• Proceedings of the KSME Conference
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• 2000.04b
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• pp.813-818
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• 2000

The objective of this study is to elucidate the characteristic performance of Roots-type vacuum pump with Cassini oval lobe shape. The modelled lobe shape of Roots-type vacuum pump is two-lobe spur gear. The numerical analyses are performed fer leak flows, using 4th-order Runge-Kutta method and are compared with experimental results. Results show that for the case of involute lobe shape the total amount of the leak flow conductance is greater than that of cycloid and Cassini oval lobe shapes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1359-1367
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• 2004

The demand of vacuum pump has been increased in the process of semi-conduct manufacturing, as a core component. The response of the system for vacuum pump performance test can be utilized to assess the system and to obtain the reliability of the apparatus for the test. The system consists of gas supply tank, pressure chamber, measurement chamber and transmission line. Transient analysis for compressible fluid has been conducted to evaluate the dynamic characteristic of the volume terminated transmission line. Numerical approach based on the method of characteristics is used for the analysis. The response is evaluated with the important parameters for the system: i.e., length and diameter of the line, volume of the terminal tank. Using the numerical results, pumping speeds are calculated and then compared to the experimental results.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2011-2016
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• 2004

In order to develop a high efficiency fire pump, its performance characteristics with various operating conditions are investigated. The governing equations are derived from making using of three-dimensional Navier-Stokes equations with the standard ${\kappa}-{\varepsilon}$ turbulence model and SIMPLE algorithm. Using a commercial code, CFX, pressure distribution and flow fields in a fire pump are calculated with various ranges of rotating speed 800-2400 rpm. Particularly, calculations with multiple frames of reference method between the rotating and stationary parts of the domain are carried out. With the help of numerical results, correlation formula between the casing pressure and the efficiency is derived.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.5
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• pp.337-345
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• 2003

In the case of heat exchangers operating under frosting condition, the growth of frost layer causes the heat exchanger to increase the thermal resistance and pressure loss of the air flow. In this paper, a transient characteristic prediction model of the heat transfer for multi inverter heat pump with frosting on its surface was presented taking into account the change of the fin efficiency due to the growth of the frost layer. In this dynamic simulation program, which was peformed for a basic air conditioning system model, such as evaporator, condenser, compressor, linear electronic expansion valve (LEV) and bypass circuit. The theoretical model was driven from the obtained heat transfer coefficient and mass transfer coefficient, independently. And we consider heat transfer performance was only affected by a decrease of the wind flow area. The calculated results were compared with some cases of experiments for frosting conditions.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.185-190
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• 2001

The cavitation causes suction performance and efficiency of the high-speed pump to be reduced significantly To diminish these effects, the inducer has been used. Most of the inducer is designed at a maximum efficiency point of the pump, therefore suction performance drop due to effects of flow separation and inlet inverse flow is often observed at off-design point. The objective of this study is to find out the cavitation modes at various conditions by applying event detection technique and to design an inducer reducing cavitation. The pressure fluctuations at each cavitating condition were measured at inducer inlet and outlet locations using pressure transducers, which were located 90 degrees apart from each other to identify the cavitation modes. The time-frequency characteristics were analyzed by using Choi-williams distribution. In the second part of this paper, the inducer design method which uses nominal performance characteristic and onset condition of cavitation is introduced and applied to real situation.

• Journal of the Korean Solar Energy Society
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• v.34 no.2
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• pp.66-72
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• 2014

Ground source heat pump system can achieve high efficiency of performance by utilizing annually constant underground temperature to provide heat source for space heating and cooling. Generally, the depth of constant-temperature zone under the ground depends on surface heat flux and soil properties. The deeper the ground heat exchanger is installed, the higher the heat exchange rate can be acquired. However, in order to optimally design the system, it is necessary to consider both the installation cost and the system performance. In this study, performance analysis of ground source heat pump system according to the depth has been conducted through the case study.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.3
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• pp.156-163
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• 2013

Ground Source Heat Pump (GSHP) systems utilize geothermal energy as a thermal source or sink, for heating, cooling and domestic hot water. It is well known that GSHP is environmentally friendly, and saves energy dramatically. For this reason, many investigative researches have been conducted on commercial and governmental buildings. However, studies on residential GSHP are few, because of the small capacity and cost. In this study, we experimented with the characteristic performance of heating, cooling and seasonal performance factor for a residential GSHP system, which consisted of two 180 m deep u-tube ground heat exchangers, a heat pump and measurement instruments. The installed capacity of the heat pump was 5RT, and the conditioning area was $62.23m^2$. From the experimental results, the cooling COP of the heat pump was 4.13, and the system COP was 3.51, while the CSPF was 3.32. On the other hand, the heating COP of the heat pump was 3.87, and the system COP was 3.39, while the HSPF was 3.39. Also, in-situ cooling COP and capacity were 93.7% and 96.4% compared with the EWT certification data, respectively, and that of heating were 98.3% and 95.7%, respectively.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.05a
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• pp.191-196
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• 2004

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1059-1065
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• 2010

An analysis was conducted to predict the hydraulic performance of a reactor coolant pump (RCP) of SMART at the off-design as well as design points. In order to reduce the analysis time efficiently, a single passage containing an impeller and a diffuser was considered as the computational domain. A stage scheme was used to perform a circumferential averaging of the flux on the impeller-diffuser interface. The pressure difference between the inlet and outlet of the pump was determined and was used to compute the head, efficiency, and break horse power (BHP) of a scaled-down model under conditions of steady-state incompressible flow. The predicted curves of the hydraulic performance of an RCP were similar to the typical characteristic curves of a conventional mixed-flow pump. The complex internal fluid flow of a pump, including the internal recirculation loss due to reverse flow, was observed at a low flow rate.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.5
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• pp.481-489
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• 2016

Method of characteristic(MOC) has been widely used as a transient analysis technique for pressurized pipeline systems. There are substantial studies using MOC for the water hammer triggered through instantaneous valve closures, pump stoppage and pump startup for pipelines systems equipped with a centrifugal pump. Considering restrictions of MOC associated with courant number condition for complicated pipeline systems, an impulse response method(IRM) was developed in the frequency domain. this study implements the impact of centrifugal pump using transfer function in frequency domain approach. Using pump performance curve and the affinity law, this study formulated transfer functions which relate complex pressure head at upstream of pump system to that of downstream location. Simulations of simple reservoir-pump-valve system using IRM with formulated transfer function were similar to those obtained through MOC.