The research goal is to develop a new solar water heater system(SWHS) that uses a solar bubble pump instead of an electric pump.The pump is powered by the steam produced from an evacuated tube collector.Therefore,heat...The research goal is to develop a new solar water heater system(SWHS) that uses a solar bubble pump instead of an electric pump.The pump is powered by the steam produced from an evacuated tube collector.Therefore,heat could be transferred downward from the collector to a hot water storage tank.The designed system consists of two sets of heat-pipe evacuated tube collectors,a solar bubble pump installed at an upper level and a water storage tank with a heat exchanger at a lower level.Discharge heads of 1 and 5 m were tested.The bubble pump could operate at the collector temperature of about 90-100 ℃ and vapor gage pressure of 80-90 kPa.It is found that water circulation within the SWHS depends on the incident solar intensity and system discharge head.Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly,daily and long-term performance tests.The thermal performance of the proposed system is compared with conventional solar water heaters.The results show that the proposed system achieves system characteristic efficiency of 10% higher than that of the conventional systems using electric pump if taking the consumption of electric power into account.And the former is a zero carbon system.展开更多
Animal performance is affected by high air temperature and it is known that shade reduces the absorption of radiant temperature, and water for immersion facilitates heat loss. This study intends to find preferences of...Animal performance is affected by high air temperature and it is known that shade reduces the absorption of radiant temperature, and water for immersion facilitates heat loss. This study intends to find preferences of resources that contribute for the well-being of cattle and how they alterdaily behaviour. During summer, six Caracu and six Red Angus bulls were submitted to two different treatments： availability of artificial shade and water for immersion and availability of water for immersion. The categories observed were： positions （in the sun, under the shade, in the water）, posture （standing, lying down） and activities （grazing, ruminating leisure）. The behavioural patterns were recorded using the focal sampling method every 15 minutes （from 6：00 a.m. to 6：00 p.m.）. When shade and water for immersion coexists, cattle in this study prefer shade to avoid solar radiation. Both breeds had remained more time grazing, followed by ruminating in the Caracu breed, and by resting in the Red Angus breed. The Caracu breed had presented clear preference for the shade resource, but that fact was not always observed in the Red Angus breed. In hot climates, resources for defence against heat load, as shade and water for immersion improve the well-being of cattle.展开更多
A visualization study on the behavior of bubbles has been carried out for pool boiling of R141b on a horizontal transparent heater at pressure 0.1 MPa. The behaviors of bubbles were recorded by a high-speed camera pla...A visualization study on the behavior of bubbles has been carried out for pool boiling of R141b on a horizontal transparent heater at pressure 0.1 MPa. The behaviors of bubbles were recorded by a high-speed camera placed beneath the heater surface. The departure diameter, departure time of bubbles and nucleation site density at different heat flux were obtained. The visualization results show that bubble departure diameter and departure time decrease, while the nucleation site density increases as the heat flux increases. R is also observed that there is no liquid recruited into the microlayer in the experiment. Based on the experimental results, boiling curve for R141b was predicted by using the dynamic microlayer model. As a resuR, the agreement between the predictive result based on the dynamic microlayer model and the experiment data for boiling curve of R141b is good at high heat flux.展开更多
An imaginary plane method for calculation of radiative heat trensfer and its application in the freeboard of AFBC boiler is presented in this paper. The combustion reaction and particle concentration are taken into ac...An imaginary plane method for calculation of radiative heat trensfer and its application in the freeboard of AFBC boiler is presented in this paper. The combustion reaction and particle concentration are taken into account in this method. With is method, one-dimensional freeboard model for radiative heat transfer has been made. Results from this model have been compared with the experimental results of a 130 t/h AFBC boiler. The distribution of flue gas temperature and heat flux at the waterwell are obtained. It is shown that this model has the advantage of good accuracy and requiring less computation time. The applicability of the predicted results in the AFBC boiler design and operation was also discussed.展开更多
Metal foams with hierarchically porous structures are highly desirable in energy applications as active materials or their host substrates.However,conventional preparation methods usually have a quite limited flexibil...Metal foams with hierarchically porous structures are highly desirable in energy applications as active materials or their host substrates.However,conventional preparation methods usually have a quite limited flexibility of adjusting pore size of metal foams.Herein,an alternative new method based on gaseous thermal oxidation-nitridation-denitridation processes was developed to prepare metal(copper and nickel)foams with adjustable pore size by controlling the thermal nitridation temperature.Moreover,this environment-friendly method is independent of the shape of starting pure metal substrates and can be repeatedly applied to the metal substrates to create hierarchical porous structures containing different size pores.As a demonstration of the advantages of the resultant foams with abundant pores by this method,compared with its starting material(commercial Ni foam with the pore size of several millimeters),the resultant hierarchical porous Ni foam gives the remarkably enhanced performance of electrochemical water splitting as HER/OER electrodes and electrochemical energy storage as the host substrate of capacitive material MnO2.The metal foams with adjustable pore size prepared by the developed method will find a wide range of important applications in energy storage and conversion areas.展开更多
基金Project(2011-0021376) supported by Basic Science Program through the National Research Foundation (NRF) Funded by the Ministry of Education,Science and Technology of Korea
文摘The research goal is to develop a new solar water heater system(SWHS) that uses a solar bubble pump instead of an electric pump.The pump is powered by the steam produced from an evacuated tube collector.Therefore,heat could be transferred downward from the collector to a hot water storage tank.The designed system consists of two sets of heat-pipe evacuated tube collectors,a solar bubble pump installed at an upper level and a water storage tank with a heat exchanger at a lower level.Discharge heads of 1 and 5 m were tested.The bubble pump could operate at the collector temperature of about 90-100 ℃ and vapor gage pressure of 80-90 kPa.It is found that water circulation within the SWHS depends on the incident solar intensity and system discharge head.Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly,daily and long-term performance tests.The thermal performance of the proposed system is compared with conventional solar water heaters.The results show that the proposed system achieves system characteristic efficiency of 10% higher than that of the conventional systems using electric pump if taking the consumption of electric power into account.And the former is a zero carbon system.
