Through the years different materials and designs were used in construction of eutectic evaporator plates. Earlier designs were produced by truck refrigeration
industries where eutectic holdover plates using 14 gauge carbon material inside and outside welded tanks
brine eutectic solution inside. What made them more efficient than today's plates is the evaporator coils inside were attached to the tanks
skin lowering box temperature faster than the solution could be frozen. Other methods used to stop dissimilar material corrosion evaporators were steel
and other chemicals were added to neutralize the brine corrosion. Finally the expansion air space is tank was evacuated and replaced with nitrogen. Many of these eutectic plates used by Crasby and Grunert and others 30 years ago are still in service
in blue water
cursing boats. They are generally identified by coating of cold galvanizing paint
over plan carbon steel
and fill plug
is welled in.
Eutectic plates in mobile refrigeration
need to avoid problems like: Evaporator coil or tubing need to be spaced no more than 2 inches apart hopefully covering entire solution. No solder or brazed tubing joints inside plate if possible. Evaporator coil must be attached to plate inside or wedged against plate sides to prevent it from act with the dynamic motion of boat
when solution partly frozen.
When I compared the Brine and Proprietary secret solution plates against Food
grade Propylene glycol my plates needed to be fifteen percent larger to be equal to Brine plate performance. Most every one today uses Glycol in eutectic plates because it is not corrosive.
Glycol water mix does not freeze solid like ice water alone. Glycol water mix frozen resembles soft crystals of a Popsicle. Normall a eutectic plate will not freeze solid completely at the beginning because of the thermostat setting, true performance is a couple of days later.