Plain Tube Research Articles

Thermo-hydraulic Investigation of a Heat Exchanger Tube Equipped with 3D-Printed Swirl Flow Generators

AbstractHeat transfer capabilities of the heat exchangers require enhancements to save energy and decrease their size. For this purpose, the swirl generators have been widely preferred. However, the swirler inserts have not reached their optimum shape. Thus, this study experimentally and numerically investigates the impact of novel 3D-printed swirler inserts with varying twist angles in the range of 0°–450° on the thermo-hydraulic performance of solar absorber tube heat exchangers under laminar flow (Re = 513–2054) condition. Friction factor, Nusselt number, and performance evaluation criterion (PEC) were used to assess heat exchanger performance, and related correlations are provided. Tangential velocity components were also used to explore fluid flow characteristics in local analysis. Numerical investigation was done by using computational fluid dynamics adopting Finite Volume Method in ANSYS Fluent. Results show that 3D-printed swirlers considerably increase heat transfer compared to plain tube. The swirler with a twist angle of 450° led to the maximum enhancements of nearly 217% in average Nusselt number and around 1630% in friction factor at Reynolds number of 2054. Overall, increasing Reynolds number enhanced Nusselt number. The highest PEC of 1.15 was observed at a Reynolds number of 1031 using the swirler with 150° twist angle. Flow near the swirler has higher tangential velocities, hence contributing to local Nusselt number enhancement up to 453.8% compared to plain tube when swirler with twist angle of 450° utilized. It is anticipated that findings of this study can guide further related research and increase the usage of swirlers in heat exchangers.

Correlations on heat-transfer rate and friction factor using radial and axial v-cut geometry on a twisted tape in a double-pipe heat exchanger

This study explores the transformative potential of varying radial and axial v-cut angles within twisted tape inserts in the context of heat transfer enhancement within a double-pipe heat exchanger. The research is driven by the need to enhance energy efficiency in heat exchange systems, with a focus on understanding how v-cut angles influence heat-transfer rates, friction factors, and overall performance. Using water as the working medium, a comprehensive experimental investigation is conducted across a Reynolds number range of 5500–10,000. The findings reveal compelling correlations between the Nusselt number (Nu), friction factor ( f), and performance evaluation criteria concerning different v-cut angles within the twisted tape inserts. Remarkably, the study underscores the pivotal role of radial v-cut twisted tapes in elevating heat exchanger performance, surpassing even axial v-cut configurations. The Nusselt number achieves its pinnacle (96.51) at a Reynolds number of 10,000, whereas the highest friction factor (0.0582) and performance evaluation criteria (1.65) emerge at a Reynolds number of 5500, specifically with a 45-degree radial v-cut angle. This configuration showcases remarkable enhancements in the Nusselt number (98.68%), friction factor (38.87%), and performance evaluation criterion (39.36%) compared to a plain tube, underlining the transformative potential of optimized twisted tape inserts. The presented study offers more than theoretical insights; it provides practical guidelines for designing heat exchangers with superior performance. Derived correlations for the Nusselt number and friction factor, established through regression analysis involving key parameters such as Reynolds number (Re), Prandtl number (Pr), radial v-cut angle ( ϕ), and axial v-cut angle ( θ), demonstrate robust results within a narrow range of ± 5% for the Nusselt number and ±7% for the friction factor. In summary, this investigation not only advances our understanding of heat transfer enhancement but also presents tangible pathways for implementing enhanced heat exchanger designs, contributing significantly to energy-efficient thermal systems.