文摘Animal performance is affected by high air temperature and it is known that shade reduces the absorption of radiant temperature, and water for immersion facilitates heat loss. This study intends to find preferences of resources that contribute for the well-being of cattle and how they alterdaily behaviour. During summer, six Caracu and six Red Angus bulls were submitted to two different treatments： availability of artificial shade and water for immersion and availability of water for immersion. The categories observed were： positions （in the sun, under the shade, in the water）, posture （standing, lying down） and activities （grazing, ruminating leisure）. The behavioural patterns were recorded using the focal sampling method every 15 minutes （from 6：00 a.m. to 6：00 p.m.）. When shade and water for immersion coexists, cattle in this study prefer shade to avoid solar radiation. Both breeds had remained more time grazing, followed by ruminating in the Caracu breed, and by resting in the Red Angus breed. The Caracu breed had presented clear preference for the shade resource, but that fact was not always observed in the Red Angus breed. In hot climates, resources for defence against heat load, as shade and water for immersion improve the well-being of cattle.
文摘A visualization study on the behavior of bubbles has been carried out for pool boiling of R141b on a horizontal transparent heater at pressure 0.1 MPa. The behaviors of bubbles were recorded by a high-speed camera placed beneath the heater surface. The departure diameter, departure time of bubbles and nucleation site density at different heat flux were obtained. The visualization results show that bubble departure diameter and departure time decrease, while the nucleation site density increases as the heat flux increases. R is also observed that there is no liquid recruited into the microlayer in the experiment. Based on the experimental results, boiling curve for R141b was predicted by using the dynamic microlayer model. As a resuR, the agreement between the predictive result based on the dynamic microlayer model and the experiment data for boiling curve of R141b is good at high heat flux.
文摘An imaginary plane method for calculation of radiative heat trensfer and its application in the freeboard of AFBC boiler is presented in this paper. The combustion reaction and particle concentration are taken into account in this method. With is method, one-dimensional freeboard model for radiative heat transfer has been made. Results from this model have been compared with the experimental results of a 130 t/h AFBC boiler. The distribution of flue gas temperature and heat flux at the waterwell are obtained. It is shown that this model has the advantage of good accuracy and requiring less computation time. The applicability of the predicted results in the AFBC boiler design and operation was also discussed.
基金the National Natural Science Foundation of China(51825204)the Key Research Program of Frontier Sciences CAS(QYZDB-SSW-JSC039)。
文摘Metal foams with hierarchically porous structures are highly desirable in energy applications as active materials or their host substrates.However,conventional preparation methods usually have a quite limited flexibility of adjusting pore size of metal foams.Herein,an alternative new method based on gaseous thermal oxidation-nitridation-denitridation processes was developed to prepare metal(copper and nickel)foams with adjustable pore size by controlling the thermal nitridation temperature.Moreover,this environment-friendly method is independent of the shape of starting pure metal substrates and can be repeatedly applied to the metal substrates to create hierarchical porous structures containing different size pores.As a demonstration of the advantages of the resultant foams with abundant pores by this method,compared with its starting material(commercial Ni foam with the pore size of several millimeters),the resultant hierarchical porous Ni foam gives the remarkably enhanced performance of electrochemical water splitting as HER/OER electrodes and electrochemical energy storage as the host substrate of capacitive material MnO2.The metal foams with adjustable pore size prepared by the developed method will find a wide range of important applications in energy storage and conversion areas.
