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J. YANG, F. B. CHEUNG,J. L. REMPE,S. B. KIM,서균렬 한국원자력학회 2006 Nuclear Engineering and Technology Vol.38 No.2
An experimental study was performed to evaluate the effects of surface coating and an enhanced insulation structure onthe downward facing boiling process and the critical heat flux on the outer surface of a hemispherical vessel. Steady-stateboiling tests were conducted in the Subscale Boundary Layer Boiling (SBLB) facility using an enhanced vessel/insulationdesign for the cases with and without vessel coatings. Based on the boiling data, CHF correlations were obtained for bothplain and coated vessels. It was found that the nucleate boiling rates and the local CHF limits for the case with micro-porouslayer coating were consistently higher than those values for a plain vessel at the same angular location. The enhancement inthe local CHF limits and nucleate boiling rates was mainly due to the micro-porous layer coating that increased the localliquid supply rate toward the vaporization sites on the vessel surface. For the case with thermal insulation, the local CHFlimit tended to increase from the bottom center at first, then decrease toward the minimum gap location, and finally increasetoward the equator. This non-monotonic behavior, which differed significantly from the case without thermal insulation, wasevidently due to the local variation of the two-phase motions in the annular channel between the test vessel and the insulationstructure.
Development of the ASHRAE Global Thermal Comfort Database II
Fö,ldvá,ry Lič,ina, Veronika,Cheung, Toby,Zhang, Hui,de Dear, Richard,Parkinson, Thomas,Arens, Edward,Chun, Chungyoon,Schiavon, Stefano,Luo, Maohui,Brager, Gail,Li, Peixian,Kaam, Soazig Elsevier 2018 Building and environment Vol.142 No.-
<P><B>Abstract</B></P> <P>Recognizing the value of open-source research databases in advancing the art and science of HVAC, in 2014 the ASHRAE Global Thermal Comfort Database II project was launched under the leadership of University of California at Berkeley's Center for the Built Environment and The University of Sydney's Indoor Environmental Quality (IEQ) Laboratory. The exercise began with a systematic collection and harmonization of raw data from the last two decades of thermal comfort field studies around the world. The ASHRAE Global Thermal Comfort Database II (Comfort Database), now an online, open-source database, includes approximately 81,846 complete sets of objective indoor climatic observations with accompanying “<I>right-here-right-now</I>” subjective evaluations by the building occupants who were exposed to them. The database is intended to support diverse inquiries about thermal comfort in field settings. A simple web-based interface to the database enables filtering on multiple criteria, including building typology, occupancy type, subjects' demographic variables, subjective thermal comfort states, indoor thermal environmental criteria, calculated comfort indices, environmental control criteria and outdoor meteorological information. Furthermore, a web-based interactive thermal comfort visualization tool has been developed that allows end-users to quickly and interactively explore the data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The scope, development, contents, and accessibility of the Comfort Database is documented. </LI> <LI> The Comfort Database II includes approximately 76,000 complete sets of thermal comfort data. </LI> <LI> The Comfort Database provides access to the collected raw data. </LI> <LI> Web-based interactive visualization tool was developed that allows end-users to interactively explore the data. </LI> </UL> </P>
Final report for the APMP.T-K4: Comparison of realizations of aluminium freezing-point temperatures
Gam, K S,Joung, W,Yamazawa, K,Cheung, C P,Kho, H Y,Wang, L,Tsai, S F,Norranim, U,Hafidzah, O,Gupta, J K Springer-Verlag 2013 Metrologia Vol.50 No.-
<P>The comparison APMP.T-K4 is the regional extension of the CCT-K4: an intercomparison of the realizations of the freezing-points of Al (660.323 °C) and Ag (961.78 °C). The comparison was organized in two loops and four sub-loops with high temperature standard platinum resistance thermometers (HTSPRTs) as transfer thermometers in the freezing-point comparisons. The comparison involved eight APMP NMIs (KRISS, NMIJ, SCL, NMC, CMS, NIMT, SIRIM, NPL), and KRISS and NMIJ acted as linking laboratories to the CCT-K4.</P><P>The transfer HTSPRTs showed a strong drift during the transportation between the NMIs. In the case of the Ag freezing-point comparison, the comparison results were scattered much more than expected. In the APMP meeting held in 2009, the participants agreed that the Ag comparison results would be omitted in the report. It revealed that the measurement results at the Al freezing-point of participants were in agreement with the key comparison reference value of the CCT-K4 within 4 mK except for one laboratory. Details of the comparison results, the uncertainty evaluation and the drift of the HTSPRTs are described in this report.</P><P>Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.</P><P>The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).</P>
