The experiments of the onset of nucleate boiling using R134a as working fluid were conducted in vertical helically-coiled tubes. The experiments were carried out with a range of pressure from 450 to 850 kPa, inlet sub...The experiments of the onset of nucleate boiling using R134a as working fluid were conducted in vertical helically-coiled tubes. The experiments were carried out with a range of pressure from 450 to 850 kPa, inlet subcooling from 4.7 to 15.0℃, heat flux from 0.11 to 8.9 kW/m2 and mass flux from 218. 2 to 443. 7 kg/（ m2 · s ）. The heat flux, superheat and temperature undershoot at the ONB are analyzed in vertical helically-coiled tubes. Also, the effects of mass flux, system pressure, inlet subcooling and geometric parameters on the ONB are studied. The results demonstrate that the inception heat flux and superheat increase with increasing mass flux and inlet subcooling, but decrease with increasing system pressure and helix diameter. The pitch of the helical coil has a slight effect on the wall superheat and heat flux at the ONB. The correlation of heat flux at the ONB of subcooled flow boiling in helical coil is developed based on the experimental data, and it shows a good agreement with the experimental data.展开更多
The amount of waste heat in a space facility became larger, because of increase in the space platform size and its power consumption. It requires development of high-performance space thermal management systems handli...The amount of waste heat in a space facility became larger, because of increase in the space platform size and its power consumption. It requires development of high-performance space thermal management systems handling a large amount of waste. Boiling two-phase flow could become powerful means for this system because a boiling and condensation system is one of the most efficient modes of heat transfer due to phase change （liquid-vapor）. However, gravity effects on boiling two-phase flow phenomena and the corresponding heat transfer characteristics are not clear. Therefore, we prepare the experiments of boiling two-phase flow utilizing a long-term microgravity environment onboard a Japanese Experimental Module ＂KIBO＂ in the International Space Station （ISS） as one of the JAXA official projects. In this paper, recent progress of the preparation for the project is reported.展开更多
A space experiment on bubble behavior and heat transfer in subcooled pool boiling phenomenon has been performedutilizing the temperature-controlled pool boiling (TCPB) device both in normal gravity in the laboratoryan...A space experiment on bubble behavior and heat transfer in subcooled pool boiling phenomenon has been performedutilizing the temperature-controlled pool boiling (TCPB) device both in normal gravity in the laboratoryand in microgravity aboard the 22^(nd) Chinese recoverable satellite. The fluid is degassed R113 at 0.1 MPa andsubcooled by 26℃ nominally. A thin platinum wire of 60 μm in diameter and 30 mm in length is simultaneouslyused as heater and thermometer. Only the dynamics of the vapor bubbles, particularly the lateral motion and thedeparture of discrete vapor bubbles in nucleate pool boiling are reported and analyzed in the present paper. It'sfound that these distinct behaviors can be explained by the Marangoni convection in the liquid surrounding vaporbubbles. The origin of the Marangoni effect is also discussed.展开更多
Boiling flow instability of nitrogen in a vertical tube is experimentally investigated in the present study. The experiments reveal that pressure has a significant effect on the characteristics of the heat flux-mass f...Boiling flow instability of nitrogen in a vertical tube is experimentally investigated in the present study. The experiments reveal that pressure has a significant effect on the characteristics of the heat flux-mass flux type boiling flow instability.First.the pressure has strong effects on both the developing time and the fluctuation amplitude.Especially increasing pressure leads to decrease the fluctuating amplitude of mass flux.Then,the mass flux evolving curves under different pressures feature out a shape like a leaf.The characteristics of the heat flux-mass flux type boiling flow instability under lower pressure are very complicated,however,with increasing pressure,this type of instability is gradually suppressed.展开更多
基金The National Natural Science Foundation of China(No.50776055,51076084)the Natural Science Foundation of Shandong Province(No.ZR2016YL005)
文摘The experiments of the onset of nucleate boiling using R134a as working fluid were conducted in vertical helically-coiled tubes. The experiments were carried out with a range of pressure from 450 to 850 kPa, inlet subcooling from 4.7 to 15.0℃, heat flux from 0.11 to 8.9 kW/m2 and mass flux from 218. 2 to 443. 7 kg/（ m2 · s ）. The heat flux, superheat and temperature undershoot at the ONB are analyzed in vertical helically-coiled tubes. Also, the effects of mass flux, system pressure, inlet subcooling and geometric parameters on the ONB are studied. The results demonstrate that the inception heat flux and superheat increase with increasing mass flux and inlet subcooling, but decrease with increasing system pressure and helix diameter. The pitch of the helical coil has a slight effect on the wall superheat and heat flux at the ONB. The correlation of heat flux at the ONB of subcooled flow boiling in helical coil is developed based on the experimental data, and it shows a good agreement with the experimental data.
文摘The amount of waste heat in a space facility became larger, because of increase in the space platform size and its power consumption. It requires development of high-performance space thermal management systems handling a large amount of waste. Boiling two-phase flow could become powerful means for this system because a boiling and condensation system is one of the most efficient modes of heat transfer due to phase change （liquid-vapor）. However, gravity effects on boiling two-phase flow phenomena and the corresponding heat transfer characteristics are not clear. Therefore, we prepare the experiments of boiling two-phase flow utilizing a long-term microgravity environment onboard a Japanese Experimental Module ＂KIBO＂ in the International Space Station （ISS） as one of the JAXA official projects. In this paper, recent progress of the preparation for the project is reported.
基金supported financially by the Na tional Natural Science Foundation of China under the grant of 10432060 the Chinese Academy of Sci ences under the grant of KJCX2-SW-L05.
文摘A space experiment on bubble behavior and heat transfer in subcooled pool boiling phenomenon has been performedutilizing the temperature-controlled pool boiling (TCPB) device both in normal gravity in the laboratoryand in microgravity aboard the 22^(nd) Chinese recoverable satellite. The fluid is degassed R113 at 0.1 MPa andsubcooled by 26℃ nominally. A thin platinum wire of 60 μm in diameter and 30 mm in length is simultaneouslyused as heater and thermometer. Only the dynamics of the vapor bubbles, particularly the lateral motion and thedeparture of discrete vapor bubbles in nucleate pool boiling are reported and analyzed in the present paper. It'sfound that these distinct behaviors can be explained by the Marangoni convection in the liquid surrounding vaporbubbles. The origin of the Marangoni effect is also discussed.
基金the Postdoctoral Scientific Foundation of China(No.20070410722)
文摘Boiling flow instability of nitrogen in a vertical tube is experimentally investigated in the present study. The experiments reveal that pressure has a significant effect on the characteristics of the heat flux-mass flux type boiling flow instability.First.the pressure has strong effects on both the developing time and the fluctuation amplitude.Especially increasing pressure leads to decrease the fluctuating amplitude of mass flux.Then,the mass flux evolving curves under different pressures feature out a shape like a leaf.The characteristics of the heat flux-mass flux type boiling flow instability under lower pressure are very complicated,however,with increasing pressure,this type of instability is gradually suppressed.
