ULTRA FAST FREEZING OF WARM PRODUCT USING CRYOGENIC SLUSH

摘要

When the immersion in liquid nitrogen of a warm product doesn’t produce a quick enough freezingrnprocess, we sometime need a faster method. One solution consists of replacing pure liquid nitrogen by arncryogenic slush; a suspension of solid particles in liquid nitrogen. The calefaction in slush is significantlyrndifferent than the calefaction in pure liquid nitrogen and this impacts the heat transfer. The purpose of thisrnstudy is to quantify the heat transfer improvement we can get from a liquid-nitrogen-based slush. Severalrnmixtures of liquid nitrogen with water ice crystal (H2O), carbon dioxide snow (CO2), solid nitrous oxidern(N2O) and solid nitrogen (N2) have been tested at lab-scale. The slush was tired in a Dewar and the heatrntransfer was measured with a temperature probe fitted in a copper ball. The results show that the heatrntransfer can be significantly enhanced (doubled) when using the right slush.