Search results for: Kazuaki Tokuhashi

Items from 1 to 20 out of 39 results

article

Rate constants for the reactions of OH radicals with CF₃CX=CY₂ (X = H, F, CF₃, Y = H, F, Cl)

Kazuaki Tokuhashi, Kenji Takizawa, Shigeo Kondo

Environmental Science and Pollution Research > 2018 > 25 > 15 > 15204- 15215

The rate constants of OH radicals with CF₃CF=CCl₂, CF₃CH=CF₂, CF₃CF=CH₂, CF₃CH=CH₂, and (CF₃)₂C=CH₂ have been measured over the temperature range 250–430 K. Kinetic measurements have been carried out using flash photolysis and laser photolysis methods combined respectively with laser-induced fluorescence technique. The Arrhenius rate parameters have been determined as k(CF₃CF=CCl₂) = (6.50 ± 0.22)...

article

Quenching distance measurement of highly to mildly flammable compounds

Kenji Takizawa, Naoharu Igarashi, Shizue Takagi, Kazuaki Tokuhashi, more

Fire Safety Journal > 2015 > 71 > Complete > 58-68

Quenching distance measurements were carried out for 11 highly to only mildly flammable gases (which include alkanes, fluorinated alkanes and alkenes, and ammonia) to elucidate the ignition and quenching characteristics of low-GWP (global warming potential) alternative materials. For buoyant flames of mildly flammable compounds, conventional 25mm diameter parallel plates in the vertical position provided...

article

Effect of high humidity on flammability property of a few non-flammable refrigerants

Shigeo Kondo, Kenji Takizawa, Kazuaki Tokuhashi

Journal of Fluorine Chemistry > 2014 > 161 > Complete > 29-33

The effect of high humidity on the flammability property was examined in air for non-flammable refrigerant materials of R-410A, R-410B, R-134a, and R-125. The high humidity here means the relative humidity of up to 50% at 60°C. The measurements were done in a 12L spherical glass flask following the ASHRAE method. Under the present humidity condition, R-410A, R-410B, and R-134a became flammable, whereas...

article

Rate constants for the gas-phase reactions of cyclo-CXCXCF2CF2– (X=H, F) with OH radicals at a temperature range of 253–328K

Xiaoqing Jia, Liang Chen, Junji Mizukado, Shuzo Kutsuna, more

Chemical Physics Letters > 2013 > 572 > Complete > 21-25

Using a relative rate method, rate constants of cyclo-CFCFCF ₂ CF ₂ –, cyclo-CHCFCF ₂ CF ₂ –, and cyclo-CHCHCF ₂ CF ₂ – reaction with OH radicals were determined to be (3.15±0.93)×10 ⁻¹³ exp[(630±90)/T], (4.60±1.31)×10 ⁻¹³ exp[(600±80)/T], and (3.28±0.57)×10 ⁻¹³ exp[(190±50)/T] between 253 and 328K, and (3.79±0.11)×10 ⁻¹⁴...

article

Flammability limits of binary mixtures of ammonia with HFO-1234yf, HFO-1234ze, HFC-134a, and HFC-125

Shigeo Kondo, Kenji Takizawa, Kazuaki Tokuhashi

Journal of Fluorine Chemistry > 2013 > 149 > Complete > 18-23

Flammability limits of binary mixtures of ammonia with HFO-1234yf, HFO-1234ze, HFC-134a, and HFC-125 were measured in dry air. The measurements were made in a 12L spherical glass flask using ASHRAE method. It has been found that the flammability limits of ammonia and HFO-1234yf mixtures are extremely different from the values predicted by Le Chatelier's equation. Modification of Le Chatelier's equation...

article

Effects of temperature and humidity on the flammability limits of several 2L refrigerants

Shigeo Kondo, Kenji Takizawa, Kazuaki Tokuhashi

Journal of Fluorine Chemistry > 2012 > 144 > Complete > 130-136

Flammability limits were measured in air for several compounds classified as 2L refrigerants by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The compounds treated are ammonia, CH ₂ F ₂ (HFC-32), CH ₃ CF ₃ (HFC-143a), CH ₂ CFCF ₃ (HFO-1234yf), and CHFCHCF ₃ (HFO-1234ze). The measurements of flammability limits...

article

On the pressure dependence of flammability limits of CH2=CFCF3, CH2F2 and methane

Shigeo Kondo, Akifumi Takahashi, Kenji Takizawa, Kazuaki Tokuhashi

Fire Safety Journal > 2011 > 46 > 5 > 289-293

Flammability limits of CH ₂ =CFCF ₃ (HFO-1234 yf), CH ₂ F ₂ (HFC-32), and methane were measured at pressures from ambient to 2500kPa in a 5l stainless-steel spherical vessel. For HFO-1234 yf, as the pressure rises from ambient, the lower flammability limit is shifted downward and the upper limit is shifted upward. The changes to the lower flammability limits are, in...

