The velocity field in the area of heat and mass transfer in a drying chamber of heat pump was investigated experimentally and an optimal configuration was determined. Four kinds of inlet velocity (1.50

2.00

2.50

and 3.00 m/s) were used and five kinds of chamber structures

i.e.

no static pressure layer and no variable cross section

with a static pressure layer but no variable cross section

with both static pressure layer and variable cross section whose angles were arctan (3/40)

arctan (1/10)

and arctan (1/8) respectively

were compared. Furthermore

the suitable inlet temperature range for the optimized structure was investigated by changing the inlet temperature (40

50

and 60 ?C). The results show that the structure with both static pressure layer and variable cross section whose angle was arctan (1/10) was the optimal and the inlet velocity was recommended as 2.50 m/s. The inlet temperature can be determined using the dried materials because the suitable inlet temperature range is large.