Reasonably-pure drinking water is an absolute necessity of life and clean, fresh-tasting drinking water is one of its pleasures. Most persons in well-developed countries like the United States have access to safe, reasonably-pure drinking water. But even in areas having water suitable for human consumption, such water may contain minerals, e.g., iron and calcium, and/or chemicals and other substances.
While such non-water constituents may not be harmful to humans, they often impart an unpleasant taste or odor to the water. And normally-high-quality drinking water sometimes contains bacteria or other microorganisms which may impart a bad taste to the water or otherwise impair its quality. Often, such an eventuality results from a temporary deficiency in the water treatment facility.
One well-known approach for removing impurities from drinking water is distillation. Distillation involves boiling water to form water vapor and then cooling such vapor to a temperature below the condensation temperature, i.e., below about 212.degree. F. The resulting liquid, sometimes referred to as condensate or distillate, is collected for drinking or the like. Distillation separates pure water from the entrained minerals and other potentially bad-tasting impurities. And quite aside from improving the sensory quality of water, the high temperatures involved in the process are sufficient to kill many types of potentially-harmful microorganisms.
Water distillers commonly use a heating coil to boil, as steam, the water from a raw water container. A fan blows air across condensing coils which cools the steam and condenses it back to now-purified water.
Commonly, water which is being distilled has some usually-modest quantity of solids dissolved in it. Calcium is an example. As water is boiled, some (but not all) of these dissolved solids "settle out" of the water and gravitate to the bottom of the boiling tank as visible particles. As the water boils away, steam carries the remaining (but undesirable) dissolved solids along.
A way to "strip" such dissolved solids from the flow of steam is to pass such steam through a relatively-long vertical columnar path. Since some small-but-significant pressure is required to move the steam along the path, the increased pressure at the bottom of the column has been found to cause dissolved solids to settle out of the steam. While the arrangement shown in U.S. Pat. No. 4,261,796 (Lemoine) might suggest such a purpose, the patent explains that the vertical arrangement permits gravity flow of input water and distilled water so that no pump is necessary.
Another way to strip dissolved solids from the flow of steam is to use baffles or the like to create a serpentine steam path. This technique is similar in operating principle to the vertical column approach discussed above and for column pressure-increasing purposes, retains the "apparent" length of the columnar path while shortening its actual length.
FIG. 6 of U.S. Pat. No. 4,045,293 (Cooksley) suggests this technique but an analysis of the specification makes it clear that what is being depicted is a heat exchanger having a spiral tube element. It is known that using such an element increases the heat-exchange surface area without significantly increasing heat exchanger size.
The water purification apparatus of the Cooksley patent has a baffle installed between a boiling tank and a stack, the base of which is attached to the tank by welding. However, such baffle is apparently not provided for the purpose of stripping dissolved solids from steam. Rather, the baffle is said to remove water droplets from steam vapor.
A disadvantage of known apparatus for stripping dissolved solids from steam is that they occupy very substantial volumetric space. While this may not be objectionable in a commercial water distiller, a household consumer is quite unlikely to purchase a distiller having a tall "stack." And the reluctance to purchase is likely not to be diminished by shortening the stack and configuring a serpentine path therein. The consumer wants and expects a countertop distiller, i.e., a distiller which has a height less than the distance between a kitchen counter and the cupboards above such counter, typically 16 inches (about 41 cm.).
Another disadvantage of such known apparatus is that they are relatively expensive to manufacture. And, of course, cost of manufacture is reflected in the purchase price to the user.
Yet another disadvantage of such known apparatus is that periodic cleaning is difficult, even with a smooth-tube long column. And in an apparatus with a serpentine path, solids tend to coat path surfaces and are difficult to reach and dislodge, at least merely because the path is serpentine.
Still another disadvantage of known apparatus is that given the column length of the apparatus, steam cooling is likely to occur and, with it, condensation. While such condensation is not, per se, objectionable, some condensate is likely to trickle back into the boiling tank. This is inefficient--the objective is to put distilled water into a pure-water container, not back into the boiling tank.
A countertop distiller with an improved solids-removing baffle arrangement that addresses shortcomings of the prior art would be a distinct technical advance.