Circumference Of Tube Research Articles

Comparative study on slaughter performance, meat quality, and rumen microbiota of Hainan Dong goat and its hybrid with Nubian goat.

The Hainan Dong goat (DG) is a local meat breed widely raised in Hainan, China because of its good adaptability to local hot and humid weather. However, the growth rate of these DG is much slower than that of commercialised breeds improved in European countries, resulting in poor carcase characteristics, including smaller slaughter weight and carcase weight, which have become increasingly prominent. In recent decades, Nubian goats have been continuously imported into China to improve the production performance of local breeds. In this study, the effects of breed on growth performance, carcase and meat quality, and ruminal microbiota were analysed in 40 goats, including 20 DGs and 20 hybrid F3 offspring generated by crossing the DG and Nubian hybrids (NH). All the goats were averagely aged 90 days and weighed at 11 ± 1.34 kg. They were assigned to two treatments, with three replicates per treatment. The two groups were fed the same diet for 90 days before slaughter. The results showed that the average daily gain, F/G ratio, slaughter weight, and carcase weight of the NH group were higher than those of the DG group (p < 0.05). However, tube circumference, meat-to-bone ratio, and eye muscle pH were lower in the NH group than in the DG group (p < 0.05). The NH group showed a smaller fibre crosssectional area and fibre diameter, but a larger fibre density than the DG group (p < 0.05). Bacteroidetes and Firmicutes were the most dominant phyla in the two groups; however, the two breeds had different ruminal microbial communities. In the present study, the differences in growth performance between two groups of goats under the same feeding environment and feed conditions were compared. The correlation between feed sources and rumen flora has been demonstrated, and the results of this study show that the same diet has similar effects on rumen microorganisms, which in turn have related effects on growth and production performance. In summary, hybrids can improve the growth and slaughter performance of local breeds, which may be related to changes in the rumen microorganisms. This study revealed that crossbreeding of Nubian goats with Dong goats has the potential to be used in a wide range of applications owing to its effectiveness in increasing production efficiency.

Heat Transfer in Double Pipe Heat Exchangers with Small Tube Spacing

Abstract In this current work, the heat transfer in double pipe heat exchangers with small tube spacing is analysed. This type of heat transfer is generally described in many literary sources, however, in laminar flow, the resulting values of the theoretical equations differ. Moreover, the small spacing of the pipes can affect the fluid flow and subsequent heat transfer. The suitability of using available theoretical methods for the design of double pipe heat exchangers (the Stephan, VDI and Baehr methods) was evaluated. A series of experiments was carried out on a double pipe heat exchanger with a tube spacing of 1.4 mm. The experimentally determined value of the heat transfer coefficient was up to two times higher in comparison with the values calculated according to theoretical methods. The relative increase was more significant for the lower Reynolds number values. At the same time, the difference of the wall temperature along the circumference of the outer tube was detected. This phenomenon was theoretically analysed and can be explained by tube misalignment in the small tube spacing. The procedure of quantification of this effect was proposed. This effect may cause an inhomogeneity of the media flow and temperature distribution and, as a result, increase the performance of the heat exchanger by tens of percent.

Possibility of the magnitude of the chiral vector having an effect on the terahertz radiation generation by hot electrons in zigzag carbon nanotubes driven by DC-AC fields

The possibility that the magnitude of a chiral or circumferential vector (Chv) influences the generation of terahertz radiations (T-rays) by hot electrons in zigzag carbon nanotubes (z-CNTs) driven by direct current (DC) and alternating current (AC) fields is taken into consideration. The study conducted a semiclassical theoretical analysis by using the Boltzmann kinetic equation to determine current density in relation to high AC field frequency (ω) and z-CNT circumference (|Chv|) when hot electrons were present. A numerical analysis was performed by varying the magnitude of the circumference of the tube at a fixed temperature and the strong hot electron injection rate at a predetermined value. When the circumference of the semiconducting zigzag carbon nanotubes (sz-CNTs) is increased, the current density's lowest and highest peaks are also enhanced (i.e., large amplitudes). This increases positive differential conductivity (PDC), necessitating enhanced domain suppression for higher potential generation of T-rays. In contrast, it was observed that reducing the tube's circumference in metallic zigzag carbon nanotubes (mz-CNTs) resulted in an increase in both the lowest and highest peaks of current density, which enhanced the PDC. These findings imply that larger circumferential sz-CNTs and smaller circumferential mz-CNTs may be more suitable candidates for a higher potential generation of T-rays with applications pertinent to modern science and technology.

