Pressure Loss Reduction Research Articles

Experimental Investigation of Micro Cooling Units on Impingement Jet Array Flow Pressure Loss and Heat Transfer Characteristics

With the development in additive manufacturing, the use of surface treatments for gas turbine design applications has greatly expanded. An experimental investigation of the pressure loss and heat transfer characteristics within impingement jet arrays with arrays of target surface micro cooling units is presented. The discharge coefficient and Nusselt number are measured and determined for an evaluation of the pressure loss of the flow system and heat transfer level, respectively. Considered are effects of impingement jet Reynolds number ranging from 1000 to 15,000 and micro cooling units (square pin fin) height (h) with associated values of 0.01, 0.02, 0.05, 0.2, and 0.4 D, where D is the impingement hole diameter. Presented are variations of Nusselt number, and Nusselt number ratio, discharge coefficient, discharge coefficient ratio, discharge coefficient correlation. Depending upon the micro cooling unit height, discharge coefficient ratios slightly decrease with height, and the ratio values generally remain unit value (1.0). When Rej = 1000 and 2500 for several cooling units height values, discharge coefficient ratios show the pressure loss decreases about 2–18% and 3–6%, respectively, when compared to the data of a baseline smooth target surface plate. The observed phenomenon is due to the effects of flow blockage of micro cooing units, local flow separation, and near-wall viscous sublayer reattachment. Results also show that heat transfer levels increase 20–300% for some of the tested toughened target surface plates when compared to smooth target surface plates. The heat transfer level enhancement is because of an increase in thermal transport and near-wall mixing, as well as the increased wetted area. In addition, micro cooling units elements break the viscous sublayer and cause greater turbulence intensity when compared to the smooth target surface. Overall, results demonstrate that the target surface micro cooling units do not result in a visible increment in pressure loss and reduce pressure loss of the flow system for some of the tested patterns. Moreover, results show the significant ability of micro cooling units to enhance the surface heat transfer capability of impingement cooling relative to smooth target surfaces.

Effect of conical angle on the hydraulic properties of orifice plate flows: A numerical approach

Orifice flowmeters are widely used in industry due to their simple design, ruggedness, and easy installation. However, high-pressure losses, measurement accuracy, and long pipe length requirements are still significant concerns. Typically, conical entry orifice plates at a 45-degree conical angle are recommended by orifice standards, especially for low Reynolds numbers instead of the sharp-edged orifice plates, which pose stability. The primary goal here is to develop the conical entry orifice plates further over a broader range of Reynolds numbers. In this case, a 45-degree conical angle may seem questionable since the optimization of conical angles has not been studied so far. To clarify that point and reach the new technical data about the conical entry orifice plates, orifice plates in different orifice diameter ratios (0.4, 0.5, 0.63) and beveled with different conical angles (15°, 30°, 45°) were tested numerically through water flow simulations inside a pipe with an inner diameter of 50.8 mm at different Reynolds numbers (5000,18,400, 91,100, 240,000).According to the analysis made, the 30-degree conical angle orifice plate was the best in reducing pressure losses, resulting in pressure losses 37–52% less than that of sharp-edged orifice plates in the min-max range. Furthermore, it reduced the pressure losses by 13–21 % more than that of the 45-degree conical angle. These last outcomes indicate that current orifice standards needs a modification into the recommended conical angles. Through these findings, pressure losses in multi-hole plate flow conditioners can be reduced considerably when the holes are beveled at the 30-degree conical angle.Also in the study, the axial characteristic lengths relevant to recirculation region, flow recovery and vena contracta were predicted approximately, along with the derived numerical correlations resulting with constants. Moreover, the effect of orifice plates exposed to an upstream distorted velocity profile on orifice flows was tested numerically. According to this evaluation, the lowest measurement errors were observed at the 30-degree conical angle orifice plate, about 30–70 % less than that of the sharp-edged orifice plate in the min-max range.

