Research On Thermal Characteristics Of Fermentation Tank By The Influence Of Solar Irradiation

Now in China,the energy shortage,the unreasonable energy use structure and the total amount of biomass energy is huge but seriously wasteful is the present situation,the vigorous development of biogas projects is a very good solution.To study the thermal performance of thermostatic anaerobic fermentatio n tanks is necessary to keep the temperature in the fermentation tank stable and run the biogas project efficiently.Solar irradiation will cause the temperature of the fermentation tanks'surface increasing,resulting in heat dissipation reducing,but the re is no further study on this.In this paper,the influence of solar irradiation on the thermal performance of thermostatic anaerobic fermentation tanks was studied and the heat loss model of the fermenter was established,the theory of heat transfer was used to analyze the heat loss of the incoming materials and the heat dissipation of the building envelope.Based on this,the solar irradiation theoretical analysis was used to study the influence of solar irradiation on heat dissipation of fermenter.Thro ugh the field test of Beijing Comfort Biogas Project,the current status of the operation was analyzed and summarized.Using the established theoretical model,Comfort Biogas Project was used as an example to calculate and clarified the energy loss law in t he operation,and verified using test data.The main research contents and conclusions of this paper are as follows:(1)A theoretical model for the heat loss of fermenter was established.The heat loss includes the heat dissipation of the tank envelope struct ure,the heat loss of the incoming materials,and the heat taken by the biogas and water vapor.In addition,the biogenic heat will make up part of the heat loss.In this paper,the heat dissipation of the tank enclosure structure and the heat loss of the i ncoming materials are calculated.The proportion of the remaining parts is very small and ignored.Because the calculation cycle of the fermenter's heat loss is long,the fluctuation of the operation parameters is small,and the structure is simple,one-dimensional steady-state heat transfer model can be used.The law of solar radiation has a certain randomness and it is difficult to calculate and predict.This paper uses a calculation model that quantifies the altitude and atmospheric conditions of the targe t.It can calculate the radiation intensity of the sun at any geographical location and time.According to the size of the fermenter,The calculation formula for total radiation and absorption is proposed.Using the heat flow superposition principle,the ca lculation method of the influence of solar radiation on the heat dissipation of the fermenter was proposed.(2)According to Beijing meteorological data,Beijing Comfort biogas project was used as an example to calculate its thermal performance.Irrespective of solar irradiation,the maximum heat loss of the fermenter is 100872MJ in January,and the minimum is 39622MJ in August,total annual loss is 845149MJ.Using combined heat and power(CHP)methane engine to heat consumes 121600m~3 of biogas in one year,when the heat loss is the largest,it consumed 474m~3 of biogas daily.The gas production from biogas projects meets the requirements.Theoretically,the CHP units can fully meet the thermal requirements of the fermentation system,solar collector and air-source heat pumps are only used as spares,the system has thermal redundancy.In the heat loss,the heat loss of the incoming materials is the largest,the ratio is86%-93%,in summer,the heat dissipationis greatly reduced,causes the heat loss ratio of the incoming materials increases.The heat dissipation of side walls of the envelope structure is the largest,the bottom's is smallest and the top's between two parties.In July the monthly total radiation and the effective radiation absorption on the fermenter surface is maximum,in June the daily total radiation and the effective radiation absorption on the fermenter is maximum and in December they are both the minimum.The radiation energy is huge,but the proportion that can effectively conduct to the inside of the tank is small.In December,the heat dissipation is reduced by only3.77%.In July,it can be reduced by 24.70%.Solar radiation can effectively reduce the energy consumption of the system.In solar radiation,the direct radiation accounts for the largest proportion,the ground reflections and the sky radiation is almost same.(3)According to the field test data,the error between the actual heat dissipation and the theoretical calculation in this paper is 44.6%~51.8%,the error is large,but the trend is same basically,the theoretical heat dissipation model needs to be revised,the correction coefficient is 1.90,The corrected error is kept within 8.6%,which is acceptable in engineering applications.The revised model is reasonable and credible,and can provide guidance for actual project operation and design.The innovation of this article:This paper studies the influence of direct solar radiation that was often neglected in the past research on fermentation systems'energy consumption,and established the theoretical calculation model of the influence of solar radiation on the thermal performance of the biogas fermentation tank.The theory proves that the solar irradiation can effectively reduce the systems'energy consumption.This paper guided the calculation of energy consumption of the constant temperature fermentation system in the future.