China has abundant solar energy resource. Solar thermal collectors, particularly all-glass evacuated tubular collectors, have been studied and developed for 30 years, and solar thermal industry has developed rapidly f...China has abundant solar energy resource. Solar thermal collectors, particularly all-glass evacuated tubular collectors, have been studied and developed for 30 years, and solar thermal industry has developed rapidly for 15 years. There are various solar thermal systems, with an operation area of around 108 million m2 in 2007. These systems mainly provide domestic hot water, but some other applications are under extensive study and development as well.展开更多
Solar water collectors that uses for domestic and industrial applications within temperature up to, are classified under two main types: Flat Plate collector (FP), and Evacuated Tube collector (ET). Thermal performanc...Solar water collectors that uses for domestic and industrial applications within temperature up to, are classified under two main types: Flat Plate collector (FP), and Evacuated Tube collector (ET). Thermal performance test results showed that each type have different thermal features. Comparison between (FP & ET) collectors showed that they could take advantages of different thermal features of two types when they work in the same climatic conditions and overlap of these thermal features when they work in different operational conditions. They can take advantage of these features through (compound) solar collector. Compound solar water Collector (CO) composed of a part of flat plate collector shape (FP), and a part of evacuated tube collector shape (ET). Booth have equal reference area, and connected together to be as one Solar collector (CO). Water entered first flat part (FP), then evacuated tube part (ET) then to tank or end-use. In this paper, present design and manufacturing as well the thermal performance test of (compound) solar collector, according to Standard Specification of tests, was EN12975:2001. Mechanical test for (CO) collector conducted successfully according to durability, reliability, and safety requirements. In addition, thermal performance was tested in steady state at the climatic conditions of Damascus city, and concluded the thermal performance of (FP & ET) that constitute (CO) collector. The results showed enhancement of thermal performance.展开更多
Energy consumption in buildings is considered a significant portion of gross power dissipation, so a great effort is required to design efficient construction. In severe hot weather conditions as Kuwait, energy requir...Energy consumption in buildings is considered a significant portion of gross power dissipation, so a great effort is required to design efficient construction. In severe hot weather conditions as Kuwait, energy required for building cooling and heating results in a huge energy loads and consumption and accordingly high emission rates of carbon dioxide. So, the main purpose of the current work is to convert the existing institutional building to near net-zero energy building (nNZEB) or into a net-zero energy building (NZEB). A combination of integrated high concentrated photovoltaic (HCPV) solar modules and evacuated tube collectors (ETC) are proposed to provide domestic water heating, electricity load as well as cooling consumption of an institutional facility. An equivalent circuit model for single diode is implemented to evaluate triple junction HCPV modules efficiency considering concentration level and temperature effects. A code compatible with TRNSYS subroutines is introduced to optimize evacuated tube collector efficiency. The developed models are validated through comparison with experimental data available from literature. The efficiency of integrated HCPV-ETC unit is optimized by varying the different system parameters. Transient simulation program (TRNSYS) is adapted to determine the performance of various parts of HCPV-ETC system. Furthermore, a theoretical code is introduced to evaluate the environmental effects of the proposed building when integrated with renewable energy systems. The integrated HCPV-ETC fully satisfies the energy required for building lighting and equipment. Utilizing HCPV modules of orientation 25? accomplishes a minimum energy payback time of about 8 years. Integrated solar absorption chiller provides about 64% of the annual air conditioning consumption needed for the studied building. The energy payback period (EPT) or solar cooling system is about 18 years which is significantly larger than that corresponding to HCPV due to the extra expenses of solar absorption system. The li展开更多
The experimental system of heat loss of all-glass evacuated solar collector tubes(evacuated tube) is firstly designed and constructed,which uses electric heater as thermal resource.The equilibrium temperatures are les...The experimental system of heat loss of all-glass evacuated solar collector tubes(evacuated tube) is firstly designed and constructed,which uses electric heater as thermal resource.The equilibrium temperatures are less than±1℃during the test.and the temperature differences of up/middle/low node in the tube are less than 1℃,3℃,and 7℃respectively.The heat loss of evacuated tube increases about 2.7%with vacuum state of 0.01--1 mPa,and it has the best performance at tube temperature of 20--280℃.The invalidation tube(>200 mPa) has the biggest heat loss that increases linearly with the tube temperature.The evacuated tubes with the vacuum of 0.01-1 mPa are suitable for most solar adsorption refrigeration.展开更多
Heat transfer in the evacuated collector tube is a three-dimensional laminar natural convection prob-lem driven by buoyancy. Because of its complexity, no effective theoretical model is available despiteof limited exp...Heat transfer in the evacuated collector tube is a three-dimensional laminar natural convection prob-lem driven by buoyancy. Because of its complexity, no effective theoretical model is available despiteof limited experimental work which is confined to one aspect- The present work aims to depict theconvective heat transfer inside a tweended inclined tube with East-West symmetric heat input us-ing numerical methods. Based on reasonable assumptions, governing equations of the inside fluid areestabllshed. The corresponding discretizated equations are solved by employing numerical methods.The calculated results are displayed for velocity and temperature profiles on different cross-sectionalplanes, which present the flow pattern characterized by upflow and dowallow along the axial direc-tion and adherent flow along the peripheral direction, and the heat transfer process from the wall tothe center. Furthermore, the transient Nusselt number and average temperature level are shown anddiscussed. Finally, the parametric effects of the tube radius and the heat input on the flow and heattransfer are also given.展开更多
文摘China has abundant solar energy resource. Solar thermal collectors, particularly all-glass evacuated tubular collectors, have been studied and developed for 30 years, and solar thermal industry has developed rapidly for 15 years. There are various solar thermal systems, with an operation area of around 108 million m2 in 2007. These systems mainly provide domestic hot water, but some other applications are under extensive study and development as well.
