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 TRENDS IN POST HARVEST TECHNOLOGY
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REVIEW ARTICLE

Evaporative Cooled Storage Structures: An Indian Scenario

K.V. Vala1*, F. Saiyed2 and D.C. Joshi3
1,3
College of Food Processing Technology and Bio-Energy, Anand Agricultural University, Anand, (Gujarat), India.
2
College of Agricultural Engineering and Technology, Anand Agricultural University, Godhra (Gujarat), India.

Abstract
Evaporative cooling is a well-known system to cool the
environment. This is adiabatic process, in which ambient air is cooled as a
*Corresponding Author: result of transferring its sensible heat to the evaporated water carried with
the air. In the evaporative cooled structure, the maximum advantage of the
K.V. Vala
natural environment is taken for lowering down the temperature of outside
Email: kvvala66@gmail.com ambient air to a considerable low level. Evaporative cooling storage system
is easy to operate, efficient and affordable most especially for peasant
farmers in developing countries who may find other methods of
preservation quite expensive and unaffordable. In this review different
Received: 14/08/2014 evaporative cooling systems developed, their construction materials and
efficiency in improving the shelf life of various agricultural commodities
Revised: 25/09/2014 have been discussed.
Accepted: 27/09/2014
Keywords: Evaporative cooling, evaporatively cooled, saturation
efficiency, relative humidity, zero energy cool chamber, evaporatively
cooled storage structure.

Introduction commodities; also proper relative humidity is required

The immense diversity in agro-climatic to be maintained during storage (Kadar, 1992). The
conditions across the different regions enables India to storage life of fruits and vegetables can be extended
produce a large variety of fruits and vegetables that are greatly by removing the field heat and applying cooling
generally grown under sub-tropical and as soon as possible after harvesting. The optimum
temperate climatic conditions. However, due to poor storage temperature of most fruits and vegetables is
handling of the produce, post-harvest losses have been above their freezing point (FAO, 1995). Proper storage
high, resulting in a significant gap between gross is an important for marketing and distribution of
production and the net availability to the consumer horticultural commodities. Storage also balances the
(Singh and Satapathy, 2006). Due to their highly daily fluctuations of supply and demand (Chakraverty
perishable nature, about 20-30% of total fruit et al., 2003). Losses can be minimized by using best
production and 30- 35% of total vegetable production post-harvest handling techniques during storage,
go waste during various steps of the post-harvest chain transportation and distribution to market. There are
(Chadha, 2001; Suryawanshi et al., 2005; FAO, 2006; various technologies available to create and maintain
Arya et al., 2009; Basediya et al., 2013; Assocham, optimal temperature, relative humidity and atmospheric
2013) and the monetary losses are over Rs 2 lakh crore composition for harvested fruits and vegetables during
annually in country (Assocham, 2013). storage (Chakraverty et al., 2003). Temperature can be
The lack of sufficient cool storage space at farm controlled by using energy consuming methods such as
level and refrigerated storage at market level further air-cooling, hydro-cooling, vacuum-cooling, chilling,
enhances loss of fruits and vegetables (APO, 2006, ice cooling, freezing, etc., and less or no energy
FAO, 2006). Reducing the losses in postharvest fruit method i.e. evaporative cooling system (Thomson et.
and vegetable operations is a worldwide goal (Clement al., 1998). Former is achieved by mechanical
et al., 2009). Since ages, the human race has been refrigeration system while later uses evaporative
practicing different methods to increase the shelf life of cooling principle for lowering temperature.
these commodities. Temperature and humidity play
major role in storage of fruits and vegetables. Mechanical refrigeration
Temperature is the single most important factor Refrigerated storage is a well-established
affecting the deterioration rate of freshly harvested technology widely used for storing horticultural crops

