Low Pressure Loss Research Articles

Study on wellbore fluid flow and heat transfer of a multilateral-well CO2 enhanced geothermal system

Research efforts towards CO2 enhanced geothermal systems (CO2-EGS) are increasing due to potentially high heat extraction efficiencies. It is well known that CO2 properties are highly sensitive to the temperature and pressure and have noticeable effects on CO2-EGS heat extraction. Consequently, an understanding of wellbore CO2 fluid flow and heat transfer mechanisms is necessary when considering variable CO2 properties. In this paper, a coupled wellbore and reservoir fluid flow and heat transfer model is used to estimate multilateral-well CO2-EGS efficiency. The model is calibrated and validated by field data from the HGP-A well in Hawaii. Schematically, concentric tubulars are used allowing single well injection and production. Multiple cases are analyzed using this model. These include effects of CO2 pressure work on wellbore CO2 fluid flow and heat transfer, assessment of differences in heat extraction using varying wellbore sizes and central tubing insulation lengths, and evaluations of efficiencies under different injection-production well configurations. Results show that CO2 pressure work can induce a dramatic temperature reduction in the central tubing of the multilateral-well CO2-EGS. The majority of pressure loss occurs in the formation and central tubing. The optimized design suggests that a three-layer central tubing with a central diameter of 0.19 m will maximize heat insulation and heat extraction. The effect of annulus diameter on heat extraction is negligible. Also, a lower injection well configuration results in a higher outlet temperature, thermal power output, and lower pressure losses compared to an upper injection well configuration. These results provide significant suggestions for wellbore designs that can potentially optimize multilateral-well CO2-EGS efficiency.

DEVELOPMENT AND RESEARCH OF VIBRATION IRREGULARITY IN PIPING SYSTEMS AND PATHS OF TURBOMACHINES ON THE BASIS OF MATHEMATICAL MODELING

Abstract: The present paper presents a comparison of the performance of different flow conditioners. The numerical investigation is carried out using ANSYS FlUENT. Flow conditioners efficiency is evaluated on the basis of the ability of these devices to produce a uniform velocity profiles with low pressure loss under high-level disturbance conditions, such as those produced by gate and ball valves. A new flow conditioner device, which consists of two perforated conic plates has been designed, and demonstrated a high performance within a short distance downstream of the flow conditioner.

Performance of a new type of solar air collector with transparent-vacuum glass tube based on micro-heat pipe arrays

In this study, a novel solar air collector with transparent-vacuum glass tube is designed and investigated through experiment and numerical simulation. The collector consists of micro-heat pipe arrays (MHPA), selective absorption film and transparent-vacuum glass tube. The absorption film is directly pasted on the MHPA by using heat-conducting glue, which is then placed into transparent-vacuum glass tube. The efficient heat conduction of MHPA and good thermal insulation of the transparent-vacuum glass tube contribute to the high efficiency and low pressure loss of the collector. The collector average efficiency can reach 82.7% and the pressure loss is less than 20 Pa. This collector form for heating spaces and drying crops is new and effective. Increasing the air volume flow rate can considerably improve the collecting efficiency. The ambient temperature in winter results in a higher efficiency than that in summer. Furthermore, a calculation numerical model, which is used to develop 20 collecting units, is established and verified for validity. This model can obtain temperature increase in each collecting unit. Considering the temperature increase in each collecting unit and the thermal efficiency, the proposed maximum collecting unit quantity is 20. Study results provide a theoretical guidance for designing MHPA solar air collector.