Investigation of heat exchanger tube fitted with triangular perforated nail head twisted‐tape inserts

AbstractA numerical investigation of the Nusselt number, heat transfer augmentation efficiency, and friction factor in a laminar flow tube with triangular perforated nail head twisted tape (TPNHTT) is reported using ANSYS 19.2 Fluent. The effects of triangular cut (each side 3 mm) in the middle pitch of the tape along the height, diameter, and top diameter of the nail head (10, 2, and 2.5 mm, respectively) have been explored for (300 ≤ Re ≤ 1800) in a tube of 22 mm diameter. In this paper, implementation has been done with a TPNHTT varying width (14 ≤ b ≤ 20) twist ratio (TR) ranging from (3 ≤ TR ≤ 6), inserts in a tube for laminar flow. Twisted tape (TT) produces a swirl flow associated with fluid resulting in heat transfer enhancement and pressure drop characteristics other than that for the plain tube (PT). The performance of the Nusselt number and friction factor increased up to 123.62% and 495.30%, respectively, on the application of TPNHTT as compared with PT. A maximum thermal performance efficiency of 2.98 has been achieved using the twisted‐tape ratio of the current tube in laminar flow at a Reynolds number of 1700. In addition, correlation equations (11) and (12) have been developed for the friction factor and Nusselt number valid for 300 ≤ Re ≤ 1800, 14 ≤ b ≤ 20, and 3 ≤ TR ≤ 6. The study has proved that applying TT is an upgraded approach for laminar convection heat transfer. This novel work finding will be supportive for researchers to design the latest heat exchangers.

Influence of the twisting and nano fluids on performance of a triangular double tube heat exchanger

Abstract The hydraulic and thermals performance of flow in a double-tube heat exchanger with an inner twisted triangle tube of length L = 1 m has been studied numerically. Equations for energy, turbulence, and Navier–Stokes were used to model the fluid flow and heat transfer in a double-tube heat exchanger with an inner twisted triangle tube. The Reynolds number range was 5000–30,000 for nanofluid (water-Al2O3) as a working fluid under a turbulent flow regime. The considered configuration was examined by varying the volume concentration of nanofluid while keeping the twist ratio constant (Tr = 5). Different cases of volume concentration of nanofluid are triggered (0.05 %, 1 %, 2.5 %, and 4 %, respectively). The numerical outcomes of a double-twisted tube heat exchanger with an inner triangle-twisted tube are validated with the obtainable numerical data. The governing equations were solved with ANSYS Fluent 18.2. The findings reveal that the larger volume concentration of nanofluid (4 %) gives a greater Nusselt number and vice versa due to the increased thermal conductivity of the nanofluid in the double twist tube heat exchanger compared with a plain tube. However, the nanofluid Nusselt number grows with the rise of both the Reynolds number and volume concentration (Ø), and the best value of the Nusselt number is 210 when Reynolds number = 30,000 and Ø = 4 %. The effectiveness of the heat exchanger grows with an increase in the concentration of the nanofluid and a reduction in the torsion ratio compared to the normal tube. The effectiveness of the double-tube heat exchanger with an inner twist triangle tube increases to the highest value of 0.38 at Reynolds 30,000 and Ø = 4 %.

Correlation of serum NFкB levels with neutrophil-lymphocyte ratio and platelet -lymphocyte ratio in breast cancer patients

ObjectiveThe main objective of this study was to analyze the serum levels of Nuclear factor-kappa B (NFкB) in breast cancer as compared to age-matched healthy individuals. It also aimed to investigate variations in NFкB levels across stages, types of breast cancer and also its correlation with Neutrophil-Lymphocyte Ratio (NLR) and Platelet-Lymphocyte Ratio (PLR). MethodologyBlood samples of 40 female breast cancer patients and 33 healthy controls were collected in anticoagulant and plain tubes. Hematological parameters were evaluated with an automatic analyzer, and NFкB levels were measured using ELISA. Statistical analysis was performed with GraphPad Prism 8 software. ResultsSignificant elevation of serum NFкB levels (p < 0.0001) was observed in breast cancer patients when compared to the healthy females. Subtype analysis indicated higher NFкB levels in Triple Negative Breast Cancer (TNBC), suggesting a potential role in the aggressiveness of this subtype. Correlation analysis with hematological parameters, including NLR and PLR, showed weak associations. However, Receiver Operating Characteristic (ROC) analysis indicated the promising role of NFкB as a diagnostic biomarker for breast cancer with a sensitivity of 75 % and specificity of 74.8 % at a cutoff value of 0.447 ng/ml. ConclusionSerum NFκB levels were significantly elevated in breast cancer patients when compared to healthy individuals, suggesting its potential as a diagnostic biomarker for the disease. While weak correlations were observed with hematological parameters like NLR, and PLR in breast cancer patients, the study highlights the promising diagnostic potential of NFκB and its significant association with breast cancer.

