• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.539-543
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• 2009

When the suction pressure of compressor decreases under its limit, the compression ratio is increased causing the malfunctions of compressor. As the method to decrease the compression ratio, hot gas bypass system is usually adopted in heat pump system. In the hot gas bypass system, the discharged gas from the compressor is bypassed into the compressor suction, which causes the increase of suction pressure and the decrease of compression ratio. In this study, the characteristics and performances of the hot gas bypass system in heat pump was investigated experimentally with a variation of the bypass flow rate ratio. With the increase of the bypass rate ratio, the compressor suction pressure was increased, even though the total capacity and COP was decreased. From the analysis of the experimental results, the optimum pressure control algorithm was suggested in this study.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.1-9
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• 2019

Infrared signal and exhaust gas temperature distribution with bypass ratio were measured using a micro turbojet engine. Micro turbojet engine was modified to simulate the turbofan engine behaviour. Core flow was simulated using the jet flow of the micro turbojet engine, and high-pressure air was supplied to its external duct to simulate bypass flow. The effects of bypass ratios (0.5, 1.0, and 1.4) were examined. The experimental results indicate that the infrared signal decreases as the bypass ratio increases. And also gas temperature decreases with bypass ratios. Additionally, Schlieren visualization of the exhaust gas plume was conducted. From the exhaust gas temperature distribution and Schlieren images, the structure of jet plume with various bypass ratios was understood.

• Plant Journal
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• v.14 no.4
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• pp.33-38
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• 2018

In this study, it was confirmed whether the cooling water bypass ratio of packing for plume abatement matched designed value during winter operation of combined cycle power plant. Designed operating wet bulb temperature of the plume abatement cooling tower with 29 Gcal/h capacity had a range from $13^{\circ}C$ to $-20^{\circ}C$, while its designed bypass ratio was from 0 % to 78%, so that increasing rate of the designed bypass ratio was $2.36%/^{\circ}C$ when the external temperature decreased. When the wet bulb temperature at cooling tower inlet had a range from $7.8^{\circ}C$ to $-11.8^{\circ}C$ in a normal operation, it was measured that actual bypass ratio of packing for plume abatement had a range from 23.8 % to 74.3%. While increasing rate of the actual bypass ratio was $2.71%/^{\circ}C$ in a range from $7.8^{\circ}C$ to $-9.55^{\circ}C$, it was $1.61%/^{\circ}C$ under $-10^{\circ}C$ in cold weather condition according to atmospheric temperature drop, therefore it was confirmed that the increasing rate of the bypass ratio for packing was lowered than its design.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.240-246
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• 2002

Bypass air conditioning systems are divided into three types; an outdoor air bypass, a mixed air bypass and a return air bypass system. What makes the return air by pass system more effective is that it directs all of moist outdoor air through the cooling coil. The bypass air conditioning system can maintain indoor R.H (Relative Humidity) less than a conventional CAV (Constant Air Volume) air conditioning system by adjusting face and bypass dampers at part load. When a design sensible load (the ratio of sensible load to total sensible load) is 70 percent (at this time, RSHF (Room Sensible Heat Factor) . 0.7), indoor R.H was maintained 59 percent by the return air bypass system, but 65 percent by the conventional CAV air conditioning system (valve control system). The bypass air conditioning system can also improve IAQ (Indoor Air Quality) in many buildings where the number of air change is high.

• Journal of Chest Surgery
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• v.28 no.10
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• pp.892-899
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• 1995