Trends in Post Harvest Technology | July-September, 2014 | Vol 2 | Issue 3 | Pages 22-32
© 2014 Jakraya Publications (P) Ltd
 Vala et al…Evaporative Cooled Storage Structures: An Indian Scenario

all over the world (Chakraverty et al., 2003; 2010; Nitipong and Sukum, 2011; Banyat and Bunjerd,
Chaudhary, 2004; Singh and Satapathy, 2006; 2013).
Sunmonu et al., 2014). However, mechanical Refrigeration system decreases both temperature
refrigeration is energy intensive and expensive involves and humidity while evaporative cooling decreases less
high initial investment, cannot be quickly and easily temperature and increases humidity, which is more
installed, requires uninterrupted supply of electricity, suitable for storage of agriculture produce, which does
high operational cost, and cannot be constructed in not require very low temperature (Wilson et al., 1995;
remote area and not eco-friendly too. Because of these Nitipong and Sukum, 2011).
reasons this method is not widely used in many tropical ECSS due to their low investment, almost no
and sub-tropical countries, where refrigeration is energy requirement and with other advantages over
needed most (Kumar and Nath, 1993; Thakral et al., refrigeration system become a quite popular and better
2000; Kumar et al., 2003; Adamu et al., 2006; alternative for storage of horticultural produce (Dash
Nitipong and Sukum, 2011). This method is not also and Chandra, 1999; Rayaguru et al., 2010; Nitipong
affordable to small farmers, retailers and wholesalers and Sukum, 2011). ECSS does not use energy or very
(Samira et al., 2013). Besides, it is not suitable for on- less energy hence called zero energy cool chambers
farm storage in the rural areas (Basediya et al., 2013). (ZECC) (Roy and Khurdiya, 1986). Only limitation
Moreover several tropical fruits and vegetables like with this system is it requires dry and hot climate (high
banana, tomatoes, orange, leafy vegetables etc., cannot temperature and less humidity), open space for
be stored in the refrigerator because they sustain movement of air and small quantity of water.
chilling injury and colour change (Adebisi et al., 2009; In India hot and dry weather prevails for a
Liberty et al., 2013). Use of chlorofluorocarbon (CFCs) significant part of the year. Ambient hot and dry
and hydro chlorofluorocarbon (HCFCs) refrigerants in weather is suitable for efficiently working of the
refrigeration system are partly responsible for ozone evaporative cooling concept storage structure (Jha and
layer depletion and global warming (Xuan et al., 2012). Chopra, 2006; Vala and Joshi, 2012). Perishable
Because of these reasons its application has become agriculture commodities can be safely stored in ECSS.
limited. Evaporative cooling storage structure is an Use of evaporative cooling concept in storage of
alternative of mechanical refrigeration system agricultural produce may be one alternate as it can be
(Nitipong and Sukum, 2011). used for short-term on-farm storage of perishables as
well as for pre-cooling of fruits and vegetables before
Evaporative cooling storage structure transit and storage in cold storage (Jha and Aleksha,
Evaporative cooling storage structure (ECSS) is 2006; Maini and Anand, 1992). Evaporative cooling is
a double wall structure having space between the walls the simplest and cheapest method for extending shelf
which is filled with porous water absorbing materials life of fruits and vegetables and can also be used as
called pads (Roy and Khurdiya, 1986; Singh and ripening chamber for banana (Bhatnagar et al., 1990;
Satapathy, 2006; Jha and Aleksha Kudos, 2006). These Das and Chandra, 2001; Dharmasena and Kumari,
pads are kept constantly wet by applying water. When 2005; Jha, 2008; Okunade and Ibrahim, 2011).
unsaturated air passes through wet pad, transfer of Many scientists carried out it efficacy for
mass and heat takes place and the energy for the increasing shelf-life of fruits and vegetables namely;
evaporation process comes from the air stream. tomato, potato, mango, grapes, orange, santara, sapota,
Evaporative cooling is an adiabatic process occurring banana, plums, aonla, bitter gourd, capsicum,
at constant enthalpy (Dash and Chandra, 2001; Kumar cauliflower, pineapple, peach, green pepper, cluster
et al., 2003; Bucklin et al., 2004; Vala and Joshi, 2010; bean, brinjal, cucumber, chili, ladies finger, beat, peas,
Banyat and Bunjerd, 2013). This is the most carrot, radish and leafy vegetables (Ganesan et al.,
economical way of reducing the temperature by 2004; Habibunnisa et al., 1988; Jha, 2008; Kumar and
humidifying the air. It has many advantages over Nath, 1993; Mishra et al., 2009; Nagaraju and Reddy,
refrigeration system, as it does not use refrigerant so it 1995; Roy and Khurdiya, 1986; Singh et al., 1998;
is friendly to environment (reduces CO2). It does not Singh and Satapathy, 2006; Samira et al., 2013;
make noise as there is no moving part. It does not use Umbarkar et al., 1991). They also constructed various
electricity i.e. saves energy. It does not require high sizes ECSS using different construction materials. The
initial investment as well as operational cost is storage size of ECSS varies from few kilograms to few
negligible. It can be quickly and easily installed as this tones. Some researchers also evaluated ECSS using
simple in design. Its maintenance is easy. It can be various pad materials, environment parameters,
constructed with locally available materials in remote operational parameters, produce parameters for
area and most important, it is eco-friendly as it does not temperature drop and increasing relative humidity. The
need chlorofluorocarbons (Jha, 2008; Gomez et al., published information on all the above was reviewed

