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European Food Research and Technology

, Volume 221, Issue 3–4, pp 351–356 | Cite as

Determination of thermal conductivity and convective heat transfer coefficient during deep fat frying of “Kroštula” dough

  • Bernarda ŠerugaEmail author
  • Sandra Budžaki
Original Paper

Abstract

In this study, the influence of oil temperature, water migration and surface temperature of “Kroštula” dough on convective heat transfer coefficient was investigated. The convective heat transfer coefficient during deep fat frying was determined at temperatures 160, 170, 180 and 190±1 °C. Heat transfer coefficient was the highest at the start of deep fat frying process; 579.12±2.46, 583.88±1.81, 597.05±1.10 and 657.91±0.95 W/m2 K for 160, 170, 180 and 190 °C of oil temperature, respectively. The smallest heat transfer coefficient was in the case of setting up a uniform period of water migration from sample, which corresponded to surface temperatures slightly higher than 100 °C; 26.53±0.63, 14.42±0.56, 56.78±0.49 and 37.52±0.54 W/m2 K for 160, 170, 180 and 190 °C of oil temperature, respectively. Higher oil temperature for deep fat frying increased values of heat transfer coefficient. A steady-state method was used to determine thermal conductivity of “Kroštula” dough in temperature range of 40–70±1 °C. The thermal conductivity first increased with temperature and then after reaching maximum values decreased. The maximum value 0.5985±0.0196 W/(m K) was determined at 47.5 °C. The minimal value 0.4723±0.0192 W/(m K) was determined at 65 °C.

Keywords

Deep fat frying Heat transfer coefficient Thermal conductivity Dough 

Abbreviations

A

surface area (m2);

cp

specific thermal capacity (kJ/kg);

(dm/dt)

drying rate (g/s);

h

heat transfer coefficient (W/m2 K);

ΔHvap

heat of water vaporization (kJ/kg);

k

thermal conductivity (W/(m K));

q

heat flow across the surface (W);

Tf

final temperature of water for accumulation of energy (°C);

Ti

initial temperature of water for accumulation of energy (°C);

To

oil temperature (°C);

Ts

surface temperature of the sample (°C);

Δt

time for reaching steady state (h);

ΔT

temperature difference between heated and cooled surface (°C);

w

water loss rate change (g/s);

W

mass of water for accumulation of energy (kg);

Δx:

thickness (m)

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of Process Engineering, Faculty of Food TechnologyJosip Juraj Strossmayer University of OsijekOsijekCroatia

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