ection Flender GmbH Flender MD Connection dim B4-CH-12-D Bevel-helical speed reduction gearbox B4

Flender/Flender Gear Units/Bevel-helical speed reduction gearbox B4

than other dryers for small-scale operations in tropical regions. In indirect-mode solar dryers, the hot air while passing through the bed of material carries the moisture and ultimately escapes out through duct or chimney. The decreasein density of air on heating inside the chimney further increases the bouncy force andthus induces higher linear velocity of the exhaust air (1,. typical unit of this type of solar-drying system consists of an inclined (2 ) solar collector (0.9 times the latitude), batch dryer, and an identical collector positioned verti-cally (which acts as chimney). All these are joined in series and face due south. Besidesreceiving solar energy on the inclined collector to preheat the air before it enters the dryer,the exhaust air from the dryer is further heated in the vertical chimney, which causes theair to escape through the chimney at higher velocity. Because of this, an adequate airowthrough the product ensures an increased drying rate and reduced drying time. The drying time with this system depends on the depth of the bed, initial moisture content, humidity of the ambient air, the level of solar energy, and other meteorologicalparameters. The drying rates for the products decrease with the increase in bed thickness.This makes the design unsuitable for packed bed conguration in which air circulation 1 Das and Chakraverty by natural convection would be greatly hindered. However, in some modied designs, installation of wind-driven fan at the exhaust end of the chimney shows some improve-ment in the efciency of the system (. 5.2.2 Forced Convection Solar Dryers In this category of solar dryers, operating blowers ensure adequate air circulation through the product. Thus, larger mass of materials can be handled with much reduction in dryingtime. Higher thermal efciency is possible with some designs. Bin-type forced convectionsolar dryers are quite common. In all drying bins, there is false or perforated oor withas much as 1% or more