通过对单效蒸发、热力蒸汽再压缩(TVR)蒸发和机械蒸汽再压缩(MVR)蒸发过程进行分析,提出了生蒸汽耗量模型。以5400 kg/h Na OH溶液的蒸发浓缩为工程实例,对单效蒸发、TVR蒸发和MVR蒸发进行能耗对比分析,结果表明,TVR蒸发和MVR蒸发能耗...通过对单效蒸发、热力蒸汽再压缩(TVR)蒸发和机械蒸汽再压缩(MVR)蒸发过程进行分析,提出了生蒸汽耗量模型。以5400 kg/h Na OH溶液的蒸发浓缩为工程实例,对单效蒸发、TVR蒸发和MVR蒸发进行能耗对比分析,结果表明,TVR蒸发和MVR蒸发能耗仅为单效蒸发能耗的78%和23.8%。展开更多
Exhaust hot water （EHW） is widely used for various industrial processes. However, the excess heat carried by EHW is typically ignored and discharged into the environment, resulting in heat loss and heat pollution. A...Exhaust hot water （EHW） is widely used for various industrial processes. However, the excess heat carried by EHW is typically ignored and discharged into the environment, resulting in heat loss and heat pollution. An organic Rankine cycle （ORC） is an attractive technology to recycle heat from low-temperature energy carriers. Herein, ORC was used to recycle the heat carried by EHW. To investigate the energy and exergy recovery effects of EHW, a mathematical model was developed and a parametric study was conducted. The energy efficiency and exergy efficiency of the EHW-driven ORC system were modeled with R245fa, Rl13 and R123 as the working fluids. The results demonstrate that the EHW and evaporation temperatures have significant effects on the energy and exergy efficiencies of the EHW-driven ORC system. Under given EHW conditions, an optimum evaporation temperature exists corresponding to the highest exergy efficiency. To further use the low-temperature EHW, a configuration retrofitted to the ORC by combining with flash evaporation （FE） was conducted. For an EHW at 120 ~C and 0.2 MPa, the maximum exergy efficiency of the FE-ORC system is 45.91% at a flash pressure of 0.088 MPa. The FE-ORC performs better in exergy efficiency than the basic FE and basic EHW-driven ORC.展开更多
High purity （99.999% or 5N, mass fraction） indium （In） was obtained through vacuum distillation using a 2N （99%） In as input material under a dynamic vacuum of 5 Pa. The glow discharge mass spectrometry （GDMS）...High purity （99.999% or 5N, mass fraction） indium （In） was obtained through vacuum distillation using a 2N （99%） In as input material under a dynamic vacuum of 5 Pa. The glow discharge mass spectrometry （GDMS） was applied for the analysis of input material and the distilled indium. The results indicate that high-volatile impurities namely Cd, Zn, T1 and Pb can be removed from the indium matrix at the low fraction stage of 1 223 K for 120 min; Low-volatile impurities such as Fe, Ni, Cu, Sn can be reduced at the high fraction stage of 1 323 K for 120 min. The separation coefficient ,8i and activity coefficient Yi of impurities are calculated according to the experiments to fill the inadequate data of the thermodynamics.展开更多
Refrigeration coefficient, ε, is usually calculated by using the First Law of Thermodynamics. In this paper, a new derivation process is introduced through the combination of the Second Law of Thermodynamics with the...Refrigeration coefficient, ε, is usually calculated by using the First Law of Thermodynamics. In this paper, a new derivation process is introduced through the combination of the Second Law of Thermodynamics with the First Law of Thermodynamics. As a result, two new calculation equations for refrigeration coefficient are proposed. One equation is equivalent to the common method, but its form is a little complicated for real calculation. Another equation is the further simplification, and can be used to calculate the refrigeration coefficient instead of common method with a oermit error.展开更多
When a liquid undergoes sudden reduction in the surrounding pressure below its saturation pressure, the liquid then enters in a metastable state. In order to regain equilibrium, part of the liquid evaporates quickly i...When a liquid undergoes sudden reduction in the surrounding pressure below its saturation pressure, the liquid then enters in a metastable state. In order to regain equilibrium, part of the liquid evaporates quickly in a phenomenon called ＂flash evaporation＂, and the excess sensible heat contained in the liquid is converted into latent heat of vaporization. Therefore, temperatures of both the liquid and the generated vapor decline to the saturation temperature for the reduced pressure. As the heat and mass transfer occur in direct contact between the liquid and its own vapors, the process involves a very high heat transfer rate which makes it suitable for exchanging heat between sources of relatively small temperature difference. Moreover, dispensability of the heat exchange surfaces in this process is a considerable advantage as these surfaces constitute major part of the total system expenses in addition to the associated maintenance problems, especially when dealing with corrosive fluids such like seawater in the thermal desalination processes and in the OTEC （ocean thermal energy conversion） systems. This paper reports on the heat flux variation profiles during the flash evaporation of superheated water jets at various flow conditions. Heat flax was found to grow with time attaining a peak value before it starts to decrease monotonically.展开更多
The pinch point is important for analyzing heat transfer in thermodynamic cycles. With the aim to reveal the importance of determining the accurate pinch point, the research on the pinch point position is carried out ...The pinch point is important for analyzing heat transfer in thermodynamic cycles. With the aim to reveal the importance of determining the accurate pinch point, the research on the pinch point position is carried out by theoretical method. The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties. In most cases, the pinch point locates at the bubble point for the evaporator and the dew point for the condenser. However, the pinch point shills to the supercooled liquid state in the near critical conditions for the evaporator. Similarly, it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser. It even can shift to the working fluid entrance of the evaporator or the supereritical heater when the heat source fluid temperature is very high compared with the absorb- ing heat temperature. A wrong position for the pinch point may generate serious mistake. In brief, the pinch point should be founded by the itcrativc method in all conditions rather than taking for granted.展开更多
