Nowadays,the limits on greenhouse gas emissions are becoming increasingly stringent.In present research,a two-dimensional numerical model was established to simulate the deep removal of 1,1,1,2-tetrafluoroethane(R134a...Nowadays,the limits on greenhouse gas emissions are becoming increasingly stringent.In present research,a two-dimensional numerical model was established to simulate the deep removal of 1,1,1,2-tetrafluoroethane(R134a)from the non-condensable gas(NCG)mixture by cryogenic condensation and de-sublimation.The wall condensation method was compiled into the Fluent software to calculate the condensation of R134a from the gas mixture.Besides,the saturated thermodynamic properties of R134a under its triple point were extrapolated by the equation of state.The simulation of the steam condensation with NCG was conducted to verify the validity of the model,the results matched well with the experimental data.Subsequently,the condensation characteristics of R134a with NCG and the thermodynamic parameters affecting condensation were studied.The results show that the section with relatively higher removal efficiency is usually near the inlet.The cold wall temperature has a great influence on the R134a removal performance,e.g.,a 15 K reduction of the wall temperature brings a reduction in the outlet R134a molar fraction by 85.43%.The effect of changing mass flow rate on R134a removal is mainly reflected at the outlet,where an increase in mass flow rate of 12.6% can aggravate the outlet molar fraction to 210.3% of the original.The research can provide a valuable reference for the simulation of the deep removal of various low-concentration gas using condensation and de-sublimation methods.展开更多
The Enhanced Geothermal System(EGS) is a recognized geothermal exploitation system for hot dry rock(HDR), which is a rich resource in China. In this study, a numerical simulation method is used to study the effects of...The Enhanced Geothermal System(EGS) is a recognized geothermal exploitation system for hot dry rock(HDR), which is a rich resource in China. In this study, a numerical simulation method is used to study the effects of geothermal fluid dryness and non-condensable gas content on the specific enthalpy of geothermal fluid. Combined with the organic Rankine cycle(ORC), a numerical model is established to ascertain the difference in power generation caused by geothermal fluid dryness and non-condensable gas content. The results show that the specific enthalpy of geothermal fluid increases with the increase of geothermal fluid temperature and geothermal fluid dryness. If the dryness of geothermal fluid is ignored, the estimation error will be large for geothermal fluid enthalpy. Ignoring non condensable gas will increase the estimation of geothermal fluid enthalpy, so the existence of the non-condensable gas tends to reduce the installed capacity of a geothermal power plant. Additionally, both mass flow of the working medium and net power output of the ORC power generation system are increased with increasing dryness of geothermal fluid, however there is some impact of geothermal fluid dryness on thermal efficiency.展开更多
A multicomponent thermal multi-relaxation-time(MRT)lattice Boltzmann method(LBM)is presented to study collapsing cavitation bubble.The simulation results satisfy Laplace law and the adiabatic law,and are consistent wi...A multicomponent thermal multi-relaxation-time(MRT)lattice Boltzmann method(LBM)is presented to study collapsing cavitation bubble.The simulation results satisfy Laplace law and the adiabatic law,and are consistent with the numerical solution of the Rayleigh-Plesset equation.To study the effects of the non-condensable gas inside bubble on collapsing cavitation bubble,a numerical model of single spherical bubble near a solid wall is established.The temperature and pressure evolution of the two-component two-phase flow are well captured.In addition,the collapse process of the cavitation bubble is discussed elaborately by setting the volume fractions of the gas and vapor to be the only variables.The results show that the non-condensable gas in the bubble significantly affects the pressure field,temperature field evolution,collapse velocity,and profile of the bubble.The distinction of the pressure and temperature on the wall after the second collapse becomes more obvious as the non-condensable gas concentration increases.展开更多