Trends in Post Harvest Technology | July-September, 2014 | Vol 2 | Issue 3 | Pages 22-32
© 2014 Jakraya Publications (P) Ltd
23
 Vala et al…Evaporative Cooled Storage Structures: An Indian Scenario

and briefly presented here under four different heads;

namely structural parameters, pad materials, operating Operating parameters of EC structure
parameters and performance in terms of shelf-life of Cooling efficiency, temperature drop and
farm produce. increase in humidity inside the cool chamber largely
depends on operating parameters. Optimum designed
Structural parameters of EC structure parameters for a given size gives better performance in
Many researchers used different structural terms of saturation efficiency. Many scientists
materials viz.; bricks, wood, mild steel, aluminum evaluated ECSS by using various operating parameters;
sheet as walls of the ECSS. Roof of the ECSS was also pad thickness, pad density, pad face velocity, water
made of light weight, cheaper and easily available flow rate, pad orientation, pad volume, porosity
materials; asbestos sheet, gunny bag, jute bags, (Thakur and Dhingra, 1983; 1985; 1986; Umbarkar et
plywood, etc. (Chouksey, 1985; Roy and Khurdiya, al., 1991; Yadav et al., 2002; Jha and Aleskha-Kudos,
1986; Umbarkar et al., 1991; Rama and Narasimham, 2006; Vala and Joshi, 2010). Optimum pad density,
1991; Garg et al., 1997; Kapdi et al., 1997; Sandhu and pad thickness, air flow rate and water flow rate are the
Ghuman, 2002; Kumar et al., 2003; Olosunde, 2006; important parameters and required to be designed for
Jha, 2008; Mishra et al., 2009; Vala and Joshi, 2010; better cooling (Table 3).
Samira et al., 2011). These materials are cheaper and Improvement in cooling efficiency can be
easily available. This makes construction cost of ECSS increases with increase in pad density and pad
lower as compared to mechanical refrigeration (Table thickness at certain level with proper water flow rate
1). and pad-face velocity, than decreases for a particular
material. Pad density, pad thickness, air flow rate and
Pad materials of EC structure water flow rate are the important parameters required
Pad is important part of ECSS. Many to be considered for efficient design.
researchers have studied the effect of cooling pads on
cooling efficiency (Table 2). There is a lot of research Performance of EC for different agro
studying the characteristics and performance of various produces
types of evaporative cooling pads, namely sand, clay, EC storage structures evaluated for their
brick bats, date palm fibres and leaves, clay, wood usefulness in increased shelf-life of commodity,
saving, sack, saw dust, wheat straw, jute, PVC sponge, reduction in physiological loss in weight, retention of
morum, pumice stone, coconut coir, rice husk, nutritive value, curing effect, better ripening and other
charcoal, cotton fabric, green house shedding net (Roy uses. The EC storage structure have been found
and Khurdiya, 1986; Umbarkar et al., 1991; Abdalla et suitable for extending shelf-life of potato, grape,
al., 1995; Mekonnen, 1996; Kapdi et al., 1997; Al- orange, banana, carrots, ber, pointed gourd, aonla, leafy
Sulaiman, 2002; Liao and Chiu, 2002; Sandhu and vegetables, sapota, kinnow, bitter guard, capsicum,
Ghuman, 2002; Lalmani et al., 2004; Gunhan et al., cauliflower, pineapple, peach and some other fruits and
2007; Jha, 2008; Tilahan, 2010; Vala and Joshi, 2010; vegetables (Roy and Pal, 1991; Das, 1999; Das and
Chinenye, 2011; Kulkarni, 2011; Nitipong and Sukum, Chandra, 2001; Singh and Satapathy, 2006; Jha, 2008).
2011; Samira et al., 2011; Banyat and Bunjerd , 2013) The EC storage structure can be utilized for short-term
and man-made commercial cooling pads; aspen pad storage of perishable commodities, when outside
and rigid pad (cel-dek) (Abdalla et al., 1995; Al- climate is hot and dry. Evaporative cooling system
Sulaiman, 2002; Vala and Joshi, 2010; Kulkarni, should be recommended for use by small scale farmers,
2011). Although commercial pads gave good saturation retailers, wholesalers and exporters to nearby
efficiency, as they are specially made but they are neighboring countries (Table 4).
expensive and not suitable to low income farmers and Looking to the advantages and suitability of
traders. Locally and easily available pads performed ECSS in country, this can be constructed in many parts
better with RH above 90% and maximum temperature for storage of fruits and vegetables at low cost as
drop of 25°C. However, performance is dependent on compared to costly mechanical refrigeration system.
outside weather but saturation efficiency can further be Being simple in design and operation, this system will
increased by creating good porosity and air-water be helpful in reducing the post-harvest losses at farm
contact within pad. level.
Performance of the pad material depends on
outside weather, both temperature and humidity but the
material having good porosity and air-water contact Conclusions
within the pad performed better as compared to others. Evaporative cooling system could be more
efficient for storage of fruits and vegetables where the

