• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.6
• /
• pp.326-332
• /
• 2009

The purpose of the study is to decrease the refrigerant temperature at the outlet of the compressor under high thermal load conditions for air cooled vapor compression refrigeration system. The subcooling bypass line called subcooling bypass technology(SBT) is installed to the window type A/C system to investigate the performance test. The standard air calorimeter test method is applied to measure the refrigerant temperature at the outlet of the compressor, cooling capacity, power consumption, and system EER. The refrigerant temperature at the outlet of the compressor decreases as the bypass rate increases. When the bypass rate is 8.2%, the refrigerant temperature at the outlet of the compressor decreases $2.8^{\circ}C$ while the cooling capacity and EER are the same as the conventional A/C unit.

• Journal of Chest Surgery
• /
• v.28 no.7
• /
• pp.678-683
• /
• 1995

Arterial bypass for the chronic ischemia of the lower extremities underlying atherosclerotic obliterans has been performed with a number of alternative conduits from 1941 by Kunlin. It is indicated for the limb salvage of patients with threatened limb loss despite of several controversies in surgical treatment of atherosclerotic obliterans. From March 1991 to January 1995, 26 arterial bypasses were performed in 23 patients with the chronic ischemia of the lower extremities in our hospital. Their mean follow up period is 18.9 months ranging from 4 months to 44 months. Mean age is 60.9 years ranging 47 years to 76 years and the most prevalent incidence is the 6th decade. 21 patients are male and 2 patients are female. 19 of 23 patients are smokers. Clinical classifications by Fontaine are class II[21.7% , class III[34.8% and class IV[43.5% .Diabetes mellitus[47.8% , hypertension[43.5% , hyperlipid-emia[26% , tuberculosis[21.7% , cerebrovascular accident[13.0% and cardiac diseases[8.7% are associated. Aorto-single femoral bypass in 4 cases, aorto-bifemoral bypass in 5 cases, aortofemoral & femoropopliteal bypass in 2 cases, femoropopliteal bypass in 10 cases, popliteotibial bypass in 3 cases, femoropedal bypass[composite graft bypass in 2 cases were surgically approached. There are complicated early thrombosis in 4 cases those are required immediately reoperation, wound infection in 3 cases, hematoma in 3 cases, and so on. Postoperative complication rate is 53.8%.Postoperative patency rates are 84.6% at 6 months, 75.0% at 1 year, 70.0% at 2 years and 66.7% at 3 years. We usually used 6 mm & 8 mm graft for bypass, and the rate of thrombosis formation is 28.6%[2/7 in 6 mm graft and 12.5%[2/16 in 8 mm separately. In according to the graft materials, the rate of thrombosis formation is higher in the group using artificial graft than in that using autologous saphenous vein[16.6% vs 12.5% . Limb salvage rate is 76.9%. Postoperative mortality rate is zero %.

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

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.7
• /
• pp.513-519
• /
• 2011

The object of this study is to investigate the performance characteristics of refrigerators using a single-circuit multi cycle and a bypass two-circuit multi cycle. Each refrigeration cycle was tested by varying secondary fluid mass flow rate and temperature. Based on the experimental data, the optimum refrigerant charge was 48 g and the COP at the optimum secondary fluid mass flow rate was 1.53 for the single-circuit multi cycle. For freezer(F)-only mode, both the single-circuit multi cycle and the bypass two-circuit multi cycle were operated at overcharge conditions, resulting in an increase of the secondary fluid mass flow rate. The maximum COPs of the single-circuit multi cycle and the bypass two-circuit multi cycle were 1.22 and 1.35, respectively. The COP increased by 10.7% with the application of the bypass two-circuit multi cycle.

