Journal of Light & Visual Environment

Papers

Heat-Transfer in Reflector-type Self-Ballasted Compact Fluorescent Lamps

Takeo YASUDA, Masahiro TODA, Shinichiro MATSUMOTO, Yuichiro TAKAHARA

2008 Volume 32 Issue 1 Pages 5-13
Published: 2008
Released on J-STAGE: August 12, 2008

DOIhttps://doi.org/10.2150/jlve.32.5

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Self-ballasted compact fluorescent lamps (SBCFL) are widely used to replace incandescent lamps (IL) to save energy. We studied the heat-transfer phenomena of SBCFLs with outer envelopes by measuring the temperatures of the lamp parts, the power consumption, and the luminous output, and by calculating the energy balance. The methods applied were heat-transfer network analysis and computational fluid dynamics (CFD) using FLUENT^® software. The heat loss increased in reflector-type SBCFLs as compared to SBCFLs with non-reflective outer envelopes, and was estimated at about 3 W when the total lamp power was 22 W. This results in a temperature rise of 20 K in the plastic holder, and a maximum rise of 10 K at the electronic components on the circuit board. Accordingly, we have developed a 12 W reflector-type SBCFL, which replaces a 60 W incandescent, not a 22 W SBCFL replacing a 100 W incandescent R-lamp, due to the importance of thermal reliability.

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Classification of Sky Conditions by the Ranges of Insolation Indices Considering CIE Standard for General Sky

Noriko UMEMIYA, Takai KANOU

2008 Volume 32 Issue 1 Pages 14-19
Published: 2008
Released on J-STAGE: August 12, 2008

DOIhttps://doi.org/10.2150/jlve.32.14

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This study introduces a method to classify sky conditions from overcast to clear by the values of insolation indices. Number of sky types and combination of insolation indices to classify sky types were investigated. Fifteen groups were clustered regarding nine indices by nearest centroid sorting method. Then groups were put together into sky conditions by considering the frequency distributions of CIE general sky types for each group and the frequency distribution of groups for each luminance distribution type. Seven sky conditions were found as a result. Indices to discriminate next sky conditions were found and then the most appropriate combination for total discrimination was decided: turbidity, clearness index, brightness and normalized global illuminance. Sky condition discrimination tree on the basis of the value of the indices was formed by a yearly data of International Daylight Measurement Program at Kyoto station and verified by the data of another year. By this method, illuminance and irradiance measurements can be separated into seven sky conditions considering CIE general sky types by the ranges of four indices without sky luminance distribution measurements.

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Research Notes

Evaluation of Indoor Illuminance from Light Guides

Jitka MOHELNIKOVA

2008 Volume 32 Issue 1 Pages 20-26
Published: 2008
Released on J-STAGE: August 12, 2008

DOIhttps://doi.org/10.2150/jlve.32.20

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Visual comfort in buildings is one of main demands for quality of indoor environment in buildings. Ensuring appropriate daylighting in interiors is architectural and technical problem. Tubular light guides serve opportunity to solutions of daylighting windowless interiors. Their function is based on the principle of light transport from outdoor to distant indoor places due to multi- reflections on their highly reflective internal surfaces. This presentation describes a method for evaluation of internal illuminance from light guides on the basis of determined luminance of a light guide ceiling diffuser. As luminance values of the diffuser are needed for indoor illuminance calculations under real daylight conditions the luminance camera was used and luminance photographs of the ceiling diffuser for clear, partly cloudy and overcast sky were monitored. The calculation results were compared with data from measurements on the practical installation of the light guide. The described method presents a design tool for the evaluation of indoor daylighting in rooms illuminated form tubular light guides.

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Alternative Scenario to Prove the Initial Value Problem of Effective Emissivity of Semi-infinite Cylindrical Blackbody Cavity by Wiener-Hopf Method

Yoshinari ISHIDO

2008 Volume 32 Issue 1 Pages 27-32
Published: 2008
Released on J-STAGE: August 12, 2008

DOIhttps://doi.org/10.2150/jlve.32.27

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With the use of Wiener-Hopf method in collaboration with the initial value theorem for Laplace transformation, which is alternative way to the Buckley’s first evaluation, it can be proved rigorously that the initial value problem for the radiant interchange in the semi-infinite cylindrical blackbody cavity, that is to say, the effective emissivity at its mouth is valued to be square root of the wall emissivity. Finally, a conjugate final value problem is a little commented on.