Effect of droplet characteristics on heat transfer of mist/air cooling in a pin-finned channel

Effects of droplet characteristics of mist/air cooling on heat transfer for three pin-fin structures are investigated. The round-tip pin-fin structure is newly proposed with partial detachment from one endwall with a round-shaped tip structure. A flat-tip pin-fin with partial detachment and a traditional pin-fin with full attachment serve as references. Reynolds-averaged Navier-Stokes equations and the shear-stress-transport turbulence model are applied. Influences of initial mist temperature, initial mist diameter and initial mist velocity are analyzed in the Reynolds number range 15,000 to 50,000. The round-tip pin-finned channel has highest heat transfer coefficient and lowest pressure loss among the structures. Heat transfer enhancement increases first gradually and then decreases sharply with increasing initial mist diameter but an optimal diameter exists for the highest Nusselt numbers. Nusselt number decreases monotonically with increasing initial mist temperature. Droplet movement and heat transfer are nearly independent of initial mist velocity.

The effects of control methods on energy efficiency and position tracking of an electro-hydraulic excavator equipped with zonal hydraulics

Abstract Compared to conventional central hydraulic systems still typically used in most off-road machinery, the main advantages of zonal hydraulics are lower pressure losses, lower power demand, and thus, lower energy consumption on a system level and easy automatisation. In this case study, zonal hydraulics is realised with Direct Driven Hydraulics (DDH), and it is implemented as a replacement for the conventional centralised hydraulic system of a micro excavator. A simulation model for the front attachment of the excavator with three individual DDH units is presented. The proposed model of a single DDH unit was partially validated with a standalone test setup. Various common working cycles, such as digging and dumping with differing payloads and levelling, were adopted for this simulation study. Two controllers—a conventional proportional-integral-derivative (PID) controller and a flow-rate-matching feedforward plus PID controller—were designed for each DDH unit. Thereafter, detailed comparisons were provided, consisting of energy consumption, energy efficiency and position tracking performance between the two controllers. The results showed that the proposed feedforward plus PID controller had better performance than a conventional PID in the studied case. By adopting this controller, higher system energy efficiency (improved by 11–24% without regeneration and by 8–28% when considering regeneration) and better position tracking performance (root mean square tracking error and max errors lowered by 20–87% and 35–83%, respectively) were achieved simultaneously. Therefore, this work can be applied to zonal hydraulics to facilitate the electrification and automatisation of construction machinery.

Numerical Analysis of Air Flow in a Modular Fan Unit Using CFD Simulation

The current regulation of European Commission No. 1253/2014 regarding Ecodesing requirements for ventilation units, which classified them based on the Specific Fan Power (SFP), has been driving the innovation in the sector of air-handling systems. The required energy saving can be met by applying modern and energy efficient Electronically Commutated (EC) motor which, at the same time, significantly change the internal geometry of the fan unit. The paper deals with design of a new type of modular fan unit ALTEKO Alton with EC motor and unhoused backward curved impeller. The design development and optimization of the fan unit leading to the reduction of generated aerodynamic noise, lower pressure loss and better outflow characteristics is supported by the Computational Fluid Dynamic (CFD) simulations, which enables visualization of air streamlines, velocities and pressure contours within the unit. Such a design is an iterative process between CFD specialist and construction team, where, based on the simulated results, the critical spots are identified, the geometry is improved and again verified throughout the CFD simulation. The paper describes in detail the individual steps of the optimization study, starting with the import of the detailed geometry from the design CAD software and its necessary simplification for the use in the CFD study, meshing of the model and consequent simulation. The methods of the fan rotation approximation are discussed as well. Additionally, the optimum position of heat exchanger in front of the fan unit is addressed. The presented work is a part of a project supported by the EU under the Operational Program Enterprise and Innovation for Competitiveness.

Cooling methods for gas turbine blade leading edge: Comparative study on impingement cooling, vortex cooling and double vortex cooling

To compare the behavior of different cooling methods for gas turbine blade leading edge, configurations of impingement cooling, vortex cooling and double vortex cooling are established. The coolant chamber is specially introduced to make models closer to real leading edge cooling system. Numerical computation is performed based on the 3D viscous steady Reynolds Averaged Navier-Stokes (RANS) equations and the k-ω turbulence model. Results show that the flow mass of nozzles in all configurations increases from upstream to downstream with the introduction of the coolant chamber. Besides, it is found that the anti-crossflow ability of nozzles is important to the flow and heat transfer performance. Lower crossflow velocity as well as smaller upwind nozzle area contributes to stronger anti-crossflow ability of nozzles. The vortex cooling proves to be a good cooling method with the highest heat transfer intensity and thermal performance factor, but its pressure loss is much larger. The middle-double vortex cooling is actually the optimization of the impingement cooling configuration and it has the lowest pressure loss. The tangential-double vortex cooling isn't applicable to leading edge cooling due to poor flow and heat transfer performance.

