• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.1
• /
• pp.1-8
• /
• 2009

The simulation of a heat pump dryer has been carried out to figure out the effect of air flow rate on the drying performance represented by MER, SMER, and so on. The simulation includes the analyses of one-stage heat pump cycle and simple drying process using the drying efficiency. The heat pump cycle with Refrigerant 134a has been considered. In the dryer, some of drying air from the drying chamber flows through the heat pump system, the rest of air bypasses the heat pump system. The two air flows joins before the drying chamber inlet. The performance parameters considered in the present study are MER, SMER, the temperature and humidity of drying air. Those parameters are compared for different total air flow rate or bypass air flow rate.

• Nuclear Engineering and Technology
• /
• v.55 no.4
• /
• pp.1310-1323
• /
• 2023

A reactor coolant pump (RCP) is essential for transporting coolant in the primary loop of pressurized water reactors. In the advanced passive reactor, the absence of a long pipeline between the steam generator and RCP serves as a transition section, resulting in a non-uniform flow field at the pump inlet. Therefore, the characteristics of the pump should be investigated under non-uniform flow to determine its influence on the pump. In this study, the pressure pulsation characteristics were examined in the time and frequency domains, and the sources of low-frequency and high-amplitude signals were analyzed using wavelet coherence analysis and numerical simulation. From computational fluid dynamics (CFD) results, non-uniform inflow has a great effect on the flow structures in the pump's inlet. The pressure pulsation in the pump at the rated flow increased by 78-128.7% under the non-uniform inflow condition in comparison with that observed under the uniform inflow condition. Furthermore, a low-frequency signal with a high amplitude was observed, whose energy increased significantly under non-uniform flow. The wavelet coherence and CFD analysis verified that the source of this signal was the low-frequency pulsating vortex under the steam generator.

• The KSFM Journal of Fluid Machinery
• /
• v.18 no.4
• /
• pp.36-42
• /
• 2015

This is a study about one of the most widely used hydro machinery all over the world - pump-turbine. The system has an impeller which pumps water to an upper reservoir during the night and the same impeller acts as a runner for turbine mode during the day for providing stable electrical power to the grid. The internal flow analysis is investigated in this study to help understand how the water passes through the passage of the vanes and blades, providing the designer with useful information on the behavior of recirculation flows which could reduce the efficiency of the pump-turbine. The 100 kW pump-turbine model has H = 32 m, $Q=0.336m^3/s$ and $N=1200min^{-1}$. For this study there are 7 blades, 19 stay vanes and 20 guide vanes. From this study, it was observed that this pump-turbine design showed very good internal flow characteristics with no flow separation and no recirculation flows in normal operation mode.

• Journal of the Korean Society of Visualization
• /
• v.18 no.2
• /
• pp.18-27
• /
• 2020

Air lift pump operated by buoyancy is mainly used for the continuous circulation and the purification of fluids. In this study, the computational flow analysis has been performed with the geometric and operating conditions of the air lift pump. The numerical data from the analysis have been verified by comparing with the previous experimental data. The following results are obtained which advance the efficiency of the air lift pump. As the submergence length of pipe increases and the pipe length over the water surface decreases, the non-dimensional mass flow ratio increases in both cases. When the position of the air injection hole is within the pipe, the circulation range of the surrounding fluid becomes widened with the distance between the air injection hole and the pipe inlet relatively becoming narrower. It is more efficient both when the air injection velocity is at 10 m/s and at 15 m/s, and when the diameter of the pipe with holes is doubled near the water surface. It is expected that these results can be provided as fundamental data for operating the air lift pump.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.1
• /
• pp.34-40
• /
• 2022

In this paper, a flow analysis of a swash-plate type hydraulic piston pump installed on a hydraulic flow supply system for marine vessels is presented. A model and governing equations for computational fluid dynamics (CFD) analyses of swash-plate type hydraulic piston pumps were built, and simulation results regarding the internal flow field of the pump were obtained. By analyzing the internal flow of the swash-plate type hydraulic piston pump, we can confirm the time-dependent stroke of each piston as the pump rotates. We also verified that by analyzing the pulsating flow against the slope of the swash plate, the simulation results match well with the experimental results. The natural frequency of the system was computed to be approximately 380 Hz by applying and analyzing the fast Fourier transform (FFT) of each swash plate slope evaluated.

