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Energy Efficiency

, Volume 7, Issue 5, pp 777–790 | Cite as

Effects of airflow induction on heat transfer and energy consumption while freezing passion fruit pulp in stacked boxes

  • Natália Cristina Belchior
  • Tales Márcio de Oliveira Giarola
  • Jaime Vilela de ResendeEmail author
Original Article

Abstract

The objectives of this work were to characterize the energy consumption and the heat transfer process by the determination of the convective heat transfer coefficient (h) of passion fruit pulp contained in high-density polyethylene (HDPE) boxes and frozen in two conditions: without and with airflow induction, which was achieved through the installation of obstacles. To determine the convective heat transfer coefficients, HDPE boxes containing passion fruit pulp (contained in polyethylene bags) were interspersed with boxes containing metal tanks filled with low freezing point solutions. Three types of solutions were used: ethylene glycol, propylene glycol, and ethanol. The airflow induction under the stacks of passion fruit pulp provided higher h values than without airflow induction. The calculated average values and standard deviation were 6.340 ± 0.87 W/m2 °C, respectively, without airflow induction and 8.419 ± 1.39 W/m2 °C with airflow induction. The average reduction of the freezing time was 25 % for the boxes located at the top and 20 % in the base of the stack. This proved that directing the airflow under the stacked product promoted more uniform and efficient heat transfer. The analysis of the electrical parameter measurements revealed an approximate decrease of 16.7 % in energy consumption due to the reduction of the freezing time, without compromising the quality and operation of the electrical system. This practice was shown to be viable for small producers and agribusinesses that desire reductions in processing time and energy consumption and, consequently, the overall cost of the final product.

Keywords

Effective heat transfer coefficient Energy consumption Air-blast freezing Frozen fruit pulp Freezing time 

Nomenclature

A

Heat transfer area (square meter)

AD

Active demand (kilowatt)

AE

Active energy (kilowatt hour)

AEM

Active energy/month (kilowatt hour)

AP

Amount of product/batch (kilogram)

Bi

Biot number

Bis

Biot number = h2L/k

CD

With air induction

Cp

Specific heat (kilojoule per kilogram per degree Celsius)

CF

Charge factor

D

Diameter (meter)

e

Error (percent)

E

Equivalent heat transfer dimensionality

h

Convective heat transfer coefficient (watt per square meter per degree Celsius)

k

Thermal conductivity (watt per meter per degree Celsius)

m

Mass (kilogram)

MAD

Maximum active demand (kilowatt)

NBM

Number of batches/month

PF

Power factor

PPM

Physical production/month (kilogram)

RE

Reactive energy (kilovolt-ampere-reactive-hour)

SC

Specific consumption (kilowatt hour per kilogram of pulp)

SD

Without air induction

T

Temperature (degree Celsius)

t

Time (hour)

X

Length in the coordinate system (meter)

Y

Height in the coordinate system (meter)

Z

Width in the coordinate system (meter)

Zn, Zm

Roots of a transcendental equation of the type C = αtanα

Znm

Defined by Eq. (12).

Greek symbols

βi

Ratio of dimension to characteristic dimension, i = 1, 2

Δ

Difference

Air cooling

Subscripts

Air

Air

AN

Dimensionality analytically derived

Eff

Effective

eq

Equivalent

etg

Ethylene glycol

eth

Ethanol

exp

Experimental

f

Freezing

max

Maximum

pred

Predicted´

prop

Propylene glycol

slab

Slab

sol

Solution

tq

Tank

0

Unfrozen

Notes

Acknowledgments

The authors wish to thank the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG-Brazil), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq-Brazil) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES-Brazil) for financial support for this research.

