Approximate approach for improving pressure attenuation accuracy during hydraulic transients

The quasi-steady friction model is generally adopted in water hammer simulation in pipe network systems, which cannot accurately reflect the attenuation of pressure, while the existing unsteady friction model is challenging to use in complex pipe network systems. In this study, a convenient method for treating the friction term is proposed based on the Moody diagram. The attenuation process of water hammer pressure can be accurately reflected by reading the relationship curve between Reynolds number and the Darcy friction factor in the pipeline transient process. Combined with the classical water hammer experiment and the long pipe valve closing experiment in our laboratory, the accuracy of this model is verified, and the influence of absolute roughness (e) and Reynolds number (Re) on the model was analyzed as well. The results show that the pressure attenuation using the Method of Characteristics (MOC) and the proposed friction model has a good agreement with the experimental data. The absolute roughness has little influence on the results in hydraulically smooth pipe, while the minimum Reynolds number has a significant influence. When selecting the minimum Reynolds number, 2% ∼ 5% of the initial flow rate is recommended for calculation.

Experimental and numerical assessment on failure pressure of textured pipelines

A series of physical tests and finite element (FE) analyses are conducted to evaluate the failure of smooth (conventional) and textured (proposed concept) pipes. To do so, hydrostatic pressure tests are performed on aluminium beverage cans (ductile failure) and additively manufactured Ti6Al4V-0406 titanium pipes (brittle failure). Mechanical material properties are obtained from tensile tests of coupon samples. In absence of physical burst pressure tests, FE models are validated against experimental results of external pressure tests and are used to predict the buckle initiation (Pi) and burst pressure (Pb) capacity of the textured pipes with different number of circumferential triangles, N, and base angles, a. Results show that buckle initiation pressures of the textured concept is 2.34 and 1.80 times greater than those of the smooth aluminium cans and titanium pipes, respectively. However, the burst pressure of the textured pipe can only get 3% greater than the smooth pipe. Based on the current results a textured pipe with N=6 and a=30° is the optimum textured design.

Study of Flow and Heat Transfer Characteristics of Lead-Based Liquid Metals in a Turbulent Tube Flow and the Impacts of Roughness

Lead-based liquid metals (LLMs) such as lead–bismuth eutectic (LBE) and lead, are currently the most interesting candidate coolants for fast reactors because of their excellent physical properties, which can improve safety and reduce costs. However, in comparison to other liquid metals, previous research on the flow and heat-transfer characteristics of LLMs has been limited. Therefore, this work carried out flow and heat-transfer experiments in LBE flowing through a circular tube in the Natural Circulation Capability Loop (NCCL) facility. The results show a significantly higher friction factor than that of water flowing in a smooth pipe. Furthermore, the Nusselt numbers were found to be lower than those found in data in the literature for experiments carried out in a smooth tube at low Péclet numbers, while they were higher at high Péclet numbers. Therefore, theoretical analyses were performed for LLMs flowing in both smooth and rough pipes, and the impacts of roughness on the heat transfer of an LLM were examined. The theoretical relations for a smooth pipe and a rough pipe were validated using experimental data from the literature and the results of the NCCL experiments, respectively. The results of the theoretical relation for a smooth pipe fitted the literature data well. The derived theoretical relation for a rough pipe with a relative roughness of 0.004 fitted the NCCL data best. Moreover, it was established from the theoretical analysis that roughness has two competitive impacts on the heat transfer of an LLM: it reduces conductive heat transfer while enhancing convective heat transfer. Because conductive heat transfer is important for liquid metals, even with turbulent flow, a small roughness will lead to heat-transfer deterioration at low Péclet numbers, and it may even deteriorate across the whole typical Péclet-number range. This discovery has important implications for the thermal–hydraulic design of LLM reactors, because corrosion and erosion by an LLM will lead to a rough surface after long operating times.

The optimisation of the cylinder-spiral soil-cultivating roller

Designed cylinder-tillage spiral skating rink with spiral work items, which form a fine lumpy structure of the sowing layer of soil with grain size corresponding to agrotechnical requirements, while helping the soil surface, mulching the top layer of soil over the seeds, seal the depth of their placement, providing the required contact of seeds with soil is necessary to ensure the uniformity of germination. At the theoretical level, it is determined that an increase in the pinching angle leads to an increase in the size of the hollow smooth pipe of the roller. This occurs while increasing the depth of deformation of the layer of crushed soil and the radius of the clump of soil. However, a change in the radius of a hollow smooth roller of more than 0.3 m does not lead to a slight increase in the pinching angle. Therefore, increasing the radius of the hollow smooth roller over 0.3 m is not rational, as it will increase the metal content of the structure. After analyzing the obtained mathematical models of the soil treatment process with a roller, we optimized the parameters of a cylindrical-spiral roller: speed of 11 km/h, mass of ballasting loads of 100 kg, step of the spiral turn of 40 mm, and the departure of the spiral screw of 35 mm. These modes ensure the formation of a qualitatively compacted soil layer in the zone of planting seeds of agricultural crops, which is confirmed by the maximum value of the processing quality criterion for matching the density of the soil after rolling with a cylindrical-spiral roller CCS = 0.98 (while the density of the sown layer addition 1185...1215 kg/m3), which fully satisfies the agrotechnical optimum. The yield of barley of the Nutans-553 variety became higher after the use of an innovative cylindrical-spiral roller by 6.4 % and 9.3 %, respectively, of the yield after the impact of serial ККSh rollers and ring rollers of the seeding machine. In the course of evaluating the metal consumption of structures of the innovative cylindrical-spiral roller and the ring-spur roller, a difference of 70% per unit width of the grip was revealed.

Investigation of Steady-State Heat Extraction Rates for Different Borehole Heat Exchanger Configurations from the Aspect of Implementation of New TurboCollector™ Pipe System Design

When considering implementation of shallow geothermal energy as a renewable source for heating and cooling of buildings, special care should be taken in the hydraulic design of the borehole heat exchanger system. Laminar flow can occur in pipes due to the usage of glycol mixtures at low temperature or inadequate flow rates. This can lead to lower heat extraction and rejection rates of the exchanger because of higher thermal resistance. Furthermore, by increasing the flow rate to achieve turbulent flow and satisfactory heat transfer rate can lead to an increase in the pressure drop of the system and oversizing of the circulation pump which leads to impairment of the seasonal coefficient of performance at the heat pump. The most frequently used borehole heat exchanger system in Europe is a double-loop pipe system with a smooth inner wall. Lately, development is focused on the implementation of a different configuration as well as with ribbed inner walls which ensures turbulent flow in the system, even at lower flow rates. At a location in Zagreb, standard and extended thermal response tests were conducted on three different heat exchanger configurations in the same geological environment. With a standard TRT test, thermogeological properties of the ground and thermal resistance of the borehole were determined for each smooth or turbulator pipe configuration. On the other hand, extended Steady-State Thermal Response Step Test (TRST) incorporates a series of power steps to determine borehole extraction rates at the defined steady-state heat transfer conditions of 0/–3 °C. When comparing most common exchanger, 2U-loop D32 smooth pipe, with novel 1U-loop D45 ribbed pipe, an increase in heat extraction of 6.5% can be observed. Also, when the same comparison is made with novel 2U-loop D32 ribbed pipe, an increase of 18.7% is achieved. Overall results show that heat exchangers with ribbed inner pipe wall have advantages over classic double-loop smooth pipe designs, in terms of greater steady-state heat extraction rate and more favorable hydraulic conditions.