Comparative Study on Performance of Regenerator for Miniature Pulse Tube Cryocooler with Metal Matrix Materials at Ultra High Frequencies

A Miniature Pulse Tube Cryocooler (MPTC) is the first selection for the cooling of IR sensors, infrared detectors, etc. in space technology. The regenerator is one of the key components to operate an MPTC at high efficiency. The objective of this study is to explore the possibilities of the different matrices as regenerator filler materials for MPTC operating at ultra-high frequencies. REGEN 3.3 is one of the best software available for the design and optimization of cryocooler regenerators. We have used REGEN 3.3 for numerical simulations of the three different regenerator matrix materials viz. stainless steel wire mesh screen (SS 635#), brass wire mesh screen (500#) and copper wire mesh screen (500#) at the hot end and cold end temperatures of 300[Formula: see text]K and 80[Formula: see text]K for COP, cooling power, total power losses and pressure losses, at an ultra-high frequency of 100[Formula: see text]Hz and 200[Formula: see text]Hz. The simulation results depict that the regenerator using stainless steel mesh screen shows better results than that of the brass mesh screen and copper mesh screen at 100[Formula: see text]Hz. However, the performance of brass mesh screen and copper mesh screen performs better than the stainless steel at 200[Formula: see text]Hz. Therefore, the proposed matrix materials can be used as regenerator materials for the MPTC at ultra-high frequencies with better performances.

Pressure Drop Measurements and Simulations for the Protective Mesh Screen Before the Gas Turbine Compressor

This paper characterizes the pressure drop of incompressible airflow when passing by a metal mesh screen which acts as a protection from sucking foreign solid matters before the gas turbine compressor. The wire diameter is 1.2mm and the mesh number is 3. Two experiments are conducted in different time period of a day to guarantee the experimental repeatability. The experimental data are used in regression analysis to obtain a quadratic correlation between the pressure drop across the screen and the fluid velocity. Numerical simulations are utilized to investigate detailed velocity and pressure fields around the wires and the Standard k-ε turbulence model is used. The results show that the fluid suffers from around 140Pa and 250Pa total pressure drop at the velocity of 20m/s and 30m/s respectively. The pressure closely upstream of the wires is as high as 4 times of the inlet flow level, while wide negative pressure regions are observed downstream of the wires resulting from fluid stagnation, reverse flow and recirculation. The empirical correlation obtained in the paper has a high confidence level and can be used in calculating the overall pressure drop of the gas turbine air intake system.

Performance evaluation of monocrystalline and polycrystalline silicon solar photovoltaic modules under low and high irradiance conditions in Kumasi, Ghana

One of the biggest drawbacks of photovoltaic (PV) for many applications is the uncertainty in the energy output due to losses attributed to efficiency loss at low irradiance levels. In this study, the electrical performance of as received monocrystalline silicon (mono-c-Si) and polycrystalline silicon (poly-c-Si) PV modules were evaluated at high and low irradiance conditions in Kumasi, Ghana using I-V Tracer. The low irradiance level of 200W/m2 was achieved by covering the surface of the PV modules with a calibrated mesh screen. Maximum output power (Pmax) of 87.9 W and 136.7 W were recorded for the mono-c-Si and poly-c-Si modules at high irradiance respectively. The corresponding average values at low irradiance were 8.29 W and 12.13 W representing percentage reductions of 90.57% and 91.60% respectively for the two technologies. These results indicate that when irradiance drops to 200 W/m2 and below, the PV modules generate around only 10% of their nominal output power. This has implications for the number of modules that are required for installation in areas that experience many hours of low irradiance. Efficiency reductions of 64.4% and 59.01% for the mono-c-Si and poly-c-Si modules respectively at low irradiance is reported. The results also indicate that the mono-c-Si is affected more by light induced degradation effect than the poly-c-Si module after a few hours of exposure to the natural light. The novelty of this work is that knowledge of the performance at low irradiance will enable designers determine the number of modules required during the sizing of PV plants.

Pore-Scale Simulation of the Interaction between a Single Water Droplet and a Hydrophobic Wire Mesh Screen in Diesel

Recently, the trend towards sustainable energy production and pollution control has motivated the increased consumption of ultra-low-sulfur diesel (ULSD) or bio-fuels. Such fuels have relatively low surface tension with water and therefore, the separation of water from fuel has become a challenging problem. The separation process relies on using porous structures for the collection and removal of water droplets. Hence, understanding the interaction between water droplets and the separators is vital. The simplest geometry of a separator is the wire mesh screen, which is used in many modern water–diesel separators. Thus, it is considered here for systematic study. In this work, pore-scale computational fluid dynamics (CFD) simulations were performed using OpenFOAM® (an open-source C++ toolbox for fluid dynamics simulations) coupled with a new accurate scheme for the computation of the surface tension force. First, two validation test cases were performed and compared to experimental observations in corresponding bubble-point tests. Second, in order to describe the interaction between water droplets and wire mesh screens, the simulations were performed with different parameters: mean diesel velocity, open area ratio, fiber radii, Young–Laplace contact angle, and the droplet radius. New correlations were obtained which describe the average reduction of open surface area (clogging), the pressure drop, and retention criteria.