Combined Genome-Wide Association Study and Haplotype Analysis Identifies Candidate Genes Affecting Growth Traits of Inner Mongolian Cashmere Goats.

In this study, genome-wide association analysis was performed on the growth traits (body height, body length, chest circumference, chest depth, chest width, tube circumference, and body weight) of Inner Mongolian cashmere goats (Erlangshan type) based on resequencing data. The population genetic parameters were estimated, haplotypes were constructed for the significant sites, and association analysis was conducted between the haplotypes and phenotypes. A total of two hundred and eighty-four SNPs and eight candidate genes were identified by genome-wide association analysis, gene annotation, and enrichment analysis. The phenotypes of 16 haplotype combinations were significantly different by haplotype analysis. Combined with the above results, the TGFB2, BAG3, ZEB2, KCNJ12, MIF, MAP2K3, HACD3, and MEGF11 functional candidate genes and the haplotype combinations A2A2, C2C2, E2E2, F2F2, I2I2, J2J2, K2K2, N2N2, O2O2, P2P2, R1R1, T1T1, W1W1, X1X1, Y1Y1, and Z1Z1 affected the growth traits of the cashmere goats and could be used as molecular markers to improve the accuracy of early selection and the economic benefits of breeding.

Weighted gene co-expression network analysis reveals genes related to growth performance in Hu sheep

Hu sheep are a unique breed in our country with great reproductive potential, the extent of whose breeding has been steadily rising in recent years. The study subjects in this experiment were 8-month-old Hu sheep (n = 112). First of all, the growth performance, slaughter performance and meat quality of their eye muscle quality were assessed, meanwhile their live weight, carcass weight, body length, body height, chest circumference, chest depth and tube circumference were respectively 33.81 ± 5.47 kg, 17.43 ± 3.21 kg, 60.36 ± 4.41 cm, 63.25 ± 3.88 cm, 72.03 ± 5.02 cm, 30.70 ± 2.32 cm and 7.36 ± 0.56 cm, with a significant difference between rams and ewes (P < 0.01). Following that, transcriptome sequencing was done, and candidate genes related to growth performance were identified using the weighted co-expression network analysis (WGCNA) approach, which was used to identified 15 modules, with the turquoise and blue modules having the strongest association with growth and slaughter performance, respectively. We discovered hub genes such as ARHGAP31, EPS8, AKT3, EPN1, PACS2, KIF1C, C12H1orf115, FSTL1, PTGFRN and IFIH1 in the gene modules connected with growth and slaughter performance. Our research identifies the hub genes associated with the growth and slaughter performance of Hu sheep, which play an important role in their muscle growth, organ and cartilage development, blood vessel development and energy metabolic pathways. Our findings might lead to the development of potentially-useful biomarkers for the selection of growth and slaughterer performance-related attributes of sheep and other livestock.

Analysis of super Cr13 stainless-steel internal fracture growth effects during skew mill piercing process

The seamless tube piercing process of super Cr13 martensitic stainless steel is addressed in this paper by comparing industrial piercing tests, laboratory hot tensile tests for material behavior characterization, and finite element simulations. Particular focus is given to the effect of process parameters on internal fracture growth and geometrical homogeneity of the tube. The geometrical non-homogeneities found on industrial pierced tubes are closely related to the change of flow stress of super Cr13 stainless steel during the piercing process. This way, the non-uniform strain rate along the tube's cross-section during piercing affects the fracture growth and, consequently, the thickness homogeneity of the tube, which varies from tip to tail. Due to obtained results, the mean value of pierced tube perimeter is 660 mm, while the mean value of the tube perimeter in the FEM simulation was predicted to be 2 % more (675 mm). The contact temperature of the plug and piercing tube was predicted at 1100 °C, and the mean value of pierced tube diameter in the simulation (210 mm) was 1.5 % more than the mean value of the actual tube (207 mm). The morphology of δ-ferrite affects the origin of primary crack initiation during the piercing process. Short and thick grains of δ-ferrite created at low strain rates that lengthen with increasing strain rate affect fracture sensitivity at the tip of the plug, favoring the non-homogeneity of the material.

