CFD SIMULATION OF HEAT TRANSFER WITH SPIRAL-WIRE DISPLACEMENT ON THE PIPE

The results of the study of the intensification of the heat transfer process under forced air convection in the annular gap of a pipe-in-pipe heat exchanger with a spiral-wire intensifier located near the outer surface of the inner pipe are presented. The intensifier does not touch the pipe surface. The height of the wire of the intensifier is taken as 1.5 mm. The change in the winding pitch varied within the range of 12-20mm. Boundary conditions of the first kind + 20 ° C are set on the inner surface of the inner pipe. The temperature of the air moving in the annular gap is 300 ° C. The air velocity varied from 6 to 15 m / s. For the CFD model of a pipe-in-pipe heat exchanger, the use of a computational grid with 4.7 million elements is justified. The CFD model was validated using literature data. Based on the analysis of the ratio of the intensified Nusselt number to the Nusselt number for a smooth pipe, a 1.7-fold increase in heat transfer was found for Reynolds numbers from 5000 to 7000. This result is explained by the periodic destruction of the boundary layer along the pipe. With a further increase in Reynolds numbers to 13000, the intensification of heat transfer decreases from 1.7 to 1.3, which is explained by an increase in the vortex zone immediately behind the wire and the appearance of recirculation zones that make a minimum contribution to heat transfer. It has been determined that the spiral-wire intensifier with the maximum possible step of 20 mm contributes to the greatest increase in heat transfer by 1.7 times and has the smallest coefficient of hydraulic friction of 0.076-0.06 for the studied range of Reynolds numbers.

ALMA Super-resolution Imaging of T Tau: r = 12 au Gap in the Compact Dust Disk around T Tau N

Based on Atacama Large Millimeter/submillimeter Array (ALMA) observations, compact protoplanetary disks with dust radii of r ≲ 20–40 au were found to be dominant in nearby low-mass star formation regions. However, their substructures have not been investigated because of the limited spatial resolution achieved so far. We apply a newly developed super-resolution imaging technique utilizing sparse modeling (SpM) to explore several au-scale structures in such compact disks. SpM imaging can directly solve for the incomplete sampling of visibilities in the spatial frequency and potentially improve the fidelity and effective spatial resolution of ALMA images. Here we present the results of the application to the T Tau system. We use the ALMA 1.3 mm continuum data and achieve an effective spatial resolution of ∼30% (5 au) compared with the conventional CLEAN beam size at a resolution of 17 au. The reconstructed image reveals a new annular gap structure at r = 12 au in the T Tau N compact disk, with a dust radius of 24 au, and resolves the T Tau Sa and Sb binary into two sources. If the observed gap structure in the T Tau N disk is caused by an embedded planet, we estimate a Saturn-mass planet when the viscous parameter of the disk is 10−3. Ultimately, ALMA observations with enough angular resolution and sensitivity should be able to verify the consistency of the super-resolution imaging and definitely confirm the existence of this disk substructure.

Intensification of heat transfer in the inlet of the convective stage of the recuperative-burner unit

The study of aerodynamics and heat transfer in the recuperator convective stage of the recuperative-burner unit with the jet leakage of the flue gas flow onto the outer cylindrical surface is carried out. Numerical modeling of the problem was carried out in a three-dimensional formulation using the ANSYS Fluent software package. It was found that in the original design of the recuperative-burner unit, there is a significant unevenness of heat transfer along the length and perimeter of the working surface of the convective stage. In the initial section of the annular gap, a stagnant zone with the lowest heat transfer rate is observed. To eliminate the stagnant zone and to intensify heat transfer on the surface in this area, it is proposed to make the entrance to the perforated pipe in the form of an inner quarter of a torus; to install smooth protrusions on its surface; to locate an annular flow divider on the inner surface of the heat transfer wall, which separates the front part of the annular channel with formation of a set of vortex chambers. The research results are presented.