• Transactions of the Korean hydrogen and new energy society
• /
• v.26 no.6
• /
• pp.652-658
• /
• 2015

The purpose of this study is to investigate the effects of changing dimension of a soft tube in a peristaltic pump on deformation, stress and fluid flow rate of the peristaltic pump. Geometries of the peristaltic pump is created in a Catia drawing software based on specifications of a real peristaltic pump. Afterwards, the geometries of this pump is imported into a commercial Ansys software to calculate deformation, stress, and fluid flow rate of this pump. The simulation results showed that the deformation and stress of the soft tube is increased by increasing soft tube diameter from 2 mm to 4 mm. When the tube diameter is increased to 5 mm and tube thickness is reduced to 0.5 mm, the soft tube is damaged. The highest fluid flow rate could be found at the tube thickness and diameter of 1 mm and 4 mm, respectively.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.5
• /
• pp.17-21
• /
• 2010

A volumetric gear pump is often used in extensive industrial applications to provide both high pressure and sufficiently high flow rate by physical displacement of finite volume of fluid with each revolution. To better understand the unsteady flow characteristics within the pump, numerical simulations were conducted by using moving dynamic meshing (MDM) techniques in commercially available CFD software, FLUENT. The effects of rotor clearance size and rotational speed of rotor on the flow characteristics, specially the temporal variation of velocity and pressure field, which is a main source of flow noise, was investigated. The results showed that significant reverse flow is developed in the rotor clearance and that its size is one of the most important factors affecting flow characteristics and pressure pulsation.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.1
• /
• pp.72-79
• /
• 2009

The effect of symmetric and asymmetric micro regenerative pump impellers on their pressure performance was studied. The shut off head of the pump with the symmetric impeller was about 2.5 times as that with the asymmetric impeller. The computation of the internal flow was performed to clarify the cause of the increase of the head. It was found that the contribution of the angular momentum supply was larger than that of shear stress for the head development in both cases. The larger head and momentum supply in the case of the symmetric impeller were caused by larger recirculated flow rate and larger angular momentum difference between the inlet and outlet to the impeller. The larger recirculated flow rate was caused by smaller pressure gradient in the direction of recirculated flow. The decrease of the circumferential velocity in the casing was attributed to the smaller local flow rate in the casing.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.19 no.1
• /
• pp.11-18
• /
• 2020

The emergence of the flow-through cell (FTC) method has made up for the limitations of previous dissolution test methods, but the high cost of the FTC dissolution devices have seriously hindered the progression of research and application of the FTC. This new design uses a peristaltic pump to simulate the sinusoidal flow rate of a piston pump. The flow profile of each peristaltic pump was sinusoidal with a pulsation of 120 ± 1 pulses per minute, and the flow rate ranged from 1.0 - 36.0 mL/min. The flow control of each channel was adjusted independently so the flow errors of the seven channels were close to 2%. The structure of the system was simplified, and the cost was reduced through manual sampling and immersing the FTC in a water bath. The dissolution rate of the theophylline and aminophylline films was determined, and good experimental results were obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.10a
• /
• pp.441-445
• /
• 2009

The most of the goals of pump designers and users are efficient operation and productivity. But the safety-grade pumps in nuclear power plants are needed to operate continuously for an essential condition of system operation. Also, most of the rules and regulatory standards that have been prepared for nuclear pumps are dedicated to achieve public safety. The study examined pump vibration in a pump outlet flow and distinguished the regions of pump vibration frequency cause by cavitation and recirculation. The study made a counterproposal in determination of pump outlet flow so that the discharge flow will be able to minimize the long-term damage of the pump.