Trends in Post Harvest Technology | July-September, 2014 | Vol 2 | Issue 3 | Pages 22-32
© 2014 Jakraya Publications (P) Ltd
24
 Vala et al…Evaporative Cooled Storage Structures: An Indian Scenario

Table 1: Structural Parameter of EC

Source Structure details

Chouksey (1985) Developed a solar-cum-wind aspirator type ventilated EC storage structure for potato, onion and
other perishables. The details of the structure are;
(I) Size : 10.0 x 5.0 x 3.5 m
(ii) Shape : long and narrow
(iii) Capacity : 20 tones
(iv) Structural material: brick
(v) Wall thickness : 32 cm
(vi) Roofing material : asbestos sheet
Roy and Khurdiya Developed EC zero energy cool chamber for storing fresh horticultural produce (Pudina,
(1986) Dhania, Palak, Methi, Tinda, Chilli, Kerela, Bhindi, Radish, Beet, Carrot, Turnip, Peas, and
Cauliflower). During peak summer average cool chamber temperature was maintained to about
23°C.
(i) Size : 1.65 x 1.15 x 0.67 m
(ii) Structural material: brick, khaskhas, bamboo, gunnybag
Umbarkar et al. Constructed double brick walled EC storage structure under a shed for extending the shelf life
(1991) of oranges.
(i) Size : 0.75 x 0.75 x 0.75 m
(ii) Capacity : 25 kg
(iii) Structural material: brick, cement, mortar, gunny bag, bamboo
Rama and Constructed metallic EC storage chamber, which was covered with G. I. tray as lid and was
Narasimham (1991) placed in a G. I. tray. The surfaces of the EC chamber were covered with cotton cloth & kept in
shade for storing potato.
(i) Size : 1.00 x 0.25 x 0.50 m
(ii) Capacity : 25 kg
(iii) Structural material: aluminium sheet (28 gauge), cotton cloth,
polystyrene sheet
Garg et al. (1997) Developed three non-refrigerated storage structures namely, EC storage, passive draft EC
storage and farm storage chamber. EC storage of tomato showed good results as compared to
other storages.
(i) Size : 1.80 x 1.36 x 1.65 m
(ii) Structural material: Thick deodar wood, thermocole
Kapdi et al. (1997) Developed a two walled small size evaporative cooled structure and same was evaluated with
respect to the temperature drop obtained and saturation efficiency.
(i) Size : 1.0 x 1.0 x 0.75 m
(ii) Capacity : 100 kg
(iii) Structural material: mild steel, plastic polymer sheet
Thakral et al. (2000) Developed different models namely pot type, almirah model, basket type and zero energy cool
chambers. Almirah model showed good results in terms of temperature drop obtained and
saturation efficiency as compared to others. Structural details not mentioned.
Sandhu and Ghuman Designed and constructed double wall EC storage structure by using low cost locally available
(2002) materials for potato.
(i) Size : 5.49 x 5.49 x 3.39 m
(ii) Capacity : 8 tones
(iii) Structural material: brick, sand
Kumar et al. (2003) Constructed and evaluated three different capacity double walled evaporative cooled storage
structures for potato. Outdoor domestic type store performed better than the other two.
(i) Size : (a) 1.89 x 1.28 x 0.07 m (indoor, cap-50 kg)
(b) 2.00x 2.00 x 0.75 m (outdoor, cap-100 kg)
(c)5.5 x 5.5 x 3.5 m (large outdoor, cap-100 bag)
(ii) Structural material : brick, jute bag
Babarinsa (2006) Constructed a double-walled rectangular evaporative cooled storage structure for tomato.
(i) Size : 108 x 108x 120 cm
(ii) Capacity : 1.38 m3
(iii) Structural material: Bricks, sand, cement, particle board