Cyclodextrin cross-linked polymer monolith for efficient removal of environmental pollutants by flow-through method

β-cyclodextrin (β-CD) cross-linked polymer has been proved to be critical adsorbents for removal of many kinds of environmental pollutants from water resources. This study deals with the fabrication of β-CD cross-linked polymer monolith (CD monolith) through novel phase separation technique and effective removal of the pollutants by using prepared CD monolith columns. CD monoliths were prepared by the reaction of monochloro triazine group modified β-cyclodextrin derivative and polyethyleneimine in water. The obtained CD monoliths showed three dimensional interconnected porous structures, high surface area, and sufficient mechanical properties. The diameter of macroporous structures of CD monoliths was precisely controllable from micro-to nano-meters. This morphological control enables effective water flow based application with low pressure loss. We demonstrated that CD monolith showed high adsorption performance in the adsorption of model pollutants by flow-through experiment.

Pareto-optimal design and assessment of monolithic sponges as catalyst carriers for exothermic reactions

Monolithic sponges combine low pressure losses and excellent heat transport properties and are consequently considered as promising catalyst carriers for fixed-bed reactors. Insights on how to design porosity and window size of monolithic sponges to resolve conflicting relations between low pressure losses, high thermal conductivities, and high space-time-yields (STY), i.e., a high catalyst inventory, are still unknown, especially at pilot or production scales. This study quantifies the outlined tradeoffs and assesses the potential of monolithic sponges as catalyst carriers compared to conventional packed beds of pellets. A state-of-the-art heterogeneous reactor model was applied in combination with a genetic multi-objective optimization algorithm to predict Pareto-optimal sets of sponge designs (max. STY, min. Δp,ΔTmax⩽ΔTtol). As example, the methanation of CO2 was chosen. The Pareto-optimal set of sponge designs shows that small windows are necessary to obtain high space-time-yields comparable to the ones of conventional packed beds. As a consequence, the expected low pressure loss cannot be achieved. Because of excellent heat transport properties, which are weakly dependent on the throughput, monolithic sponges however allow stable operation under varying gas loads. The results demonstrate that monolithic sponges will probably not replace packed pellet beds of pellets for the steady-state production of chemicals. Instead, they provide a competitive option for small-scale, decentralized production for example within chemical energy storage and CO2 utilization.

Numerical investigation and optimization on the micro-ramp vortex generator within scramjet combustors with the transverse hydrogen jet

An effective fuel supply strategy with high mixing efficiency, large penetration depth and low stagnation pressure losses determines the overall performance of the scramjet (supersonic combustion ramjet) engine. In this paper, the transverse hydrogen injection flow field with a micro-ramp located upstream of the wall orifice has been investigated numerically based on the code validation. There are four design variables considered in the current study, namely the width, length, and height of the micro-ramp and the distance between the center of the wall orifice and the trailing point of the micro-ramp. Nine cases predicted by the three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations coupled with the two equation k–ω shear stress transport (SST) turbulence model are used for parametric analysis, and the parametric analysis has been carried out by the extreme difference analysis approach. Three optimization cases are obtained, and they have different objectives, namely the minimization of the mixing length, the maximization of the penetration depth and the minimization of the stagnation pressure losses. The flow structures of all cases have been discussed and compared. The quantitative evaluation results of three optimization cases show that the extreme difference analysis approach is an efficient parametric analysis method, and it can obtain the optimal strategy for the micro-ramp within scramjet combustors with the transverse hydrogen jet.

