【正文】 the interspacebetween the fluidized bed and its blastcap．In this experiment system．1 0％一20％ fresh air was estimated mi xing into the flow in air circulation between the condenser and the fluidized bed．Hence type 2 with a certain fresh air ratio can be chosen as the best air circulation used in the following experiments．4．2 Efects of air flow quantity through the evaporator Two experiments were performed．In one experiment．1 00 k2 grains were put into the fluidized bed with a moisture of about 25％ fits denominator contains no water)，and then the system was started and the airflow through the evaporator was kept relatively low at about 500 m ／h． The performances of the heat pump are shown in figures 24．In the other experiment， the system was started firstly and the airflow through the evaporator was kept high at about 2500 m3／h． after the temperature at the outlet of the condenser reached about 70。C． 100 kg grains with a moisture of 27％ were put into the fluidized bed．The heat pump performances are shown in figures 57． The air flow through the condenser is about the sameof 1 650 m3／h for both experiments．Figure 2 Pressure variation of the refrigerant in the dry ing process at v~=soo ma／h．Figure 3 Performance of the heat pump in the drying process at v~=5oo ma／h．Figure 4 COPoftheheatpump atv~=5ooIll3，l1Figure 5 Pressure variation of the refrigerant in the drying process at v~=25oo ma／h．In figures 3，4 and 6，7，the theoretical results are all calculated from the ideal refrigeration circulation respectively coresponding to the high and low pres。sures of the refrigerant in figures 2 and 5．The parison between figures 3 and 6 shows that the heat output from the condenser greatly increases by in creasing the air flow through the evaporator and the COP is much closer to the idea1 value in figure 7 than that in figure 4．Thus the airflow quantity through the evaporator is very important to the performance of the heat pump．In fact，the growing of the air flow quantity through the evaporator greatly enhances the heat transfer rate between the air and the surface of the evaporator resulting the worldng medium in it absorb more heat at the same temperature difference．Th e theoretical analysis also show that as the airflow increases further,the heat absorbed by the evaporator will reach its peak and then level off．Figure 6 Performance of the heat pump in the drying process atv,=25oom3／h．Figure 7 COP of the heat pump at v~=2soo m3／h．4．3 Drying process of the heat pump assisted fluidized bed grain dryerFigure 8 shows the temperature variations at the inlet and the outlet of the fluidized bed during the drying process under the same condition to the experiment at Ve=2500 m ／h．It shows that both the temperatures rise gradually with time．At such temperature variation，the wheat drying process is shown in figure 9，which displays the wet moisture(the fraction of the water quantity contained in the grains to its total quantity)and dry moisture(the fraction of the water quantity contained in the grains to its absolute dry quantity)variations of wheat wifh drying time．W e can see that it takes about 60 min for the wheat to drv from a wet moisture of 213％ to 13％ ．Figure 8 Temperature variations at the inlet and outlet of the fluidized bed during the drying process at v,=2500m3／h．Figure 9 W heat moisture variations during the dry ingprocess at v,=2500 m3／h4．4 Economical evaluationThe factors afecting the mercial eficiency of the drying system are the drying time，the COP and power consumption of the heat pump．However the drying time mainly depends on the air temperature at the inlet of the fluidized bed．In order to analyze the ercial efficiency of the system．we assume that the wheat is continuously dried bv the system as it was done by the most dryers in industry，the temperature at the inlet of the fluidized bed is about 70。C which wasobtained in the experiment．In such assumptions，we can obtain that the drying time needed for wheat to dry from its wet moisture of 20％ t0 13％ is about 35min，which is deduced from another experiment[2]and will not be presented here． According to the known parameters mentioned above and the heatpump power consumption in figure 6，including the blower power consumption in the system，the averaged power consumption of the system is gotten (about 5．5 kW)during the drying process．Considering the capability of the fluidized bed is about 100 kg，we can conclude its totally power consumption per unit grain output is about 0．0321 kW h／kg or that per unitwater removed from the grain is 0．458 kW h／kg(H20)5 Conclusions(1)Th e appropriate air cycle for drying grain is that the air discharged from the fluidized bed directly flows into the condenser of the heat pump with 10％ 一20％ flesh air where it is heated and then flows into the fluidized bed to form a circulation(2)The airflow through the evaporator is very important to the perform ance of the heat pump．The higher the flow quantity，the beaer the perform ance ofthe heat pump．(3)Th e economical evaluation shows that if the system working at continuous state，its power consumption for removing a kilogram water from the grains is about 0．485 kWh／kg(H2O)and shows great potentiality in the future market．NomenclatureV,Ve,Vc:Th e flow quantities for the fluidized bed，the evaporator and the condenser,respectively；u:The air velocity at the measured point．m／s；N:Th e number of the measured points；A：Th e tube across area，m ；Qe,Qc:Th e refrigerating and heating outputs of the heat pump，kW ；rρair:Th e air density，kg／m ；Cρ:Th e air specific heat capacity，kJ／(kg‘。c)；toe,tie:Th e temperatures at the inlet and the outlet of the evaporator。C：toc,tic:Th e temperatures at the inlet and the outlet of the condenser,。C：Ip:Th e averaged phase current of the pressor,A。Vp:Th e phase voltag