Trends in Post Harvest Technology | July-September, 2014 | Vol 2 | Issue 3 | Pages 22-32
© 2014 Jakraya Publications (P) Ltd
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 Vala et al…Evaporative Cooled Storage Structures: An Indian Scenario

Jha (2008) Constructed a double walled evaporative cooled storage structure for storage of potato, tomato,
kinnow with RCC roof having 22 inclinations with horizontal.
(i) Size :3x3x3m
(ii) Capacity : 2tones
(ii) Structural material: Bricks, cement, sand, iron rods
Mishra et al. (2009) Constructed a double walled evaporative cooled storage structure for storage of potato.
(i) Size :6x6m
(ii) Capacity : 5 tones
(ii) Structural material : Bricks, cement concrete
Rayaguru et al. Constructed a double walled evaporative cooling structure for storage of potato, tomato, brinjal,
(2010) mango, banana and leafy vegetables.
(i) Size : 1.650 × 1.150 × 6.75 m.
(ii) Structural material : Bricks, sand, cement concrete
Tilahan (2010) Constructed forced ventilation evaporative cooling storage structure and worked out feasibility
and economics of the structure for storage fruit and vegetables, reported that that the
evaporative cooling system was capable of significantly (P<0.001) reducing the temperature and
significantly (P<0.001) increasing the relative humidity as required for short time storage of
selected fruits and vegetables such as carrot, mango, papaya, banana, mandarin, orange, lemon
and tomato.
(i) Size :2 x 2 x 1.3m
(ii) Capacity : 0.5 ton
(iii) Structural material: M.S. sheet, angles, wire mesh
Vala and Joshi Designed and developed a forced draft metallic EC storage chamber covered with thick cotton
(2010) cloth.
(i) Size : 1525 x 1006 x 1220 mm
(ii) Capacity : 100 kg
(ii) Structural material: M.S. sheet, angles, wire mesh, thick cotton cloth
Chinenye N M Constructed a jacketed type double walls evaporative cooling structure for storage of tomato.
(2011) The top of the structure covered with an aluminium foil.
(i) Size : 60 cm x 52 cm x 85cm
(ii) Structural material : clay, bamboo stick, aluminium foil
Samira et al. (2011) Developed a multi pad evaporative cooler having three units, viz., an air conditioning unit, a
watering system and a storage chamber for storage of green pepper.
(i) Size : 2 x 2 x 1.3 m
(ii) Capacity : 0.5 tone
(ii) Structural material : Sheet metal, iron angles, gunny bag