Numerical and experimental investigation of heat transfer enhancement in double tube heat exchanger using nail rod inserts

The Double-tube heat exchanger (DTHX) is widely favored across various industries due to its compact size, low maintenance requirements, and ability to operate effectively in high-pressure applications. This study explores methods to enhance heat transfer within a DTHX using both experimental and numerical approaches, specifically by integrating a nail rod insert (NRI). A steel nails rod insert, 1000 mm in length, is introduced into the DTHX, which is subjected to turbulent flows characterized by Reynolds numbers ranging from 3200 to 5700. Three different pitches of NRI (100 mm, 50 mm, and 25 mm) are investigated. The results indicate a significant increase in the Nusselt (Nu) number upon the insertion of nail rods, with further improvements achievable by reducing the pitch length. Particularly noteworthy is the Nu number enhancement ratio for the 25 mm pitch NRI, which is 1.81–1.9 times higher than that for the plain tube. However, it is observed that pressure drop increases in all configurations with NRI due to heightened turbulence and obstruction by the NRI. Among the various pitch lengths, the 25 mm pitch exhibits the highest pressure drop values. Moreover, exergy efficiency is found to improve across all cases with NRI, corresponding to increased heat transfer, with the 25 mm pitch length showing a remarkable 128% improvement. Numerical analysis reveals that the novel insert enhances flow turbulence through the generation of secondary flows, thereby enhancing heat transfer within the DTHX. This study provides a comprehensive analysis, including temperature, velocity, and pressure drop distributions derived from numerical simulations.

Pool boiling heat transfer characteristics of low-GWP refrigerants in a horizontal tube bundle configuration

Heat transfer enhancement techniques have been adapted on the shell side to improve the overall performance of the flooded evaporators, such as finned tubes. In recent years, it has been demonstrated that the metal foam structure can offer enhanced heat transfer performance under pool boiling conditions. However, there are not much research in the open literature that examine the feasibility of metal foam embedded tubes in horizontal tube bundle configurations. Therefore, this paper proposed a novel metal foam embedded tube (i.e., foam embedded outside the tube) to improve the heat transfer behavior of flooded evaporators. The experiments were performed on a horizontal tube bundle with a staggered arrangement. Moreover, the performance of low global warming potential (GWP) refrigerants (R-1234yf and R-1234ze(E)) is compared against R-134a for both plain tubes and metal foam tubes with porosities of 81%, 75%, and 62%. The results showed that a metal foam tube with a porosity of 62% showed a maximum heat transfer coefficient (HTC) enhancement of 291% compared to the plain tube. As compared with R-134a, the HTCs of R-1234yf and R-1234ze(E) are nearly 10% higher and 5% lower, respectively.

Ranferon-12 tonic mitigates haematological abnormalities in cyclophosphamide-treated rats

