Solar Drying: Fundamentals,Applications and Innovations - National ...

Visavale - Principles, Classification and Selection of Solar Dryers
Sharma (1987), described the design details and performance of two types of
low cost solar crop dryers, conventional cabinet dryer with direct heating mode and an
integrated solar collector-cum-drying system based on the principle of natural convection.
Results obtained with several vegetables viz. cauliflower, green peas and potato
showed satisfactory overall efficiency and performance of both dryers. Banout et al.
(2011) recently had studied the design and performance of a double pass solar dryer for
drying of red chilli and Montero et al. (2010) has studied the design and performance for
drying of agro-industrial by-products.
Several attempts at developing forced convection solar dryers (both of the cabinettype
and the tunnel-type) have been investigated and experimented on, over the years,
and are described in the literature. The forced convection solar crop dryer design include:
direct, indirect and mixed-mode solar-dryers. Comparative studies on these three
dryer designs suggested that the performance of the mixed-mode forced convection solar
dryer is potentially most effective and it appears to be particularly promising in tropical
humid regions. The forced convection type solar cabinet dryer, basically a cabinettype
of solar dryer with attached solar air heater and forced airflow, has been considered
favorable since such a dryer utilizes solar energy directly, as well as the convective
energy of the heated air. Bennamoun (2003), presented the effect of surface of the
collector, the air temperature and the product characteristics during solar drying of
onion. Nandwani (2007), has discussed the design and development of a multipurpose
fruit and vegetable dryer for domestic use.
1.8.2.2. Solar Drying of Marine Products
Marine products i.e. fish being highly perishable are processed by freezing, canning,
salting and dehydration (Posomboon, 1998). In most of the developing countries, it has
been estimated that about 40% of fish landing is still preserved by either sun-drying or
salt curing or drying. Prawns are treated with boiling water prior to drying to reduce the
microbial flora to an acceptable level and to improve the flavor of dried prawns. Jain
(2006) studied the drying of Bombay duck to determine the heat and mass transfer coefficients
by solar drying. Bala and Mondol (2001) described the use of solar tunnel drying
as an effective method for drying of silver jew fish (Johnius argentatus) along with salting
pretreatment and Reza et al. (2009) have optimized marine fish drying using solar
tunnel drying. Jain and Pathare (2007) studied the drying behaviour of prawn and chelwa
fish (Indian minor carp), by open sun drying. Sankat and Mujaffar (2004) studied the
sun and solar cabinet drying of salted shark fillets. Baird et al. (1981) have extensively
reviewed the solar drying of seafood by forced air convection and by direct insolation, as well
as hot smoking fish with a solar assisted fish smoker. Kittu et al. (2010) had simulated the
thin layer drying model of tilapia fish using a solar tunnel dryer. As a number of solar
dryers exist for a large variety of products to be dried, the preference of one over the
rests depends on a number of factors like ease of material handling, its drying characteristics,
final product quality and sometimes the available resources. Table 1.1 (section
1.12) presents a general checklist to be considered in the preliminary selection of a solar
dryer, and the steps involved in consideration are described (Perry, 2007).
18 Drying of Foods, Vegetables and Fruits