Condensation oscillation characteristic of steam with non-condensable gas through multi-hole sparger at low mass flux

Zhang Dandi,Tong Lili,Cao Xuewu 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.2

To study oscillation characteristic of steam and non-condensable gas direct contact condensation through multi-hole sparger at low mass flux, a series of experiments of pure steam and mixture gas condensation have been carried out under the conditions of steam mass flux of 20e120kg/m2s, water temperature of 20e95 C and mass fraction of non-condensable gas of 0e5%. The regime map of pure steam condensation through multi-hole sparger is divided into steam chugging, separated bubble, aggregated bubble and escaping aggregated bubble. The bubbles behavior of synchronization in the same hole columns and desynchronized excitation between different hole columns can be found. The coalescence effect of mixture bubbles increases with water temperature and non-condensable gas content increasing. Pressure oscillation intensity of pure steam condensation first increases and then decreases with water temperature increasing, and increases with steam mass flux increasing. Pressure oscillation intensity of mixture gas condensation decreases with water temperature and non-condensable gas content increasing, which is significantly weaker than that of pure steam condensation. The oscillation dominant frequency decreases with the rise of water temperature and non-condensable gas content. The correlations for oscillation intensity and dominant frequency respectively are developed in pure steam and mixture gas condensation at low mass flux.

컨덴세이트 저류층의 지하저장시설 활용 해석에 대한 다성분 시뮬레이션과 블랙오일 시뮬레이션의 특성 비교 연구

신창훈,이정환 한국자원공학회 2010 한국자원공학회지 Vol.47 No.4

In order to examine the validity of the previous results done by the black oil simulation, an investigation on the differences between results of compositional simulation and black oil simulation for the case that a condensate reservoir is used as an underground gas storage was carried out. Concludingly, the compositional simulation model was successfully developed to examine the multi-component multi-phase behavior for the gas which is expected to be imported and stored into the storage and predict the composition changes of produced gas. Hence, additional investigations on the pressure changes due to the phase change which is not shown in the black oil simulation are possible in this compositional simulation. The pressure difference between two models and gradual expanding of pressure difference by operation are observed as well. Besides, in case of the higher CGR condensate reservoir, the compositional simulation is necessary since the error and it's increment by operation become more serious. 컨덴세이트 저류층의 지하저장시설 활용 검토 시 블랙오일 모델을 통한 해석의 신뢰도를 판단하고자, 다성분 시뮬레이션과 블랙오일 시뮬레이션을 동시에 수행하여 두 모델의 차이점에 대한 비교 검토를 시행하였다. 결과적으로, 향후 도입, 저장이 예상되는 대표성분의 가스에 대한 저류층 다성분 다상거동 특성을 검토하고 생산가스의 성분예측과 품질관리를 위한 다성분 해석모델을 성공적으로 구축하였다. 이를 통하여, 기존 블랙오일 모델에서는 규명될 수 없었던 상변화에 따른 저류층의 압력변화에 대한 추가적인 검토가 가능하였다. 결과적으로, 주입되는 가스 성분차이에 따른 두 모델간의 압력차이가 발생함과 압력차이가 운영의 지속에 따라 점차적으로 확대될 수 있음을 시뮬레이션을 통하여 확인하였다. 아울러 CGR이 높은 컨덴세이트 저류층의 경우는 편차의 수준이나 운영에 따른 편차의 증가가 심각하여 다성분 해석모델의 적용이 필수적임을 확인하였다.

Effect of Exhaust Gas Cooling on PM in a Flue Gas Emitted from Spray Combustion of Sulfur-contained Fuel

( Y. Wu ),( K. Yamamoto ),( H. Wachi ),( T. Furuhata ),( M. Arai ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-

Heat recovery from flue gas is very effective to economize fossil fuel, and results in the reduction of CO2 emission. However, the temperature of flue gas decreased with increasing the amount of recovery heat. It is thought that the decrease of temperature causes formation of secondary condensed particles in a flue gas. Furthermore, there is a possibility that sulfur in fuel promotes the formation of those particles when sulfur-contained fuel such as heavy fuel oil is burned. In this study, sulfur-contained kerosene (thiophene (C4H4S) added kerosene; mass fraction of sulfur was 1000ppm) was burned using a spray combustion furnace with long stack, and diameter distributions and compositions of particles in a flue gas were measured in order to understand the formation of secondary condensed particle. A water-cooled heat exchanger was used to cool down the flue gas before stack for the simulation of latent heat recovery. Flue gas was sampled from the stack with a thermal dilution sampling to analyze the characteristics of particles. When the flue gas was gradually and slightly cooled down in the stack, it was found that there was a peak between 10nm and 100nm in the diameter distribution. However, the peak disappeared with the thermal dilution sampling at 150°C or 300°C. It seemed that the disappeared particles were condensed ones such as sulfuric acid mist. When the flue gas was quickly cooled down with the heat exchanger, a similar peak was found with the dilution sampling at room temperature, but the peak did not disappeared and shifted to smaller diameters with the thermal dilution sampling at 150°C or 300°C. This result suggested that condense particles which were hard to evaporate or nano-size solid particles were formed in the process of heat recovery.