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Letters

Experimental Study on the Mercury Vapor Pressures in Amalgam-Dosed Discharge Tubes for Compact Fluorescent Lamps during Switch-off Period

Takeo YASUDA, Masashi KANDO

2008 Volume 32 Issue 1 Pages 33-38
Published: 2008
Released on J-STAGE: August 12, 2008

DOIhttps://doi.org/10.2150/jlve.32.33

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Ballast-integrated compact fluorescent lamps are widely used for replacing incandescent lamps as energy saving alternative light sources. In spite of their high efficacies, the luminous run-up characteristics of the lamps having outer globes are slow and rather unsatisfactory, especially within a second or two. This problem is due to the lower mercury vapor pressure P_Hg of amalgam dosed in the discharge tube than that of liquid mercury. In order to improve the luminous flux at starting the lamp ignition, the P_Hg changes in the discharge tubes including bismuth-indium main amalgam and indium auxiliary amalgam were studied during switch-off period by atomic absorption spectrometry using 254 nm line. The amounts of mercury absorbed in both the main and auxiliary amalgam were also measured by wet chemical analyses. It is found that the P_Hg during switch-off period is not controlled by only the auxiliary amalgam but also the main amalgam.

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Near-ultraviolet LED of the External Quantum Efficiency Over 45% and its Application to High-color Rendering Phosphor Conversion White LEDs

Hiroaki SAKUTA, Takeshi FUKUI, Tsutomu MIYACHI, Kunihito KAMON, Hideki ...

2008 Volume 32 Issue 1 Pages 39-42
Published: 2008
Released on J-STAGE: August 12, 2008

DOIhttps://doi.org/10.2150/jlve.32.39

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Highly luminous efficiency and color rendering index (CRI) of 70 lm/W and 95 under low correlated color temperature (CCT) of 3177 K has been obtained by phosphor conversion (PC) white light-emitting diodes (LEDs) using near-ultra violet (n-UV) LEDs with the external quantum efficiency (EQE) of 46.7%. The homogeneous spatial color uniformity on chromaticity of PC white LEDs excited by n-UV LEDs are particularly adequate to the general lighting applications.

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Development of White Light Emitting Diodes by Multi-layered Red, Green, and Blue Phosphors Excited by Near-ultraviolet Light Emitting Diodes

Takeshi FUKUI, Hiroaki SAKUTA, Kazuya MISHIRO, Tsutomu MIYACHI, Kunihi ...

2008 Volume 32 Issue 1 Pages 43-45
Published: 2008
Released on J-STAGE: August 12, 2008

DOIhttps://doi.org/10.2150/jlve.32.43

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Cascade excitation process and cascade excitation loss (absorption loss) have been investigated by bilayer (BL-) LEDs. The cascade excitation loss was suppressed by multi-layered (ML-) LED structure, in which red phosphor is placed at the bottom. We have also developed white LEDs by using a ML-structure of red, green, and blue phosphors for the purpose of reducing the cascade excitation. Luminous flux of ML-white LEDs showed higher value under low correlation color temperature (CCT=2613K) and high color-rendering index (Ra=94) conditions than conventional phosphor mixed-white LEDs. The angular distribution of chromaticity in the ML-R/G/B white LED was comparable to that in mixed-RGB white LED and was very small.

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Committee Report

Applying the Geodesic Dome to Daylight Simulation

—the Activities on the Daylight Simulation Working Group in Japan—

Nozomu YOSHIZAWA, Hirotaka SUZUKI, Naoya HARA

2008 Volume 32 Issue 1 Pages 46-50
Published: 2008
Released on J-STAGE: August 12, 2008

DOIhttps://doi.org/10.2150/jlve.32.46

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The exact daylight simulation is quite difficult even now in the practical field of architectural and lighting design. The sub-working group on daylight simulation in Architectural Institute of Japan was established in 2003 to find solutions for that situation. This working group has three sections: a benchmark group, an interface development group and an evaluation group. This paper will introduce activities of the interface development group and the benchmark group at present. The interface group is now developing the input/output interfaces for daylight simulation programs, and the purpose of the benchmark group is to evaluate the accuracy of software. Geodesic Dome is applied for daylight source as input interface and a test case for evaluating accuracy of inter-reflection calculation.

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