The application of Na-Bi MOF as a heterometallic coordination polymer and 2,2-dimethoxypropane as an in-situ-generating ternary solvent for the extraction and preconcentration of some phthalate and adipate esters from tap, well, surface, and river water samples

In this study, the first-ever attempt was done to apply a heterometallic metal–organic framework (MOF) called Na-Bi MOF for the extraction and preconcentration of some phthalate and adipate esters. Also for the first time, 2,2-dimethoxypropane was adopted as an efficient in-situ generating ternary solvent for the desorption aim. Diverse real samples including tap, well, surface, and river waters underwent the developed extraction procedure. For performing the process of extraction, only 5 mg of Na-Bi MOF was added into a sodium sulfate-enriched aqueous solution containing the target compounds and vortexed. So, the analytes were adsorbed onto the MOF particles. Centrifugation separated the analyte-loaded MOF from the aqueous solution. The MOF was treated with only 500 µL of 2,2-dimethoxypropane. By centrifugation, the organic phase was separated and subjected to evaporation using a gas splitter device. After the complete evaporation of the organic phase, only 5 µL of 1,2-dibromoethane was applied for the elution of the inner perimeter of the conical bottom glass test tube by vortexing. Eventually, two microliters of the organic phase were injected into a gas chromatograph equipped with flame ionization detection. High enrichment factors (520–800), satisfactory extraction recoveries (52–80 %), low limits of detection and quantification (0.66–1.20 and 2.18–3.97 µg/L, respectively), favorable relative recoveries without dilution (86–117 %), wide linear ranges (3.97–500 µg/L), and high coefficients of determination (0.9903–0.9944) were recorded for the developed method. Low amount use of the MOF and organic solvents, diversity of real samples, no need for dilution, and short chromatographic run (a quarter) are the highlights of the developed method.

Dynamics of blood conveying copper, gold, and titania nanoparticles through the diverging/converging ciliary micro-vessel: Further analysis of ternary-hybrid nanofluid

Following the relevance and significance of blood transporting copper, gold, and titania nanoparticles through the diverging/converging ciliary micro-vessel in biomedical and physiological applications, little is known about the dynamics using Jeffrey fluid model, with a focus on the influence of specific regulatory factors. This report presents the results of a mathematical simulation for evaluating the hemodynamic effects of a bloodstream infused with ternary hybrid nanoparticles through a diverging/converging ciliary micro-vessel while taking into account the combined effects of a heat source, buoyancy, viscoelastic, electro-osmotic, and Lorentz forces. The homotopic perturbing approach was used to address the re-scaled leading equations. The ternary-hybrid nano-blood velocity is elevated by electroosmosis and the aiding Helmholtz-Smoluchowski velocity parameters in the core domain of the diverging/converging tube, but the opposite tendency is seen in the tube's perimeter zone. The circulation of the ternary-hybrid nanofluid is reduced by lengthening the cilia. Diversely shaped ternary-hybrid nanoparticles are employed in surgical procedures to attain the required heat flow rate. Increased blood loadings of ternary-hybrid nanoparticles are associated with increased blood temperature. Additionally, ternary nanoparticles have more effective physio-thermal properties when injected into the circulation (117.6%) compared to binary (89%) or unitary (48.3%) nanoparticles. Additionally, the divergent micro-vessel wall has a faster heat transfer rate than the convergent one.

Detection of key gene InDels in JAK/STAT pathway and their associations with growth traits in four Chinese sheep breeds

ObjectiveThe Janus kinase/signal transducer and transporter activator (JAK/STAT) signaling pathway plays crucial roles in lipid metabolism, glucose metabolism and cell senescence, suggesting that they are potential candidate genes affecting growth traits in animals. The present study aimed to evaluate the association between InDels in the JAK/STAT pathway and growth traits of four Chinese sheep breeds, including Tong sheep, Hu sheep, Small-tailed Han sheep and Lanzhou fat-tailed sheep. ResultsSeventy-six indel loci of 11 genes in JAK/STAT were detected, and three genotypes were selected at four loci by PCR amplification, electrophoresis and sequencing, including one locus in STAT3, one locus in STAT5A, and two loci in JAK1. The Correlation analysis indicated that there was no significant correlation between STAT3 and growth traits in four sheep breeds (P > 0.05); STAT5A was significantly associated with body height, rump width and tube circumference in Hu sheep and body length in Tong sheep (P < 0.05); JAK1 was significantly correlated with body height, body oblique length, cross height and tube circumference in Hu sheep (P < 0.05) and body oblique length, cross height and tube circumference in small-tailed Han sheep (P < 0.05). ConclusionOverall, our results indicated a potential association between the growth traits of sheep and the InDels of JAK1 and STAT5A.