PERFORMANCE OF AIR CONDITIONERS WITH A GAS-LIQUID SEPARATION CONDENSER AND ONE-TANK LAMINATED EVAPORATO

유성연,지명석,이대웅 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.5

In this study, a parallel flow condenser and laminated evaporator for an automotive air-conditioning system were modified to improve performance. Gas-liquid separation type condensers, in which the condenser and receiver drier are integrated, and one-tank laminated type evaporators were developed, and their performances were investigated experimentally using HFC-134a. Heat transfer characteristics in the condenser are examined by means of air temperature, air velocity entering the condenser and inlet pressure of the refrigerant; heat transfer characteristics in the evaporator are examined by means of air temperature, relative humidity, flow rate of air, outlet pressure of refrigerant and superheat. Pressure drops for both evaporator and condenser are also measured, and correlations for pressure drop are derived for the condenser and evaporator, respectively. Air velocity and mass flow rate of the refrigerant have a significant effect on the overall heat transfer coefficient, and flow pass is not significantly influenced by the cooling capacity of the condenser. The overall heat transfer coefficient of the evaporator increases as air flow rate, air temperature and relative humidity increases. In this study, a parallel flow condenser and laminated evaporator for an automotive air-conditioning system were modified to improve performance. Gas-liquid separation type condensers, in which the condenser and receiver drier are integrated, and one-tank laminated type evaporators were developed, and their performances were investigated experimentally using HFC-134a. Heat transfer characteristics in the condenser are examined by means of air temperature, air velocity entering the condenser and inlet pressure of the refrigerant; heat transfer characteristics in the evaporator are examined by means of air temperature, relative humidity, flow rate of air, outlet pressure of refrigerant and superheat. Pressure drops for both evaporator and condenser are also measured, and correlations for pressure drop are derived for the condenser and evaporator, respectively. Air velocity and mass flow rate of the refrigerant have a significant effect on the overall heat transfer coefficient, and flow pass is not significantly influenced by the cooling capacity of the condenser. The overall heat transfer coefficient of the evaporator increases as air flow rate, air temperature and relative humidity increases.

Simulation-based optimization of gas condensate wells to mitigate the heavy hydrocarbon condensation through supercritical CO2 injection

Kun Sang Lee,Jinsuk Choi,ByungIn Choi,Jiho Lee 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.8

In gas-condensate reservoirs suffering from condensate banking, the supercritical CO2 injection process is regarded as one of the most effective technical remedies to reduce the liquid formation and achieve higher quality gas production. With proper well configuration and spacing designs, the injected CO2 can decrease the loss of heavy components effectively. The main goal of this study was to minimize the loss of heavy components during CO2 injection by implementing a proper well configuration. The results show that the integration of pressure maintenance and chemical reactions, including reduced viscosity and interfacial tension, improves the C7+ component recovery by 42.9, 49.4, and 49.3% for the base five-spot, inverted five-spot, and line drive cases, respectively. The total recovery is the highest for the line drive pattern with a recovery factor of 72.7%. The results also indicate that there is a critical length maximizing the effect of gas cycling.

배기가스 이코노마이저의 성능개선을 위한 Soot Blow 시스템에 관한 연구

김홍렬,김부기 한국기계기술학회 2023 한국기계기술학회지 Vol.25 No.6

In this study, a condensate drain valve was newly installed in the steam inlet pipe line of the soot blower to reduce the amount of condensate contained in the steam for the soot blower. When the economizer is inactive, the condensate drain valve on the soot blower steam inlet pipe line is always opened to drain the condensate. It is intended to reduce environmental pollution and improve economizer performance by reducing the water hammer that inevitably occurs in facilities using steam, and reducing the amount of condensate water generated during the shutdown of the soot blower and the release of soot containing condensate water into the atmosphere when removing soot.

Modelling and improving natural gas condensate process with stripping and heat integration

Uwitonze, H.,Hwang, K.S.,Lee, I. ELSEVIER 2017 CHEMICAL ENGINEERING AND PROCESSING Vol.118 No.-

Fractionation has been proven to be an efficient method among different methods that can be used in stabilizing natural gas condensate. In this paper, an issue of improving a process that stabilizes natural gas condensate is raised and different process alternatives are proposed based on heat integration scenarios. The resulting process systems have reboilers that use the bottoms product and compressed overhead product to preheat the feed. Steady state process models for different case scenarios were developed using HYSYS software, and dynamic control of the optimal complex interacting systems are studied. A control structure is developed and tested using conventional PI controller.

