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Comparative methods of determining heat transfer coefficients over moist food materials

Production of surimi represents a potential utilization of a number of low-valued
fish species, one of which, Pacific whiting, represents the largest biomass off the West
Coast of the United States. However, a protease enzyme softens the fish flesh in Pacific
whiting and limits the expansion of surimi production.
Many studies have demonstrated the importance of time and temperature in
minimizing the texture softening. An optimal design of the surimi seafood process is
possible only when an accurate prediction of the time-varying temperature distribution
throughout the surimi product can be obtained. This provides a measure of the heating
rate and the extent of thermal processing. Such a prediction necessitates a study of the
surface heat transfer coefficient which is one of the most important parameters for the
heat transfer analysis.
Associated with automated-machinery processing of surimi seafoods, a full
understanding of the heat transfer coefficient (h) is especially important because high-quality
surimi products using Pacific whiting only can be obtained through rapid and
controlled heating. This study was intended to determine transient surface heat transfer
coefficients in a steam heating environment, simulating the widely-used steam heating of
thin-sheet surimi paste in the seafood industry.
In determining the heat transfer coefficient, many different methods have been
used including the inverse calculation method, the lumped mass method and the heat flux
method. This study employed all three to measure and model the heat transfer coefficient
(h) under similar steam conditions. A comparative evaluation was made to define the
best method and model for the h determination. The inverse calculation method produced
an h model which, when applied to a heat transfer analysis, provided the best agreement
between predicted and experimental temperature profiles at three locations in surimi paste
during a 1000-sec cooking period. The lumped mass method overestimated the heat
transfer coefficients to food; the heat flux method gave inconsistent measurements.
It is a classic inverse problem to estimate surface heat transfer coefficients from
temperature measurements inside a product, a procedure which involves solution of the
inverse heat conduction problem and parameter optimization. A whole domain function
specification procedure was developed for the inverse calculation method. This
procedure simulates heat transfer coefficients as specified functions by estimating all the
unknown parameters in the functions over the total time interval. A nonlinear regression
computer program was written for the inverse calculation of surface heat transfer
coefficients, incorporating the implict Crank-Nicolson scheme for the finite-difference
formulation of the one-dimensional heat conduction problem and the downhill simplex
method for parameter optimization. This inverse calculation method provided relatively
accurate models of the surface heat transfer coefficient. / Graduation date: 1997
Date27 June 1996
CreatorsSu, Ainong
ContributorsKolbe, Edward R.
Source SetsOregon State University
Detected LanguageEnglish

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