid and vapour subsystems, the energy conservation in the tank walls, the vapour to liquid equilibrium (VLE), and real gas properties. Following the model validation for a holding test, simulation runs were performed for various operating conditions corresponding to typical long and short voyages of the investigated ship. The simulation results demonstrate that a boil-off gas (BOG) compressor capacity of 450 kg/h along with its on/off control setting the upper and lower limits of the tank absolute pressure at 5.5 and 4 bar leads to tank overpressure avoidance and the minimum number of BOG compressor activations.
•Dynamic modelling of storage tanks of LNG fuelled ships.•Scenarios representing realistic conditions of typical voyages are investigated.•To prevent overpressure, boil-off compressor capacity of 450 kg/h is required.•Tank pressure on/off control upper/lower limits were found 5.5/4 bar (abs).
Oil storage tank detection and classification in synthetic aperture radar (SAR) images play a vital role in monitoring energy distribution and consumption. Due to the SAR side-looking imaging ...geometry and multibouncing scattering mechanism, dense oil tank detection and classification tasks have faced more challenges, such as overlapping, blurred contours, and geometric distortion, especially for small-sized tanks. To address the above issues, this paper proposes YOLOX-TR, an improved YOLOX based on the Transformer encoder and structural reparameterized VGG-like (RepVGG) blocks, to achieve end-to-end oil tank detection and classification in densely arranged areas of large-scale SAR images. Based on YOLOX, the Transformer encoder, a self-attention-based architecture, is integrated to enhance the representation of feature maps and capture the region of interest of oil tanks in densely distributed scenarios. Furthermore, RepVGG blocks are employed to reparameterize the backbone with multibranch typologies to strengthen the distinguishable feature extraction of multi-scale oil tanks without increasing computation in inference time. Eventually, comprehensive experiments based on a Gaofen-3 1 m oil tank dataset (OTD) demonstrated the effectiveness of the Transformer encoder and RepVGG blocks, as well as the performance superiority of YOLOX-TR with a mAP and mAP0.5 of 60.8% and 94.8%, respectively.
We introduce an innovative approach for determining the gas permeability of composite laminates, explicitly accounting for inter-fiber fracture. Our method forges a direct correlation between the ...Continuum Damage Mechanics (CDM) damage parameter for transverse inter-fiber fracture and the effective permeation coefficients, which are crucial in assessing leak tightness. This correlation stems from a geometric similarity between the ratio of the damaged material’s load-carrying capacity to that of its pristine state, and the relative projected crack length as crucial parameter for the effective permeability assessment. This CDM-based approach represents a significant advancement in directly deriving a laminate’s permeability from mechanical failure analysis results. This is essential for the design process of Type V hydrogen storage tanks. Literature-based experimental results validate the plausibility of our method, proving its effectiveness across various laminate orientations and damage scenarios. Nonetheless, the observed deviations highlight the need for detailed damage information, elaborate material characterization.
•Enhancement of thermal stratification via obstacles in vertical mantled hot water tank has been studied experimentally.•Four different obstacles have been placed in four different heights from the ...tank bottom.•Effect of the obstacle and its position has been investigated.•At the end of the present study, placing the obstacle inside the inner tank in vertical mantled hot water tanks has improved thermal stratification of the tank.•This result has been presented by temperature distribution, stored energy amount, Richardson Number, mantle outlet temperature and usage outlet temperature.
Thermal stratification is a significant performance parameter for thermal energy storage tanks. In present study, the thermal stratification of vertical mantled hot water tank was investigated by placing different obstacle inside the tank. Four different obstacles were placed inside the tank in four different distances from the tank bottom. Thus effects of the obstacle types and positions were investigated. At the end of study, it was found that obstacle placed inside the tank enhanced the thermal stratification. Results were presented in the terms of temperature distribution, energy storing capacity, Richardson Number, consumption outlet and mantle outlet temperature. All these values were improved by placing the obstacle inside the tank, according to ordinary tank. The best thermal stratification was obtained between Y = 200 and Y = 300 mm the distance from the tank bottom. A type obstacle supplied the best thermal stratification.
•Hybrid tanks containing water and phase change materials are studied numerically.•Phase change materials with different melting points are placed in the tanks.•The cascaded configuration is studied ...in a solar domestic hot water system context.•A system energy balance reveals the benefit of the hybrid thermal energy storage.•The hybrid system can yield increased solar fraction compared to water-only tanks.
The current paper explores a multi-tank thermal storage system for multi-residential solar domestic hot water applications. The thermal storage system includes phase change materials (PCMs) of different melting temperatures incorporated in the tanks. The PCMs are introduced as vertical cylindrical modules and water flowing along the length of tank is used as the heat transfer fluid. An enthalpy porosity model was developed to solve for the phase change process within the PCM modules. The model was validated and verified with previous work and predictions were in good agreement (less than 5% deviation). The hybrid tank model was linked with the collector performance. Typical Canadian weather data and a dispersed demand profile for a multi-residential building were considered. The performance of the hybrid system was judged based on the maximum possible storage volume reduction compared to the water only system with the same benefit to the end user. PCM maintains cooler water temperature entering the collector which results in a reduction of collector losses and extension of pump activation time. This increases the delivered energy to the load and hence increases the solar fraction. It was found that cascading four 75 L tanks containing PCMs of melting temperatures 54 °C, 42 °C, 32 °C and 16 °C gives a similar solar fraction to that for a 630 L water only tank. The multi-tank hybrid system thus allowed for over 50% reduction in the required storage volume.
The combustion behavior of two oil tank fires will be influenced by the interaction of their respective flames. This paper presents the experiments to investigate the evolution of the visible flame ...height of two oil tank fires under different diameters, lip heights and distances. The results show that when the tank spacing is small, the vortex structure plays an important role in the flame behavior showing an enhancement of the flame height. The flame height increases with the increase in lip height and reaches a local maximum value. The flame merging characteristic is influenced by the burner size and shape. A dimensionless model of the visible flame height of two oil tanks fire has been proposed, taking the tank diameter, lip height, and tank spacing into consideration. The correlation is validated using the experimental data.
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