Regarding sun＇s potential in Middle East and North Africa zone and particularly in Morocco, we focus our work on the development of the knowledge and information concerning the solar heaters for domestic applications...Regarding sun＇s potential in Middle East and North Africa zone and particularly in Morocco, we focus our work on the development of the knowledge and information concerning the solar heaters for domestic applications, in order to help the industrial and the consumer to select an adaptive technology. As a result, a Moroccan mapping of solar water heating systems is presented in this work. This mapping concerns two technologies commonly used： the FPC （flat plate collectors） and the ETC （evacuated tubes ones）. It is based on three criteria： firstly, the efficiency of the STC （solar thermal collectors）; secondly, the economic aspect and at last, the reliability requirements. Based on these information, the multi-criteria outranking methodology PROMETHEE （preference ranking organization method for the enrichment evaluations） allows us to define an adequate solar heater technology linked with the climatic zoning of Morocco.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
Passive residual heat removal heat exchanger(PRHR HX),which is a newly designed equipment in the advanced reactors of AP1000 and CAP1400,plays an important role in critical accidental conditions.The primary and second...Passive residual heat removal heat exchanger(PRHR HX),which is a newly designed equipment in the advanced reactors of AP1000 and CAP1400,plays an important role in critical accidental conditions.The primary and secondary side coupling heat transfer characteristics of the passive residual heat removal system(PRHRS)determine the capacity to remove core decay heat during the accidents.Therefore,it is necessary to investigate the heat transfer characteristics and develop applicable heat transfer formulas for optimized design.In the present paper,an overall scaled-down natural circulation loop of PRHRS in AP1000,which comprises a scaleddown in-containment refueling water storage tank(IRWST)and PRHR HX models and a simulator of the reactor core,is built to simulate the natural circulation process in residual heat removal accidents.A series of experiments are conducted to study thermal-hydraulic behaviors in both sides of the miniaturized PRHR HX which is simulated by 12 symmetric arranged C-shape tubes.For the local PRHR HX heat transfer performance,traditional natural convection correlations for both the horizontal and vertical bundles are compared with the experimental data to validate their applicability for the specific heat transfer condition.Moreover,the revised natural convection heat transfer correlations based on the present experimental data are developed for PRHR HX vertical and lower horizontal bundles.This paper provides essential references for the PRHRS operation and further optimized design.展开更多
Using combined cooling,heat and power systems can be an appropriate substitute for preventing emissions of pollutants and excessive consumption of fossil fuels.Utilizing renewable energy in these systems as a source o...Using combined cooling,heat and power systems can be an appropriate substitute for preventing emissions of pollutants and excessive consumption of fossil fuels.Utilizing renewable energy in these systems as a source of power generation can be an appropriate substitute for fossil-fuel-based systems.Therefore,in this paper,cogeneration cooling,heat and power systems based on gas-fired internal combustion engines with a solar-thermal system with evacuated tube collectors have been modelled and thermo-economic analysis has been done to compare fossil-fuel-based systems.The required rate of heat to supply the hot water is 50 kW.In the studied system,the internal combustion engine produces electrical energy.Then,the solar-thermal system with evacuated tube collectors and the gas-burning generator provide the thermal energy required by the studied building and the primary stimulus of the absorption chiller for cooling.In this study,two different scenarios are conducted in states considering simultaneous production systems and regardless of this environmental and thermo-economic analysis system.The results showed that the efficiency of the studied system was 60% in summer and 56% in winter.展开更多
文摘Regarding sun＇s potential in Middle East and North Africa zone and particularly in Morocco, we focus our work on the development of the knowledge and information concerning the solar heaters for domestic applications, in order to help the industrial and the consumer to select an adaptive technology. As a result, a Moroccan mapping of solar water heating systems is presented in this work. This mapping concerns two technologies commonly used： the FPC （flat plate collectors） and the ETC （evacuated tubes ones）. It is based on three criteria： firstly, the efficiency of the STC （solar thermal collectors）; secondly, the economic aspect and at last, the reliability requirements. Based on these information, the multi-criteria outranking methodology PROMETHEE （preference ranking organization method for the enrichment evaluations） allows us to define an adequate solar heater technology linked with the climatic zoning of Morocco.
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.
基金the National Science and Technology Major Project of China(Grant No.2017ZX06004002-006-002)the National Natural Science Foundation of China(Grant No.51906069)。
文摘Passive residual heat removal heat exchanger(PRHR HX),which is a newly designed equipment in the advanced reactors of AP1000 and CAP1400,plays an important role in critical accidental conditions.The primary and secondary side coupling heat transfer characteristics of the passive residual heat removal system(PRHRS)determine the capacity to remove core decay heat during the accidents.Therefore,it is necessary to investigate the heat transfer characteristics and develop applicable heat transfer formulas for optimized design.In the present paper,an overall scaled-down natural circulation loop of PRHRS in AP1000,which comprises a scaleddown in-containment refueling water storage tank(IRWST)and PRHR HX models and a simulator of the reactor core,is built to simulate the natural circulation process in residual heat removal accidents.A series of experiments are conducted to study thermal-hydraulic behaviors in both sides of the miniaturized PRHR HX which is simulated by 12 symmetric arranged C-shape tubes.For the local PRHR HX heat transfer performance,traditional natural convection correlations for both the horizontal and vertical bundles are compared with the experimental data to validate their applicability for the specific heat transfer condition.Moreover,the revised natural convection heat transfer correlations based on the present experimental data are developed for PRHR HX vertical and lower horizontal bundles.This paper provides essential references for the PRHRS operation and further optimized design.
文摘Using combined cooling,heat and power systems can be an appropriate substitute for preventing emissions of pollutants and excessive consumption of fossil fuels.Utilizing renewable energy in these systems as a source of power generation can be an appropriate substitute for fossil-fuel-based systems.Therefore,in this paper,cogeneration cooling,heat and power systems based on gas-fired internal combustion engines with a solar-thermal system with evacuated tube collectors have been modelled and thermo-economic analysis has been done to compare fossil-fuel-based systems.The required rate of heat to supply the hot water is 50 kW.In the studied system,the internal combustion engine produces electrical energy.Then,the solar-thermal system with evacuated tube collectors and the gas-burning generator provide the thermal energy required by the studied building and the primary stimulus of the absorption chiller for cooling.In this study,two different scenarios are conducted in states considering simultaneous production systems and regardless of this environmental and thermo-economic analysis system.The results showed that the efficiency of the studied system was 60% in summer and 56% in winter.
