ABSTRACT
Introduction .................................................................................................................................... 129 Freezing Load ................................................................................................................................ 130
Calculation ................................................................................................................................ 130 Freezing Rate and Thermal Center ........................................................................................... 130
Freezing Time or Rate Prediction .................................................................................................. 131 Plank’s Equation........................................................................................................................ 133 Nagaoka et al. Equation ............................................................................................................ 136 Levy Equation ........................................................................................................................... 136 Cleland and Earle Equation ....................................................................................................... 136 Cleland et al. Method ............................................................................................................... 137 Pham method ............................................................................................................................. 138 Modi˜ed Pham Method............................................................................................................. 138
Thawing Time Prediction ............................................................................................................... 141 Conclusions .................................................................................................................................... 142 Nomenclature ................................................................................................................................. 143
Greek Letters ............................................................................................................................. 143 References ...................................................................................................................................... 143
Freezing load or enthalpy change (∆H) to reduce the product temperature (Ti) from some level above the freezing point (TF) to some desired ˜nal temperature (T) is given by
∆H = sensible heat removed from the product solids (∆Hs ) + sensible heat removed from unfrozen water (∆Hu) + enthalpy change due to latent heat (∆HL ) + sensible heat removed from the frozen water (∆HI)
ΔH M C T T M C T T
= − + ∫( ) (6.1a) ΔH M C T T M C T Tu u pu i F u pu F= − + ʹ −( ) ( ) (6.1b)
ΔH M LL I f= (6.1c)
ΔH M C T T M C TI T
( ) (6.1d)
where MS = mass of solids, Cps = speci˜c heat of solids, Mu = mass of unfrozen water, Cpu = speci˜c heat of unfrozen water, MI = mass of ice or unfrozen water, Lf = latent heat of freezing, CpI = speci˜c heat of ice, and C′pu =speci˜c heat of unfrozen water below TF.