• Journal of Chest Surgery
• /
• v.38 no.5 s.250
• /
• pp.377-381
• /
• 2005

Background: Extra-anatomic bypass was performed in the patient who could not use anatomic bypass due to many causes. The purpose of this study is to evaluate the efficacy of extra-anatomic bypass surgery. Material and Method: We reviewed 31 patients who underwent extra-anatomic bypass surgery at Pusan national university hospital. We analysed the combined diseases, etiologic diseases, symptoms, patency rate and the factors affecting patency rate retrospectively. Result: There were 26 cases of femoro-femoral bypass and 5 cases of axillo-bifemoral bypass among 31 patients. The mean age was 70.23 years. Combined disease were hypertension, hyperlipidemia, and ischemic heart disease in order of frequency. The indications for surgery were disabled claudication, tissue necrosis, rest pain, and a cute ischemia. We analysed the ages, smoking history, hypertension, ischemic heart disease, severity of limb ischemia, and hyperlipidemia as factors affecting patency rate. We could not find any statistical differences between these factors. The primary graft patency rates were $73.65\%$ one year, $73.65\%$ two year, and $65.46\%$ three year respectively according to the Kaplan-Meier method. Conclusion: Nevertheless extra-anatomic bypass has a relatively low patency rate, it has good merits that is less dangerous, simple and easy re-do surgery compared to anatomic bypass. We think that extra-anatomic bypass is one of the good treatment modalities for the high risk vascular patients.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1919-1922
• /
• 2003

Bypass anastomosis are frequently adopted for surgical treatments. After the bypass grafting, the bypass artery is often occluded due to restenosis and/or anastomotic neointimal fibrous hyperplasia phenomena. Optimal coronary bypass anastomosis should be investigated to improve the patency for the arterial bypass techniques. The objective of this study is to investigate the influence of bypass with sequential bypass effects in the stenosed coronary artery. Numerical analyses are focused on the understanding of the flow patterns for different sequential anastomosis techniques. Blood flow field is treated as two-dimensional incompressible laminar flow. The finite volume method is adopted for discretization of the governing equations. The Carreau model is employed as the constitutive equation for blood. To find the optimal sequential bypass anastomotic configurations, the mass flow rates at the outlet of different models are compared quantitatively.

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

• Proceedings of the KOSOMBE Conference
• /
• v.1996 no.11
• /
• pp.254-257
• /
• 1996

An aorto-coronary bypass graft is frequently adopted for the interventional therapy of the diseased atherosclerotic coronary artery grafting. The bypass artery is often occluded due to restenosis and/or anastomotic neointimal fibrous hyperplasia after bypass graft. The optimal aorto-coronary bypass procedure must be studied in order to improve patency rate for the arterial bypass techniques. The objective of this study is to investigate the influences of geometric dimensions of bypass on the hemodynamics around the anastomosis in the stenosed coronary artery with aorto-coronary bypass.

• Journal of Chest Surgery
• /
• v.28 no.3
• /
• pp.274-279
• /
• 1995

To evaluate clinical pattern and operative outcome of atherosclerotic obstructive disease in the lower extremity, surgical experience in 25 patients between September 1987 and June 1994 was analyzed. There were 24 male patients and 1 female patient. The age of the patients ranged between 36 and 77 years[mean:60.9 years . Disabing intermittent claudication, rest pain, or ischemic gangrene[or ulceration was the operative indication. The patients were classified into three groups according to the level of obstruction: Aortoiliac level[11 cases/44% , femoropopliteal level[6 cases/24% , and whole level[8 cases/32% . Anatomic bypass with prosthetic graft was performed in all cases: aortobifemoral or aortofemoral bypass in 15 procedures, iliofemoral bypass in 5 procedures, femoropopliteal bypass in 13 procedures. The perioperative mortality rate was 12%. Two patients received postoperative major amputation. Twenty two patients were followed-up for 1 to 70 months[mean: 21 months . Late graft obstruction occurred in two patients. The cumulative patency rate at 3 years was 69.5%. The cumulative limb salvage rate at 3 years was 92.0%.

• Nuclear Engineering and Technology
• /
• v.51 no.1
• /
• pp.54-59
• /
• 2019

The main objective of nuclear reactor safety is to maintain the nuclear fuel in a thermally safe condition with enough safety margins during normal operation and anticipated operational occurrences. In this research, core flow bypass is studied under the conditions of the unavailability of safety systems. As core bypass occurs, the core flow rate is assumed to decrease exponentially with a time constant of 25 s to new steady state values of 20, 40, 60, and 80% of the nominal core flow rate. The thermal hydraulic code PARET is used through these calculations. Reactor thermal hydraulic stability is reported for all cases of core flow bypass.