Numerical Prediction and Reduction of Pressure Loss of Air Flow Inside a Sharp 90˚ Elbow Using Turning Vanes

The aim of this study is to calculate the pressure loss and the effect of turning vanes on the pressure loss incurred by the flow in a duct with a 90˚ sharp elbow using numerical fluid mechanics. The main focus this study was to calculate the effects of the number of turning vanes and the length of the turning vanes on the pressure loss. Computational Fluid Dynamics calculations have been carried out using ANSYS Workbench software. Two turbulence models have been used in these calculations. They are the standard k- and the k- turbulence models. The number and length of the vanes were changed in the study to calculate their effects on pressure loss. The length of the vanes was varied from 0mm to 400mm in steps of 100mm on both sides of the bend and the number of vanes was changed from 0 to 3. It was found that a single curved turning vane can reduce the pressure loss significantly. The pressure loss does not reduce further when the length of the vanes was extended. As the number of turning vanes increased beyond one, the predicted pressure loss starts increasing. The turning vanes in duct systems can be used in industries and factories to reduce the pressure loss.

Numerical Study of Thermal-Hydraulic Performance of a New Spiral Z-Type PCHE for Supercritical CO2 Brayton Cycle

Printed circuit heat exchangers (PCHEs) have the characteristics of high temperature and high pressure resistance, as well as compact structure, so they are widely used in the supercritical carbon dioxide (S-CO2) Brayton cycle. In order to fully study the heat transfer process of the Z-type PCHE, a numerical model of traditional Z-type PCHE was established and the accuracy of the model was verified. On this basis, a new type of spiral PCHE (S-ZPCHE) is proposed in this paper. The segmental design method was used to compare the pressure changes under 5 different spiral angles, and it was found that increasing the spiral angle θ of the spiral structure will reduce the pressure drop of the fluid. The effects of different spiral angles on the thermal-hydraulic performance of S-ZPCHE were compared. The results show that the pressure loss of fluid is greatly reduced, while the heat transfer performance is slightly reduced, and it was concluded that the spiral angle of 20° is optimal. The local fluid flow states of the original structure and the optimal structure were compared to analyze the reason for the pressure drop reduction effect of the optimal structure. Finally, the performance of the optimal structure was analyzed under variable working conditions. The results show that the effect of reducing pressure loss of the new S-ZPCHE is more obvious in the low Reynolds number region.

Experimental and Numerical Study of Turbulent Flow and Heat Transfer in a Wedge-shaped Channel with Guiding Pin Fins for Turbine Blade Trailing Edge Cooling

Gas turbine blades employ wedge-shaped channels for the trailing edge internal cooling. Detailed experimental and numerical analyses have been done on the heat transfer and turbulent flow structures in a wedge-shaped channel with arrays of streamlined pin fins for the Reynolds number range from 20,000 to 80,000. The study examines two different configurations of the streamlined guiding pin fins in the wedge-shaped channels, which show the potential of flow guiding and heat transfer improvement for the turbine blade trailing edge internal cooling. The experiments indicate that the streamlined shape of the guiding pin fins causes significantly reduced pressure losses compared to the baseline circular pin fin arrays. Depending on two different configurations the guiding pin fin arrays can achieve pressure loss reduction by up to about 37.3% and 8.7%, respectively, while obtaining appreciably higher average heat transfer on the bottom wall by up to about 8.8% and 12.0%, respectively, compared to the baseline circular pin fin arrays. Besides, the conjugate numerical simulations obtain the total Nusselt numbers of the different pin fin array configurations. Depending on two different configurations the guiding pin fin arrays increase the total Nusselt numbers by up to 11.5% and 13.8%, respectively, compared to the baseline circular pin fin arrays. Additionally, the heat transfer enhancement and pressure loss reduction present more significant promotions for the guiding pin fin arrays as the Reynolds number increases. Also, the numerical simulations reveal the detailed flow structures in the wedge-shaped channels with different pin fin configurations and demonstrate the flow guiding mechanism of the guiding pin fin arrays. Due to the flow optimizations by the guiding pin fin arrays in the wedge-shaped channels, the heat transfer and flow distribution uniformities are improved.