基金Projects（51704069, 51734004, 71403175） supported by the National Natural Science Foundation of China Project（N162504011） supported by the Fundamental Research Funds for the Central Universities, China
文摘Exhaust hot water （EHW） is widely used for various industrial processes. However, the excess heat carried by EHW is typically ignored and discharged into the environment, resulting in heat loss and heat pollution. An organic Rankine cycle （ORC） is an attractive technology to recycle heat from low-temperature energy carriers. Herein, ORC was used to recycle the heat carried by EHW. To investigate the energy and exergy recovery effects of EHW, a mathematical model was developed and a parametric study was conducted. The energy efficiency and exergy efficiency of the EHW-driven ORC system were modeled with R245fa, Rl13 and R123 as the working fluids. The results demonstrate that the EHW and evaporation temperatures have significant effects on the energy and exergy efficiencies of the EHW-driven ORC system. Under given EHW conditions, an optimum evaporation temperature exists corresponding to the highest exergy efficiency. To further use the low-temperature EHW, a configuration retrofitted to the ORC by combining with flash evaporation （FE） was conducted. For an EHW at 120 ~C and 0.2 MPa, the maximum exergy efficiency of the FE-ORC system is 45.91% at a flash pressure of 0.088 MPa. The FE-ORC performs better in exergy efficiency than the basic FE and basic EHW-driven ORC.
基金Project(2009AA003) supported by Science and Technology Innovation Plan of Yunnan Province, China
文摘High purity （99.999% or 5N, mass fraction） indium （In） was obtained through vacuum distillation using a 2N （99%） In as input material under a dynamic vacuum of 5 Pa. The glow discharge mass spectrometry （GDMS） was applied for the analysis of input material and the distilled indium. The results indicate that high-volatile impurities namely Cd, Zn, T1 and Pb can be removed from the indium matrix at the low fraction stage of 1 223 K for 120 min; Low-volatile impurities such as Fe, Ni, Cu, Sn can be reduced at the high fraction stage of 1 323 K for 120 min. The separation coefficient ,8i and activity coefficient Yi of impurities are calculated according to the experiments to fill the inadequate data of the thermodynamics.
基金Supported by Shanghai Leading Academic Displine Project(No.B604)
文摘Refrigeration coefficient, ε, is usually calculated by using the First Law of Thermodynamics. In this paper, a new derivation process is introduced through the combination of the Second Law of Thermodynamics with the First Law of Thermodynamics. As a result, two new calculation equations for refrigeration coefficient are proposed. One equation is equivalent to the common method, but its form is a little complicated for real calculation. Another equation is the further simplification, and can be used to calculate the refrigeration coefficient instead of common method with a oermit error.
文摘When a liquid undergoes sudden reduction in the surrounding pressure below its saturation pressure, the liquid then enters in a metastable state. In order to regain equilibrium, part of the liquid evaporates quickly in a phenomenon called ＂flash evaporation＂, and the excess sensible heat contained in the liquid is converted into latent heat of vaporization. Therefore, temperatures of both the liquid and the generated vapor decline to the saturation temperature for the reduced pressure. As the heat and mass transfer occur in direct contact between the liquid and its own vapors, the process involves a very high heat transfer rate which makes it suitable for exchanging heat between sources of relatively small temperature difference. Moreover, dispensability of the heat exchange surfaces in this process is a considerable advantage as these surfaces constitute major part of the total system expenses in addition to the associated maintenance problems, especially when dealing with corrosive fluids such like seawater in the thermal desalination processes and in the OTEC （ocean thermal energy conversion） systems. This paper reports on the heat flux variation profiles during the flash evaporation of superheated water jets at various flow conditions. Heat flax was found to grow with time attaining a peak value before it starts to decrease monotonically.
基金Project 51306198 supported by National Natural Science Foundation of China is gratefully acknowledged
文摘The pinch point is important for analyzing heat transfer in thermodynamic cycles. With the aim to reveal the importance of determining the accurate pinch point, the research on the pinch point position is carried out by theoretical method. The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties. In most cases, the pinch point locates at the bubble point for the evaporator and the dew point for the condenser. However, the pinch point shills to the supercooled liquid state in the near critical conditions for the evaporator. Similarly, it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser. It even can shift to the working fluid entrance of the evaporator or the supereritical heater when the heat source fluid temperature is very high compared with the absorb- ing heat temperature. A wrong position for the pinch point may generate serious mistake. In brief, the pinch point should be founded by the itcrativc method in all conditions rather than taking for granted.
