Nam-Sub Woo

Performance Investigation of the Hybrid-Renewable Energy System With Geothermal and Solar Heat Sources for a Residential Building in South Korea

This study investigates annual performance of the hybrid energy system with geothermal and solar heat sources for hot water, heating and cooling of a residential house in South Korea. A small-scale hybrid-renewable energy system (H-RES) consists of a geothermal heat pump for heating and cooling, solar collectors for hot water, a gas fired backup boiler, and incidental facilities. All pipelines are designed for heat flow between the modules such as storage tank, heat production units, and radiators. Also, all systems automatically operated by the integrated sensing and control system. The average coefficient of performance of geothermal module during cooling and heating seasons is evaluated as about 4.1 and 3.5, respectively. Solar fraction for hot water is calculated as over 54%. And annual energy consumption of the H-RES is estimated as much as about 40% of conventional energy systems.

Experimental Study on the Helical Flow in a Concentric Annulus With Rotating Inner Cylinder

This experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin friction coefficients have been measured for fully developed laminar flows of water and of 0.4% aqueous solution of sodium carboxymethyl cellulose, respectively, when the inner cylinder rotates at the speed of 0–600rpm. The results of the present study show the effect of the bulk flow Reynolds number Re and Rossby number Ro on the skin friction coefficients. They also point to the existence of a flow instability mechanism. The effect of rotation on the skin friction coefficient depends significantly on the flow regime. In all flow regimes, the skin friction coefficient is increased by the inner cylinder rotation. The change in skin friction coefficient, which corresponds to a variation of the rotational speed, is large for the laminar flow regime, whereas it becomes smaller as Re increases for transitional flow regime and, then, it gradually approaches to zero for turbulent flow regime. Consequently, the critical bulk flow Reynolds number Rec decreases as the rotational speed increases. The rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.

Flow of Newtonian and non-Newtonian fluids in a concentric annulus with a rotating inner cylinder

We examine the characteristics of helical flow in a concentric annulus with radii ratios of 0.52 and 0.9, whose outer cylinder is stationary and inner cylinder is rotating. Pressure losses and skin friction coefficients are measured for fully developed flows of water and a 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), when the inner cylinder rotates at the speed of 0∼62.82 rad/s. The transitional flow has been examined by the measurement of pressure losses to reveal the relation between the Reynolds and Rossby numbers and the skin friction coefficients. The effect of rotation on the skin friction coefficient is largely changed in accordance with the axial fluid flow, from laminar to turbulent flow. In all flow regimes, the skin friction coefficient increases due to inner cylinder rotation. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, becomes smaller as the Reynolds number increases for the transitional flow regime, and gradually approaches zero for the turbulent flow regime. The value of skin friction coefficient for a radii ratio of 0.52 is about two times larger than for a radii ratio of 0.9. For 0.4% CMC solution, the value of skin friction coefficient for a radii ratio of 0.52 is about four times larger than for a radii ratio of 0.9.

Numerical Study for Development of Submerged Seawater Lift Pump

*Minreal Resources Research Division, KIGAM, Daejon, Korea**Naval Architecture, Ocean and IT Engineering, Kyungnam Univer sity, Changwon, KoreaKEY WORDS: Seawater lift pump 해수펌프, Mixed flow pump 사류펌프, Floating production storage and offloading 부유식원유생산설비, Total head 전양정ABSTRACT: Seawater lift pump systems are responsible for maintaining open canal levels to provide the suction flow of circulating water pumps at the set point. The objective of this paper is to design a 2- stage mixed flow pump (for seawater lifting), investigate the n ew impeller modeling method, and performance improvements of the impeller by using a commercial CFD code. The rotating speed of the impeller is 1,7 50 rpm with a flow rate of 2,700 m3/h. A finite volume method with a structur ed mesh and realized k-e turbulent model is used to guarantee a more accurate prediction of turbulent flow in the pump impeller. The performa nce variables such as the static head, brake horsepower, and ef ficiency of the mixed flow pump are compared based on changes in the impeller blade s hape.교신저자 우남섭: 대전광역시 유성구 과학로 124, 042-868-3134, nswoo@kigam.re.kr본 연구는 2011년 울산에서 개최된 해양플랜트설계연구회 춘계워크숍에 발표된 논문을 근간으로 하고 있음을 밝힙니다 .