Table 2: Efficiency of EC Pad Materials

Source Pad material Performance

Roy and Khurdiya (i) River bed sand Inside temperature of cool chamber was 20°C less than the ambient
(1986) temperature and relative humidity was 95% during peak summer
months.
Umbarkar et al. (i) Fine sand, Maximum temperature drop of 18.5°C and maximum RH of 94.8%
(1991) (ii) Brick bat, were observed for brick batt which were significantly superior over
(iii) Coarse sand the fine sand and coarse sand material throughout the storage
period. Coarse sand and fine sand showed more or less equal drop
in temperature.
Abdalla et al. (i) Date palm fibres, Evaluated for 100 mm pad thickness and reported that best cooling
(1995) (ii) Date palm leaves, was obtained by Cel-dek (temp. drop 12-23° C, SE 75.3-90.5%)
(iii) Cel-dek followed by date fibre pad (temp drop 11-21°C, SE 69-83.3%) and
date leave pad (temp drop 9-18°C, SE 54-69 %).
Mekonnen (1996) (i) Clay particles, Clay showed higher saturation efficiency and temperature
(ii) Wood shaving, reduction (8°C, RH 76%) than others. Wood shavings and sack
(iii) Sack showed susceptibility to decay.
Kapdi et al. (1997) (i) Brick bat, Brick bat gave better performance (temp drop 4.2- 8.8°C, RH 85-
(ii) Saw dust, 98 %, SE 48.5-97% over that with wheat straw (temp drop 2.1-
(iii) Wheat straw 5.9°C, RH 65.9-94.3%, SE 32-62.5%) and saw dust (temp. drop
1.5-7.2°C, RH 68.6-95.9%, SE 19-91 %).

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 Vala et al…Evaporative Cooled Storage Structures: An Indian Scenario

Al-Sulaiman 2002) (i) Jute Jute performed better with cooling efficiency of 62.1% followed by
(ii) Luffa luffa (55.1%), commercial (49.5%) and palm fibre (38.9%).
(iii) Commercial pad
(iv) Palm fibre
Liao and Chiu (i) Coarse fabric Reported saturation efficiency ranged from81.75% -84.48% with
(2002) PVC sponge Coarse fabric PVC sponge whereas 76.68% - 91.64% with fine
(ii) Coarse fine PVC fabric PVC sponge
sponge
Sandhu and (i) Sand Observed temperatures drop of 8–14.9ºC with RH 90-96.3 %
Ghuman (2002) inside the structure.
Lalmani et al. (i) River bed sand, (ii) Reported temperature drop of 15.4º C, 14.4º C & 14.2º C in river
(2004) Morum, bed sand, morum and mixture of riverbed sand and morum,
(iii) mixture of riverbed respectively and maintained more than 80% RH in all three.
sand and morum
Olosunde (2006) (i) Jute, Reported that the jute material had the overall advantage over the
(ii) Hessian, other materials.
(iii) Cotton waste.
Gunhan et al. (i) Pumice stones It was found that volcanic tuff performed better and gave saturation
(2007) (ii) Volcanic tuff efficiency of 63-81%.
(iii) Greenhouse shedding
net
Jha S N (2008) (i) Partal wood shavings The maximum drop in temperature in no-load condition was
observed 20ºC as against outside temperature 45ºC. Whereas RH
maintained about 75%.
Vala and Joshi (i) Wood wool, The highest temperature drop of 12.06°C was achieved with wood
(2010) (ii) Coconut coir, wool as compared to coconut coir and wood shavings. Coconut
(iii) wood shavings coir and wood shavings showed more or less equal drop in
temperature.
Chinenye (2011) (i) clay Maximum temperature reduction of up to 10°C and relative
humidity 92 % observed during storage period.
Kulkarni (2011) (i) Aspen fibre The higher saturation efficiency in the range of 93.7–87.5% was
(ii) Rigid cellulose observed with aspen fibre followed by 86.2-77.5%, 80.2 – 88.4%
(iii) Corrugated paper and 81.9 – 89.7% with rigid cellulose, corrugated paper and HDPE
(iv) HDPE respectively.
Nitipong and (i) Rice husk The average saturation efficiency of 55.9% and 29.1% was
Sukum (2011) (ii) Recycled HDPE observed with rice husk and recycled HDPE respectively.
Samira et al. (i) Charcoal Maximum temperature drop of 12°C and RH between 70–82.4%
(2011) observed during storage period
Banyat and (i) Curtain fabric Curtain fabric gave higher average saturation efficiency of 54.8%
Bunjerd (2013) (ii) raw cotton fabric as compared to raw cotton fabric of 33.2%.

