Liquefied natural gas(LNG) is the most economical way of transporting natural gas(NG) over long distances. Liquefaction of NG using vapor compression refrigeration system requires high operating and capital cost. Due ...Liquefied natural gas(LNG) is the most economical way of transporting natural gas(NG) over long distances. Liquefaction of NG using vapor compression refrigeration system requires high operating and capital cost. Due to lack of systematic design methods for multistage refrigeration cycles, conventional approaches to determine optimal cycle are largely trial-and-error. In this paper a novel mixed integer non-linear programming(MINLP)model is introduced to select optimal synthesis of refrigeration systems to reduce both operating and capital costs of an LNG plant. Better conceptual understanding of design improvement is illustrated on composite curve(CC) and exergetic grand composite curve(EGCC) of pinch analysis diagrams. In this method a superstructure representation of complex refrigeration system is developed to select and optimize key decision variables in refrigeration cycles(i.e. partition temperature, compression configuration, refrigeration features, refrigerant flow rate and economic trade-off). Based on this method a program(LNG-Pro) is developed which integrates VBA,Refprop and Excel MINLP Solver to automate the methodology. Design procedure is applied on a sample LNG plant to illustrate advantages of using this method which shows a 3.3% reduction in total shaft work consumption.展开更多
A steam power plant can work as a dual purpose plant for simultaneous production of steam and elec-trical power. In this paper we seek the optimum integration of a steam power plant as a source and a site utility sys-...A steam power plant can work as a dual purpose plant for simultaneous production of steam and elec-trical power. In this paper we seek the optimum integration of a steam power plant as a source and a site utility sys-tem as a sink of steam and power. Estimation for the cogeneration potential prior to the design of a central utility system for site utility systems is vital to the targets for site fuel demand as well as heat and power production. In this regard, a new cogeneration targeting procedure is proposed for integration of a steam power plant and a site utility consisting of a process plant. The new methodology seeks the optimal integration based on a new cogenera-tion targeting scheme. In addition, a modified site utility grand composite curve(SUGCC) diagram is proposed and compared to the original SUGCC. A gas fired steam power plant and a process site utility is considered in a case study. The applicability of the developed procedure is tested against other design methods(STAR? and Thermoflex software) through a case study. The proposed method gives comparable results, and the targeting method is used for optimal integration of steam levels. Identifying optimal conditions of steam levels for integration is important in the design of utility systems, as the selection of steam levels in a steam power plant and site utility for integration greatly influences the potential for cogeneration and energy recovery. The integration of steam levels of the steam power plant and the site utility system in the case study demonstrates the usefulness of the method for reducing the overall energy consumption for the site.展开更多
Photo/electro-thermal evaporation is a promising tactic for alleviating the scarcity of fresh water,but its practical application still faces many challenges such as weak photoabsorption,high vaporization enthalpy and...Photo/electro-thermal evaporation is a promising tactic for alleviating the scarcity of fresh water,but its practical application still faces many challenges such as weak photoabsorption,high vaporization enthalpy and serious water-electrolysis during photo-thermal/electrothermal evaporation.To solve these problems,inspired by black rose petal and electric heater,we report a biomimetic design of fabric for achieving efficient photothermal/electrothermal desalination.The photo/electrothermal fabric is fabricated by decorating super-hydrophilic MnO_(2)nanoplates as shell on hydrophobic carbon fiber(CF)as core via an electro-deposition method.MnO_(2)nanoplate decoration as a stone confers three fascinating features(birds):(I)the hydrophilic nature of MnO_(2)contributes to the fabric’s superhydrophilicity and decreased evaporation enthalpy(2032 kJ kg^(−1))in comparison with that(2410 kJ kg^(−1))of pure water;(II)nanoplate structure confers the light-trapping effect and thus the improved photoabsorption efficiency of 95.1%;(III)CF-core/MnO_(2)-shell structure can effectively suppress electrolysis of water and lead to good electrothermal conversion property.As a result,CF/MnO_(2)fabric-based hanging evaporator shows the high photo-thermal evaporation rate of 2.3 kg m^(−2)h^(−1)at 1 sun(1 kW m^(−2))and electrothermal evaporation rate of 5.3 kg m^(−2)h^(−1)at 3 V.Importantly,by the combined effects of 1 sun and 3 V,CF/MnO_(2)fabric achieves a striking synergetic evaporation rate of 8.5 kg m^(−2)h−1,exceeding the sum(7.5 kg m^(−2)h−1)of the individual photo-thermal and electro-thermal evaporation rates.The present high synergetic evaporation performance benefits from efficient photo/electrothermal conversion of the fabric and sufficient water-supplementation at the fiber-water interface resulting from thermosiphon effect.Thus,this study offers a novel possibility in the rational design of photo-electrothermal materials for efficient evaporation of seawater.展开更多
文摘Liquefied natural gas(LNG) is the most economical way of transporting natural gas(NG) over long distances. Liquefaction of NG using vapor compression refrigeration system requires high operating and capital cost. Due to lack of systematic design methods for multistage refrigeration cycles, conventional approaches to determine optimal cycle are largely trial-and-error. In this paper a novel mixed integer non-linear programming(MINLP)model is introduced to select optimal synthesis of refrigeration systems to reduce both operating and capital costs of an LNG plant. Better conceptual understanding of design improvement is illustrated on composite curve(CC) and exergetic grand composite curve(EGCC) of pinch analysis diagrams. In this method a superstructure representation of complex refrigeration system is developed to select and optimize key decision variables in refrigeration cycles(i.e. partition temperature, compression configuration, refrigeration features, refrigerant flow rate and economic trade-off). Based on this method a program(LNG-Pro) is developed which integrates VBA,Refprop and Excel MINLP Solver to automate the methodology. Design procedure is applied on a sample LNG plant to illustrate advantages of using this method which shows a 3.3% reduction in total shaft work consumption.