자동차 에어컨 냉매 가스 누설에 대한 고장사례 고찰

이일권(Il Kwon Lee),국창호(Chang Ho Kook),문학훈(Hak Hoon Moon),유창배(Chang Bae You) 한국가스학회 2016 한국가스학회지 Vol.20 No.2

이 논문의 목적은 자동차 에어컨 가스 누설에 관련된 고장사례를 분석하고 고찰한 것이다. 첫 번째 사례는 냉매가 누설된 상태에서 에어컨 컴프레서가 계속 작동되었다. 이로 인해 에어컨 컴프레서 내부의 피스톤이 윤활부족으로 인해 피스톤이 부분적으로 에어컨 컴프레서 내부의 실린더에 소착되는 현상이 발생하였다. 이것이 엔진작동 중 부하를 증대시켜 엔진의 회전수 변동과 함께 엔진의 작동이 정지되는 현상이 발생된 것으로 확인되었다. 두 번째 사례는 에어컨 라인과 관련 시스템을 확인한 결과 에어컨 컴프레서에서 뒤쪽으로 가는 컨덴서 고압파이프에서 미세한 균열에 의해 에어컨 냉매 가스가 누설되는 것을 확인하였다. 세 번째 사례는 에어컨 컨덴서 핀 부에서 육안으로 확인하기 어려운 미세한 크랙에 의해 컨덴서 내부 안쪽에서 에어컨 가스가 미세하게 누설되는 것을 확인하였다. 따라서, 에어컨 시스템은 에어컨 냉매가스에 의해 자동차의 실내의 온도를 낮춰 공기조화를 하는 시스템이므로 최적의 상태를 유지할 수 있도록 철저한 관리를 하도록 하여야 한다. This paper is to analyze and study the failure examples of refrigerant gas in automotive air conditioner. The first example, the air conditioner compressor continually operated that the refrigerant was leaked in air conditioner system. By lubrication shortage, the piston was partially sticked on cylinder of air conditioner compressor inner part. This was caused the phenomenon of engine operation trouble by load increasing with engine rpm variation during engine running. The second example, it sought the fact that the air conditioner refrigerant gas was leaked from air conditioner compressor to condenser high pressure pipe toward rear air conditioner checking with the lines of air conditioner. The third example, the refrigerant gas of air conditioner found that was leaked imperceptible from condenser inner by crack that was generated on the fins of air conditioner condenser. Therefore, the air conditioner system that maintain the air conditioner by decreasing the in-car temperature must meticulously manage to not leak the air conditioner refrigerant gas.

Condensation mode transition and condensation heat transfer performance variations of nitrogen ion-implanted aluminum surfaces

Kim, Kiwook,Jeong, Ji Hwan Elsevier 2018 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.125 No.-

<P><B>Abstract</B></P> <P>Aluminum substrate specimens are irradiated with nitrogen ions at various ion dose and ion energy levels in order to realize dropwise condensation on the specimen surfaces. Dropwise steam condensation initially occurs on these specimens, but the condensation mode changes into filmwise condensation. When the condensation mode changes to filmwise condensation, the heat transfer coefficient is measured to be approximately 40% lower than that predicted using the Nusselt theory; in addition, the color of the surface changes from yellow-brown to silver-white. This surface color change is the result of the hydrolysis reaction between the condensate and the nitrogen ion-implanted aluminum surface. Non-condensable gas is generated by the hydrolysis reaction, and this non-condensable gas diminishes the heat transfer coefficient. In addition, the material composition of the specimen’s surface changes and causes the transition of the condensation mode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nitrogen ions are irradiated on aluminum substrates. </LI> <LI> Dropwise condensation initially occurs but change into film condensation soon. </LI> <LI> Hydrolysis reaction produces non-condensable ammonia gas. </LI> </UL> </P>

Numerical simulation of bubble formation and condensation of steam air mixture injected in subcooled pool

Qu, Xiaohang,Revankar, Shripad T.,Tian, Maocheng Elsevier 2017 Nuclear engineering and design Vol.320 No.-

<P><B>Abstract</B></P> <P>Bubble formation and condensation of steam-air mixture vertically injected in a subcooled water pool was simulated, combining thermal phase change model into the two continuous phase free surface model of ANSYS CFX 17.1. Continuous surface force model was used to calculate surface tension force and the influence of non-condensable gas was accounted for by component transportation equation and assumption of interface temperature equal to saturation temperature at local partial steam pressure. The thermal phase change model includes an experimental correlation for liquid side sensible heat transfer. Based on available experiment data from literatures, singular pure steam bubble and steam-mixture bubble in a pool were first simulated to see the predictability of the proposed method and then, the same method was applied to the bubble formation, detachment and condensation process of injected steam air mixture from a nozzle. Bubble dimeter, water subcooling and non-condensable gas concentration studied range from 4.9mm to 50mm, 12K to 40K, and 0 to 31.5% respectively. The results of the computations indicate that the present method can predict very well the bubble formation and condensation both for pure steam case and with non-condensable gas.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bubble formation and condensation process injected from a nozzle is studied numerically. </LI> <LI> Euler-Euler two-fluid free surface model and species model from are coupled together. </LI> <LI> Influence of non-condensable gas is considered. </LI> <LI> Bubble shape variation histories are shown in comparison with experiments. </LI> </UL> </P>