Pressure drop of flowing ice slurries in industrial heat exchangers

Experiments were conducted to determine the characteristics of ice flows through industrial heat exchangers (a Tetra Plex® C6-SR and a Tetra Spiraflo® MTC70/W-3). This type of equipment presents many problems with respect to cleaning and is therefore of particular interest when considering a pigging system using ice slurry. Moderately thick ice slurries (in the range 15–60% solids) were successfully pumped through commercial heat exchangers. Measured pressure drops were greater than those with water, and rose with increasing ice fraction and flow rate. Evidence was seen for an exponential dependence of pressure drop on ice fraction, in addition to a water-like dependence on the square of flow rate. Blocking events were observed at higher ice fractions, or when large crystal masses were thought to be present in the ice slurry. It is likely that the risks of this could be mitigated by better mixing of the bulk ice slurry prior to and during delivery. For some tests the ice crystals may have grown to almost 1 mm in diameter, which is close to the characteristic dimension of the flow channels in the PHE (mean width 4 mm), increasing the likelihood of blockages forming.