Cyclophosphamide (CPA) has anticancer property with many side-effects including haematotoxicity while ranferon-12 tonic (RFT) possesses haematinic effect. This study investigated the mitigating effects of RFT on haematotoxicity in CPA-treated rats. Twenty-four animals were grouped into four (n=6) and treated orally as indicated: Group A: (Control) received 0.4 mL of physiological saline (PS) for 7 consecutive days; Group B: (CPA) received 0.4 mL of PS for 7 days followed by a single intraperitoneal dose of CPA (200 mg/kg) on the 7th day; Group C: (RFT) received RFT at 0.029 mL/kg for 7 days; Group D: (RFT+CPA) received RFT at 0.029 mL/kg for 7 days followed by a single intraperitoneal dose of CPA on the 7th day. Twenty-four hours after the final treatment, the animals were weighed, anaesthetised and sacrificed. Blood was obtained via cardiac puncture and transferred to EDTA and plain tubes for further analysis. Result showed that a single dose of CPA (200 mg/kg) significantly (p &lt; 0.05) reduced the level of white blood cells, haemoglobin, red blood cells, packed cell volume, and platelet (values &gt;36%). Additionally, the body temperature was significantly (p&lt;0.05) elevated by 5.1 %. Furthermore, decreased levels of superoxide dismutase and catalase with a concomitant rise in MDA content were observed. All these alterations were mitigated; to some extent, in animals pre-treated with RFT prior to CPA-administration. The study suggests that RFT could mitigate haematotoxicity in CPA-administered rats by suppressing oxidative stress via modulation of haematopoietic factors, which in turn promotes haematopoiesis.

Hydrothermal performance analyses of an isothermal tube with punched twisted tape turbulator (PTT)

This study represents a pioneering investigation into the impact of a punched twisted tape turbulator on the hydrothermal parameters of a pipe operating under constant surface temperature conditions. The punched turbulator was specifically designed by incorporating cuts with diverse geometries, including semicircular, square, and triangular shapes, into the basic twisted tape turbulator. To evaluate the performance of the punched twisted tape, a comparative analysis was conducted with both a smooth tube and a tube equipped with a basic turbulator. The criterion for selecting the optimal cut geometry was the thermal enhancement factor. Subsequently, the influence of the cut area on the hydrothermal parameters was thoroughly elucidated. The enhancement factor was again utilized to identify the most optimal area. Based on the comprehensive evaluations, it was observed that the turbulator with a semicircular cut geometry and a diameter of 5 mm exhibited superior thermal performance compared to all other geometries. By employing this specific turbulator design, a remarkable enhancement in heat transfer and pressure drop within the heat exchanger was achieved, offering improvements of up to 1.63 and 3.65 times, respectively, when contrasted with the plain tube. The maximum enhancement factor value recorded during the investigation reached 1.09.

A comprehensive analysis of heat transfer in a heat exchanger with simple and perforated twisted tapes based on numerical simulations

One of the most important methods to promote heat transfer (HT) in a heat exchanger (HE) is to use a twisted tape (TT) inside tubes. Therefore, in this paper, the result of the effect of TTs on the Nusselt number (Nu), and the performance coefficient of HEs in a laminar flow are investigated. plain tube (PT), simple TTs and perforated twisted tapes (PTTs) at 3 torsion ratio, blade numbers (N) 2, 4, 6 and 8 in the Reynolds numbers (Re) from 200 to 1000 are investigated. Ansys-Fluent computing software is used for this simulation. The findings indicate a positive correlation between the number of blades and both the Nu and the friction factor. It is important to acknowledge that the objective is to enhance the efficiency of the higher HE. Additionally, since there is an undesirable ratio between the rise of the Nu and the boost of the friction factor, so the HE coefficient decreases as the number of blades in TTs increases, from 6 to 8. The PTT with 6 blades provides the best performance coefficient. Compared to the simple TT, in the PTT, the Nu increases to 15.24%, the friction factor decreases to 22.26%, and the coefficient of thermal performance grows to 18.07%.

