• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.2
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• pp.102-110
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• 2012

The objective of this study is to improve the performance of a hybrid ground source heat pump (HGSHP) by optimizing the flow distribution ratio of secondary fluid flow rate between a ground loop and a supplemental loop. Initially, a conventional ground source heat pump (GSHP) was tested to determine an optimum flow rate of the secondary fluid. Based on the selected optimum value, the HGSHP was also tested by varying the flow distribution ratio of the secondary fluid flow rate between the ground loop and the supplemental loop, such as 9:1, 7:3, 5:5, and 3:7. The results showed that the optimum flow distribution ratio of the secondary fluid flow rate was 7:3. The COP of the HGSHP was improved by 19% over the GSHP at a flow distribution ratio of 7:3 and an entering water temperature of $40^{\circ}C$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.741-748
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• 2002

The present study investigated the two-phase flow characteristics of refrigerant R-22 in T-branch with horizontal and vertical inlet tube The key experimental parameters were the orientation of inlet and branch tubes (horizontal and vertical), diameter ratio of branch tube to inlet tube (1 and 0.61), inlet mass flux (200~500 kg/$m^2$s) and inlet quality (0.1~0.4). Predicted pressure profile agreed with the measured data within 25.4%. The flow distribution ratio decreased as the mass flux increased. The flow distribution ratio decreased by 12~25% as the tube diameter ratio decreased from 1 to 0.61, and decreased by 38~47% as the orientation of branch changed from horizontal to vertical upward for horizontal inlet tubes. As the orientation of inlet tube changed from horizontal to vertical upward for horizontal branch, the flow distribution ratio increased by 15~68%, but the quality in the branch tube decreased by 28~92% due to phase separation.

• Journal of environmental and Sanitary engineering
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• v.24 no.1
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• pp.13-24
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• 2009

This study was performed to determine the effect of the influent flow distribution ratio and hydraulic retention time(HRT) on removal of organic matter, nitrogen and phosphorus when domestic sewage was treated by the advanced step aeration(ASA) process. Results of the experiment for the determination of the optimum influent flow distribution ratio between the anaerobic reactor and the anoxic reactor showed BOD removal efficiencies of above 92.0% at all influent flow distribution ratios from 9:1 to 4:6. The highest T-N removal efficiency was 82.6% at the influent flow distribution ratio of 6:4. On the other hand, the highest T-P removal efficiency was 67.8% at the influent flow distribution ratio of 9:1. Considering both the T-N and T-P removal efficiencies, the influent distribution ratio of 6:4 was considered the optimum. Results of the experiment for the determination of the optimum HRT at the optimum influent flow distribution ratio of 6:4 revealed BOD removal efficiencies better than 92.7% at all HRTs from 12hr down to 6hr. The highest T-N and T-P removal efficiency were 82.6% and 59.5%, respectively both at the HRT of 8hr. In conclusion, the optimum influent flow distribution ratio and HRT for treatment of domestic sewage by the ASA process were determined to be 6:4 and 8hr, respectively.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.717-727
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• 2006

The present study experimentally investigated the effect of flow direction and other flow parameters on two-phase flow distribution of refrigerants at a T-junction, and also suggested a prediction model for refrigerant in a T-junction by modifying previous model for air-water flow. R-22, R-134a, and R-410A were used as test refrigerants. As geometric parameters, the direction of the inlet or branch tube and the tube diameter ratio of branch to inlet tube were chosen. The measured data were compared with the values predicted by the models developed for air-water or steam-water mixture in the literature. We propose a modified model for application to the reduced T-junction and vertical tube orientation. Among the geometric parameters, the branch tube direction showed the biggest sensitivity to the mass flow rate ratio for the gas phase, while the inlet quality showed the biggest sensitivity to the mass flow rate ratio among the inlet flow parameters.