Ips sexdentatus Mass-Trapping: Mitigation of Its Negative Effects on Saproxylic Beetles Larger Than the Target

Research Highlights: We investigated the negative effects of bark beetle mass trapping, especially non-target catches among the target’s natural enemies. Slot traps modified with mesh screen and escape windows were tested to improve their selectiveness. Background and Objectives: Two of the main natural enemies of bark beetles, Thanasimus formicarius (L.) and Temnoscheila caerulea (Olivier), are frequently trapped in high numbers in Ips sexdentatus (Böerner) pheromone traps, along with other saproxylic insects; this may lead to much larger pest populations in the successive 4–20 beetle generations. From 2016–2019, during I. sexdentatus mass-trapping in a pine forest of Tuscany (Italy), non-target catches were tallied. Trap modifications were evaluated to mitigate non-target catches, especially those concerning bark beetles’ natural enemies. Materials and Methods: A total of 25 bark-beetle slot traps were placed about 75 m apart in a pine stand infested by I. sexdentatus. Traps were baited with I. sexdentatus aggregation pheromone, whose main components are ipsenol, ipsdienol, and 2-methyl-3-buten-2-ol. Catches were collected every 10 days from March to December. In 2019, 13 traps were modified by applying a 6-mm mesh screen on top of the collection container and by providing three 60 mm × 8 mm escape windows immediately above the screen. These “modified traps” and their captures were considered separately from the 12 remaining “standard traps.” All bark beetle species were recorded, as well as all beetle species > 8 mm. Results: Overall, target catches amounted for <10% of the total beetle catches. The most-collected species was the bark beetle Orthotomicus erosus Wollaston. Trap modification allowed the escape of larger species, resulting in the reduction of the average size of caught specimens. Even though non-target catches among predators were still high, the proportion of major predators (T. formicarius and T. caerulea) to bark beetles showed a statistically significant reduction of predator catches in modified traps, an encouraging outcome. Conclusions: Trap modifications may mitigate the problem of non-target catches during mass trapping, especially reducing catches of beetle species larger than the target. However, the key is to schedule mass trapping only during those seasons when the target adults are more active than the main predator adults, thus limiting their catches and, consequently, the negative effects on pest management and biodiversity.

Improvement of Fiber Fines Retention and Mechanical Properties of Board Paper Using Corn and Tapioca Starch- A Handsheet Study

Steadily increasing production cost in the paper industry require more efficient resource allocation and utilization of recycled materials and the use of renewable materials and additives to become more environmentally friendly. With this project, 100 g/m² TAPPI handsheets from industrial processed OCC fiber material were produced, without starch and starch in cooked and uncooked form, air-dried at 23°C and contact-dried at 120°C. Starch addition levels were 6.0, 18.0 and 24.0 kg/mt (12.0, 36.0, and 48.0 lbs./st) for pearl and cationic starch, and 2.0, 6.0 and 8.0 kg/mt (4.0, 12.0, and 16.0 lbs./st) for tapioca starch. Fines were measured with a Britt Jar devise having a 75 μm (200 mesh) screen. The highest tensile index improvement of 35.71% for uncooked tapioca starch at an addition rate of 16 lbs./st. The highest tear index improvement of 1.86% was for pearl starch at an addition rate of 12 lbs./st for the cooked & contact dried application. The highest burst index improvement of the produced handsheets was for uncooked & contact dried cationic starch at an addition rate of 12 lbs./st with an improvement of 21.49%. Application of pearl starch showed the largest difference in fines content at the 12 lbs./st and 48 lbs./st of fiber concentrations, reducing the fines content by 22.2% and 24.7% based on solids content respectively. Pearl starch outperformed cationic and tapioca starch products and showed the highest potential for fiber savings and net profit value.

Stability of aerobic granular sludge under low energy consumption: Optimization of granular size distribution by a novel internal component

To enhance the stability and pollutant removal performance of an aerobic granular sludge (AGS), four groups of AGS reactors with different pore sizes of mesh screen (R1 is control reactor,...

An experimental justification of industrial water strainer brush cleaner properties

Purpose. Theoretical calculation of the friction resistance of the brush cleaner on the mesh screen of the strainer filter FRU-190-2 for industrial water. Experimental determination of the stiffness of one bristle of a brush cleaner. Experimental study of the resistance to movement of the brush cleaner on the strainer filter mesh screen. The purpose of writing this article is the theoretical calculation of the friction resistance of the brush cleaner on the strainer filter mesh screen of the industrial water strainer filter. Filters with a mesh screen are used in heavy industry for the first stage of water treatment. To design and calculate the properties of the brush cleaner, it is necessary to determine the geometric characteristics of the brush cleaner and the frictional resistance force when moving the brush cleaner on the strainer filter mesh screen. To confirm the results of the theoretical calculation of the frictional resistance of the brush cleaner, performed by methods of strength of materials, it is necessary to conduct an experimental study to determine the stiffness of one bristle of the brush cleaner and the resistance to movement of the brush cleaner bristles on the filter element. The methodology of research consists in theoretical calculation by methods of strength of materialsof friction resistance of a brush on a surface of a mesh filter element of the FRU-190-2 filter for industrial water, development of a technique of carrying out experiment, confirmation of the received analytical results of theoretical calculations by experimental researches. Findings. To determine the drag force of the brush cleaner, analytical solutions have been developed that take into account the influence of physical and geometric parameters of the bristles. Experimental confirmation of theoretical calculations is obtained. Scientific novelty is to establish and prove the cubic dependence of the force on one wire of the brush cleaner on its deflection. Analytical dependences of calculation of effort of movement of a brush on its geometrical parameters are revealed. Practical implications. The developed design technique and the results of calculations and experimental researches provide an possibility at the design stage to justification the geometric and physical properties of the brush cleaner of the strainer filter of industrial water.

Self-rotating Stir Mesh Screen Sorptive Extraction for analyzing Chlorpyrifos by Ion Mobility Spectrometry

A mesh screen was electrochemically coated with polypyrrole and used as a sorptive extractor device, for the first time. This configuration acts in such a way that it has self-rotating...