References

  1. Andrade, J.C., Pereira, L.V., Santos, C.C., Fráguas, J.C., Abrahão, E., Alvarenga, A.A. & Silva, V.J. (2003). Mercado de frutas em Lavras. Circular Técnica – CTSM, 161–169.Google Scholar
  2. ASHRAE (1997). ASHRAE handbook—fundamentals. Chapter 20, Physical properties of secondary coolants (brines). Atlanta: ASHRAE.Google Scholar
  3. ASHRAE (2002). ASHRAE handbook—refrigeration. Chapter 8, Thermal properties of foods. Atlanta: ASHRAE.Google Scholar
  4. Barbin, D. F., Neves Filho, L. C., & Silveira Junior, V. (2010). Convective heat transfer coefficients evaluation for a portable forced air tunnel. Applied Thermal Engineering, 30, 229–233.CrossRefGoogle Scholar
  5. Carslaw, H. S., & Jaeger, J. C. (1959). Conduction of heat in solids (2nd ed.). London: Oxford University Press.Google Scholar
  6. Cleland, A. C. (1992). Food refrigeration process: analysis, design and simulation. London: Elsevier Applied Science.Google Scholar
  7. Cleland, D. J., Cleland, A. C., & Jones, R. S. (1994). Collection of accurate experimental data testing the performance of simple methods for food freezing time prediction. Journal of Food Process Engineering, 17, 93–119.CrossRefGoogle Scholar
  8. Delgado, A. E., & Sun, D. W. (2001). Heat and mass transfer models for predicting freezing processes—a review. Journal of Food Engineering, 47(3), 157–174.CrossRefGoogle Scholar
  9. Hossain, M. M., Cleland, D. J., & Cleland, A. C. (1992). Prediction of freezing and thawing times for foods of two-dimensional irregular shape by using a semi-analytical geometric factor. International Journal of Refrigeration, 15(4), 235–240.CrossRefGoogle Scholar
  10. IBGE. (2010). Instituto Brasileiro de Geografia e Estatística. Available in: http://www.ibge.gov.br/home/estatistica/economia/pam/2010/PAM2010_Publicacao_completa.pdf. Accessed on 13 August 2013.
  11. Incropera, F. P., & Dewitt, D. P. (2003). Fundamentos de transferência de calor e de massa (5th ed.). São Paulo: LTC.Google Scholar
  12. Lind, I. (1988). Surface heat transfer in thawing by forced air convection. Journal of Food Engineering, 7, 19–39.CrossRefGoogle Scholar
  13. Meleti, L.M.M. (2011). Avanços na cultura do maracujá no Brasil. Revista Brasileira de Fruticultura,33, no.spe1, doi: 10.1590/S0100-29452011000500012
  14. Pereira, C. G., Resende, J. V., Pereira, G. G., Giarola, T. M. O., & Prado, M. E. T. (2013). Thermal conductivity measurements and predictive models for frozen guava and passion fruit pulps. International Journal of Food Properties, 16, 778–789.CrossRefGoogle Scholar
  15. Pham, Q. T. (1986). Simplified equation for predicting the freezing time of foodstuffs. Journal of Food Technology, 21(6), 209–219.MathSciNetGoogle Scholar
  16. Reno, M. J., Resende, J. V., Peres, A. P., Giarola, T. M. O., & Prado, M. E. T. (2011). Heat transfer and energy consumption in the freezing of guava pulp in large containers. Applied Thermal Engineering, 31, 545–555.CrossRefGoogle Scholar
  17. Resende, J. V., Prado, M. E. T., & Silveira Junior, V. (2013). Non-uniform heat transfer during air-blast freezing of a fruit pulp model in multilayer boxes. Food and Bioprocess Technology, 6, 146–159.CrossRefGoogle Scholar
  18. Salvadori, V. O., & Mascheroni, R. H. (1996). Freezing of strawberry pulp in large containers: experimental determination and prediction of freezing times. International Journal of Refrigeration, 19(2), 87–94.CrossRefGoogle Scholar
  19. Santos, C. A., Carciofi, B. A. M., Dannenhauer, C. E., Hense, H., & Laurindo, J. B. (2007). Determination of heat transfer coefficient in cooling-freezing tunnels using experimental time–temperature data. Journal of Food Process Engineering, 30, 717–728.CrossRefGoogle Scholar
  20. SENAI.RS. (2003). Evaluation of energy. Porto Alegre: Centro Nacional de Tecnologias Limpas.Google Scholar
  21. Thompson, J. F. (2004). Pre-cooling and storage facilities. In USDA (Ed.), Agriculture handbook number 66—DRAFT. Washington, DC: United States Department of AgricultureGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • Natália Cristina Belchior
    • 1
  • Tales Márcio de Oliveira Giarola
    • 1
  • Jaime Vilela de Resende
    • 1
    Email author
  1. 1.Department of Food Science, Laboratory of Food RefrigerationFederal University of LavrasLavrasBrazil

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