文摘A steam power plant can work as a dual purpose plant for simultaneous production of steam and elec-trical power. In this paper we seek the optimum integration of a steam power plant as a source and a site utility sys-tem as a sink of steam and power. Estimation for the cogeneration potential prior to the design of a central utility system for site utility systems is vital to the targets for site fuel demand as well as heat and power production. In this regard, a new cogeneration targeting procedure is proposed for integration of a steam power plant and a site utility consisting of a process plant. The new methodology seeks the optimal integration based on a new cogenera-tion targeting scheme. In addition, a modified site utility grand composite curve(SUGCC) diagram is proposed and compared to the original SUGCC. A gas fired steam power plant and a process site utility is considered in a case study. The applicability of the developed procedure is tested against other design methods(STAR? and Thermoflex software) through a case study. The proposed method gives comparable results, and the targeting method is used for optimal integration of steam levels. Identifying optimal conditions of steam levels for integration is important in the design of utility systems, as the selection of steam levels in a steam power plant and site utility for integration greatly influences the potential for cogeneration and energy recovery. The integration of steam levels of the steam power plant and the site utility system in the case study demonstrates the usefulness of the method for reducing the overall energy consumption for the site.
基金National Key Research and Development Program of China(2022YFB3804902,2022YFB3804900)the National Natural Science Foundation of China(52161145406,42376045)+1 种基金the Fundamental Research Funds for the Central Universities(2232024Y-01,CUSF-DH-T-2023023)the Iran National Science Foundation(4001793).
文摘Photo/electro-thermal evaporation is a promising tactic for alleviating the scarcity of fresh water,but its practical application still faces many challenges such as weak photoabsorption,high vaporization enthalpy and serious water-electrolysis during photo-thermal/electrothermal evaporation.To solve these problems,inspired by black rose petal and electric heater,we report a biomimetic design of fabric for achieving efficient photothermal/electrothermal desalination.The photo/electrothermal fabric is fabricated by decorating super-hydrophilic MnO_(2)nanoplates as shell on hydrophobic carbon fiber(CF)as core via an electro-deposition method.MnO_(2)nanoplate decoration as a stone confers three fascinating features(birds):(I)the hydrophilic nature of MnO_(2)contributes to the fabric’s superhydrophilicity and decreased evaporation enthalpy(2032 kJ kg^(−1))in comparison with that(2410 kJ kg^(−1))of pure water;(II)nanoplate structure confers the light-trapping effect and thus the improved photoabsorption efficiency of 95.1%;(III)CF-core/MnO_(2)-shell structure can effectively suppress electrolysis of water and lead to good electrothermal conversion property.As a result,CF/MnO_(2)fabric-based hanging evaporator shows the high photo-thermal evaporation rate of 2.3 kg m^(−2)h^(−1)at 1 sun(1 kW m^(−2))and electrothermal evaporation rate of 5.3 kg m^(−2)h^(−1)at 3 V.Importantly,by the combined effects of 1 sun and 3 V,CF/MnO_(2)fabric achieves a striking synergetic evaporation rate of 8.5 kg m^(−2)h−1,exceeding the sum(7.5 kg m^(−2)h−1)of the individual photo-thermal and electro-thermal evaporation rates.The present high synergetic evaporation performance benefits from efficient photo/electrothermal conversion of the fabric and sufficient water-supplementation at the fiber-water interface resulting from thermosiphon effect.Thus,this study offers a novel possibility in the rational design of photo-electrothermal materials for efficient evaporation of seawater.