Mud-Removal Efficiency Boost by Engineered Scrubbing Spacer in Cementing Operations at Caspian Sea

Long-term well integrity and zonal isolation are the ultimate objectives for cementing in the well construction process. Effective mud removal plays an essential role in obtaining competent zonal isolation and hence should not be overlooked and underestimated. The negative consequences of poor mud removal can lead to microannulus, channeling, or gas migration, which might require costly time-consuming remediation. The conventional approach of optimizing spacers based on chemical interactions with the mud layer does not always yield desired results and, thus, demanding further improvement. In this paper we discuss the approach taken to boost the mud removal efficiency by implementing an innovative engineered scrubbing spacer containing fibers in a challenging environment, resulting in notable improvement in long-term cement sheath integrity. The engineered scrubbing fibers were thoroughly tested in the laboratory to ensure spacer stability and efficiency. The new spacer with an additional scrubbing capability was introduced to one of the major operators on the Caspian shelf and after successful implementation, it has now been used on more than 20 cementing operations. Scrubbing fibers concentration was optimized through thorough laboratory testing covering flowability, dispersibility, and mud removal efficiency; later, it was applied on most of the cement operations, including 4½-in. liners characterized by a very narrow annular gap across the hanger sections. Cement evaluation log results from those cementing operations demonstrated an improvement in mud removal efficiency, suggesting no issues associated with microannulus, channeling, or gas migration, thus confirming the effectiveness of the newly implemented engineered scrubbing spacer. The typical challenges associated with meeting the zonal isolation requirement on one of the offshore fields of the Caspian shelf, and the success of the approach taken to overcome those challenges by implementing the new engineered scrubbing spacer are discussed. The comparison of cement bond evaluation log results of the jobs where conventional spacer systems were used vs. those where the spacer with scrubbing capability was used are also presented, demonstrating the clear difference and improvement.

Shear and tensile delamination of ice from surfaces : The Ice Adhesion Peel Test (IAPT)

For decades, researchers have sought to understand the adhesion of ice to surfaces so that low-cost ice mitigation strategies can be developed. Presently, the field of ice adhesion is still without formal standards for performing ice adhesion tests. The U.S. Army Corps Engineers’ Research and Development Center’s Cold Regions Research and Engineering Laboratory (ERDC-CRREL) has a longstanding history as an independent third party for ice adhesion testing services. Most notably, CRREL’s Zero-Degree Cone Test (ZDCT) has been an industry favorite for more than 30 years. Despite its wide acceptance, the ZDCT contains some shortcomings, namely that freshwater ice is formed on the surface of interest within the confines of an annular gap. To address this limitation, CRREL developed and uses the Ice Adhesion Peel Test (IAPT) for testing ice adhesion. This test employs an open planar substrate from which the ice can be removed under either tensile or shear loading, thereby allowing ice to be grown directly on the target substrate without the use of molds. The IAPT configuration is therefore amenable to different ice types and geometries and will provide utility to research studies that aim to develop surface treatments to mitigate ice in a wide range of environments. This report describes the IAPT and its use for characterizing the ice adhesion properties of materials.

Sealing Advancements for Rotating Control Devices

Some of the most critical elements of a rotating control device (RCD) are the rotary seals that prevent a pressurized abrasive drilling fluid from destroying the rolling element bearings. The rotary seals prevent the drilling fluid from damaging the bearings by sealing the annular gap between the rotating mandrel and the stationary bearing housing. The combination of pressure causing seal material to bulge into the annular gap and the relative runout between the mandrel and housing can cause extrusion damage of the seal. The relative rotation and runout between the seal and mandrel in an abrasive environment leads to abrasive wear of the seal. Finally, the relatively high surface speed and contact pressure between the seal and mandrel leads to adhesive wear of the seal. When the drilling fluid pressure below the RCD is low there are several suitable rotary seal designs that can provide acceptable RCD life at most rotary drilling speeds. To meet higher speed and pressure conditions for the 100 hour minimum duration, established in API 16RCD, many RCD designs employ a sealing approach that splits the sealing tasks across two seals. One seal excludes the abrasive drilling fluid at low differential pressure and another seal, capable of operating at high differential pressure, retains a clean lubricant that is at nearly the same pressure as the drilling fluid. This sealing system generally requires an external lubricant pressurization system to provide the necessary fluid and pressure environment for the seals. Some drilling sites that operate at these conditions cannot accommodate these large, complex, expensive lubricant systems due to space or access constraints, or economic considerations. This paper describes an innovative sealing system that enables an RCD to operate at 1,500 psi and 100 RPM for 200 hours without requiring an external lubricant pressurization system. This claim is based on extensive laboratory testing of three new technologies included in this sealing system. Key results and summaries from the test program are included in this paper. The three key technologies are: A hydrodynamic spring-loaded lip seal that can be used to exclude abrasive drilling fluid at low-differential pressure or retain a clean lubricant at high differential pressure. A direct-compression hydrodynamic seal that can retain a clean lubricant at high differential pressure. A self-actuating miniature valve that replaces the lubricant supply function of an external lubricant pressurization system.