CHF enhancement by vessel coating for external reactor vessel cooling
Yang, J.,Dizon, M.B.,Cheung, F.B.,Rempe, J.L.,Suh, K.Y.,Kim, S.B. Elsevier 2006 Nuclear engineering and design Vol.236 No.10
<P><B>Abstract</B></P><P>In-vessel retention (IVR) is a key severe accident management (SAM) strategy that has been adopted by some operating nuclear power plants and proposed for some advanced light water reactors (ALWRs). One viable means for IVR is the method of external reactor vessel cooling (ERVC) by flooding the reactor cavity during a severe accident. As part of a joint Korean–United States International Nuclear Energy Research Initiative (K-INERI), an experimental study has been conducted to investigate the viability of using an appropriate vessel coating to enhance the critical heat flux (CHF) limits during ERVC. Toward this end, transient quenching and steady-state boiling experiments were performed in the subscale boundary layer boiling (SBLB) facility at the Pennsylvania State University using test vessels with micro-porous aluminum coatings. Local boiling curves and CHF limits were obtained in these experiments. When compared to the corresponding data without coatings, substantial enhancement in the local CHF limits for the case with surface coatings was observed. Results of the steady-state boiling experiments showed that micro-porous aluminum coatings were very durable. Even after many cycles of steady-state boiling, the vessel coatings remained rather intact, with no apparent changes in color or structure. Moreover, the heat transfer performance of the coatings was found to be highly desirable with an appreciable CHF enhancement in all locations on the vessel outer surface but with very little effect of aging.</P>
Ha, K.S.,Cheung, F.B.,Park, R.J.,Kim, S.B. North-Holland Pub. Co 2012 Nuclear engineering and design Vol.253 No.-
The process of two-phase natural circulation flow induced in the annular gap between the reactor vessel and the insulation under external reactor vessel cooling conditions was investigated experimentally and analytically in this study. HERMES-HALF experiments were performed to observe and quantify the induced two-phase natural circulation flow in the annular gap. A half-scaled non-heating experimental facility was designed by utilizing the results of a scaling analysis to simulate the APR1400 reactor and its insulation system. The behavior of the boiling-induced two-phase natural circulation flow in the annular gap was observed, and the liquid mass flow rates driven by the natural circulation loop and the void fraction distribution were measured. Direct flow visualization revealed that choking would occur under certain flow conditions in the minimum gap region near the shear keys. Specifically, large recirculation flows were observed in the minimum gap region for large air injection rates and small outlet areas. Under such conditions, the injected air could not pass through the minimum gap region, resulting in the occurrence of choking near the minimum gap with a periodical air back flow being generated. Therefore, a design modification of the minimum gap region needs to be done to facilitate steam venting and to prevent choking from occurring. To complement the HERMES-HALF experimental effort, an analytical study of the dependence of the induced natural circulation mass flow rate on the inlet area and the volumetric air injection rate was performed using a loop integration of the momentum equation. The loop-integrated momentum equation was formulated in terms of the dimensionless mass flow rate and the area ratio. Asymptotic solutions were obtained for two limiting cases for which the dimensionless mass flow rate was either very large or very small. First-order approximate solution was also obtained and was found to agree with the experimental data within 20% in most situations. The natural circulation mass flow rate was found to increase as the water inlet area and the volumetric air injection rate were increased. For large inlet areas, the mass flow rate was found to depend almost linearly on the inlet area. By adjusting the inlet and outlet areas of the insulation in HERMES-HALF experiments, a natural circulation flow rate could be generated up to 200kg/s, corresponding to about 1.3-1.5MW/m<SUP>2</SUP> critical heat flux at the top of the reactor lower head (90<SUP>o</SUP>) according to the data of KAIST and SULTAN.