We have developed a loop thermosyphon for cooling electronic devices. The cooling performance of a thermosyphon deteriorates with an increasing amount of non-condensable gas (NCG). Design of a thermosyphon must consid...We have developed a loop thermosyphon for cooling electronic devices. The cooling performance of a thermosyphon deteriorates with an increasing amount of non-condensable gas (NCG). Design of a thermosyphon must consider NCG to provide guaranteed performance for a long time. In this study, the heat transfer performance of a thermosyphon was measured while changing the amount of NCG. The resultant performances were expressed as approximations. These approximations enabled us to predict the total thermal resistance of the thermosyphon by the amount of NCG and input heating. Then, using the known leakage in the thermosyphon and the amount of dissolved NCG in the water, we can predict the amount of NCG and the total thermal resistance of the thermosyphon after ten years. Although there is a slight leakage in the thermosyphon, we are able to design a thermosyphon with a guaranteed level of cooling performance for a long time using the proposed design method.展开更多
This paper utilizes numerical analysis method to determine the influence of non-condensation gas on the thermal performance of a heat pipe. The temperature difference between the evaporation and condensation sections ...This paper utilizes numerical analysis method to determine the influence of non-condensation gas on the thermal performance of a heat pipe. The temperature difference between the evaporation and condensation sections of a single heat pipe and maximum heat capacity are the index of the thermal performance of a heat pipe for a thermal module manufacturer. The thermal performance of a heat pipe with lower temperature difference between the evaporation and condensation sections is better than that of higher temperature dif- ference at the same input power. The results show that the maximum heat capacity reaches the highest point, as the amount of the non-condensation gas of a heat pipe is the lowest value and the temperature difference between evaporation and condensation sections is the smallest one. The temperature difference is under 1?C while the percentage of the non-condensation gas is under 8 × 10?5%, and the heat pipe has the maximum heat capacity.展开更多
Searching for alternative energy sources continues to grow in recent times due to the fear of energy insecurity in the near future and environmental and sociopolitical issues associated with the use of fossil fuel. Am...Searching for alternative energy sources continues to grow in recent times due to the fear of energy insecurity in the near future and environmental and sociopolitical issues associated with the use of fossil fuel. Among the renewable energy sources, biomass is the only source that has carbon in its building blocks which can be processed to liquid fuel. In this study, pyrolysis of oil palm residues (trunk, frond and empty fruit bunch) was carried out in a fixed bed tubular reactor under nitrogen atmosphere at 30 mL/min, 30?C/min heating rate and 600?C reaction temperature. Pyrolysis products (bio-oil, bio-char and non-condensable gas) were characterized. Water content, acidity (pH), higher heating value (HHV) and oxygen content of the bio-oil varied between 39.28 - 43 wt%, 2.92 - 3.20, 19.29 - 21.92 MJ/kg and 58.47 - 59.85 wt% respectively. Low pH, highwater and oxygen contents in the oil make it unsuitable for being used as fuel and therefore require upgrading. Scanning electron microscopy and ultimate analysis of the bio-char suggests that it is a porous material and consists mainly carbon between 82.22 - 84.96 wt% and has HHV in the range of 25.98 - 27.65 MJ/kg. This may be used as solid biofuel, adsorbent and source of carbon. High percentage of hydrogen (H2) and carbon monoxide (CO) were observed in the non-condensable gas which may be processed to transportation fuel via Fisher-Tropsch process. Oil palm residues represent good source of renewable energy when all the pyrolysis products are efficiently utilized.展开更多
Geothermal power plants(GPP)with high non condensable gases(NCG)content geothermal fluid have shown to be environmental impacting relating to their energy production,which could be critical if no corrective actions ar...Geothermal power plants(GPP)with high non condensable gases(NCG)content geothermal fluid have shown to be environmental impacting relating to their energy production,which could be critical if no corrective actions are achieved.The GPP of Kizildere 3 U1,located in Türkiye(Denizli),in where the geothermal fluid contains high percentage of CO_(2),99%of the NCG fraction,which represents the 3%of the geothermal fluid mass,is taken as a relevant case study to implement a new innovation consisting of NCG reinjection to reduce the amount of NCGs released to the atmosphere.In order to calculate the present environmental impacts which the plant is causing(baseline);and the potential reduction of environmental impacts which can be achieved with the innovation(reinjection),a