Experimental investigation on effect of perforated double V-cut twisted tape on thermo-hydraulic characteristics of heat exchanger tube

ABSTRACT To enhance overall thermal performance factor of tubular heat exchanger, use of twisted tape has been very effective. Twisted tape creates turbulence in the flow which enhances rate of heat transfer and friction factor. Present experimental study aims to limit this penalty of increase in friction factor and achieve high thermal performance factor. For this, present article analyzes the effect of different design modifications in twisted tape on thermo-hydraulic performance of heat exchanger tube. Different inserts, i.e. Simple Twisted tape (STT), Double V-Cut Twisted Tape (DVCTT) and Perforated Double V-Cut Twisted Tape (PDVCTT), of varying twist ratio (TR) 3, 4 and 5 are considered for the investigation. Further design modification such as V-cut with width of cut (wc) 5 mm, depth of cut (dc) 4 mm, and perforation of 5 mm diameter is produced in twisted tape. Water is used as the working fluid for the study. Data pertaining to Nusselt number and friction factor is collected for the analysis in turbulent region where Reynolds number varied from 4000 to 16,000. Maximum enhancement in Nusselt number and friction factor is recorded 2.44 times and 3.71 times of plain tube respectively at Re = 4000 in case of TR = 3. Further PDVCTT leads to maximum decrement in Nusselt number and friction factor 3.83% and 27.35% when compared with DVCTT. Maximum thermal performance obtained is 1.71 in case of PDVCTT with TR of 3 at Re = 4000.

Experimental investigation of the impact of non-condensing gas on the condensation of n-propanol on a low-finned tube

This paper investigates the impact of a non-condensing gas on the condensation heat transfer of n-propanol on a low-finned and plain tube. Despite the potential of low-finned tubes to enhance outer heat transfer during condensation, the literature lacks measurement data on the condensation of solvents and bulk chemicals on these tubes. No experimental investigations on the impact of non-condensing gas on the heat transfer during the condensation of solvents on low-finned tubes are available in the literature. This paper addresses these gaps by presenting measurements of the heat transfer during the condensation of n-propanol in the presence of nitrogen on a horizontal GEWA-K28 low-finned tube and a plain tube using a novel test rig design. The results show that even a small amount of nitrogen significantly reduces the outer heat transfer coefficient. This effect is more pronounced on the low-finned tube than on the plain tube. The experimental data provided in this article can serve as a basis for developing calculation models for the condensation heat transfer of substances from the chemical industry on low-finned tubes.

Innovative twist design for solar water heaters: Experimental findings and implications

More effective use of solar energy in hot water systems is made possible by optimising heat transfer and flow resistance. In light of this, Research has been conducted to enhance convective heat transfer while analysing flow friction characteristics for best performance, resulting in the design of novel inserts known as customised twists, which increase the efficiency of the solar hot water system. A conventional, plain tube heater is used as a baseline for the study on thermal characteristics, heat transportation and flow friction attributes. A thorough analysis and comparison of the thermal behaviour of the system with customised twist inserts that have been modified using rods and spacers of different lengths is performed. As a result of the induced disturbance in the fluid particle flow pattern throughout the length of risers, a significant improvement in the coefficient of convective heat transfer is observed. The study validated the correlations for the convective heat transfer coefficient and the resistance coefficient against previous research findings. The findings indicated that the thermal efficiency of the full-length twist-inserted system is almost three times greater than that of a plain collector while doubling its pressure drop. The findings of this research could be useful in designing low-cost, compact solar water heaters.

Effect of Wettability Gradient on the Scale Formation in Falling Film Flow

Abstract Mitigation of scale formation and performance degradation remains a vital challenge for falling film evaporators in various industries. In this work, an experimental study of falling film flow on a horizontal tube is conducted to investigate the effects of wettability gradients on thermal, hydraulic, and fouling behavior. It is revealed that certain hydrophobic coating patterns, such as strip, ring, and grid patterns, lead to unwetted heat transfer area, which results in decreased heat transfer compared to fully wetted plain tube. By adjusting the geometry and position of the wettability gradient, the hybrid coating demonstrates improved heat transfer performance. Based on the characteristics of horizontal tube falling film flow, impinging jet, thin film flow, and liquid retention at the tube bottom, a hybrid coating pattern is developed to improve surface wetting and mitigate the scaling coverage. It is revealed that scale deposition is regulated by wettability gradient. Crystals tend to be dense and compact in hydrophilic areas, while they appear scattered or even absent in hydrophobic regions, depending on the dimension of the hydrophobic area. While at the hydrophilic/hydrophobic boundary, a noticeable scale thickness step is observed, which raises the potential for self-cleaning. The balance of minimization of scaling layer coverage and maximization of wetting area requires an optimal design in coating dimensions, for which a systemic study of both flow dynamics and fouling characteristics on the falling film is necessary in the future.