Adjoint shape optimization coupled with LES-adapted RANS of a U-bend duct for pressure loss reduction

Nowadays, as industrial designs are close to their optimal configurations, the challenge lies in the extraction of the last percentages of improvement. This necessitates accurate evaluations of the performance and represents a significant higher computational cost. The present work aims at integrating Large Eddy Simulations in the optimization framework for an accurate evaluation of the flow field. The number of expensive evaluations is kept to a minimum by using the adjoint method for the evaluation of the gradient of the objective function. Divergence of the gradients due to the chaotic flow motion is avoided by an additional step which decouples the Large Eddy Simulations from the gradient calculations. An adaptation process based on a Reynolds Averaged Navier-Stokes simulation is therefore sought to mimic the more accurate Large Eddy Simulation results. The obtained field is then used in combination with an adjoint shape optimization routine. The method is tested on the design of a U-bend for internal cooling channels by minimizing its pressure loss. Starting from an optimized geometry obtained through a classical approach based on RANS evaluations, further improvements of the design are achieved with the application of the proposed strategy when performances are evaluated by means of LES.

Implication of self-throttling on combustion performance in a strut-based scramjet combustor

The present work describes the numerical investigation on the implication of self-throttling on combustion performance of a strut-based scramjet combustor. Firstly, the mixing characteristics of a strut with and without self-throttling are compared and evaluated to portray the effect of self-throttling in a DLR based scramjet combustor. Later, a separate study is performed to investigate the influence of location of self-throttling on the combustion performance of a strut-based scramjet combustor. Our study reveals that the self-throttling increases the enthalpy of formation and the generates the strong shock waves which improves the mixing rate of fuel and air. Further, the mixing commences relatively earlier with reduced pressure losses when the self-throttling is employed. It is observed that the volume of core flame region and the thickness of a flame depends on the distance between the reflected shock and the self-throttling injection slot.Also, the combustion performance deteriorates with the increase in distance between the reflected shock and the injection slot of self-throttling. Further, the combustion and mixing efficiency is found to be optimalwhen self-throttling is employed at the distance of100 mm from the inlet of the combustor.

FC 088DUAL BLOCKADE OF ENDOTHELIN A RECEPTOR (ETA) AND SODIUM-GLUCOSE COTRANSPORTER 2 (SGLT2) TO PREVENT DIABETIC KIDNEY DISEASE PROGRESSION ON A TYPE 2 MURINE MODEL

Abstract Background and Aims Sodium-glucose cotransporter 2 inhibitors (SGLT2i) and endothelin A receptor (ETA) antagonist have shown nephroprotective effects in diabetic kidney disease (DKD) through blood pressure and urinary albumin loss reduction. The protective impact and the pathways through which they exert this protection have not yet been elucidated. This study aimed to investigate the effects of the add-on therapy of SGLT2i and ETA antagonists on a type 2 diabetes murine model. Method 12 weeks-old db/db mice were treated for 8 weeks with different combinations of empagliflozin 10 mg/Kg/day (SGLT2i), atrasentan 7 mg/Kg/day (ETA antagonist) or ramipril 8 mg/Kg/day. A group of non-diabetic mice (db/m) was included as negative control. In vivo variables were recorded during treatment, including transdermal measured glomerular filtration rate (GFR) and urinary albumin-to-creatinine ratio (UACR). After treatment kidneys were preserved for histopathological studies. Results After 8 weeks of treatment empagliflozin decreased fasting blood glucose alone or in combination with atrasentan or ramipril (234.2 mg/dL mean reduction in three treated groups when compared to db/db). Ramipril decreased blood pressure (BP) in monotherapy or in add-on therapy. Empagliflozin or atrasentan alone did not have any effect on blood pressure, but combination of atrasentan and ramipril had a synergistic effect and reduced both systolic (9.0 mmHg, CI 95%: -16.3 to -1.1; P=0.028) and diastolic BP (11.9 mmHg, CI 95%: -17.7 to -3.1; P=0.005) when compared to ramipril alone. The combination of atrasentan and ramipril significantly reduced UACR (1002 ug/mg, CI 95%: -2312.0 to -32.4; P=0.043). Empagliflozin treatment alone or in combination also reduced UACR (686.0 ug/mg mean reduction in three treated groups), although this reduction was not statistically significant. In the kidney, empagliflozin in monotherapy or combination reduced glomerular mesangial matrix expansion (4.85% mean mesangial reduction in three treated groups). Treatments with atrasentan and ramipril also reduced measangial matrix expansion. Conclusion Both empagliflozin and atrasentan demonstrated possible beneficial effects in DKD by reducing BP, UACR, and mesangial matrix expansion. The add-on therapy did not show greater protective effects in the analysed variables. Further studies are needed to characterize these protective effects and pathways involved.