Heat transfer characteristics of PCM inside a modified design of shell and tube latent heat thermal energy storage unit

Shell and tube latent heat thermal energy storage systems are compact and effective among other types of energy storage systems. The present numerical study deals with geometry optimization of a modified design of shell and tube latent heat thermal energy storage system over melting and solidification cycles. The modified design was produced by splitting the single inner tube into three smaller inner tubes arranged in a line array with different orientations. The numerical model covered four different line array orientations: 0°, 30°, 60°, and 90°, along with a storage model consisting of a single inner tube. The surface temperature, perimeter of inner tubes, and mass of PCM in all numerical cases were assumed to be identical. The numerical model has been validated by comparing the melting fraction contours and the PCM temperature with the experimental published data. It has been found that the line array of 0° orientation has the minimum full cyclic duration with an improvement of 44.4% compared to the base case. Conversely, the line array of 90° orientation has the maximum full cyclic time; 15.83% longer compared to the base case of a single inner tube. Lastly, the orientation of the line array is more significant for melting compared to the solidification.

Exhaustive extraction of pesticides through MOF-801-oriented dispersive micro solid phase extraction coupled with gas-assisted evaporation

In this study, for the first time, metal-organic framework-801 (MOF-801) was applied as an adsorbent for pesticide analysis. The high surface area of the adsorbent (780 m2 g-1) positively affected the extraction efficiency. Also, the first-ever attempt was done to couple an MOF-oriented adsorptive process with evaporation for preconcentration aim. The process was followed by dissolving the residue in a microliter level of an organic solvent. Initially, the particles of MOF-801 were subjected to the solution of interest having dissolved sodium sulfate and vortexed. After centrifugation and discarding the supernatant, acetonitrile was added onto the adsorbent and vortexed. After centrifugation, the acetonitrile phase underwent evaporation using the designed device. After complete evaporation, a microliter level of 1,2-dibromoethane was used to elute the inner perimeter of the conical bottom glass test tube by vortexing. Finally, one microliter of the organic phase was injected into a gas chromatography equipped with a flame ionization detector. Reaching the exhaustive extraction conditions with higher than 90% extraction recoveries, low limits of detection (0.35–2.10 μg L-1) and quantification (1.16–7.00 μg L-1), high enrichment factors (455−490), using bare MOF-801 in analytical method development, nearly no analyte loss during the extraction, and decreasing the applied volume of organic solvent in the process are the main highlights of the research.

Low-pressure steam dropwise condensation on durable PFA-coated horizontal tube: Droplet dynamics in active region

The performance of low-pressure steam condensers is vital to the thermal energy utilization efficiency of the power cycle, refrigeration, heat pump, and seawater desalination systems. Dropwise condensation demonstrates better heat transfer performance than traditional filmwise condensation, and its performance is determined by the condensate droplet dynamic behaviors on hydrophobic surfaces. However, the droplet dynamics behavior on the horizontal tube has not been adequately investigated. In this study, a durable PFA-coated copper tube is achieved to sustain stable dropwise condensation at the vapor pressure ranging from 5 to 100 kPa. By optical observation of condensation on the horizontally oriented tube, the droplet dynamic characteristics and the influence of vapor pressure on the droplet dynamics are examined. We show that an ‘active droplet region’ (ADR), which is characterized by frequent droplet shedding and surface renewal promoting more active nucleation, growth, and departure of droplets, exists along the tube circumference. As a result of the varying droplet dynamics, a skew-normal distribution of sliding droplet numbers presents along the tube circumference. The droplets departing within ADR account for 80% of the total departure droplets. Then, the effect of steam pressure on the droplet dynamics behavior in ADR is studied systematically. The average sweeping frequency of droplets under steam pressure of 100 kPa increases by -122% more than that under steam pressure of 5 kPa. The growth rate of droplets and migration speed improve with steam pressure. Thus, the evolution rate of the transient size distribution becomes rapid as the vapor pressure increases. Taking vapor pressure and circumferential angle into consideration, a semi-empirical model for the prediction of condensate droplet departure radius on a horizontal tube is proposed, of which the standard deviation can be reduced to less than 15%. These findings and insights into droplet dynamic behaviors on PFA-coated hydrophobic horizontal tube are of great significance for the novel surface design strategy for the enhancement of dropwise condensation heat transfer.