Experimental Evaluation of Condensation of R32 and R134a over a Plain Tube

The rise in demand for universal energy, combined with environmental concerns, prompted a search for a new technology that was compatible with the existing scenario. Nowadays, most conventional refrigerants are being phased out due to environmental restrictions, which has led to the development of alternative refrigerants. Such newly developed alternative refrigerants need further experimental assessment regarding their thermophysical properties. The current work has experimentally looked at the heat transfer phenomena that occur when the refrigerants R32 and R134a condense over a single horizontal plain tube at saturation temperatures of 40–50 °C, wall sub-cooling temperatures ranging from 3 °C to 11 °C, and heat fluxes of 8–31 kW/m2. The results showed that at a saturation temperature of 40 °C, R32 and R134a have a coefficient of condensation heat transfer about 4.0–9.0% higher than that at saturation temperatures of 45 °C and 50 °C. At the same wall sub-cooling temperature, R32 has a 50–55% higher condensing-side heat transfer coefficient than R134a. The validation of the experimental condensing-side heat transfer coefficient with Nusselt’s model revealed a deviation of ±10%. Further, a modified correlation based on Nusselt’s model predicted the experimental condensing-side heat transfer coefficient with an error band of ±5%.

Plasma Lipid Profile and Apolipoproteins in Patients with Coronary Artery Diseases and Healthy Persons, in Sana'a City, Yemen

Background: Cardiovascular disease (CVD) is the primary cause of all disease loads and accounts for almost half of all fatalities. The early detection of coronary artery disease (CAD) has drawn a lot of attention because it is anticipated that the global burden of cardiovascular disease will rise by almost 75% by 2020. They are easily oxidized, which causes an increase in affinity for arterial proteoglycans and a decrease in affinity for LDL receptors. It demonstrates significant CAD importance.&#x0D; Objective: The measurement of plasma lipid profiles and apolipoproteins (ApoA-1, ApoB, and Apo B/A-1 ratio) in healthy individuals and patients suffering from coronary artery disease.&#x0D; Methods: In this cross-sectional comparative study, 90 Yemeni subjects aged 45 to 70 years were divided into three groups: Group I: 30 cases as CAD positive (CAD+). Group II: 30 cases CAD negative (CAD -). Group III: 30 healthy person was as control. A standardized questionnaire was administered to collect demographic and clinical data from participants. Venous blood (10 ml) was collected from each individual and divided into two portions. The first portion was 5 ml in plain tubes, ApoA-1 and Apo B vacuum tubes for freezing at -20°C until analysis. 5ml in a plain tube for measuring fasting blood glucose, and lipid profile.&#x0D; Results: ApoB and Apo B/A ratios were significantly higher in CAD+ and CAD− subjects compared to controls. In addition, ApoB and Apo B/A ratios were significantly higher in CAD+ subjects compared to CAD- subjects. (P. value =0.002). In contrast, Apo A-1 was significant in CAD+ compared to CAD- and controls, and not significantly different between CAD and controls P. value = (0.001, 0.032). Furthermore, FBS and LDL-c were significantly higher in CAD+ compared to CAD subjects (P value = 0.05). In contrast, HDL-c was significantly lower in CAD+ compared to CAD and controls, with no significant difference between CAD and controls (P value=0.038, 0.004, 0.70). However, TG was not substantially different between CAD- and controls, but it was significantly greater in CAD+ compared to controls (P. value =0.002, 0.09, 0.31). Nevertheless, there was no difference in TC between study groups (P. value = 0.08, 0.12, 0.98).&#x0D; Conclusions: The degree of CAD is significantly positively correlated with WHR. More important than overall obesity, abdominal obesity is a risk factor for coronary heart disease (CHD). A significant positive connection has been observed between the Apo B/Apo A ratio and CAD. One thing to think about as a CAD risk factor is Apo B.

