Solar, Biomass and Hybrid Dryers - BioEnergy Discussion Lists

stove at one end and a chimney at the other. Noting that the maximum permissibletemperature for fruits and vegetable drying is about 60°C, the design temperature atthe outlet of the heat exchanger should not be less than this value.Eight galvanised iron (GI) pipes with outer diameter 50 mm and inner diameter 44mm are used to provide the required heat transfer area of the heat exchanger; thetubes are arranged in a staggered manner, as shown in Figure 3.2. The tube bank isplaced inside mild steel shell of length: 1.72 m, width: 0.6 m and height: 0.16 m.120mm70mmFigure 3.2: Arrangement of tubes in the heat exchangerThe stove is made of mild steel and has a cross-sectional area of 0.3m x 0.275m andheight 0.4 m; it has a grate punched with 44 holes of diameter 1.5 cm. The insidewalls of the stove are insulated with castable refractory cement. For supplyingdrying air at 70°C, the rate of briquette consumption is about 2.45 kg/hr.The chimney, which provides the draft needed for flue gas from the stove to flowthrough the heat exchanger tubes, has a cross-sectional area of 0.275m x 0.16m andheight 1 m.Figure 3.3: Biomass stove-heat exchanger unit without insulation22