This experimental investigation was conducted on the flow boiling performance of refrigerant R134a in two types of parallel microchannels:sintered porous microchannels(PP-MCs)and smooth parallel microchannels(SP-MCs)....This experimental investigation was conducted on the flow boiling performance of refrigerant R134a in two types of parallel microchannels:sintered porous microchannels(PP-MCs)and smooth parallel microchannels(SP-MCs).The tests were performed under controlled conditions including an inlet subcooling of 5±0.2℃,saturation temperature of 33℃,mass fluxes of 346 and 485 kg/m2·s,and a range of heat fluxes.Key findings reveal that the sintered porous microstructure significantly enhances bubble nucleation,reducing the wall superheat required for the onset of nucleate boiling(ONB)to only 0.13℃ compared to 2.2℃ in smooth channels.The porous structure also improves heat transfer coefficients at low and medium heat fluxes(<20–30 W/cm^(2))and low vapor quality(x<0.2–0.4)due to augmented thin-film evaporation and intensified nucleate boiling.However,smooth microchannels exhibit superior performance under high heat flux and high vapor quality conditions,as the porous structure is prone to early dry-out and flow blockage.Notably,the porous microchannels demonstrate lower flow resistance and enhanced stability,with pressure drop fluctuations reduced by up to 46.4%in amplitude and 44.8%in standard deviation,attributed to improved capillary-assisted liquid replenishment and suppressed flow oscillations.The results underscore the potential of PP-MCs as a high-performance cooling solution for high-heat-flux applications.展开更多
The multiphoton ionization dissociation of HFC 152a and HFC 134a under the irradiation of 355 nm and 266 nm was studied in this work. Their photolyzed products were analyzed by time of flight mass spectrum instrument....The multiphoton ionization dissociation of HFC 152a and HFC 134a under the irradiation of 355 nm and 266 nm was studied in this work. Their photolyzed products were analyzed by time of flight mass spectrum instrument. The photolyzed products of HFC 152a include H +( m/z =1), C +( m/z =12), CH + 3( m/z =15), C + 2( m/z =24), CF 2H +( m/z =51), and CF +( m/z =31), whereas there is no clear products for HFC 134a photolyzation. Further, the application prospects of HFC 152a and HFC 134a in refrigeration sector were also evaluated from the view point of environmental protection, synthesis conditions and usage performance. It is suggested that HFC 152a is a better alternative compared to HFC 134a in refrigeration sector.展开更多
基金ported by the Beijing Municipal Science&Technology Commission(Z231100006123010)Guizhou Provincial Major Scientific and Technological Program(XKBF(2025)031)a grant from Tianjin Key Laboratory of Refrigeration Technology(2025TKLRT002).
文摘This experimental investigation was conducted on the flow boiling performance of refrigerant R134a in two types of parallel microchannels:sintered porous microchannels(PP-MCs)and smooth parallel microchannels(SP-MCs).The tests were performed under controlled conditions including an inlet subcooling of 5±0.2℃,saturation temperature of 33℃,mass fluxes of 346 and 485 kg/m2·s,and a range of heat fluxes.Key findings reveal that the sintered porous microstructure significantly enhances bubble nucleation,reducing the wall superheat required for the onset of nucleate boiling(ONB)to only 0.13℃ compared to 2.2℃ in smooth channels.The porous structure also improves heat transfer coefficients at low and medium heat fluxes(<20–30 W/cm^(2))and low vapor quality(x<0.2–0.4)due to augmented thin-film evaporation and intensified nucleate boiling.However,smooth microchannels exhibit superior performance under high heat flux and high vapor quality conditions,as the porous structure is prone to early dry-out and flow blockage.Notably,the porous microchannels demonstrate lower flow resistance and enhanced stability,with pressure drop fluctuations reduced by up to 46.4%in amplitude and 44.8%in standard deviation,attributed to improved capillary-assisted liquid replenishment and suppressed flow oscillations.The results underscore the potential of PP-MCs as a high-performance cooling solution for high-heat-flux applications.
文摘The multiphoton ionization dissociation of HFC 152a and HFC 134a under the irradiation of 355 nm and 266 nm was studied in this work. Their photolyzed products were analyzed by time of flight mass spectrum instrument. The photolyzed products of HFC 152a include H +( m/z =1), C +( m/z =12), CH + 3( m/z =15), C + 2( m/z =24), CF 2H +( m/z =51), and CF +( m/z =31), whereas there is no clear products for HFC 134a photolyzation. Further, the application prospects of HFC 152a and HFC 134a in refrigeration sector were also evaluated from the view point of environmental protection, synthesis conditions and usage performance. It is suggested that HFC 152a is a better alternative compared to HFC 134a in refrigeration sector.
