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CDesign and Parameter Optimization of Steam Heating System for Rice Seedling Greenhouse in Cold Regi

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Tutor: WangChun
School: Heilongjiang Bayi Agricultural University
Course: Agricultural Mechanization Engineering
Keywords: Rice seedling,Forced (rice) germination,Steam heating system,Responsesurface met
CLC: S223.13
Type: Master's thesis
Year:  2014
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Heilongjiang province is one of the major grain producing provinces, the main cropsof rice, maize and soybean, the main crops were of rice, maize and soybean. But because itlies in the north area of China, has a specific characteristic of climate in there. Such as haslower annual average amount of solar radiation and shorter crop growth period. Whichmakes it is difficult to develop some late maturing and high-yielding varieties in this area.Especially the rice cultivation, often through early covering plastic tunnel to improvetemperature, increased the effective accumulated temperature, so as to achieve the highyield of rice.The main research goal of this assay is the production process of rice planting earlygermination and seedling. Aiming at a series of problems exist in the current rice seedling,tried to put forward a set of steam germination system that could be widely used innorthern cold area of our country.The steam temperature increase seedling system was consisted of electric steamgenerator, temperature controller, pressure head, the convection fan, three links, elbow,stainless steel seamless tube, relay and plastic shed (5*2*1m). The small shed was erectedin the internal of a conventional greenhouse equipped with a conventional boiler insulationsystem, so that the temperature is maintained at18-22¡æ. The working principle was that,after the steam generator power began to work, when the steam pressure steam generatoroutput more than the pressure of steam head, the steam was started to injected into the shedvia four pressure heads. The fifteen temperature sensors were distributed in the floor of thesmall shed to collect the temperature values then feedback to the temperature controller,when the temperature of any point of the fifteen temperature sensors exceeds thetemperature control instrument sets the upper limit (31¡æ) or lower (29¡æ), then a relaysignal would be sent to the electric relay, which could close or open the steam generatorand the convection fan power. As a result, achieve the purpose of the temperature control.In this experiment, the four main operating parameters of steam temperature system,namely, A: the number of steam head; B: the pressure of steam head; C: the revolutions ofconvection fan and D: the time of steam injection, were selected as the influent factors to investigate the performance of the steam temperature system. Through the analysis offitting regression equations for the central composite experimental results, obtained aquadratic regression equation which made the variance of the temperature observationvalue among the fifteen temperature probes used as the function, and the four factors wereused as independent variable. Using Design Expert software analysis of variance for theregression equation, the results showed that the effects of A, B, and C on the response weresignificant, and the factor D was not significant. As to the interactions among the factors,only the interactive influence between A and C was significant. All the results showed thatthe optimum operation parameters of the steam temperature system were that the numberof steam head was four, the pressure of steam head was2.5bar, the revolutions ofconvection fan was2000rpm and the time of steam injection was30s. In this condition,the variance value of the fifteen temperature measuring points was least of0.0183.In order to verify the practicality of the steam heating system, the experiment of theactual stage and seedling raising in the later stage of experiment, selecting three differentvarieties of rice seeds and established the control group test. The results showed that, thesame variety of rice seed, equipped with steam heating system in a shack growth overall issignificantly better than the control group (without any additional artificial warmingmeasures). In particular, the emergence time, overall germination rate and seedling qualityof the experimental group were better than the control group.
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