Optimization of micro gas-turbine-recuperator heat transfer surface

Making highly efficient recuperator, that will have minimal dimensions, high recovery rate, and low-pressure loss is one of the key tasks in a micro gas turbine design process. This paper presents recuperator with Frenkel-type heat-exchange matrix. Design and dimension choice of envelopes, which comprise recuperator heat-exchange surface is validated through gas-dynamic calculations, which are described in this paper.

Numerical investigation of uniformity of flow distribution in parallel micro-channels with different manifolds and working fluids

Uniformity of flow distribution is an application subject in many engineering equipment such as in drug delivery and fuel processing reactors. With a uniform distribution of flow during their operation, better heat transfer, temperature control, and low pressure loss can be achieved. In this work, uniformity of flow distribution was studied in parallel micro-channels which were placed in different levels. Four shapes for distributor were studied with two working fluids, blood (as Newtonian fluid and power-law non-Newtonian fluid). Results show that there is different uniformity in each levels as in last level, the flow is less uniform. This trend found in other Reynolds numbers. However, with increasing Reynolds number, the flow is less uniform. Also, RTG distributor has better uniformity in each level than other shapes of distributor with Newtonian fluid, while, when power-law non-Newtonian fluid was used as working fluid, the better uniformity was achieved with TRG distributor.

Removing Diesel Exhaust Particulate with Parallel-plate Hole-type Electrostatic Precipitator

An electrostatic precipitator (ESP) has such advantages as high collection efficiency of high concentration particles and low pressure loss. However, it can cause the re-entrainment phenomenon, and the hole-type ESP is considered to suppress this phenomenon. The authors developed a parallel-plate hole-type ESP after investigating the characteristics of collection efficiency with the hole-type electrode having a double-cylinder. In this study, the authors examined the right conditions for particle collection and electrode configuration. In the case of large particles, the collection efficiency decreased when the discharge current increased. However, with respect to the particle size of 300nm or less, the greater collection efficiency was achieved when the discharge current increased. The collection efficiency was improved by moving the position of the needle electrode toward the ESP outlet. The collection efficiency also reached the highest point when the hole diameter was 5mm.

Flow and heat transfer measurements in swirl tubes with one and multiple tangential inlet jets for internal gas turbine blade cooling

In this paper, we present a detailed experimental and numerical study of the flow phenomena and the heat transfer in swirl tubes with one and multiple tangential inlet jets. Such tangential jets induce a highly 3D swirling flow and an enhanced turbulence in the tube, increasing the convective heat transfer. Thus, a swirl tube is considered as an effective cooling method for technical applications with high thermal loaded components like gas turbine blades.The flow field, the heat transfer and the pressure loss are examined in a swirl tube with three different inlet jet configurations with one (MI1), three (MI3) or five (MI5) tangential inlet jets in axial direction. For this purpose, we measured the flow field via stereo-PIV (Particle Image Velocimetry) and the heat transfer by applying a transient technique using thermochromic liquid crystals for several Reynolds numbers. The numerical simulations are performed via Detached Eddy Simulation.The PIV results reveal a complex axial velocity changing after each inlet due to the additional mass flow. Two main structures occur in the swirl tube with five inlet jets: a vortex in the tube center in a wave-like form and large spiral vortices around the tube axis especially near the inlet jets. In the inlet region(s) the highest heat transfer occurs and decreases continuously until the next inlet or towards the tube outlet for the swirl tube with one inlet. The swirl tubes with multiple inlets show lower maximum heat transfer rates compared to the swirl tube with only one inlet due to lower inlet jet velocities. However, the heat transfer distribution is more homogeneous over the entire tube length at a much lower pressure loss. The homogeneous heat transfer can be explained by two mechanisms. At the inlets, the tangential jets impinge onto the concave wall and cause an enhanced convective heat transfer correlating with large spiral vortices. Secondly, the axial velocity becomes stronger further downstream after each inlet jet and causes an enhanced heat transfer between the inlet jets.The thermal performance parameter for all investigated swirl tube configurations is in the same order of magnitude. Thus, all swirl tube configurations are suitable for cooling. If one is interested in a maximum heat transfer paid by a high pressure loss, the swirl tube with one inlet is the best choice. If a lower but more homogeneous heat transfer with a low pressure loss is desired, one should choose the swirl tube with multiple inlets.

