[Marmot]

Yeah, we use flash evaps running at around 162 - 170 F, just high enough to kill bacteria but minimize scaling. The only treatment involved at that point is an anti-foaming compound that also helps keep the scale soft enough to be chemically cleaned when it gets too thick. Virtually none of that makes it through to the distillate though.

The distillate is not treated, there is a valve that sends it to the distilled water tanks, the potable tanks, or the bilge. When it's good enough to save, it's all the same water.

When distilled water becomes feed water there are so many chemicals added that it is technically contaminated water with potassium hydroxide added to obtain a pH of around 11 and until recently laden with hydrazine to scavenge oxygen, and more phospates than the runoff from a third world laundromat. Pretty nasty stuff and makes terrible tea that really would give you the runs.

[brian eiland]

Originally Posted by brian eiland

It certainly appears as though the rim-driven propulsor concept has a lot of potential as a component in a jet pump drive system……ie, a rim driven impeller (“a new era of impeller design” as noted by YachtForums). Now we know there is considerable work being done on rim-drive technology, particularly those incorporating permanent-magnet electric motor components to power-up the rim. These electrical driven rim-drives may prove too advanced, overly complicated, and/or too expensive for small PWC or RIB jet applications.

Abstract

A concept investigation has been carried out into the possibility of using a tip driven electro-magnetic propulsor as part of a waterjet propulsion unit. The primary advantage is that there is no need to insert a drive shaft within the waterjet inflow. This significantly reduces cyclic variations in the propulsor inflow and removes an area of flow separation around the shaft. It also provides the designer with greater freedom as to the types of propulsion systems available and where they can be placed within the ship.

The viability of the concept has been examined by considering the performance of an axial flow electromagnetic thruster developed for the ROV market and numerically studying its performance within a typical waterjet inflow. A study was also conducted to examine the scalability of such propulsion units. It is concluded that for a typical size of waterjet with an input power requirement of 110 kW and diameter of 0.25m the maximum delivered power at 2,200 rpm would be 90 kW. This design would have the benefits of no shaft induced losses and reduced cyclic blade loadings and should deliver a higher thrust than comparable conventional waterjet units using geared electric motor drives
http://eprints.soton.ac.uk/22746/