life cycle assessment(LCA)calculation were developed.Primary data were collected for all the relevant stages of the energy conversion cycle and complemented where necessary with secondary data from other geothermal power plants studies.The main results of the baseline environmental assessment show that the construction phase is the most impacting phase due to the materials used in the power plant building construction,electrical generation equipment and distributed machinery and infrastructures;the effects in the operation phase are dominated by the geothermal fluid composition.In this sense,the application of CO_(2) reinjection at the Turkish site into the reservoir will prevent the emission of 1,700 tons⋅year1 in the pilot site and 10%of the total emissions released along the life span of the GPP.展开更多
In many heat recovery processes,temperature control of heat source is often required to ensure safety and high efficiency of the heat source equipment.In addition,the management of recovered heat is important for the ...In many heat recovery processes,temperature control of heat source is often required to ensure safety and high efficiency of the heat source equipment.In addition,the management of recovered heat is important for the proper use of waste heat.To this aim,the concept of thermal management controller(TMC),which can vary heat transfer rate via the volume variation of non-condensable gas,was presented.Theoretical model and experimental prototype were established.Investigation shows that the prototype is effective in temperature control With water as the working fluid,the vapor temperature variation is only 1.3℃when the heating power varies from 2.5 to 10.0 kW.In variable working conditions,this TMC can automatically adjust thermal allocation to the heat consumer.展开更多
Condensation is a phase-change heat-transfer phenomenon crucial in many industries involving latent heat release and mass transfer.Shell-and-tube condensers are essential contributors to the condensation process,and t...Condensation is a phase-change heat-transfer phenomenon crucial in many industries involving latent heat release and mass transfer.Shell-and-tube condensers are essential contributors to the condensation process,and their tube bundles serve as a substrate.Here,the thermal-hydraulic characteristics of condensation in a longitudinal-flow shell-and-tube condenser were investigated numerically.The shell-side longitudinal-flow condensation on the horizontal tube bundles was studied considering inlet flow rate,overheating temperature,and non-condensable gases.Related pressure drops and heat transfer coefficients were subdivided into several components to provide further insights.Two-phase interface behavior analyses were conducted to demonstrate the outcomes with respect to the non-condensable gas layer,vapor quality,and non-condensable gas type.Based on the thorough quantitative analyses outlined above,the thermal resistance of the condensation on the horizontal tube bundle was investigated.The thermal resistance outside the tube was found to dominate the condensation process.Finally,hexagon clamping baffles(HCBs)were introduced as a novel solution to impair condensate boundary layers and provide perturbations to intensify condensation heat transfer.The results revealed that the HCBs enhanced the total heat transfer coefficients by 8.1%–40.7%while reducing the critical overheating temperature and the threshold ratio between sensible and latent heat.展开更多
Indirect evaporative cooling(IEC)is a kind of high efficiency,energy-saving and environmental protection cooling technology,which has been widely used in data centers and other fields in recent years.In this paper,the...Indirect evaporative cooling(IEC)is a kind of high efficiency,energy-saving and environmental protection cooling technology,which has been widely used in data centers and other fields in recent years.In this paper,the optimized two-dimensional non-condensation state model of indirect evaporative cooling was proposed.Meanwhile the computer program was updated to solve the developed mathematical model under variable fresh air conditions.The optimized model was verified by the experimental data,and the maximum deviation was only 4.6%.Based on the modified model and the annual hourly meteorological parameters in Tianjin,China,it was analyzed the optimal heat transfer area of IEC used as fresh air pre-cooling unit under various air volumes to provide references for system design and equipment selection.Finally,taking an IEC-primary return air conditioning system of a gymnasium as an example,the hourly energy-saving effect of whole year was simulated by the developed IEC model.The simulation results showed that IEC could control the fresh air temperature below 27℃ and the moisture content below 18 g/kg throughout the year,and undertook 102.6% of the total fresh air cooling load.The findings are useful in future system optimization and design of IEC equipment.展开更多