Heat Transfer and Pressure Loss in a Two-Pass, Rectangular Channel Featuring a Reduced Cross-Sectional Area After the 180-Deg Tip Turn With Different Turning Vane Configurations

Abstract Serpentine, multi-pass cooling passages are used in cooling advanced gas turbine blades. In the open literature, most internal cooling studies use a fixed cross-sectional area for multi-pass channels. Studies that use varying aspect ratio channels, along with a guide vane to direct the flow with turning, are scarce. Therefore, this study investigates the effect of using different guide vane designs on both detailed heat transfer distribution and pressure loss in a multi-pass channel with an aspect ratio of (4:1) in the entry passage and (2:1) in the second passage downstream of the vane(s). The first vane configuration is one solid vane with a semi-circular cross section connecting the two flow passages. The second configuration has three broken vanes with a quarter-circular cross section; two broken vanes are located downstream in the first passage, and one broken vane is upstream in the second passage. Detailed heat transfer distributions were obtained on all surfaces within the flow passages by using a transient liquid crystal method. Results show that including the semi-circular vane in the turning region enhanced the overall heat transfer by around 29% with a reduction in pressure loss by around 20%. Moreover, results show that the quarter-circular vane design provides higher overall averaged heat transfer enhancement than the semi-circular vane design by around 9% with penalty of higher pressure drop by 6%, which yields higher thermal performance by 7%, over a Reynolds number range from 15,000 to 45,000.

Experimental Study of Outflow Effects in a Rotating Turbulated Channel

Abstract The three-pass turbulated serpentine channel has many applications in internal turbine blade systems. However, the studies on the effects of the outflow ratio are lacking, which decreases the thermal analysis accuracy in such a model. To fill this gap, outflow-ratio experiments are conducted on the Nusselt number distributions of a three-pass turbulated channel. The current experimental results can guide and optimize the turbine blade internal cooling system. The results show with the mass flow of the lateral outlet increasing, the low-heat transfer region on the lateral-outflow passage gradually expands. Increasing the mass flow of the lateral outlet heightens the spanwise-averaged Nusselt number of the lateral-outflow passage, especially under the static condition. In the lateral-outflow passage, the rotation significantly improves the Nusselt number uniformity, particularly at the high mass flowrate of the lateral holes; the rotation shows slight effects on the spanwise-averaged Nusselt number of the lateral-outflow passage at low rotation numbers, whereas the profound influence is observed for the spanwise-averaged Nusselt number under high rotation-number condition. The rotation can profoundly increase the pressure coefficient leading to a reduced pressure loss with the rotation number increasing from 0.03 to 0.06.

Design and Flow Analysis of an Adjustable Check Valve by Means of CFD Method

The article presents results of research on an adjustable check valve. In particular, the article deals with improvement of flow characteristics and reduction in pressure losses of an existing valve design. The subject of the research was the valve body in the form of a steel block intended for mounting a typical cartridge valve insert. Two variants of the valve body were analysed: a standard one, which is currently in production, and the proposed new solution, in which the geometry was modified based on the results of CFD simulations. The main research task was to properly shape and arrange holes and flow channels inside the body, between the cartridge valve and the connecting plate. Using CFD analyses, a solution for minimising the flow resistance was sought and then the method of modifying flow channels geometry was developed. The CFD simulation results showed a significant reduction in pressure loss, up to 40%. The obtained simulation results were verified on a test bench using a prototype of the proposed valve block. A high degree of consistency in the results of CFD simulations and laboratory experiments was achieved. The relative difference between simulation and experimental results in the entire considered range of the flow rate did not exceed 6.0%.

Shock Waves Analysis of the Novel Intake Design System for a Scramjet Propulsion

The supersonic combustion scramjet in the inlet applies the shock waves compression mechanism tosubstitute the actual compressor from a gas turbine engine. The scramjet works with combustion of fuel throughthe air stream in supersonic condition at least with Mach 5. Novel design of a scramjet intake system was madewith variations in the angle of the fins and entrance width. The best combination of diameter and inclinationangle was 1.75 m and 15 degrees, respectively. The findings were able to increase the oblique shock waveinteractions and supplicate effective combustion and reduce pressure losses for the effective application ofscramjet system, which can be significant for aerospace industry.

