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Re: water distillation
Posted by: Scott Sorenson ()
Date: March 01, 2018 02:50PM

Here is some information that I found going through some of my books on design of the Type IXC. Hope this helps you out.


1. Introduction

This section will cover the formation of the distillate and its distribution to the battery water tanks and fresh water "distribution" tank. The drinking water system is covered under the S36 section in the IX-C report.

2. General Description

One small low-capacity distiller is installed in the maneuvering room on the IX-C for supplying the ship with its drinking and battery power. The distilled water formed is pumped from the main distillate tank by a hand pump to a gravity feed distillate tank in the overhead from where it is distributed either by a portable hose connection to individual battery water tanks, direct to No. 1 drinking water tank, or via a special filter, to "harden" the water, to No. 1 drinking water tank.

The still functions in most respects similar to the Kleinschmidt still. A basic difference, however, exists in that evaporation takes place under a vacuum whereas in the U.S. still, it takes place essentially at atmospheric pressure.

The feed water for the still is supplied to a feed regulating tank from the circulating water main. From here it passes to a feed water level regulator external to the distiller. No pump is needed because of the distiller vacuum The feed enters the distiller at the bottom where it picks up heat from the condensate and brine return coils. A set of electric heating coils is located above a simple baffle arrangement and provides the basic source of heat to the still. Evaporation takes place at approximately 206°F. A positive displacement vacuum pump at the top of the distiller draws in the vapor formed, after it passes over baffles to prevent carry-over, and discharges it at atmospheric pressure to a condenser in the top of the distiller. The heat removed from the vapor thus passes to the salt water feed in the same manor as in the U.S. distiller. The feed water is agitated by a paddle wheel arrangement (geared to the motor drive shaft). The hot condensate then passes through the above-mentioned coils to a small receiver and thence to the distillate tank by gravity. A salinity indicator is at the intake to the distillate tank. A vent and equalizing line runs from the condenser to the receiver and acts to maintain the pump discharge at atmospheric pressure. A vapor bypass is located on the vacuum pump discharge; it is used mainly during starting to reduce the load on the pump as it builds up a vacuum A brine discharge pump, geared to the vacuum pump drive, discharges the brine to the bilge via a regulating valve. A safety valve that lifts between 3.5 to 4.2 psi is fitted to the distiller casing.

The heating coils installed provide a wide range of heat input to the distiller. The six individual coils have the necessary switching arrangements so that by proper parallel or series setups heat inputs can be varied in steps from .17 KW to 3.36 KW at 110 volts, or .40 KW to 8.00 KW at 170 volts. As a result of the comparatively high heat input possible for such a small unit initial heating of the feed water can be accelerated. During steady operation, only one coil is required to provide the necessary heat.

The still is in most respects a well-designed and compact unit. All heat exchanger sections are placed within the one shell, thereby limiting the need for much external piping. The condenser, electric coils, and condensate and brine return coils can be readily removed as individual units for servicing. However, no steam trap is provided on the condensate lines so that continued attention must be given to condensate level during operation.

Test date available shows that this still has attained capacities in excess of the designed rating. On one test approximately 100 gallons/day were produced.

3. Individual Components

a. Distiller (includes heat exchanger)

Weight - 704 lbs. empty, 804 lbs. full
Measurements - 45.7 x 28.4 x 27.2 ins.
Test pressure - 4.26 psi
Working pressure - 4.6 to 5.8 ins. Hg (vacuum)
Feed water delivery - 4.2 to 5.3 gals./hr.
Capacity - 63.5 gals. per day

b. Tank capacities

Feed regulating tank - 8.2 gals.
Distillate tank - 14.5 gals.
Distillate gravity tank - 12.4 gals.
Battery water tanks - 50, 68.7 and 41 gals.

c. Vacuum vapor pump

Pump Motor
Type - Positive displacement rotary
Vacuum - 4.6 to 5.8 ins. hg
Weight - 68.2 lbs.
95 lbs.


The capacity of the distilling unit and of the battery water tanks on the IX-C submarine is far below the corresponding U.S. standards for submarines. This results in considerable hardship on the crew during long patrols and necessitates extreme measures to limit battery water consumption.

The distiller unit itself is of little exploitation value because of its low capacity. However, its compactness is of merit. By placing all of the elements within the one shell and at the same time making them easily accessible, the designers have provided a unit that requires a minimum of work for its installation and upkeep, and keeps to a minimum the weight and space requirements for the complete installation.

A comparison from an output and efficiency standpoint of the two cycles, i.e., the one with vaporization taking place at atmospheric and the other with vaporization taking place under a slight vacuum, can not be readily made because of the many variables associated with the problem. However, it appears that any advantage gained by the requirement for less input heat on the vacuum cycle is lost by the additional power required to compress the greater vapor volume.

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Subject Written By Posted
water distillation markos88 02/28/2018 10:20PM
Re: water distillation Scott Sorenson 03/01/2018 02:50PM

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