• Title/Summary/Keyword: Wave heat exchanger

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Application of Guided Ultrasonic Wave Technology for Evaluation of Welding Part in Cooling Water Pipe (냉각수 배관 용접부 평가를 위한 유도초음파 기술의 적용)

  • Gil, D.S.;Ahn, Y.S.;Park, S.K.
    • Journal of Power System Engineering
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    • v.14 no.5
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    • pp.36-40
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    • 2010
  • The ultrasonic guided wave propagates along with the given structure's wall direction. Because of this specific character, the ultrasonic guided waves arc used in many other fields. Especially, it can be readily utilized for nondestructive inspection of various structures that are made up of gas pipes, heat exchanger tubes, and thin plates. Further, the guided wave technology can be readily utilized when inspecting pipes or thin plates which pose high risk of the accident but for which the nondestructive inspection itself is impossible because it is difficult to get to them since they are coated or buried underground. In the other hand, conventional ultrasonic testing such as thickness gauging uses bulk waves and only tests the region of structure immediately below the transducer. As a result of the application about inlet and outlet cooling water line using guided wave test, we conformed that the overall corrosions were in the lower side of the 304.8 mm inlet valve and these corrosions were engaged in not locally but through the lower side of the valve line. In the near future, we can expect that the detectable defect size is smaller than before along with the development of the sensing technology.

Numerical analysis of Poiseuille-Rayleigh-Bénard convection in supercritical carbon dioxide

  • Wang, Zhipeng;Xu, Hong;Chen, Chong;Hong, Gang;Song, Zhenguo;Zhang, Yaoli
    • Nuclear Engineering and Technology
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    • v.54 no.9
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    • pp.3540-3550
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    • 2022
  • The supercritical carbon dioxide (S-CO2) Brayton cycle is an important energy conversion technology for the fourth generation of nuclear energy. Since the printed circuit heat exchanger (PCHE) used in the S-CO2 Brayton cycle has narrow channels, Rayleigh-Bénard (RB) convection is likely to exist in the tiny channels. However, there are very few studies on RB convection in supercritical fluids. Current research on RB convection mainly focuses on conventional fluids such as water and air that meet the Boussinesq assumption. It is necessary to study non-Boussinesq fluids. PRB convection refers to RB convection that is affected by horizontal incoming flow. In this paper, the computational fluid dynamics simulation method is used to study the PRB convection phenomenon of non-Boussinesq fluid-supercritical carbon dioxide. The result shows that the inlet Reynolds number (Re) of the horizontal incoming flow significantly affects the PRB convection. When the inlet Re remains unchanged, with the increase of Rayleigh number (Ra), the steady-state convective pattern of the fluid layer is shown in order: horizontal flow, local traveling wave, traveling wave convection. If Ra remains unchanged, as the inlet Re increases, three convection patterns of traveling wave convection, local traveling wave, and horizontal flow will appear in sequence. To characterize the relationship between traveling wave convection and horizontal incoming flow, this paper proposes the relationship between critical Reynolds number and relative Rayleigh number (r).

The Performance Investigation of Double-speaker-1/2 Wavelength Thermoacoustic Refrigerator (Double speaker 1/2파장 열음향 냉동기의 성능 평가)

  • Song Kyu Joe;Park Jong Ho;Lee Sung Ro
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.647-650
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    • 2002
  • A thermoacoustic refrigerator, using a resonant standing acoustic wave, has been built. It employs a loudspeaker to sustain a standing wave in a resonance tube. The stack of plates is 0.075mm-thick plastic sheet(Mylar), spirally wound to make a 40mm-diameter assembly 80mm long. and two heat exchanger are installed. The refrigerant is Helium gas. The description of thermoacoustic refrigerator are presented. The directly measured performance of the resonator. Tc/Th ( temperature ratio ) and $COP/COP_{c}$, (normalized by carnot's COP ) are plotted versus the thermal load Q applied to the cold end, for various speaker power.

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Development of 2-dimensional model for thermal comfort in train (철도 차량 온열 쾌적성에 관한 2차원 모델 개발)

  • Yeon, Bong-Joon;Kim, Moon-Uhn;Kim, Man-Hoe
    • Proceedings of the SAREK Conference
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    • 2007.11a
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    • pp.9-16
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    • 2007
  • This study aims to suggest an evaluation method of thermal environment using CFD, not an experiment, which is usual in the field. Model train is the newly introduced Mugunghwa train. Since its compartment occupies a large space and chairs and other accessories make it a complicated structure, 3-D calculation might take too much time and effort to make evaluation itself possible. Therefore, we suggest a 2-D model to replace the original 3-D model for averaged temperature and temperature distribution in the cabin.

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SNR Improvement of AE Signal for Detection of Gas Leak from Tubes under Vibratory Environment

  • Lee, Tae-Hun;Jhang, Kyung-Young;Kim, Jung-Kyu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.3
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    • pp.262-267
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    • 2007
  • Detection of gas leak from a tube is a very important issue in the quality control of machines such as the heat exchanger of an air-conditioner, because leakage of operating gas directly reduces the performance of machines. The acoustic emission (AE) method is a common way to detect leak of gas, however its application under the environment of mechanical vibration is restricted since most AE detectors are very sensitive to external vibration noise. In order to overcome this problem, we propose a method based on the mode analysis of the Lamb wave. In this method, the dominant Lamb mode and its frequency are found first, and then a proper band-pass filter is used to retain only this frequency component. In this way, we could improve the SNR (signal-to-noise ratio) of AE signal generated by gas leak from the tube even under vibratory environment.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.12
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

Study on the Temperature Separation Phenomenon in a Vortex Chamber (와류실의 온도 분리 현상에 대한 연구)

  • Ye, A Ran;Zhang, Guang;Kim, Heuy Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.9
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    • pp.731-737
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    • 2014
  • A vortex chamber is a simple device that separates compressed gas into a high-temperature stream and a low-temperature stream. It is increasing in popularity as a next-generation heat exchanger, but the flow physics associated with it is not yet well understood. In the present study, both experimental and numerical analyses were performed to investigate the temperature separation phenomenon inside the vortex chamber. Static pressures and temperatures were measured using high-sensitivity pressure transducers and thermocouples, respectively. Computational fluid dynamics was applied to simulate 3D unsteady compressible flows. The simulation results showed that the temperature separation is strongly dependent on the diameter of the vortex chamber and the supply pressure at the inlet ports, where the latter is closely related to the viscous work. The previous concept of a pressure gradient wave may not be a reasoning for temperature separation phenomenon inside the vortex chamber.