Pancreatitis is a known complication of cardiac surgery with cardiopulmonary bypass. Although ischemia is believed to be a factor, the exact cause of pancreatitis after cardiopulmonary bypass remains unknown.We prospectively studied 67 consecutive patients undergoing cardiac surgery with cardiopulmonary bypass for evaluation of the pancreatic injury after cardiopulmonary bypas. Serial measurement of amylase level in serum and urine was done postoperatively. Hyperamylasemia was detected in 15 patients[22.4% , of whom no patient had pancreatitis. There was no significant difference between serum amylase level and parameters such as cardiopulmonay bypass time, aortic cross clamp time, mean blood pressure, rectal temperature, flow rate, and use of circulatory arrest during cardiopulmonary bypass. Hyperamylasuria was detected in 8 patients[11.9% , and urine amylase level was elevated significantly in the groups with prolonged cardiopulmonary bypass, mean blood pressure more than 40mmHg, and rectal temperature more than 20 $^{\circ}$C. We recommend that serum amylase level and/or amylase-creatinine clearance ratio is measured for ealy detection and management of pancreatitis after cardiopulmonary bypass.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.1
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• pp.11-19
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• 2001

To establish optimum cycle of the inverter-driven heat pump with a variation of frequency, the bypass orifice, which was a short tube haying a bypass hole in the middle, was designed and tested. Flow characteristics of the bypass orifice were measured as a function of orifice geometry and operating conditions. Flow trends with respect to frequency were compared with those of short tube orifices and capillary tubes. Generally, the bypass orifice showed the best flow trends among them. and it would enhance the seasonal energy efficiency ratio of an inverter heat pump system, Based on experimental data, a semi-empirical flow model was developed to predict mass flow rate through bypass orifices. The maximum difference between measured data and model`s prediction was within $\pm$5%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.1
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• pp.109-116
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• 1999

To establish optimum cycle of the inverter-driven heat pump with a variation of frequency, the bypass orifice, which is a short tube having a bypass hole in the middle, was designed and tested. Flow characteristics of the bypass orifice were measured as a function of orifice geometry and operating conditions. Flow trends with respect to frequency were compared with those of short tube orifices and capillary tubes. Generally, the bypass orifice showed the best flow trends among them, that will enhance the seasonal energy efficiency ratio of an inverter heat pump system. Based on experimental data, the semi-empirical flow model was developed to predict mass flow rate through bypass orifices. The maximum difference between measured data and model's prediction was within ${\pm}5%$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.180-187
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• 2017

Major design targets such as test cell type, cell flow, cell bypass ratio, approach velocity, cell depression, front cell distortion, noise level and vibration level to construct a new 150,000 lbf thrust aircraft engine test facility were established. Based on the final aerodynamic and acoustic performance tests conducted at the newly constructed test facility, it was found that the new test facility is judged to be excellent and meets design targets.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.693-696
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• 2003

Hermetic Compressor circulates refrigerant with constant flow rate regardless of operation condition. so, at the operating condition requiring low cooling capacity, too much refrigerant flow deteriorates seasonal energy efficiency ratio(SEER). In this reason, modulated compressor is needed to improve SEER. Among many types of modulated compressor, non-inverter type modulated compressor is required for its low cost and easy to development. In the modulated scroll compressor by bypass method, EER steeply decreases for many loss like re-compression, changes of volume ratio, decrease of motor efficiency by torque variation. So. the range of modulation ratio for optimized SEER must be selected accompany with air conditioner set development.

• Journal of computational fluids engineering
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• v.14 no.2
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• pp.59-67
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• 2009

An accurate prediction of the bypass flow is of great importance in the VHTR core design concerning the fuel thermal margin. Nevertheless, there has not been much effort in evaluating the amount and the distribution of the core bypass flow. In order to evaluate the behavior and the distribution of the coolant flow, a unit-cell experiment was carried out. Unit-cell is the regular triangular section which is formed by connecting the centers of three hexagonal blocks. Various conditions such as the inlet mass flow rate, block combinations and the size of bypass gap were examined in the experiment. CFD analysis was carried out to analyze detailed characteristics of the flow distribution. Commercial CFD code FLUENT 6.3 was validated by comparing with the experimental results. In addition, SST model and standard k-$\varepsilon$ model were validated. The results of CFD simulation show good agreements with the experimental results. SST model shows better agreement than standard k-$\varepsilon$ model. Results showed that block combinations and the size of the bypass gap have an influence on the bypass flow ratio but the inlet mass flow rate does not.