基金funded by the National Natural Science Foundation of China(52076159)。
文摘Nowadays,the limits on greenhouse gas emissions are becoming increasingly stringent.In present research,a two-dimensional numerical model was established to simulate the deep removal of 1,1,1,2-tetrafluoroethane(R134a)from the non-condensable gas(NCG)mixture by cryogenic condensation and de-sublimation.The wall condensation method was compiled into the Fluent software to calculate the condensation of R134a from the gas mixture.Besides,the saturated thermodynamic properties of R134a under its triple point were extrapolated by the equation of state.The simulation of the steam condensation with NCG was conducted to verify the validity of the model,the results matched well with the experimental data.Subsequently,the condensation characteristics of R134a with NCG and the thermodynamic parameters affecting condensation were studied.The results show that the section with relatively higher removal efficiency is usually near the inlet.The cold wall temperature has a great influence on the R134a removal performance,e.g.,a 15 K reduction of the wall temperature brings a reduction in the outlet R134a molar fraction by 85.43%.The effect of changing mass flow rate on R134a removal is mainly reflected at the outlet,where an increase in mass flow rate of 12.6% can aggravate the outlet molar fraction to 210.3% of the original.The research can provide a valuable reference for the simulation of the deep removal of various low-concentration gas using condensation and de-sublimation methods.
基金support provided by the National Key Research and Development Program of China(Grant No.2018YFB1501805)the National Natural Science Foundation of China(Grant No.52176183)。
文摘The Enhanced Geothermal System(EGS) is a recognized geothermal exploitation system for hot dry rock(HDR), which is a rich resource in China. In this study, a numerical simulation method is used to study the effects of geothermal fluid dryness and non-condensable gas content on the specific enthalpy of geothermal fluid. Combined with the organic Rankine cycle(ORC), a numerical model is established to ascertain the difference in power generation caused by geothermal fluid dryness and non-condensable gas content. The results show that the specific enthalpy of geothermal fluid increases with the increase of geothermal fluid temperature and geothermal fluid dryness. If the dryness of geothermal fluid is ignored, the estimation error will be large for geothermal fluid enthalpy. Ignoring non condensable gas will increase the estimation of geothermal fluid enthalpy, so the existence of the non-condensable gas tends to reduce the installed capacity of a geothermal power plant. Additionally, both mass flow of the working medium and net power output of the ORC power generation system are increased with increasing dryness of geothermal fluid, however there is some impact of geothermal fluid dryness on thermal efficiency.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874140 and 11574072)the State Key Laboratory of Acoustics,Chinese Academy of Sciences(Grant No.SKLA201913)+3 种基金the National Key Research and Development Program of China(Grant No.2016YFC0401600)the Primary Research and Development Plan of Jiangsu Province,China(Grant No.BE2016056)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant Nos.2018B741X14 and KYCX180552)the Postgraduate Research&Practice Innovation Program of Changzhou Campus,Hohai University,China(Grant No.17B01110)。
文摘A multicomponent thermal multi-relaxation-time(MRT)lattice Boltzmann method(LBM)is presented to study collapsing cavitation bubble.The simulation results satisfy Laplace law and the adiabatic law,and are consistent with the numerical solution of the Rayleigh-Plesset equation.To study the effects of the non-condensable gas inside bubble on collapsing cavitation bubble,a numerical model of single spherical bubble near a solid wall is established.The temperature and pressure evolution of the two-component two-phase flow are well captured.In addition,the collapse process of the cavitation bubble is discussed elaborately by setting the volume fractions of the gas and vapor to be the only variables.The results show that the non-condensable gas in the bubble significantly affects the pressure field,temperature field evolution,collapse velocity,and profile of the bubble.The distinction of the pressure and temperature on the wall after the second collapse becomes more obvious as the non-condensable gas concentration increases.