article

On the temperature dependence of flammability limits of gases

Shigeo Kondo, Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi

Journal of Hazardous Materials > 2011 > 187 > 1-3 > 585-590

Flammability limits of several combustible gases were measured at temperatures from 5 to 100°C in a 12-l spherical flask basically following ASHRAE method. The measurements were done for methane, propane, isobutane, ethylene, propylene, dimethyl ether, methyl formate, 1,1-difluoroethane, ammonia, and carbon monoxide. As the temperature rises, the lower flammability limits are gradually shifted down...

article

Flammability assessment of CH2CFCF3: Comparison with fluoroalkenes and fluoroalkanes

Kenji Takizawa, Kazuaki Tokuhashi, Shigeo Kondo

Journal of Hazardous Materials > 2009 > 172 > 2-3 > 1329-1338

The burning velocity, flammability limits, and heat of combustion of CH ₂ CFCF ₃ (1234yf) have been studied to elucidate the fundamental flammability properties of this new alternative refrigerant with low global-warming potential. The burning velocity of 1234yf was measured independently by schlieren photography and the spherical vessel method. In the spherical vessel method, the...

article

Flammability limits of olefinic and saturated fluoro-compounds

Shigeo Kondo, Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi, more

Journal of Hazardous Materials > 2009 > 171 > 1-3 > 613-618

Flammability limits were measured for a number of olefinic and saturated fluoro-compounds in a 12l spherical glass vessel. The obtained data together with the ones of previous studies have been analyzed based on the F-number scheme of flammability limits. The flammability limits of these compounds have been found to be explained very well by the present scheme of interpretation. The flammability limits...

article

Flammability limits of five selected compounds each mixed with HFC-125

Shigeo Kondo, Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi, more

Fire Safety Journal > 2009 > 44 > 2 > 192-197

Flammability limits of five selected combustible gases each mixed with 1,1,1,2,2-pentafluoroethane (HFC-125) were investigated. Actually, the investigation was made for methane, propane, propylene, methyl formate, and 1,1-difluoroethane (HFC-152a). The observed data were analyzed using the extended Le Chatelier's formula. As a result, the HFC-125 mixing effect on the flammability limits of individual...

article

Burning velocity measurements of fluoropropanes by the spherical-vessel method

Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi, Shigeo Kondo, more

Journal of Fluorine Chemistry > 2008 > 129 > 8 > 713-719

Burning velocity measurements of six types of fluoropropanes including structural isomers were carried out in order to understand the flammability of hydrofluorocarbons (HFC). The burning velocity (S _u ) was determined by applying a spherical flame model to the pressure rise during combustion, which was measured at room temperature and at initial pressures of 80–107kPa over a wide range of...

article

A study on flammability limits of fuel mixtures

Shigeo Kondo, Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi, more

Journal of Hazardous Materials > 2008 > 155 > 3 > 440-448

Flammability limit measurements were made for various binary and ternary mixtures prepared from nine different compounds. The compounds treated are methane, propane, ethylene, propylene, methyl ether, methyl formate, 1,1-difluoroethane, ammonia, and carbon monoxide. The observed values of lower flammability limits of mixtures were found to be in good agreement to the calculated values by Le Chatelier's...

article

Burning velocity measurements of nitrogen-containing compounds

Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi, Shigeo Kondo, more

Journal of Hazardous Materials > 2008 > 155 > 1-2 > 144-152

Burning velocity measurements of nitrogen-containing compounds, i.e., ammonia (NH ₃ ), methylamine (CH ₃ NH ₂ ), ethylamine (C ₂ H ₅ NH ₂ ), and propylamine (C ₃ H ₇ NH ₂ ), were carried out to assess the flammability of potential natural refrigerants. The spherical-vessel (SV) method was used to measure the burning velocity over...

article

Flammability limits of isobutane and its mixtures with various gases

Shigeo Kondo, Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi, more

Journal of Hazardous Materials > 2007 > 148 > 3 > 640-647

Flammability limits of isobutane and five kinds of binary mixtures of isobutane were measured by the ASHRAE method. Propane, nitrogen, carbon dioxide, chloroform, and HFC-125 (1,1,1,2,2-pentafluoroethane) were used as the counter part gases in the mixtures. The observed data were analyzed using the equations based on Le Chatelier's formula. The flammability limits of mixtures with propane were well...

article

Burning velocity measurement of HFC-41, HFC-152, and HFC-161 by the spherical-vessel method

Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi, Shigeo Kondo, more

Journal of Fluorine Chemistry > 2006 > 127 > 12 > 1547-1553

The burning velocities of fluoromethane (HFC-41), 1,2-difluoroethane (HFC-152), fluoroethane (HFC-161) and ethane were measured by the spherical-vessel (SV) method at room temperature and at initial pressures of 80–107kPa over a wide range of HFC/air equivalence ratios (ϕ). The burning velocities were determined from the measured pressure increases by application of a spherical flame model. Schlieren...