Table 3: Effect of Operating Parameters on performance of EC Structure

Source Operating parameters Performance

Thakur and (i) Pad thickness, Saturation efficiency initially increased with increase in pad
Dhingra (1983) (ii) pad face air velocity, thickness, pad face air velocity and water flow rate then remained
(iii) water flow rate, constant or decreased marginally. Saturation efficiency was
(iv) pad orientation observed higher in horizontal pad thickness as compared to vertical
pad thickness. The effect of water flow rate remained less
pronounced than the effect of pad thickness and pad face air
velocity.
Thakur and (i) Pad face air velocity, Effect of pad-face velocity on the pressure drop was more
Dhingra (ii) Density, pronounced than that of pad density and pad thickness.
(1985) (iii) Pad thickness
Dhingra and (i) Pad density When pad density of an evaporative cooling increased, the SE
Thakur (1986) (ii) pad thickness increased. For achieving SE 70-75%, a pad thickness of 5 cm and
density in the range of 30-40 kgm-3 was desirable but when SE of
more than 90% is required, a pad thickness of 5 cm and pad density

Trends in Post Harvest Technology | July-September, 2014 | Vol 2 | Issue 3 | Pages 22-32
© 2014 Jakraya Publications (P) Ltd
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 Vala et al…Evaporative Cooled Storage Structures: An Indian Scenario

of more than 45 kgm-3 may be used.

Umbarkar et al. Pad thickness: 100, 150 and 200 Thickness of cooling pad had no influence on relative humidity.
(1991) mm The brick bat pad of 100 mm width gave best results.
Yadav et al. (i) Pad thickness If air and water flow rates were not limiting, pad thickness did not
(2002) 50, 75 & 100 mm have any effect on cooling. Selection of water flow rate depends on
(ii) Air flow rate air flow rate and pad thickness. As air flow rate increased, water
0.3, 0.45, 0.6 & 0.75 m/sec flow rate increased. The pressure drop increased with increase in
(iii) Water flow rate pad thickness.
5,10 &15 l/min
Jha and Aleskha (i) Pad thickness 3,7, 10 Partal wood shavings with 7 mm pad thickness found best for
Kudos (2006) &15 mm maximum in cooling effect and porosity than safeda wood shavings
(ii) Pad volume0.00075, 0 and root (plants).
.175,0.00250 & 0.00375 m3
(iii) Bulk density
(iv) Porosity, %
Vala and Joshi (i) Pad thickness The wood wool gave average maximum temperature drop, increase
(2010) 50, 100 & 150 mm in RH and saturation efficiency with pad thickness of 150mm and
(ii) Pad density pad density 25kg/m3. The highest saturation efficiency of 93.89%
15, 20, 25 kg/m3 was achieved with wood wool material at density 25kg/m3 and
(iii) Water flow rate thickness 150mm.
3 lph
(iv) Air flow rate
50kmph