Experimental Study on Pressure Losses in Circular Orifices With Inlet Cross Flow

The ability to understand and predict the pressure losses of orifices is important in order to improve the air flow within the secondary air system. This experimental study investigates the behavior of the discharge coefficient for circular orifices with inlet cross flow which is a common flow case in gas turbines. Examples of this are at the inlet of a film cooling hole or the feeding of air to a blade through an orifice in a rotor disk. Measurements were conducted for a total number of 38 orifices, covering a wide range of length-to-diameter ratios, including short and long orifices with varying inlet geometries. Up to five different chamfer-to-diameter and radius-to-diameter ratios were tested per orifice length. Furthermore, the static pressure ratio across the orifice was varied between 1.05 and 1.6 for all examined orifices. The results of this comprehensive investigation demonstrate the beneficial influence of rounded inlet geometries and the ability to decrease pressure losses, which is especially true for higher cross flow ratios where the reduction of the pressure loss in comparison to sharp-edged holes can be as high as 54%. With some exceptions, the chamfered orifices show a similar behavior as the rounded ones but with generally lower discharge coefficients. Nevertheless, a chamfered inlet yields lower pressure losses than a sharp-edged inlet. The obtained experimental data were used to develop two correlations for the discharge coefficient as a function of geometrical as well as flow properties.

Effects of deswirler position and its centre body shape as well as vortex finder extension downstream on cyclone performance

The performance of a cyclone is studied when changing the position of the deswirler in the vortex finder, its centre body shape and a downstream vortex finder extension. This is done with simulations applying a Reynolds stress model for the turbulence. An extension of the vortex finder (from 2.64 dvf to 6.8 dvf) has almost no effect on cyclone pressure drop or collection efficiency. Moreover, the extension does not affect the pressure losses in the vortex finder. The closer the deswirler is installed to the vortex finder inlet the more significant is its effects on cyclone performance. A streamlined ellipsoidal shape of the deswirler centre body is preferable to a cylindrical one since it leads to lower pressure losses. Installation of the deswirler with a streamlined ellipsoidal centre body 2.64 diameters downstream the vortex finder inlet reduces pressure losses in the vortex finder by 74% as compared to a standard set-up. This leads to a 32% reduction in total pressure drop without deteriorating the separation capability of the cyclone.

Regeneration of Mono-ethanolamine Solution After Biogas Purification by Electrical Heating with Assisted Ultrasonic Wave

High CO2 composition in biogas decreases biogas heating value and low gas temperature is obtained. CO2 separation with mono-ethanolamine (MEA) absorption is one effective method for biogas purification due to its low operating pressure and low methane loss. In addition, the used MEA solution could be regenerated with 80–100 °C heating and in this study, the regeneration of used MEA solution after biogas purification was carried out by electrical heating with assisted ultrasonic wave. The used MEA solution was regenerated for 75 min by electrical heating to a temperature of 70–98 °C and compared with the combination of electrical heating at 70–90 °C with 20 kHz ultrasonic wave. The solution pH value was the indicator to show the CO2 status in the solution after regeneration and the suitable pH value should not be lower than 10 similar to the new solution. The results showed that the regeneration of the used MEA solution by electrical heating with assisted ultrasonic wave could reduce the electrical energy for the regeneration and increase the CO2 absorption efficiencies in the next cycle with low energy consumption.

