Study On Heat Transfer Model Of Pig Manure Aerobic Composting Auxiliary Heat Aquaculture Water

Temperature is an important factor affecting aquaculture.The culture of Fish fry and some adult fish requires high water temperature,while the temperature control of culture water is generally high in energy consumption,and the use of pig manure aerobic compost auxiliary heat culture water can not only assist in regulating and maintaining water temperature,but also save energy.In order to study the heat transfer and temperature change process of pig manure aerobic composting auxiliary heat aquaculture water,a small test device with fermentation tank,water storage tank and simulated fish pond is built,and the geometric model of the test device is established using computational fluid dynamics software to study the heat transfer and temperature change of the test system model in different seasons and conduct economic analysis of the simulation test results,and at the same time,the validation is carried out using the small test device.The tests were carried out mainly on the following tasks:1.Determination of physical properties of compost raw materials and setup of test equipmentThe fermentation rate of composting raw materials varies under different parameters,and to ensure that the compost can meet the fermentation requirements,a suitable ratio of raw materials is required.The initial moisture content and carbon to nitrogen ratio of pig manure and straw samples were measured in four seasons,and the raw material ratio(pig manure to straw mass ratio)was determined to be 1:0.12 according to the fermentation requirements;secondly,the organic matter content and p H value of pig manure samples were measured,and the thermal conductivity and specific heat capacity of raw materials were measured in four seasons based on the raw material ratio.To analyze the accuracy of the measurement method,the determination of thermal conductivity and specific heat capacity of composting raw materials was carried out;to facilitate the subsequent simulation and validation experiments,a small test device with a fermentation tank,a water storage tank,and a simulated fish pond was built.2.Simulative experimental research and economic analysis of aerobic composting auxiliary heat culture water bodyThe geometric model was established on the basis of a small test device based on hydrodynamic software,and the physical field and boundary conditions were set according to the physical parameters of the test material and device.The temperature of the simulated fish pond was effectively increased in all four seasons,and the average temperature of the simulated fish pond increased by 14.60 ℃ in the spring simulation test,12.48 ℃ in the summer simulation test,16.54 ℃ in the autumn simulation test,and 15.91 ℃ in the winter simulation test,and the maximum heat production of the pile in summer and autumn reached 6.00× 105 KJ or more.Taking the summer simulation test as an example,1 t of pig manure can provide 6.07×106KJ during the test cycle,which can save 8.67×105 KJ of heat if used to heat the water body.3.Temperature distribution and heat transfer verification experimental researchThe test results indicated that the measured value of the pig manure pile was lower than the simulated value by 1.77 ℃ on average,the water storage tank was lower by 3.25 ℃ and the simulated fish pond was lower by 3.82 ℃,and the average actual heat production of compost was 4.67×105 KJ in four seasons,which was lower than the simulated value by 1.43×105 KJ.The average heat absorption of the simulated fish pond in the four seasons was 7.57×104 KJ,which was 3.59×104 KJ lower than the simulated value.The temperature of each device,heat production of the pile,and heat absorption of the simulated fish pond in the validation test were slightly lower than the simulated temperature in the simulation test,but the changing trend of the two was still in good agreement.The results of the simulation and validation tests show that the aerobic composting of pig manure with auxiliary heat is feasible,and the measured results of temperature change show good agreement with the simulation results,which verifies the reliability of the model to a certain extent,and the mathematical model and validation tests provide data support and theoretical basis for the composting of waste heat with auxiliary heat.