文摘Solar water collectors that uses for domestic and industrial applications within temperature up to, are classified under two main types: Flat Plate collector (FP), and Evacuated Tube collector (ET). Thermal performance test results showed that each type have different thermal features. Comparison between (FP & ET) collectors showed that they could take advantages of different thermal features of two types when they work in the same climatic conditions and overlap of these thermal features when they work in different operational conditions. They can take advantage of these features through (compound) solar collector. Compound solar water Collector (CO) composed of a part of flat plate collector shape (FP), and a part of evacuated tube collector shape (ET). Booth have equal reference area, and connected together to be as one Solar collector (CO). Water entered first flat part (FP), then evacuated tube part (ET) then to tank or end-use. In this paper, present design and manufacturing as well the thermal performance test of (compound) solar collector, according to Standard Specification of tests, was EN12975:2001. Mechanical test for (CO) collector conducted successfully according to durability, reliability, and safety requirements. In addition, thermal performance was tested in steady state at the climatic conditions of Damascus city, and concluded the thermal performance of (FP & ET) that constitute (CO) collector. The results showed enhancement of thermal performance.
文摘Energy consumption in buildings is considered a significant portion of gross power dissipation, so a great effort is required to design efficient construction. In severe hot weather conditions as Kuwait, energy required for building cooling and heating results in a huge energy loads and consumption and accordingly high emission rates of carbon dioxide. So, the main purpose of the current work is to convert the existing institutional building to near net-zero energy building (nNZEB) or into a net-zero energy building (NZEB). A combination of integrated high concentrated photovoltaic (HCPV) solar modules and evacuated tube collectors (ETC) are proposed to provide domestic water heating, electricity load as well as cooling consumption of an institutional facility. An equivalent circuit model for single diode is implemented to evaluate triple junction HCPV modules efficiency considering concentration level and temperature effects. A code compatible with TRNSYS subroutines is introduced to optimize evacuated tube collector efficiency. The developed models are validated through comparison with experimental data available from literature. The efficiency of integrated HCPV-ETC unit is optimized by varying the different system parameters. Transient simulation program (TRNSYS) is adapted to determine the performance of various parts of HCPV-ETC system. Furthermore, a theoretical code is introduced to evaluate the environmental effects of the proposed building when integrated with renewable energy systems. The integrated HCPV-ETC fully satisfies the energy required for building lighting and equipment. Utilizing HCPV modules of orientation 25? accomplishes a minimum energy payback time of about 8 years. Integrated solar absorption chiller provides about 64% of the annual air conditioning consumption needed for the studied building. The energy payback period (EPT) or solar cooling system is about 18 years which is significantly larger than that corresponding to HCPV due to the extra expenses of solar absorption system. The li
基金the National Natural Science Foundation of China(No.30771245)the Innovation Program of Shanghai Municipal Education Commission(No.09YZ229)the Leading Academic Discipline Project of Shanghai Municipal Education Commission(No.J50502)
文摘The experimental system of heat loss of all-glass evacuated solar collector tubes(evacuated tube) is firstly designed and constructed,which uses electric heater as thermal resource.The equilibrium temperatures are less than±1℃during the test.and the temperature differences of up/middle/low node in the tube are less than 1℃,3℃,and 7℃respectively.The heat loss of evacuated tube increases about 2.7%with vacuum state of 0.01--1 mPa,and it has the best performance at tube temperature of 20--280℃.The invalidation tube(>200 mPa) has the biggest heat loss that increases linearly with the tube temperature.The evacuated tubes with the vacuum of 0.01-1 mPa are suitable for most solar adsorption refrigeration.
文摘Heat transfer in the evacuated collector tube is a three-dimensional laminar natural convection prob-lem driven by buoyancy. Because of its complexity, no effective theoretical model is available despiteof limited experimental work which is confined to one aspect- The present work aims to depict theconvective heat transfer inside a tweended inclined tube with East-West symmetric heat input us-ing numerical methods. Based on reasonable assumptions, governing equations of the inside fluid areestabllshed. The corresponding discretizated equations are solved by employing numerical methods.The calculated results are displayed for velocity and temperature profiles on different cross-sectionalplanes, which present the flow pattern characterized by upflow and dowallow along the axial direc-tion and adherent flow along the peripheral direction, and the heat transfer process from the wall tothe center. Furthermore, the transient Nusselt number and average temperature level are shown anddiscussed. Finally, the parametric effects of the tube radius and the heat input on the flow and heattransfer are also given.
