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Journal of Food Science and Technology

, Volume 52, Issue 8, pp 4819–4829 | Cite as

Batch uniformity and energy efficiency improvements on a cabinet dryer suitable for smallholder farmers

  • Marcelo PrecoppeEmail author
  • Serm Janjai
  • Busarakorn Mahayothee
  • Joachim Müller
Original Article

Abstract

Drying can add value, facilitate transport and extend the storage life of agro-products; therefore, in developing countries with poorly established cool-chains, drying is particularly effective. Furthermore, drying within small-scale village-based enterprises contributes to rural development. However, most equipment suitable to such operations yields a product of non-uniform quality and shows low levels of energy efficiency. The aim of this research was to improve the batch uniformity and the energy efficiency of a cabinet dryer suitable for smallholder farmers. Experiments were carried out with the cooperation of a dryer manufacturer and a group of users. On each trial 144.5 kg of peeled and deseeded litchis were placed at the dryer’s 17 trays, that were stacked atop each other. Moisture content (wet basis) was reduced from 87 to 23 % in about 15.5 h. It was found that a low-cost modification to the dryer chamber’s air inlet was able to improve heat distribution and increase the uniformity of the fruit’s moisture content. In the original design, at the end of the drying process, moisture content of the fruits on the top tray was 38 % while at the bottom tray was 12 %. The modification to the dryer reduced this disparity and the final moisture content of the fruits placed at the top tray was 25 % while at the bottom tray was 21 %. In addition, the modification reduced the dryer’s air mass flow from 0.3 to 0.1 kg s−1 without jeopardizing drying forces, consequently the dryer energy efficiency increased from 33 to 42 %.

Keywords

Convection dryer Hot-air dryer Heat consumption Product homogeneity Moisture content Lychee 

Notation

A

Area

Est

Isosteric heat of sorption

LPG

Liquefied petroleum gas

m

Mass

\( \overset{\cdot }{m} \)

Mass flow

\( {\overset{\cdot }{n}}_{\mathrm{w}} \)

Drying rate

Ø

Undefined variable

P

Pressure

Q

Heat

\( \overset{\cdot }{Q} \)

Power

T

Temperature

v

Air velocity

\( \overset{\cdot }{w} \)

Evaporation rate

X

Moisture content

Y

Absolute humidity

Greek letters

γ

Uniformity index

η

Energy efficiency

λ

Latent heat of vaporisation

φ

Relative humidity

Subscripts

air

Drying air

dm

Dry matter

duct

Dryer’s air duct

in

Input

out

Outlet

tray

Dryer’s tray

w

Water

Notes

Acknowledgments

This study was conducted as part of an international program named “Sustainable Land Use and Rural Development in the Mountainous Regions of Southeast Asia” (SFB 564). It was funded by the Deutsche Forschungsgemeinschaft (DFG) and co-funded by the National Research Council of Thailand (NRCT). We should express gratitude to the Hmong Mae Sa Valley Cooperative, and to Likhitchewan Co., Ltd, for taking part in this research study, and would also like to thank the Faculty of Agriculture at Chiang Mai University for hosting the SFB 564 office and supporting the project’s laboratory work.

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Copyright information

© Association of Food Scientists & Technologists (India) 2014

Authors and Affiliations

  • Marcelo Precoppe
    • 1
    Email author
  • Serm Janjai
    • 2
  • Busarakorn Mahayothee
    • 3
  • Joachim Müller
    • 1
  1. 1.Institute of Agricultural EngineeringUniversität HohenheimStuttgartGermany
  2. 2.Department of PhysicsSilpakorn UniversityNakhon PathomThailand
  3. 3.Department of Food TechnologySilpakorn UniversityNakhon PathomThailand

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