In order to investigate fan performance in fan-ventilated greenhouses(Urbana,USA),the effects of guard screen and loose belts on fan ventilation airflow and power consumption in greenhouse operations were examined wit...In order to investigate fan performance in fan-ventilated greenhouses(Urbana,USA),the effects of guard screen and loose belts on fan ventilation airflow and power consumption in greenhouse operations were examined with four belt-driven fans as trial subjects.The Fans Assessment Numeration System was used to measure the airflow rate.Temperature,relative humidity and power consumption were also monitored.Results show there were significant differences in the airflow rate between the fans with a cleaned and uncleaned guard screen(P<0.05).Power consumption also differed significantly even with the same cooling effect in greenhouse.When fan belts were adjusted to the proper tension,the fan speed and airflow rate were 13.1% and 30.1% higher than those of original belts,respectively.The daily average power consumption for the fan with the original loose belts was 20.4% higher than that with the adjusted belts when the pad was not working and 24.2% higher with pad working.The ventilation performance of fans with identical specifications showed a variation by up to 13.0% in terms of the ventilating efficiency ratio.These results demonstrated that fans should be cleaned routinely,and belt tension should be checked to ensure that fan performance meets specifications.This can reduce the power consumption in greenhouses for environmental control.Moreover,reordering fan staging,so that the most efficient fans are used in areas of greatest demand,can also reduce ventilation energy costs.展开更多
Five different doses of ultraviolet-B(UV-B)radiation were supplied to tomato(Lycopersicon esculeutum.Mill)with the doubled CO_(2)concentration(700μmol·mol^(-1))in the winter plastic greenhouse.The influences on ...Five different doses of ultraviolet-B(UV-B)radiation were supplied to tomato(Lycopersicon esculeutum.Mill)with the doubled CO_(2)concentration(700μmol·mol^(-1))in the winter plastic greenhouse.The influences on the seedling growth,fruit quality and yield of tomato were investigated.Results showed that the seedling growth,and the contents of UV absorbing compounds,soluble sugar,organic acid,vitamin C and lycopene of tomato fruits,and yield of tomato increased under doubled CO_(2)concentration.Under the doubled CO_(2)concentration the effects of lost doses of UV-B radiation could further promote the effects of doubled CO_(2)concentration.However,there is no significant increase in yield of tomato.The best dose of UV-B radiation is about 1.163 kJ·m^(-2).When the dose of UV-B radiation is more than it,the effects of UV-B will be reduced.展开更多
基金financially support by the Public Welfare Trade(Agriculture)Research Project,China(201203002)the Technology Co-ordination Innovation Project of Shaanxi.Province,China(2011KTDZ02-03-02).
文摘In order to investigate fan performance in fan-ventilated greenhouses(Urbana,USA),the effects of guard screen and loose belts on fan ventilation airflow and power consumption in greenhouse operations were examined with four belt-driven fans as trial subjects.The Fans Assessment Numeration System was used to measure the airflow rate.Temperature,relative humidity and power consumption were also monitored.Results show there were significant differences in the airflow rate between the fans with a cleaned and uncleaned guard screen(P<0.05).Power consumption also differed significantly even with the same cooling effect in greenhouse.When fan belts were adjusted to the proper tension,the fan speed and airflow rate were 13.1% and 30.1% higher than those of original belts,respectively.The daily average power consumption for the fan with the original loose belts was 20.4% higher than that with the adjusted belts when the pad was not working and 24.2% higher with pad working.The ventilation performance of fans with identical specifications showed a variation by up to 13.0% in terms of the ventilating efficiency ratio.These results demonstrated that fans should be cleaned routinely,and belt tension should be checked to ensure that fan performance meets specifications.This can reduce the power consumption in greenhouses for environmental control.Moreover,reordering fan staging,so that the most efficient fans are used in areas of greatest demand,can also reduce ventilation energy costs.
基金This work was supported by both the National Nature Science Foundation of China(Grant No.30370269)the science and technology industrialization project of Shaanxi(No.01ZC07).
文摘Five different doses of ultraviolet-B(UV-B)radiation were supplied to tomato(Lycopersicon esculeutum.Mill)with the doubled CO_(2)concentration(700μmol·mol^(-1))in the winter plastic greenhouse.The influences on the seedling growth,fruit quality and yield of tomato were investigated.Results showed that the seedling growth,and the contents of UV absorbing compounds,soluble sugar,organic acid,vitamin C and lycopene of tomato fruits,and yield of tomato increased under doubled CO_(2)concentration.Under the doubled CO_(2)concentration the effects of lost doses of UV-B radiation could further promote the effects of doubled CO_(2)concentration.However,there is no significant increase in yield of tomato.The best dose of UV-B radiation is about 1.163 kJ·m^(-2).When the dose of UV-B radiation is more than it,the effects of UV-B will be reduced.