TiO2/water Nanofluid Heat Transfer in Heat Exchanger Equipped with Double Twisted-Tape Inserts

Nowadays, heat transfer enhancement plays an important role in improving efficiency of heat transfer and thermal systems for numerous areas such as heat recovery processes, chemical reactors, air-conditioning/refrigeration system, food engineering, solar air/water heater, cooling of high power electronics etc. The present work presents the experimental results of the heat transfer enhancement of TiO2/water nanofluid in a heat exchanger tube fitted with double twisted tapes. The study covered twist ratios of twisted tapes (y/w) of 1.5, 2.0, and 2.5) while the concentration of the nanofluid was kept constant at 0.05% by volume. Observations show that heat transfer, friction loss and thermal performance increase as twist ratio (y/w) decreases. The use of the nanofluid in the tube equipped with the double twisted-tapes with the smallest twist ratio (y/w = 1.5) results in the increases of heat transfer rates and friction factor up to 224.8% and 8.98 times, respectively as compared to those of water. In addition, the experimental results performed that double twisted tapes induced dual swirling-flows which played an important role in improving fluid mixing and heat transfer enhancement. It is also observed that the TiO2/water nanofluid was responsible for low pressure loss behaviors.

Effect of winglet location on performance of fin-tube heat exchangers with inline tube arrangement

Heat transfer performance of fin-tube heat exchangers can be enhanced by introducing longitudinal vortices generated using vortex generators (VGs). Location of VGs with respect to tubes plays major role in deciding the enhancement in heat transfer. Three-dimensional numerical investigations have been carried out to study the effect of winglet location on heat transfer characteristics of fin-tube heat exchangers for inline tube arrangement. In this study, rectangular winglet pair (RWP) type VGs having common flow down configuration are considered. Initially, effect of different possible locations of RWP corresponding to tube centre have been investigated to analyse the heat transfer and flow field characteristics. Further, effects of angle of attack (β) ranging from 15° to 60° and Reynolds number (Re) in the range from 2000 to 4000 have also been studied for the location associated with maximum heat transfer corresponding to mean values of β and Re in the considered range. To illustrate the interesting flow features of vortices generated due to placement of RWPs and how those affect heat transfer, streamlines and temperature contours have been investigated. Enhancement in heat transfer has been quantified using Nusselt number while pressure loss is estimated with the help of friction factor. Role of secondary flow induced by RWPs is quantified in terms of secondary flow intensity. Thermal performance factor (JF) is used to evaluate the combined effect of enhancement in heat transfer and increase in pressure drop. For upstream located RWPs, the value of JF is found to be higher due to lower pressure loss as compared to RWPs mounted in other regions. The value of JF is maximum for RWP located at ΔX = −2.0, ΔY = ±1.25 and correspondingly 37.6% enhancement in heat transfer is observed as compared to the case for the arrangement in absence of RWPs.

Overall performance design of paralleled heat release and compression system for hypersonic aeroengine

The hydrogen powered hypersonic precooled combined cycle engine is an ideal candidate for next generation high speed clean civil aviation propulsion. It utilizes the energy inside the high speed air flow to power the air compression, in order to improve engine performance. Paralleled heat release and compression system, with several separated channels, is proved to be a crucial component to guarantee the favourable performance of the hypersonic precooled combined cycle engine. The system can sharply reduce the fuel consumption and cycle compressor pressure ratio (over 34% reduction in fuel consumption and over 45% reduction in cycle compressor pressure ratio, compared with ordinary single-route flow path design). The system is theoretically and quantitatively analysed. Operation mechanism, parameters design, feasibility and installing effects of the system are discussed. A performance simulation model is built for the paralleled system. The equivalent component method is proposed for measuring its effect on the engine overall performance. Inside the system, higher compression efficiency, lower pressure loss, more branches, higher heat transfer capacity and heat exchanger effectiveness can enhance the performance, while the feasible region, weight and size effects, and technical risks cannot be ignored either. For the engine, the installation of the paralleled system remarkably improves the engine performance and simplifies the compressor design. The paralleled system, with its advantage of coolant flow and compression work reduction, also can be beneficial to other applications in energy and power field.