Through-thickness SCC susceptibility of 2024-T351 and 7050-T7451 extrudates in 3.5% NaCl solution

The through-thickness stress corrosion cracking (SCC) behaviors of thick 2024-T351 and 7050-T7451 extrudates in 3.5% NaCl solution were studied at both anodic and cathodic applied potentials using a slow strain rate test method. The SCC susceptibilities of 2024-T351 extrudate tended to change in the throughthickness direction, with the lowest susceptibility for the surface specimen. 7050-T7451 specimens, on the other hand, did not show a notable change in the through-thickness SCC susceptibility. The fractographic analysis suggested that the grain boundary played an important role in determining the SCC susceptibility. The SCC process of each alloy was discussed based on the microscopic and fractographic examinations.

An Experimental Study of Cuttings Transport in Directional Slim Hole Drilling

During drilling, the precipitation velocity of cuttings within an annulus depends on the density and configuration of the cuttings, and on the density, viscosity, and rheological characteristics of the drilling fluid. In directional drilling in particular, it is difficult to adjust and control the cuttings. In contrast to vertical drilling, it is very important to evaluate the flow characteristics of a drilling flow field. However, research on the transfer features of cuttings is inadequate. In this study, in order to identify transfer features of cuttings, an experiment was performed under wide-ranging conditions by constructing a slim hole annulus (44 mm×30 mm) device. In this experiment, the particle volume fraction were influenced by particle size, particle concentration within the flow, pipe rotation, flow volume, and inclination of the annulus. In addition, a mathematical formula for volumetric concentration was deduced and compared to the test results and behavior of cuttings under the other drilling condition was made to be predicted. Therefore, this study can provide meaningful data for vertical and horizont al drilling, and for directional drilling.

Marine Survey for Designing and Installing Offshore Oil-Gas Plant

Because offshore plant industry needs to design, deploy and operate much of equipment especially, the latest trend shows the installation of production facilities is augmented in the subsea. The installed facilities are very difficult to be repaired or changed because they are located in the subsea. For solving these problems, both the directly related information of the production like the optimal number, position and depth of wells and the distribution for effective operation and safety of equipment of subsea should be considered at the preliminary stage of FEED (Front End Engineering Design). The marine exploration is introduced in this paper for providing the fundamental technology to answer the questions related to above considering points. First, some kinds of the offshore plant facilities are enumerated and aims of marine exploration for the offshore oil/gas development are summarized. In addition to it, the main roles of marine survey, in the step of designing and installing offshore oil-gas plant, development are briefly listed. And then foreign examples are shown to help the reader’s understand. This paper is hoped to be helpful for understanding the marine exploration that can be applied to offshore oil/gas plant and to be contributed to developing the domestic techniques in this field for the future.

A Study on the Multiphase Flow Characteristics Inside Subsea Separation System

The implementation of subsea separation and liquid boosting is becoming a common development scheme for the exploration of deep water fields. Subsea separation system should be reliable to ensure successful operation in a wide range of 3-phase flow regime, without need for developments. A subsea separator can avoid or simplying costly surface platforms of floating vessels, as well as being an efficient tool to enhance hydrocarbon production. One solution of interest is the separation and re-injection of water at the seabed to avoid bringing the water up to the surface facility. In this study, multiphase flow characteristics inside subsea separation system are investigated for the design of subsea separation system.Copyright

Understanding of Offshore Drilling System and Trend Analysis

Offshore drilling refers to a mechanical process where a wellbore is drilled through a seabed. It is typically carried out in order to explore for and subsequently extract petroleum which lies in rock formations beneath the seabed. There are many different type of facilities from which offshore drilling operations take place. These include bottom founded drilling rigs, combined drilling and production facilities either bottom founded or floating platforms, and deepwater mobile offshore drilling units including semi-submersibles and drillships. These are capable of operating in water depths up to 3,000 m. In this paper, we introduce the drilling system, which is mounted on the offshore drilling facilities.

Drilling Riser System Design in Deepwater Environment

The development of deepwater oil and gas reserves constantly faces the challenge to reduce costs of all components and activities. A drilling riser is a conduit that provides a temporary extension of a subsea oil well to a surface drilling facility. With an increase in drilling operations in harsh environments, drilling riser requirements and limits have become more onerous due to uncertainties involved in response prediction and prolonged drilling programs. A high level of understanding is required of the response of the system to various conditions, and the design issues that govern the system. This paper presents an overview of the engineering challenges faced in designing drilling riser system for drill ship in water depths of 10,000 ft. Also, Static and dynamic analysis of drilling riser system have been carried out for the development of drilling riser joint.Copyright