Proximity effects of straight and wavy fins and their interruptions on performance of heat sinks utilized in battery thermal management

Miniature heat sink (MHS) is a fluid-based cooling technique for battery thermal management. This paper takes a new look at the performance enhancement of MHS by combining different geometries of integral and interrupted straight and wavy fins. To this end, four general designs are considered as basic models: Case 1: straight-straight-straight (SSS), Case 2: wavy-wavy-wavy (WWW), Case 3: straight-wavy-straight (SWS), and Case 4: wavy-straight-wavy (WSW). Then, in order to achieve simultaneous reduction in pressure loss and base temperature, four different interruption arrangements are applied to proposed models as Class 1, Class 2, Class 3, and Class 4. Moreover, the synergy principle is applied to evaluate the thermal performance of proposed geometries. The results show that employing the wavy structure enhances the thermal performance. Among the basic models, WWW has the lowest base temperature and the highest occupied space. However, the interruption is more effective when it is performed on MHS with straight fins. All things considered, the interruption has higher effects on both thermal and hydrodynamic performances of SWS and WSW compared to SSS and WWW. Excluding WWW, the interruption can improve the overall performance of the studied cases. The considered performance index discloses that the best interruption class for the WWW, SWS, and WSW is identical.

On the use of transpiration patterns for reduction of pressure losses

Abstract

Innovative TLC-densitometric method with fluorescent detection for simultaneous determination of ternary anti-diabetic mixture in pharmaceutical formulations and human plasma

Co-administration of Glimepiride (GLIM), Empagliflozin (EMPA) and Linagliptin (LING) promote a preferred glycemic control, besides additional benefits such as reduction of high blood pressure and weight loss. In the present study a feasible TLC method with reflectance/ fluorescence mode for simultaneous determination of GLM, EMPA and LING was established. Separation of the cited drugs was performed on aluminum plates pre-coated with silica gel 60 F254 and developed with (toluene: methanol: ethyl acetate (4: 3: 2 v/v/v)) as a mobile phase. The mentioned drugs were adequately detected after exposing the plate to concentrated (30–34%) hydrochloric acid vapor for 15 min. The was scanned in the reflectance/fluorescence mode at 228 nm excitation wavelength using 320 nm emission filter. The three drugs were well separated with Rf values of 0.73 ± 0.02, 0.59 ± 0.02 and 0.10 ± 0.02 for GLIM, EMPA and LING, respectively. The developed method was validated according to ICH guideline with linearity (2.61–60, 5.53 –120 and 4.68–80 ng/band for GLIM, EMPA and LING, respectively) and precision (% RSD was ± 2.98 for GLIM, 2.76 for EMPA, 2.41 for LING). The correlation coefficients were 0.9915, 0.9940 and 0.9921 for GLIM, EMPA and LING, respectively. The developed method was successfully applied for the analysis of the cited drugs in their tablets and real human plasma samples with good accuracy and precision.

Computational analysis of turbulent flow and heat transfer in latticework cooling structures under various flow configurations

Detailed computational analysis has been carried out to study the flow and heat transfer features in a latticework structure under various flow configurations. The three flow configurations include the radial flow configuration (RFC), the cross flow configuration (CFC) and the turning flow configuration (TFC). The numerical approach is validated both qualitatively and quantitatively by the comparisons between the present numerical data and the experimental data in open literature. It is found that the flow configurations show significant influences on the heat transfer, pressure loss and flow structure features in the latticework subchannels. Under the same cooling mass flow rates, the RFC latticework shows the highest averaged Nusselt numbers and the highest pressure losses, and the CFC and TFC latticework obtain appreciably lower but similar averaged heat transfer performance with much reduced pressure loss. Under the same subchannel Reynolds numbers, the latticework channels with the three flow configurations show similar averaged heat transfer enhancement but different pressure loss characteristics. Under the same subchannel Reynold number, latticework channels, especially the TFC latticework, show better overall thermal performance than rib turbulated and pin fin channels. The numerical results indicate the TFC latticework channel shows less uniform heat transfer than the RFC and CFC latticeworks due to the nonuniform flow distribution. The present study indicates that different flow configurations produce different flow characteristics including the flow turnings and interactions among the subchannels, resulting in the unique heat transfer features in the latticework cooling structures.