Association Analysis of PRKAA2 and MSMB Polymorphisms and Growth Traits of Xiangsu Hybrid Pigs.

In this study, Xiangsu hybrid pig growth traits were evaluated via PRKAA2 and MSMB as candidate genes. Sanger sequencing revealed three mutation sites in PRKAA2, namely, g.42101G&gt;T, g.60146A&gt;T, and g.61455G&gt;A, and all these sites were intronic mutations. Moreover, six mutation sites were identified in MSMB: intronic g.4374G&gt;T, exonic g.4564T&gt;C, exonic g.6378G&gt;A, exonic g.6386C&gt;T, intronic g.8643G&gt;A, and intronic g.8857A&gt;G. Association analysis revealed that g.42101G&gt;T, g.60146A&gt;T, g.61455G&gt;A, g.4374G&gt;T, g.4564T&gt;C, g.6378G&gt;A, g.6386C&gt;T, g.8643G&gt;A, and g.8857A&gt;G showed different relationship patterns among body weight, body length, body height, chest circumference, abdominal circumference, tube circumference, and chest depth. Real-time polymerase chain reaction results revealed that the expression of PRKAA2 was highest in the longissimus dorsi muscle, followed by that in the heart, kidney, liver, lung, and spleen. The expression of MSMB was highest in the spleen, followed by that in the liver, kidney, lung, heart, and longissimus dorsi muscle. These results suggest that PRKAA2 and MSMB can be used in marker-assisted selection to improve growth related traits in Xiangsu hybrid pigs, providing new candidate genes for Pig molecular breeding.

Measurement of wave propagation through a tube using dual transducers for elastography in arteries

Objective. Measuring waves induced with acoustic radiation force (ARF) in arteries has been studied over the last decade. To date, it remains a challenge to quantitatively assess the local arterial biomechanical properties. The cylindrical shape and waveguide behavior of waves propagating in the arterial wall pose complexities to determining the mechanical properties of the artery. Approach. In this paper, an artery-mimicking tube in water is examined utilizing three-dimensional measurements. The cross-section of the tube is measured while a transducer is translated over 41 different positions along the length of the tube. Motion in the radial direction is calculated using two components of motion which are measured from the two orthogonal views of the cross-section. This enables more accurate estimation of motion along the circumference of tube. Main results. The results provide more information to categorize the motion in tube wall into two types of responses: a transient response and a steady state response. The transient response is caused by ARF application and the waves travel along the length of the tube for a relatively short period of time. This corresponds to the axial and circumferential propagating waves. The two circumferential waves travel along the circumference of tube in CW (clockwise) and CCW (counter-clockwise) direction and result in a standing wave. By using a directional filter, the two waves were successfully separated, and their propagation was more clearly visualized. As a steady state response, a circumferential mode is generated showing a symmetric motion (i.e. the proximal and distal walls move in the opposite direction) following the transient response. Significance. This study provides a more comprehensive understanding of the waves produced in an artery-mimicking tube with ARF application, which will provide opportunities for improving measurement of arterial mechanical properties.

