Research On The Combined Drying Technology Of Kelp Solar Energy And Heat Pump

Laminaria Japonica is one of the common aquatic products.It has a large amount of breeding in northern coastal coastal and coastal coastal of Zhejiang and Fujian.Kelp is nutrient rich and rich in a variety of functionally active substances and mineral elements.It also has a relatively good exploitation and utilization value.Due to the strong seasonality of kelp,the harvest is large and the moisture content is high.In order to facilitate storage,dry processing is required.At present,the drying of kelp at home and abroad is mainly a single drying process,which has great limitations.The use of combined drying can make up for the shortcomings of a single drying process.In this paper,the fresh kelp is used as the raw material to maximize the utilization of solar energy,and the two drying mathematical models are obtained by investigating the drying characteristics and quality changes of kelp under two single drying modes,solar and heat pump drying of kelp,based on the above experiments and using response surface optimization,to derive the superior combined drying process with solar and heat pumps.The specific research content and results are as follows:（1）Analysis of kelp solar dryness characteristics and system construction.Using Rongcheng fresh kelp as a research object,the wet based water content of kelp reaches below 18%as the drying endpoint（one equivalent）,we recorded the changes of external temperature,humidity,light illuminance,wind speed,root wet based water content,drying rate,total polysaccharides,fucoidan,mannitol,rotary solar system,and tiling solar system cumulative power generation during drying of kelp in different weather days from June to August.Four mathematical models of drying were fitted to develop a kelch air drying model.The results show that the root thickness of kelp is different,but the initial moisture content is similar,which is between 88%and 92%.The drying process is mainly divided into warm-up phase,fast precipitation stage and slow precipitation stage.When the average temperature outside 1 h was>33℃,the average humidity was<65%,and the average illuminance was>40 000 Lx,the drying rate of kelp roots was faster,and it was suitable for drying kelp.The decrease in total polysaccharides was most obvious in the same marine belt when the bands were completely dried by sun drying,followed by fucoidan with the least change in Mannitol.Using the drying mathematical model to fit and analyze the changes of water content of kelp roots under suitable weather conditions,it was found that the Page model had the highest R²mean and the lowest R_MSEmean,which could accurately describe the water changes of kelp during the drying process.After verification,the correlation coefficient between the M_Rsimulated value and the measured value was 0.995（P<0.05）,and the two were significantly correlated.When the average illuminance of the day（5:00 am to7:00 pm）is>50 000 Lx,the solar power generation efficiency of the tracking system is about 30%-60%higher than that of the tiled solar system.Therefore,the rotary tracking system can be added to the kelp sun drying.Lighting device to improve drying efficiency of kelp during sun drying.（2）Analysis of drying characteristics and quality change of sea belt heat pumps.For the study on Rongcheng fresh kelp,heat pump drying temperatures of 45℃,50℃,55℃and drying wind speeds of 6 m/s,9 m/s,12 m/s were recorded,and the drying regimes were as follows:moisture based water content,drying rate,total polysaccharide,crude fiber,iodine,fucoidan,mannitol and color changes of kelp upon hanging.Four mathematical models of drying were fitted to establish the heat pump drying model of kelp.The results showed that the variation trend of water content of kelp under different temperatures and wind speeds was similar,and it was divided into rapid precipitation stage and slow precipitation stage.The effective water diffusion coefficient D_effof heat pump drying kelp was between 2.067 0×10^-10m²/s～4.093 4×10^-10m²/s,which was positively correlated with heat pump drying temperature and wind speed.The temperature remains unchanged,and the wind speed increases from 6 m/s to 9 m/s,which has a greater impact on the water content of kelp than when the wind speed increases from 9 m/s to 12 m/s.Fiber,iodine,fucoidan,mannitol and color damage are minimal.The wind speed remained unchanged,the temperature increased,and the drying time of kelp decreased.When the drying temperature was 45℃,the damage to the total polysaccharide,crude fiber,iodine,fucoidan,mannitol and color of kelp was the least.Using four common thin-layer drying models to fit the moisture ratio M_Rand time t in heat pump drying kelp,it is found that the Page model has the highest R²and the smallest R_MSE,and is the optimal drying model to describe the moisture change in heat pump drying kelp.It has been verified that the M_Rsimulation value and the M_Rmeasured value have a high degree of fit,and the Person correlation coefficient is 0.997（P<0.05）,and the two are significantly correlated.（3）Research on the combined drying process of kelp solar energy and heat pump.Taking Rongcheng fresh kelp as the research object,heat pump drying temperature,drying wind speed and moisture content of kelp incompletely dried by the sun are independent variables.The energy consumption of heat pump drying and the rehydration rate of kelp were dependent variables,and the three-factor and three-level response surface optimization experiment was designed through the software Design Expert 12.0.The results show that:the energy consumption of heat pump drying,the regression equation of kelp rehydration rate on heat pump drying temperature,drying wind speed and the water content of kelp after sun drying are obtained.It has been verified that the absolute value of the relative error between the simulated value and the measured value of the test is less than 5%,indicating that the regression model can better describe the energy consumption of heat pump drying and the rehydration rate of kelp,the drying temperature of the heat pump,the drying wind speed,and the drying effect of the heat pump.The relationship between changes in water content of kelp.The optimized parameters of the minimum energy consumption are:heat pump drying temperature 49℃,drying wind speed 12 m/s,kelp moisture content 30.01%after sun drying,and the minimum estimated energy consumption is 4.58 k W·h.The optimized parameters of the maximum kelp rehydration rate are:the heat pump drying temperature is 40℃,the heat pump drying wind speed is 10 m/s,the water content of kelp after drying in the sun is 30.10%,and the maximum estimated value of the kelp rehydration rate is 84.77%.Based on the above studies,when the average outside temperature for 1 h is<33°C,the average humidity is>65%,and the average illuminance is<40 000 Lx,the drying is stopped.Heat pump,using Design Expert 12.0,fixed moisture content value,can calculate the heat pump drying temperature and drying air speed required when the energy consumption is minimum and the water recovery rate is the highest.