Spray cooling myths
Spray cooling myths
Thursday, 16 April 2009
Chris James and Steve James comment on myths regarding continuous spray cooling.
In a recent book on processed meats we came across the following surprising statement that “continuous showering of a hot product traps the heat in the product because the permanent layer of water present on the surface. The thermal conductivity of water itself is very poor and by showering continuously, the cooling effect is quite limited because the layer of water on the outside of the hot product creates a barrier, acting as an insulator.”
In fact, the thermal conductivity of processed meat products (including cured sausages and hams) range between 0.272 Wm-1K-1 at 22°C to 0.482 Wm-1K-1 at 80°C (Marcotte et al., 2008), whereas the thermal conductivity of water is 1 Wm-1K-1. Thus, the thermal conductivity of water is actually more than double that of most processed meats. So clearly a layer of water on the surface of a food product will actually act as a higher conductivity path rather than an “insulator”. The reason why intermittent spray cooling can have benefits over continuous spray cooling is actually that a break in spraying allows the water on the surface of the hot product to evaporate, thus enhancing the cooling effect.
Reference
Marcotte, M., Taherian, A. R. & Karimi, Y. (2008) Thermophysical properties of processed meat and poultry products. Journal of Food Engineering. Vol. 88:3, pp315-322