| Solar assisted heat pump drying technology is one of the combined applications of solar energy and heat pump,which is also an important green drying technology.At present,the solar assisted air source heat pump drying system use mainly the heat pump evaporator.However,there is a waste heat recovery of the wet air discharged from the drying chamber and it has low heat recovery efficiency.Therefore,in order to improve the heat recovery efficiency,this paper investigated two heat recovery air source heat pump assisted solar drying system.The concrete research contents are as follows:First,it provided a summary of solar assisted air source heat pump drying system in the present.Subsequently,a new design of two heat recovery air source heat pump assisted solar drying system with drying capacity of 9 m3 was investigated.The solar system adopted a heat pump evaporator and a heat exchanger as the heat recovery device,and carried out the two waste heat recoveries for the wet air in the drying chamber.Second,the experiment was conducted to study the performance of the mango at different drying modes.The experimental results showed that the assisted drying mode was 6% higher than the single heat pump drying mode and it could save the power consumption of 3.5k Wh.Therefore,the assisted drying mode has more advantages than the separate heat pump drying mode in terms of energy consumption.Third,according to the change rule of the moisture content of the drying mango and the six drying mathematical models,the non-linear fitting method was used to determine the undetermined coefficients of different drying mathematical models.Through comparison and analysis,it was found that the Page model was in a good agreement with the experimental results of this system.the chi-square,root mean square error,correlation coefficient were 8.00879×10-5—3.55326×10-4,0.00151—0.00533,0.99589—0.99913,respectively,so it can be used as drying model of mango under combined conditions.Fourth,the TRNSYS software was used to establish the simulation model of the two wasted heat recoveries of the solar assisted heat pump drying system.Results of comparison and analysis revealed that the relative error of the simulation model was less than 10%,so it can be verified the applicability of the system simulation model.Furthermore,the simulation model provides some theoretical support for optimizing the system performance.Fifth,Combined with the irradiation condition in the system installation area,and selected four materials harvested at different seasons of a year.Meanwhile,the system drying time of different materials in different drying modes was assigned;the life cycle method was used to calculate the net present value and cumulative net present value of the system.Finally,the system recovery period was determined of a year,and the drying system is worthy from the point of view of social benefits. |