Enhancement of thermal energy storage in a phase change material heat exchanger having elliptical and circular tubes with & without fins

The objective of this study is to examine the thermal performance of a heat exchanger having multiple elliptical tubes and a phase change material (PCM) filled in the cylindrical shell of a heat exchanger. To improve the heat transmission from elliptical tubes to PCM, two and four fins are incorporated on the circumference of the elliptical tubes. The use of elliptical tubes with fins in the enhancement of heat transfer is an innovative approach in thermal performance studies of heat storage systems. The geometry of heat exchangers having elliptical tubes without fin, with two fins, and four fins are compared with the geometry of heat exchanger with circular tubes having no fin, two fins, and four fins respectively. The current investigation is carried out with the use of a 2D CFD model using a physical enthalpy-porosity technique to explore the phase transition of the solid PCM. The effect of integrating a number of fins on heat transfer has also been explored, and outcomes of elliptical and circular tube geometries in terms of PCM mean temperature and liquid percentage at two different temperatures of 50 °C and 60 °C have been compared. Results show, that PCM melting time is being reduced to 550 s in PCM heat exchanger geometry having elliptical tubes with four fins compared to 585 s for the same heat exchanger with two fins and 665 s for heat exchanger without fin at 50 °C resulting 12 % & 17 % reduction in melting time by applying two and four fins respectively. Whereas PCM melting time is 515 s in PCM heat exchanger geometry having circular tubes with four fins compared to 560 s for heat exchanger with two fins and 655 s for heat exchanger without fin resulting 14.5 % and 21 % reduction in melting time by applying two and four fins respectively. It has been concluded that adding fins on the circumference of elliptical and circular tubes enhances the heat transmission and reduces melting time as well as more heat can be transferred by circular tube geometry compared to elliptical tube heat exchanger geometries. The findings of the investigations are validated with the available simulation data and show good agreement, suggesting a 3.8 percent deviation.

Numerical investigations on boiling of moderator during PT/CT contact in 220 MWe IPHWR under postulated accidental scenario

For an Indian pressurised heavy water reactor, a numerical investigation was performed to study the boiling of moderator in a fully voided single nuclear channel during Pressure tube- calandria tube contact condition by applying variable heat flux. The setup included calandria tube, moderator, pressure tube, fuel bundle and an enclosure. It was observed that because of the contact between calandria tube and pressure tube, a notable variation in the circumferential temperature distribution of calandria tube and pressure tube were observed pointing out that contact condition drastically affects the temperatures of top and bottom portion of the tubes. It was also observed that upon increasing the heat flux, the top to bottom temperature variation decreases for pressure tube but increases for calandria tube. The phenomenon of boiling of moderator started when 1650 W/m2 heat flux was given to the system as input and the rate of boiling increased as the heat flux was increased which resulted in increasing moderator vapour fraction in the enclosure and decrease in average moderator density. The film thickness of the moderator vapour on the outer circumference of the calandria tube varied with time, following a cycle of increasing and decreasing thickness. The result showed that upto 4950 W/m2 heat flux, the moderator acted as an efficient heat sink. If the heat flux is increased further, the moderator can fail to act as a good heat sink and eventually lead to fuel channel failure.

Secondary Reflector and Receiver Positions for Uniform Heat Flux Distribution in Parabolic Trough Solar Thermal Collector

Abstract The distributions of heat flux over the circumference of the receiver tubes have an immense influence on the performance and reliability of the parabolic trough solar thermal collectors. The location of the receiver tube and the secondary reflector configuration may largely influence the performance of the system. Therefore, in this study, the effect of receiver tube position and parabolic secondary reflector configuration has been analyzed, and the non-uniformity of solar flux distribution, heat gradient, and power output has been compared. The results of the Monte Carlo ray-tracing analysis to homogenize the receiver tube flux distribution and maximize the output power, making the use of the cutting edge solar optical simulation tool Tonatiuh, has been presented. A parabolic trough collector with a rim angle of 80 deg and aperture area of 40 m2 have been used for the analysis. It has been confirmed that the circumferential heat flux gradient and the local hot spot could be greatly diminished, while the power output tended to reduce slightly due to the shading effect of the secondary reflector. Under the conditions investigated in this work, although the output power decreased by 4.83%, flux gradient reduced significantly, and the non-uniformity of flux distribution has reduced from 0.9757 to 0.5176. A simple design procedure for receiver tube position and secondary reflector configurations to homogenize the receiver tube temperature distribution has also been proposed.