Saturated water flow boiling heat transfer and pressure drop in scalably microstructured plain and finned copper tubes

Well established understanding of flow boiling heat transfer and its hydrodynamic driving mechanisms have led to the inception of surface geometry augmentation techniques that can enhance thermal-hydraulic performance. Enhancing the flow boiling heat transfer at a reasonable pressure drop enables the deployment of more compact and efficient heat exchangers and thermal systems. To enable ease of manufacturing, simplicity, and reliability, passive augmentation techniques that do not require external stimuli are preferred. In this study, a scalable copper microstructuring technique was developed on both smooth and internally finned 0.25” tubes to investigate how it affects the thermofluidic behavior of relatively higher surface tension water during saturated flow boiling. The internally finned tubes used in this study comprised of 50 fins with a helical angle of 13°. To apply the conformal microstructures on the internal tube surfaces, chemical oxidation via an alkaline mixture was used, resulting in structures having characteristic length scales approaching 200 nm −1 µm. Our results show that microstructuring of plain copper tubes provides a water flow boiling heat transfer coefficient enhancement ranging from 10 % to 90 % compared to untreated specimens for vapor qualities ranging from 0 to 0.1 and mass flow rates ranging from 255 to 485 kg/(m2·s). Augmentation is attributed to the increased roughness of the plain copper tubes that creates additional nucleation sites for enhanced liquid entrapment and increases wettability. Associated with this heat transfer augmentation is an increased pressure drop ranging from 0.5 % to 38 % relative to untreated tubes due to the increased skin friction as well as add fluid flow disruption. Overall, the performance factor ranged between 0.86 to 1.81 demonstrating that the augmentation in heat transfer overshadowed the increase in pressure drop. Interestingly, applying the conformal microstructures on internally finned copper tubes decreased the heat transfer coefficient and pressure drop by as much as 75 % and 45 %, respectively, when compared to the un-structured finned copper tubes counterparts. The decrease in heat transfer performance and pressure drop was attributed to partial wetting of the fin roots due to the presence of a vapor layer near the inner tube walls. Our work develops a mechanistic understanding of the role that microstructures play during flow boiling of water on industrially applicable smooth and finned tube geometries and designs.

Performance improvement in a heat exchanger tube using discrete X–V baffle (DXVB) turbulators

Thermal performance improvement in a heating tube (HT) using discrete X–V baffle (DXVB) as turbulators is presented. The DXVB is designed with three main goals: 1. To decrease the pressure drop in the tested tube and 2. To increase the mixing quality in the heat exchanger tube and 3. To produce powerful vortex flows. Lower pressure drop, generated vortex flows and higher mixing quality will augment a heat transfer rate and thermo-hydraulic efficiency. This study examines effects of DXVB structures, DXVB distances and placements on laminar air flow and thermal structure with Reynolds number from 100 to 2000. The current problem is numerically investigated using the finite volume technique of a commercial program/code (ANSYS-FLUENT V.2022). The created model of the HT fitted with the DXVB is numerically validated. From the numerical results, the DXVB installed affects the air flow structure in the tested tube. The vortex streams are observed. The change in fluid flow influences thermal characteristics. The vortex streams destroy some parts of the thermal boundary layer and help to increase mixing quality. These perturbed thermal boundary layer (TB-layer) and better mixing quality are two important factors that contribute to convective heat transfer enhancement. In addition, the maximum heat transfer rate and pressure loss are 10.17 and 45.75 times upper than that in the circular plain tube, respectively, while the best thermal enhancement factor (TEF) of 3.09 is observed at 15b5g, +x at Re = 2000.

