请教铸件降温问题

lliuchangming

我做了一个模拟铸件在模子中降温过程的例子。从初始温度2000开始降温的瞬态分析，结果分析过程中温度一度超过2000度，达到2010度左右，后来又降下来，我的模型里面没有任何热源，定义的模子外边界有空气对流。谁能帮我解释这个问题啊，我的命令流如下：/prep7  
et,1,plane77
MPTEMP,,,,,,,,  
MPTEMP,1,0  
MPDATA,KXX,1,,6
MPTEMP,,,,,,,,  
MPTEMP,1,0  
MPDATA,C,1,,1000
MPTEMP,,,,,,,,  
MPTEMP,1,0  
MPDATA,DENS,1,,3500
MPTEMP,,,,,,,,  
MPTEMP,1,0  
MPDATA,KXX,2,,110   
MPTEMP,,,,,,,,  
MPTEMP,1,0  
MPDATA,C,2,,1000
MPTEMP,,,,,,,,  
MPTEMP,1,0  
MPDATA,DENS,2,,1600
RECTNG,-0.55,0.55,-0.35,0.35,   
RECTNG,-0.3,0.3,-0.15,0.15,
aovlap,all  
numcmp,area
aglue,all
asel,s,area,,1
aatt,1,,1,0
asel,all,area
asel,s,area,,2
aatt,2,,1,0
asel,all,area
esize,0.05
amesh,all
FINISH  
/SOLU
antype,trans
toffst,273
timint,off
time,0.01
deltim,0.01
esel,s,mat,,1
nsle,s  
d,all,temp,2000
esel,inve   
nsle,s  
d,all,temp,25   
allsel  
SOLVE   
/SOL
lsel,s,line,,1,4
NSLL,S,1
sf,all,conv,6,25
allsel,all
TIME,100
timint,on
DELTIM,0.01,0.0001,10,1
AUTOTS,on
ddelet,all,temp
TINTP,0.005, , ,1, , ,  
LNSRCH,1
outres,all,1
SOLVE