Research On Optimal Design And Modeling Of Heat Pump Drying System

Heat pump drying equipment has been widely used in more and more drying fields due to its energy-saving and environmental protection characteristics.In this paper,according to the dehumidification standard required by the drying process,the amount of dehumidification per hour is determined,and a heat pump drying experiment platform for seafood is designed and built.The sea cucumber is selected as the drying object.Researched and designed a data collection and monitoring system that matched the heat pump drying equipment.The dried materials conformed to national standards.The mobile drying equipment can be used as a molded product to promote the sea cucumber breeding retailer.The main content of the paper is divided into the following aspects:1.The main components of the heat pump dryer are selected and designed.According to the characteristics of low-temperature drying of most seafood,a heat pump test stand with multiple operating modes of rapid heating,dehumidification and cooling was designed.After the calculation of the drying process load and the required air volume,the main unit components of the heat pump drying equipment include compression machine,condenser,electronic expansion valve and evaporator for type selection calculation.According to the design results,a heat pump drying experiment platform was built.The sea cucumber was selected as the dry material,and the drying characteristics of the sea cucumber were tested using this experimental platform.Supplement some experimental test basic physical parameters of sea cucumber for modeling and analysis.2.Simulate the heat and mass transfer laws of the materials in the drying oven.The simulation of the drying oven through the simulation software realizes the coupling of multiple physical fields such as temperature,wind speed and moisture transmission in the software.The boundary conditions are set according to the actual situation.After setting the control equations and dividing the grid,the sea cucumbers in the drying oven are simulated.The law of heat and moisture migration in the drying process.The simulation results and experimental results showed a good consistency between the changes of sea cucumber temperature and water content,and the average deviation rate was within 10%,proving that the model can be used for the same type of seafood drying.From the simulation results,it was found that with the drying process,the moisture content of seacucumbers showed a decreasing law from the surface layer to the inside,and the temperature showed a decreasing law from the oven inlet to the outlet.The temperature inside the material gradually increases with the increase of drying time,and finally approaches the inlet temperature.The time required decreases with the increase of the inlet wind speed.The water content of the central point of sea cucumber decreased from 542%,595%,682 and 516% to 50%,53%,56% and 52% respectively,and the temperature was close to the inlet temperature 45 ?,40 ?,33 ?,30 ? after 70 min,80min,120 min and180min,.The simulated water content is slightly lower than the experimental value in the early stage of drying and slightly higher than the experimental value in the later stage.The reason may be that the size shrinkage of the sea cucumber and the change in porosity caused by the actual process reduce the evaporation rate of the material.Combined with the requirements of the national standard,the quality of the dried sea cucumber is analyzed,and it is found that the formation quality of the sea cucumber is better when the heat pump drying temperature is 40 ? and the drying medium flow rate is 2m/s~4m/s.Drying time and quality are ideal drying conditions.3.After verifying the model using the test results,the aligned arrangement and staggered arrangements models were designed to explore the effect of the quantity and arrangement of materials on the change in moisture content.The results show that the water dispersion loss is faster when the materials are staggered arrangements,and in the same drying oven,with the increase of the number of dry materials,the effect of the arrangement on the moisture content is gradually obvious,so the materials should be dispersed and arranged at the same time try to choose the staggered arrangements to increase the heat exchange effect.In order to solve the uneven distribution of temperature and humidity of the flow field under a single inlet of the drying oven,a nozzle model for the air supply of the bottom plate was established.Through the change of the internal water content of the sea cucumber in the simulation results,it was found that the nozzle model can improve the drying when designing the heat pump drying oven.The temperature and moisture content of the material are uniform to avoid uneven temperature and humidity in a short time of drying,so this nozzle model can be used in actual design.4.Design data collection and monitoring platform to realize the collection andreal-time output of parameters such as temperature,humidity and wind speed in the drying oven and the pressure and temperature parameters of the main components of the unit,on this basis,the detection system of the host computer is designed,using PLC controller Realize the input and output of analog quantity,ensure the stable temperature control during the drying process,facilitate human-computer interaction,and optimize the drying process.