Red urine syndrome in dromedary camels: Clinical, etiological, hematobiochemical sonographic and pathologic findings

Background: Although blood urine is frequently observed in dromedary camels, little attention is gained and only it was reported as case reports. Aim: This study was carried out to examine dromedary camels suffering from red urine syndrome from the points of the clinical, etiological, hematobiochemical, ultrasonographic and pathological characteristics. Methods: Thirty-one camels with red urine and fifteen controls were enrolled. With a duration ranging from five days to nine months, clinical manifestations included weakness, red discoloration of the urine, dribbling of urine, straining during urination and abdominal pain. Blood was sampled in EDTA and plain tubes. Results: The urine red color intensity was marked in 23 camels. In 5 camels discolored red urine was moderate while red urine was voided intermittently in the remaining 3 camels. Wide stance of the hind legs and pain reactions during urination were recorded in 18 camels. In all 31 camels, urine samples were centrifuged and sedimentation of red deposits was found. Nephrolithiasis was detected in 3 animals. one female camel had bilateral hydronephrosis. Hyperechoic urine was imaged within the renal pelvis in 7 camels. In addition, hypoechoic fluid was imaged within the peritoneal cavity in 8 animals. Ruptured and collapsed urinary bladder was found in 2 male camels. In addition, bilateral pyelonephritis was found in another male camel. Abscessation of the left and right kidneys confirmed by ultrasound-guided aspiration was confirmed in 3 and 2 females, respectively. Peri-renal abscessation of the right kidney was detected in a female camel. Large, misshaped hypoechoic mass involving the right kidney was found in 1 female. A large mass king neoplasia was also imaged in a female camel distal to and compressing the left kidney, which proved histologically to be leiomyoma. Moderate to severe thickening and corrugation of the urinary bladder mucosa was detected in 18 of the diseased camels. Conclusion: This study's syndrome of red urine in camels resulted mainly from hematuria. The existing etiologies were the nephrolithiasis, cystitis, pyelonephritis, peri-renal and renal abscessation, and renal neoplasia. Ultrasonography was superior in assessing the renal parenchyma and urinary bladder for the verification of the existing nephrolithiasis, hydronephrosis, pyelonephritis, peri-renal and renal abscessation, cystitis and ruptured or perforated bladder.

EXPERIMENTAL ANALYSIS OF HEAT TRANSFER AND THERMAL PERFORMANCE OF PARABOLIC TYPE SOLAR COLLECTOR WITH RIBBED SURFACE TEXTURE FOR CLEAN ENERGY EXTRACTION

This paper examines the performance of a parabolic type solar collector (PTSC) that uses both plain tube and ribbed surface textured tube channels for elevating the water temperature used for various applications. The performance of a solar water heater is evaluated experimentally. During the experiment, the solar radiation intensity and the feed water flow rate of 1.0 kg/min to 5.0 kg/min in steps of 1 kg/min are taken into consideration for analyzing the effect of ribbed textured tubes on the thermal effectiveness, frictional factor, convective transfer of heat, Reynolds number, and the Nusselt number of the PTSC. Furthermore, the overall performance of the PTSC is analyzed considering the above thermo-physical parameters. Based on the result of this study, at a flow rate of 3.0 kg/min, the thermal efficiency is found to be enhanced by about 28.25&amp;#37;, the friction factor is augmented by about 0.23&amp;#37;, the convective heat transfer coefficient is improved by 24.22&amp;#37;, and the Nusselt number is increased by about 26.32&amp;#37;. On average, an overall improvement in the performance of 8.25&amp;#37; is observed for the ribbed textured tube than that of the plain tube. The experimental error analysis shows that the standard deviation for both plain and ribbed textured tubes is in the range of 3.2, which is in the acceptable limit.