• Journal of the Korean Society of Combustion
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• v.12 no.3
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• pp.24-32
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• 2007

A theoretical model was developed for rotary kiln and computational study was conducted to find the effect of feeding characteristics. One dimensional model with the variations of heating distribution, length of heating zone, excess air ratio and revolution was considered. The comparison of parallel-flow rotary kiln with that of counter-flow was conducted. For parallel-flow type, it is found that the variation of temperature of solid is not great for the zone that is following flame-heating zone. This zone is good to take the special treatment because thermal deviation is small and contacting time is enough for another treatment. Increase of excess air ratio have the effect of decreasing solid temperature. But this effect of decreasing solid temperature goes small for the great excess air ratio. The heating is efficient for the flame which has the maximum heating at the central region of the full length.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.1
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• pp.31-37
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• 2006

The present study has been experimentally investigated the effect of geometric and operating parameters on the two-phase flow distribution of refrigerants in a horizontal T-junction. The operating parameters were the kind of refrigerants (R-22, R- l34a, and R-410A), saturated temperature, and the inlet mass flux and quality. The geometric parameters were the tube diameter and the tube diameter ratio. The measured data of refrigerants were compared with the values predicted using the models developed by several researchers for air/water or steani/water two-phase flow. Among the operating parameters, the inlet Quality was the most sensitive to the mass flow rate ratio. Between the geometric parameters, the tube diameter ratio was more sensitive than tube diameter.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2803-2810
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• 2007

Three dimensional numerical studies were carried out to investigate the effect of aspect ratio on gas slip flow in rectangular microchannels. We focused on aspect ratio effect on slip velocity, pressure distribution and mass flow rate. As aspect ratio decreases the wall slip velocity also decreases. As a result nonlinearity of pressure distribution increases. The slip velocities on sides and top/bottom walls are different and this difference decreases with increasing aspect ratio. These two velocities are equal when aspect ratio is 1. The ratios of slip mass flow rate over noslip mass flow rate increases with increasing aspect ratios.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.269-273
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• 2011

In present paper focused on the influence of the inlet-outlet area ratio of counter flow manifold on the flow distribution and pressure drop characteristics of a tubular heat exchanger. The characteristics of flow distribution and pressure loss can be obtained depending on the inlet-outlet area ratio. In this paper, a tubular heat exchanger can be designed with minimum flow mal-distribution and better characteristic of pressure loss by choosing the optimum inlet-outlet area ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.6
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• pp.725-734
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• 1997

The effect of helical intake port geometry on in-cylinder swirl flow characteristics was studied. Two helical intake ports were selected to change swirl ratio, mean flow coefficient with the variation of valve lifts, valve eccentricity ratios and axial distance. The measurements were made by using an impulse swirl meter. The port B modified to increase the swirl ratio( $R_{s}$) had the tendency of the increased non-dimensional rig swirl ( $N_{r}$) distribution in comparison with that of the port A. And the $N_{r}$ distribution was remarkably improved at low valve lifts. The modification of the geometry to increase the swirl ratio ( $R_{s}$) in helical intake port resulted in the decrease of the mean flow coefficient ( $C_{f(mean)}$) regardless of valve eccentricity ratio ( $N_{y}$). And also non-dimensional rig swirl ( $N_{r}$) in the high valve lift affected the calculation of swirl ratio considerably.onsiderably.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.69-76
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• 2002

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial and the radial temperature distribution in internal spare of a tube. From the study, fellowing conclusive remarks 7an be made. First, As the number of nozzles increase, separation point move into the hot exit. Second, When we use guide vane type nozzle, the axial temperature distribution constant over the 0.75 of air mass flow rate radio. Third, When we use Spiral type nozzle, axial and radial temperature distribution in the inner space is higher than another nozzle. Fourth, Axial and radial temperature distribution in the inner space vortex-tube is determined by separation point. And separation point is moved by changing of air mass flow rate ratio. At last, A heating apparatus is possible far vortex-tube to use.