文摘We have developed a loop thermosyphon for cooling electronic devices. The cooling performance of a thermosyphon deteriorates with an increasing amount of non-condensable gas (NCG). Design of a thermosyphon must consider NCG to provide guaranteed performance for a long time. In this study, the heat transfer performance of a thermosyphon was measured while changing the amount of NCG. The resultant performances were expressed as approximations. These approximations enabled us to predict the total thermal resistance of the thermosyphon by the amount of NCG and input heating. Then, using the known leakage in the thermosyphon and the amount of dissolved NCG in the water, we can predict the amount of NCG and the total thermal resistance of the thermosyphon after ten years. Although there is a slight leakage in the thermosyphon, we are able to design a thermosyphon with a guaranteed level of cooling performance for a long time using the proposed design method.
文摘This paper utilizes numerical analysis method to determine the influence of non-condensation gas on the thermal performance of a heat pipe. The temperature difference between the evaporation and condensation sections of a single heat pipe and maximum heat capacity are the index of the thermal performance of a heat pipe for a thermal module manufacturer. The thermal performance of a heat pipe with lower temperature difference between the evaporation and condensation sections is better than that of higher temperature dif- ference at the same input power. The results show that the maximum heat capacity reaches the highest point, as the amount of the non-condensation gas of a heat pipe is the lowest value and the temperature difference between evaporation and condensation sections is the smallest one. The temperature difference is under 1?C while the percentage of the non-condensation gas is under 8 × 10?5%, and the heat pipe has the maximum heat capacity.
文摘Searching for alternative energy sources continues to grow in recent times due to the fear of energy insecurity in the near future and environmental and sociopolitical issues associated with the use of fossil fuel. Among the renewable energy sources, biomass is the only source that has carbon in its building blocks which can be processed to liquid fuel. In this study, pyrolysis of oil palm residues (trunk, frond and empty fruit bunch) was carried out in a fixed bed tubular reactor under nitrogen atmosphere at 30 mL/min, 30?C/min heating rate and 600?C reaction temperature. Pyrolysis products (bio-oil, bio-char and non-condensable gas) were characterized. Water content, acidity (pH), higher heating value (HHV) and oxygen content of the bio-oil varied between 39.28 - 43 wt%, 2.92 - 3.20, 19.29 - 21.92 MJ/kg and 58.47 - 59.85 wt% respectively. Low pH, highwater and oxygen contents in the oil make it unsuitable for being used as fuel and therefore require upgrading. Scanning electron microscopy and ultimate analysis of the bio-char suggests that it is a porous material and consists mainly carbon between 82.22 - 84.96 wt% and has HHV in the range of 25.98 - 27.65 MJ/kg. This may be used as solid biofuel, adsorbent and source of carbon. High percentage of hydrogen (H2) and carbon monoxide (CO) were observed in the non-condensable gas which may be processed to transportation fuel via Fisher-Tropsch process. Oil palm residues represent good source of renewable energy when all the pyrolysis products are efficiently utilized.
