The Study On Heat Pump Assisted Solar Energy Drying System And Drying Of Mushroom

The moisture content of fresh mushroom is as high as 80%~95%,so it’s easy to degenerate under normal temperature condition in case that it’s not timely treatment after it’s picked.Drying preservation is a common and effective method for mushroom’s preservation.However,drying is a very energy consuming operation,so it’s a very meaningful work to research the energy saving and efficient drying system with the increasingly serious environmental pollution.In this paper,the heat pump assisted solar energy drying system is built and applied to mushroom drying process,then study on the drying characteristics of mushroom provided a basis for the drying process parameters of mushroom.At the same time,aiming at the instability of solar energy application,the shell and tube latent heat thermal energy storage is studied and optimized to ensure the system’s efficient and stable operation.The main research content and conclusions are as follows:(1)The thermal energy storage is a key part in the heat pump assisted solar energy drying system,which can provide a stable heat source for the drying medium.So six shell and tube latent heat thermal energy storage models are built with the method of the ‘uniform design method’ under the condition that the thermal energy capacity is constant,the research factors include the number of fins,fin geometric parameters and inner tube radius,and the research is carried to investigate the melting process of phase change material.Moreover,the angles between fins are also researched.The results are as follows by doing simulation researches: 1)The fully melting time of phase change material in model 2 is the shortest(306 min),and the phase change material in model 3 melts quickly within the100 min at the beginning of the melting process.2)The angles between fins in model 2 are changed to get a optimized model,namely model 11,the fully melting time of phase change material is 194 min,and shortened by 36.6% comparing with model 2.(2)The experimental platform about heat pump assisted solar energy drying system is built in order to investigate the drying characteristics of mushroom.(3)The experiments are carried out by changing the drying temperature to research the drying process of mushroom,because the drying condition has a great influence on the drying process of mushroom.The results appear as shown below: 1)Under the condition of isothermal drying,the water loss of mushroom increases with the increasing drying temperature(10.59kg、14.26kg、16.35kg);The average internal temperature of mushroom rises with the drying temperature rising,and within 0.5h of the beginning drying process,the average internal temperature rise of mushroom is the largest;The drying rate of mushroom is decreasing as time going.2)Under the condition of varied drying temperature,the average internal temperature of mushroom increases obviously with the drying temperature rising.When system is restarted after shutdown,the rise of temperature within0.5h of drying process is larger than that within the first 0.5h of drying process.And in the whole drying process,the larger drying rate keeps longer,and the water loss of mushroom is16.22 kg.3)By making evaluation on dried mushroom under the condition of different drying conditions(The isothermal drying and the varied drying temperature)and the same locations in drying room,the water loss of mushroom is also taken into consideration,and it can be found that the varied drying temperature can be regarded as an effective method during the process of mushroom’s drying.