article

Extended Le Chatelier's formula for carbon dioxide dilution effect on flammability limits

Shigeo Kondo, Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi

Journal of Hazardous Materials > 2006 > 138 > 1 > 1-8

Carbon dioxide dilution effect on the flammability limits was measured for various flammable gases. The obtained values were analyzed using the extended Le Chatelier's formula developed in a previous study. As a result, it has been found that the flammability limits of methane, propane, propylene, methyl formate, and 1,1-difluoroethane are adequately explained by the extended Le Chatelier's formula...

article

Relative reactivity and regioselectivity of halogen-substituted ethenes and propene toward addition of an OH radical or O (3P) atom: An ab initio study

Ahmed M. El-Nahas, Tadafumi Uchimaru, Masaaki Sugie, Kazuaki Tokuhashi, more

Journal of Molecular Structure: THEOCHEM > 2006 > 770 > 1-3 > 59-65

This paper describes the results of ab initio investigations on the reactions of OH radical/O ( ³ P) atom addition to halogen-substituted ethenes (CH ₂ CHX, CH ₂ CX ₂ ; X=F, Cl, Br) and propene. Two reaction pathways, addition to the substituted carbon atom (α-site) and addition to the non-substituted carbon atom (β-site), have been examined. The energetic of each reaction...

article

Extended Le Chatelier's formula and nitrogen dilution effect on the flammability limits

Shigeo Kondo, Kenji Takizawa, Akifumi Takahashi, Kazuaki Tokuhashi

Fire Safety Journal > 2006 > 41 > 5 > 406-417

The effect of nitrogen dilution on the flammability limits was measured carefully for a number of fuel gases in order to make an accurate numerical analysis of the data. An extension of Le Chatelier's formula was developed to apply to mixtures containing inert gas. A numerical analysis was carried out using the extended formula for newly measured experimental values of the flammability limits. As...

article

A theoretical study on the strength of two-center three-electron bonds in the NO3 radical adducts of reduced sulfur molecules, H2S, CH3SH, CH3SCH3, and CH3SSCH3

Tadafumi Uchimaru, Seiji Tsuzuki, Masaaki Sugie, Kazuaki Tokuhashi, more

Chemical Physics > 2006 > 324 > 2-3 > 465-473

It is widely known that addition of a radical species to the sulfur atom of a reduced sulfur molecule results in formation of a two-center three-electron (2c-3e) bond, but relatively few investigations have been reported for the 2c-3e bond between the NO ₃ radical and a sulfur molecule. This article presents results of gas-phase DFT and ab initio investigations on the 2c-3e type adducts of...

Publication date

Set your own date range

INFONA - science communication portal

Search results for: Kazuaki Tokuhashi

Rate constants for the reactions of OH radicals with CF₃CX=CY₂ (X = H, F, CF₃, Y = H, F, Cl)

Quenching distance measurement of highly to mildly flammable compounds

Effect of high humidity on flammability property of a few non-flammable refrigerants

Rate constants for the gas-phase reactions of cyclo-CXCXCF2CF2– (X=H, F) with OH radicals at a temperature range of 253–328K

Flammability limits of binary mixtures of ammonia with HFO-1234yf, HFO-1234ze, HFC-134a, and HFC-125

Effects of temperature and humidity on the flammability limits of several 2L refrigerants

On the pressure dependence of flammability limits of CH2=CFCF3, CH2F2 and methane

On the temperature dependence of flammability limits of gases

Flammability assessment of CH2CFCF3: Comparison with fluoroalkenes and fluoroalkanes

Flammability limits of olefinic and saturated fluoro-compounds

Flammability limits of five selected compounds each mixed with HFC-125

Burning velocity measurements of fluoropropanes by the spherical-vessel method

A study on flammability limits of fuel mixtures

Burning velocity measurements of nitrogen-containing compounds

Flammability limits of isobutane and its mixtures with various gases

Burning velocity measurement of HFC-41, HFC-152, and HFC-161 by the spherical-vessel method

Extended Le Chatelier's formula for carbon dioxide dilution effect on flammability limits

Relative reactivity and regioselectivity of halogen-substituted ethenes and propene toward addition of an OH radical or O (3P) atom: An ab initio study

Extended Le Chatelier's formula and nitrogen dilution effect on the flammability limits

A theoretical study on the strength of two-center three-electron bonds in the NO3 radical adducts of reduced sulfur molecules, H2S, CH3SH, CH3SCH3, and CH3SSCH3

Filter options

Publication date

Content availability

Keywords

Data set

Journal

INFONA - science communication portal

Search results for: Kazuaki Tokuhashi

Add recipient

Sending message cancelled

Are you sure you want to cancel sending this message?

Send message

Filter options

Publication date

Date range setting

Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.

Content availability

Keywords

Data set

Journal

Reporting an error / abuse

Sending the report failed

Accessibility options