Table 4: Performance of EC for Different Agro Produce

Source Agric. Produce Performance

Maini et al. (1984) Potato tubers Potato tubers could be stored up to 5 weeks with PLW of 3.3 % in
evaporative cool storage compared with 18.6 % PLW at room
temperature and 9.3 % in the desert cooler for the same period.
Chouksey (1985) Potato Potato could be stored from first week of March to 16th June. Onion
could be stored from July to November with proper ventilation.
Roy and Khurdiya Leafy vegetables Shelf life of leafy vegetables increased to 3 days with PLW of 13-18
(1986) (Pudina, Dhania, Palak, % from less than 1 day with PLW of 30-58 % at ambient and for
Methi), Tinda, Chilli, other vegetables the shelf life was increased to 6 days with 5-6.8 %
Kerela, Bhindi, Radish, PLW as compared to 1-3 days in the month of May-June.
Beet, Carrot, Turnip,
Peas, Cauliflower
Singh et al. (1987) Grapes PLW was higher at room temperature storage as compared to zero
energy cool chamber under different treatments.
Thingu et al. Tomato Evaporative cooled storage showed 100% ripening index, double
(1991) lycopene content and less shrinkage as compared to control sample.
Umbarkar et al. Orange Shelf life up to 32 days with less qualitative loss and PLW.
(1991)
Reddy and Sapota Shelf life of sapota fruit cv. Kalipatti increased with reduced PLW
Nagaraju (1993) and shriveling, higher firmness and less rotting leading to recovery
of higher percent of marketable fruits.
Garg et al. (1997) Tomato Tomato could be stored up to 50 days in EC storage, 32 days in
passive draft EC storage and 30 days in farm level storage as
compared to 14 days in ambient storage.
Pal et al. (1997) Kinnow mandarins Shelf life increased up to 40 days in EC chamber as against 15 days
at room temperature.
Kumar and Gupta Potato Potatoes could be safely stored up to 13th week of storage in EC
(1999) storage as against 8th week in ambient storage without shrinkage and
sprouting.
Wasker and Roy Banana Banana fruit cv. Basrai could be stored up to 20 days as against 14
(2000) days at room temperature.
Dash and Chandra Economic feasibility EC structures could be adopted in places where cold storage facilities

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 Vala et al…Evaporative Cooled Storage Structures: An Indian Scenario

(2001) are not available or the transportation cost to the cold storage is very
high to offset the advantages of keeping produce in cold storage.
Bhardwaj and Sen Mandarin (Nagpur Mandarin fruit with neem extract treatment could be stored up to 42
(2003) santra) days for retaining post-harvest quality.
Dhemre and Mango Kesar mango fruits with wax treatment could be stored up to 25 days
Wasker (2003) as against 20 days at room temperature.
Mordi and Tomato Fresh tomatoes could be stored for 11 days as against 4 days at
Olorundu (2003) ambient temperature whereas tomatoes treated with film packaging
could be stored for 18 days as against 13 days under ambient
condition while completely sealed sample for 8 days as against 6
days under ambient condition.
Singh and Bitter guard, capsicum, The shelf life of bitter guard, capsicum & cauliflower was increased
Satapathy (2006) tomato, cauliflower, for 5 days whereas shelf life of tomato, pineapple, peach increased
pineapple, peach for about 6 to 9 days under evaporative storage as compared to
ordinary room condition.
Jha (2008) Potato, Kinnow, tomato Safe storage period was found to be 50, 25 & 4 days for potato,
kinnow and tomato respectively with 10% loss in weight
Mishra et al. Potato, tomato The shelf life of potato was observed 60 days as against 30 days in
(2009) ambient storage while tomato was safely stored for 14 days as
against 7 days at ambient condition.
Tilahan (2010) Economical feasibility The evaporative cooling system was capable of significantly
(P<0.001) reducing the temperature and significantly (P<0.001)
increasing the relative humidity as required for short time storage of
selected fruits and vegetables such as carrot, mango, papaya, banana,
mandarin, orange, lemon and tomato.
Chinenye (2011) Tomato The evaporative cooled storage was able to preserve freshly
harvested tomato for 19days.
Mogaji and Fapetu Tomato, carrot The shelf life of tomato and carrot was extended by 14 days relative
(2011) to ambient storage.
Samira et al. Green pepper The shelf-life of green pepper was effectively improved 20 days as
(2011) compared to storage under ambient condition.

climate is hot and dry, can also be used under other can have wide application if designed properly for
climatic conditions. Being low cost of construction, different locations. Evaporative cooling system is easy
negligible operational cost and having other advantages to operate, efficient and affordable most especially for
over mechanical refrigeration the evaporative cooled farmers in developing countries who may find other
storage structures can be used in any place where cold methods of preservation quite expensive and
storage facilities are not available. EC storage structure unaffordable.

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