Low-order Modeling of Can-annular Combustors

Heavy-duty land-based gas turbines are often designed with can-annular combustors, which consist of a set of identical cans, acoustically connected on the upstream side via the compressor plenum, and, downstream, with a small annular gap located at the transition with the first turbine stage. The modeling of this cross-talk area is crucial to predict the thermo-acoustic modes of the system. Thanks to the discrete rotational symmetry, Bloch wave theory can be exploited to reduce the system to a longitudinal combustor with a complex-valued equivalent outlet reflection coefficient, which models the annular gap. The present study reviews existing low-order models based purely on geometrical parameters and compares them to 2D Helmholtz simulations. We demonstrate that the modeling of the gap as a thin annulus is not suited for can-annular combustors and that the Rayleigh conductivity model only gives qualitative agreement. We then propose an extension for the equivalent reflection coefficient that accounts not only for geometrical but also flow parameters, by means of a characteristic length. The proposed model is in excellent agreement with 2D simulations and is able to correctly capture the eigenfrequencies of the system. We then perform a Design of Experiments study that allows us to explore various configurations and build correlations for the characteristic length. Finally, we discuss the validity limits of the proposed low-order modeling approach.

Influence of Heat Source/Sink on Free Convection in Annular Porous Region

The significant interpretation of this model is to explore the influence of temperature-dependent heat source/sink on laminar free-convective flow in an annular porous region such as petroleum engineering, thermal technique and groundwater hydrology. For a unified solution of the Brinkman-Darcy model, the regulatory equations solved analytically by applying the variation of parameter technique in terms of Bessel's functions for the heat source and sink. Moreover, we have investigated the Variations of Darcy number, Heat source/sink and viscosity ratio in the presence of isothermal and constant heat flux sequentially. As a result, we received the critical value of the velocity for the radii ratio (R = 2.05 and 2.92) in both the cases of source and sink (S = 1.0 and Si = 0.1) respectively which is exhibited through the graphs. Further, the numerical outcomes present of the skin friction including volume flow with annular gap by the graphs as well as tables.

Device Substantiation for Generating Artificial Rain Drops by Pneumohydraulic Liquid Spraying

The authors studied the pneumohydraulic device indicators for spraying liquids for irrigation, nutrition and protection of agricultural plants, taking into account the principles of water and energy conservation, based on preliminary gas saturation of sprayed water and the use of a cavitation effect in the design of the aerator unit during ejection and supply of air under pressure. (Research purpose) To determine the technological parameters of a pneumohydraulic device for spraying liquids to obtain controlled dispersive artificial rain and substantiate the choice of its optimal technical parameters depending on the operating modes. (Materials and methods) The authors used an algorithm for calculating parameters in EXCEL or WPS spreadsheet processor and mathematical expressions. (Results and discussion) The authors theoretically determined the minimum and maximum calculated parameters of the constructive solution geometry for spraying the liquid phase: water nozzle, air nozzle channel, mixing cell, middle annular gap, outlet nozzle. They changed indicators of operating water pressure – 0.20; 0.25; 0.30 and 0.35 megapascals; air – 0.25 and 0.30 megapascals, provided the water flow rate from 0.002 to 0.010 liter per second and air – from 0.0005 to 0.0090 kilogram per second. With an increase in the water flow rate within the specified limits and the ejection coefficient from 0.5 to 0.9, a linear increase in the average annular gap diameter from 2 to 15 millimetres was revealed, as well as a nonlinear dependence of the increase in the sprayer mixing cell diameter from 5 to 20 millimetres. The authors showed the possibility of reducing the mixing cell diameter if the water pressure was increased from 0.25 to 0.35 megapascal's and the air pressure was from 0.20 to 0.30 megapascals. They obtained the parameters values for the designed and experimental samples development, which turned out to be significantly less than when operating in the air ejection mode: the outlet nozzle and the middle annular gap – by 16 percent, the air nozzle – by 23, the diameter of the mixing cell – by 50 percent or more. (Conclusions) The authors obtained calculated data to optimize technological parameters and design solutions, which would speed up the manufacture of designed and model samples of the device and its experimental testing for the generation of dispersive artificial rain drops.