Heat transfer enhancement in Minichannel heat sinks using fully and partially filled coiled wire inserts

Enhanced heat transfer through minichannel heat sink is beneficial for engineering uses such as air conditioning, cooling system, and heat retrieval processes. In the current study, the heat transfer and friction factor were experimentally measured in a rectangular minichannel heat sink with coiled wire inserts. These coiled wires exhibited two wire diameters (0.4, 0.6 mm) and three pitches (1.2, 2.4 and 3.6 mm). The air was used as the working fluid and the Reynolds number ranged from 3000 to 10,000 in the experiments. The minichannel was either fully or partially filled with coiled wires (upstream or downstream portion). Results indicated that the coiled wire inserts tended to increase heat transfer and friction factor in the channel. The Nusselt number and friction factor increased with wire diameter, but decreased with an increase in the pitch-to-diameter ratio. The partially filled design was proposed to reduce the pressure drop caused by the wire inserts. Compared to the fully filled design, the friction factors were lower and the heat transfer enhancement was still noticeable. The partially filled inserts was particularly useful for reducing pressure losses from the thicker wires. Consequently, the minichannel with partially-filled coiled wires lead to the highest thermal performance.

Experimental study of supercritical CO2 in a vertical adaptive flow path heat exchanger

The density variation of supercritical carbon dioxide exerts significant effects on heat transfer and the adaptive flow path is verified to be effective in reducing pressure loss. Meanwhile, the effects differ from flow directions of supercritical carbon dioxide. Previous studies focused on heat transfer in vertical tubes rather than vertical heat transfer exchangers. In this paper, an experimental study of supercritical carbon dioxide in a vertical adaptive flow path heat exchanger is conducted to investigate the heat transfer and flow characteristics. The pressure of cold side varies from 14.2 MPa to 16.7 MPa and that of hot side varies from 8 MPa to 10 MPa. The inlet temperature of cold side is 328 K and that of hot side varies from 398 K to 418 K. When mass flow rate ratio increases, the minimum heat transfer effectiveness occurs at 0.6 and maximum overall heat transfer coefficient occurs at 0.65. Due to the effect of flow direction, the overall heat transfer coefficient of horizontal flow is approximately 9% higher than that of upward flow for cold side and 6% lower than that of downward flow for cold side. Hence, the downward flow (cold side) is suggested for installation of heat exchanger in Brayton cycle.

Modeling of vanadium redox flow battery and electrode optimization with different flow fields

The fibrous electrode is an essential component of the redox flow batteries, as the electrode structure influences the reactant/product local concentration, electrochemical reaction kinetics, and the pressure loss of the battery. A three-dimensional numerical model of vanadium redox flow battery (VRFB) was developed in this work. After model validation, simulations were conducted to understand the effects of electrode structural parameters on the battery performance. The gradient electrode design, specific surface area, porosity, and different flow fields were studied and optimized. The results show that in the large-size VRFB system, ensuring a large porosity can minimize the concentration polarization, which not only improves the battery performance, and also reduce the pressure loss. To further improve the mass transfer, fibers with larger diameter can be used, and the specific surface area of the electrode can be increased by modifying the surface of the fiber. The battery performance can be significantly improved with increasing specific surface area when the specific surface area is lower than 500,000. However, with further increase in specific surface area, the voltage of the battery remains almost constant at about 1.37 V. Its influence on interdigitated flow channel case is mainly in reducing pressure loss, and on serpentine flow channel case is directly reflected in improving battery performance.

Theoretical studies of air losses of air heat exchanger of indirect-evaporative type of livestock rooms

. Air heat exchangers of the side-evaporating type based on the Maisotsenko cycle have a higher transformation coefficient, so it is advisable to use them for cooling livestock premises. However, one of the tasks of increasing the efficiency of such heat exchangers is to optimize its parameters by reducing pneumatic losses. Therefore, the aim of the research is to determine the pneumatic losses of the heat-evaporating type heat exchanger and to establish the regularity of the change of pressure and power losses required for pumping air through it from its design and technological parameters. As a result of analytical researches of pressure losses of the air heat exchanger of side-evaporating type dependences of losses of pressure and power on quantity of channels, the area of section of channels, average speed of air in channels provided their equality and their form (square, equilateral triangle, circle). It is established that the most effective form of channels in the aspect of pneumatic losses (reduction of pressure losses by 23%) have channels in the form of an equilateral triangle.