文摘Geothermal power plants(GPP)with high non condensable gases(NCG)content geothermal fluid have shown to be environmental impacting relating to their energy production,which could be critical if no corrective actions are achieved.The GPP of Kizildere 3 U1,located in Türkiye(Denizli),in where the geothermal fluid contains high percentage of CO_(2),99%of the NCG fraction,which represents the 3%of the geothermal fluid mass,is taken as a relevant case study to implement a new innovation consisting of NCG reinjection to reduce the amount of NCGs released to the atmosphere.In order to calculate the present environmental impacts which the plant is causing(baseline);and the potential reduction of environmental impacts which can be achieved with the innovation(reinjection),a life cycle assessment(LCA)calculation were developed.Primary data were collected for all the relevant stages of the energy conversion cycle and complemented where necessary with secondary data from other geothermal power plants studies.The main results of the baseline environmental assessment show that the construction phase is the most impacting phase due to the materials used in the power plant building construction,electrical generation equipment and distributed machinery and infrastructures;the effects in the operation phase are dominated by the geothermal fluid composition.In this sense,the application of CO_(2) reinjection at the Turkish site into the reservoir will prevent the emission of 1,700 tons⋅year1 in the pilot site and 10%of the total emissions released along the life span of the GPP.
基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20040248055)the Education Ministry Key Investigation Project of Science and Technology(No.306004)
文摘In many heat recovery processes,temperature control of heat source is often required to ensure safety and high efficiency of the heat source equipment.In addition,the management of recovered heat is important for the proper use of waste heat.To this aim,the concept of thermal management controller(TMC),which can vary heat transfer rate via the volume variation of non-condensable gas,was presented.Theoretical model and experimental prototype were established.Investigation shows that the prototype is effective in temperature control With water as the working fluid,the vapor temperature variation is only 1.3℃when the heating power varies from 2.5 to 10.0 kW.In variable working conditions,this TMC can automatically adjust thermal allocation to the heat consumer.
基金financial support for this work provided by Natural Science Foundation of China(No.51876146)the Excellent Youth Foundation of Hubei Scientific Committee(No.2019CFA082)the Opening Funds of the Key Lab on Steam Power System(TPL2018B01)。
文摘Condensation is a phase-change heat-transfer phenomenon crucial in many industries involving latent heat release and mass transfer.Shell-and-tube condensers are essential contributors to the condensation process,and their tube bundles serve as a substrate.Here,the thermal-hydraulic characteristics of condensation in a longitudinal-flow shell-and-tube condenser were investigated numerically.The shell-side longitudinal-flow condensation on the horizontal tube bundles was studied considering inlet flow rate,overheating temperature,and non-condensable gases.Related pressure drops and heat transfer coefficients were subdivided into several components to provide further insights.Two-phase interface behavior analyses were conducted to demonstrate the outcomes with respect to the non-condensable gas layer,vapor quality,and non-condensable gas type.Based on the thorough quantitative analyses outlined above,the thermal resistance of the condensation on the horizontal tube bundle was investigated.The thermal resistance outside the tube was found to dominate the condensation process.Finally,hexagon clamping baffles(HCBs)were introduced as a novel solution to impair condensate boundary layers and provide perturbations to intensify condensation heat transfer.The results revealed that the HCBs enhanced the total heat transfer coefficients by 8.1%–40.7%while reducing the critical overheating temperature and the threshold ratio between sensible and latent heat.
基金This research is financially supported by the National Natural Science Foundation of China(No.51678385).
文摘Indirect evaporative cooling(IEC)is a kind of high efficiency,energy-saving and environmental protection cooling technology,which has been widely used in data centers and other fields in recent years.In this paper,the optimized two-dimensional non-condensation state model of indirect evaporative cooling was proposed.Meanwhile the computer program was updated to solve the developed mathematical model under variable fresh air conditions.The optimized model was verified by the experimental data,and the maximum deviation was only 4.6%.Based on the modified model and the annual hourly meteorological parameters in Tianjin,China,it was analyzed the optimal heat transfer area of IEC used as fresh air pre-cooling unit under various air volumes to provide references for system design and equipment selection.Finally,taking an IEC-primary return air conditioning system of a gymnasium as an example,the hourly energy-saving effect of whole year was simulated by the developed IEC model.The simulation results showed that IEC could control the fresh air temperature below 27℃ and the moisture content below 18 g/kg throughout the year,and undertook 102.6% of the total fresh air cooling load.The findings are useful in future system optimization and design of IEC equipment.