Ferrite-Free Closed-Loop 13,56 Mhz Inductively- Coupled Low Mercury Pressure UV Lamp

Electrical and radiation characteristics of inductively-coupled ferrite-free low mercury pressure discharges exited at a frequency of 13.56 MHz and discharge plasma power, Ppl = (5 ? 300) W, in closed-loop quartz tubes of 815 mm in length and of 16.6 mm in diameter were experimentally stud-ied. Discharges were excited and maintained with the help of one-turn induction coil made from litz wire and disposed on the tube wall surface along tube perimeter. Tubes were filled with mercury vapour (~ 10Ц2 Torr) and argon (0.5, 0.7, 1.0, and 2.0) Torr. As discharge plasma power, Ppl, were increased from 130 W to 275 W, coil resonant frequency (RF) voltage grew from (560 ? 700) V up to (840 ? 860) V, RF coil current grew from (1.4 ? 1.8) A up to (2.4 ? 2.6) ј. Coil power losses was highest in the lamp with argon pressure of 0.5 Torr and grew from 30 W (Ppl = 150 W) to 70 W (Ppl = 230 W). UV resonant (254 nm) radiation flux grew with plasma power and was highest in the lamp (pAr = 0.5 Tоrr) while UV radiation generation ef-ficiency of this lamp had maximal value of 34 % at plasma power of 130 W.

Experimental validation of a continuum model for local heat transfer in shell-and-tube moving-bed heat exchangers

• Local heat transfer coefficients in shell-and-tube moving bed heat exchangers were simulated. • Local heat transfer coefficients were measured using a small heat exchanger mockup. • Experimental results were used to validate a comprehensive thermal model. • Simulation results were in good agreement with the experiments. Moving-bed heat exchangers with a horizontal tube arrangement offer a promising solution to exchange high-temperature heat with a particle stream. However, in order to guide the design of such heat exchangers, accurate and time-efficient simulation tools capable of capturing the complex heat transfer characteristics still need to be improved. In this article we present experimental results of the local heat transfer coefficients around the tube circumference of a heat exchanger mockup. To this end, specially prepared measuring probes were developed and a test campaign was conducted. A comprehensive thermal model was applied to the setup under consideration. This model takes into account the temperature-dependent thermophysical properties of the bulk, variable temperature boundary conditions, and the increased thermal resistance caused by the stagnation and void zones. To validate the model, calculated and experimental results were compared. It turns out that the predicted heat transfer coefficients well match the experimental data, albeit with slight deviations at the stagnation and void zones of the tubes. The prediction of a tube’s area-weighted heat transfer coefficient, which constitutes the most important factor for design purposes, yields results with errors of less than 3%. Therefore, it is concluded that the proposed thermal model is able to well predicts the heat transfer in shell-and-tube moving-bed heat exchangers.

Study of the effect of the position and metal of the receiver tube on the performance of a parabolic trough solar collector

In this study, the optical behavior of a parabolic trough collector solar collector has been traced, as the effect of the position and metal of the receiver tube on the optical efficiency and the average local concentration ratio of the heat flux on the receiver tube has been studied. A modeling was performed to simplify the operation of the studied system, where the codes (SOLTRACE and MATLAB) were used. In the first stage, the distribution of heat flux density on the receiver tube's surface was studied using SOLTRACE code based on the Monte-Carlo (Ray Tracing) method. Here the average heat flux on the wall of the receiver tube was obtained after Direct Normal Irradiance was reflected by the reflective mirror. This average will be used as boundary conditions in the MATLAB code, which will allow calculating the optical efficiency of the studied solar collector and the average local concentration ratio on the circumference of the receiver tube. In the second stage of the study, the effect of the metal type of the receiver tube on the optical efficiency and the average local concentration ratio of the heat flow on the receiver tube will be studied, as three metal types were taken for the receiver tubes, the first metal is Copper Black Coated, the second is Aluminum Black Coated and the third is G. Iron Black Coated. The model validation results show good agreement with the literature, with a difference of ±3.29% compared to previous numerical studies. In addition, one of the most important observations that have been reached through this study is that by moving the receiver tube downwards, the concentration area of the heat flux widens but the maximum value of the flux decreases, and the opposite is completely true. The black-coated copper receiver tube gave the best optical efficiency (89.38%) when the focal distance value was 1.88 m, while it was estimated at 75.77% with a focal distance of 1.84 m. The obtained results are very encouraging towards the necessity of carrying out experimental work in this field in order to clarify the physical concept of the behavior of the solar collector studied from the three angles numerically, modeling and experimentally.