Abstract
A threefold- or quadruple-effect still using 10 mm diffusion distances was examined experimentally. The still was tilted at a 12° angle from the horizontal, and heated on the bottom and cooled on the top by means of naturally convective evaporation. The experimental results were compared to theoretical results based on a one-dimensional steady-state model. The findings are summarized as (1) The evaporation rate is largest at the first effect and decreases at the effects farther from the first. This is also seen in the theoretical results. (2) The theoretical total evaporation rate increases exponentially a long with the bottom heating temperature, and this is supported by the measurements. (3) Measured evaporation rate from the outer-covering fabric are in fairly good agreement with the theoretical rates, while the measured evaporation rate from the other fabrics are smaller than the theoretical rates. As a result, the measured total evaporation rate is smaller than the theoretical rate by 15 to 18 ％. (4) Polyester baking coating of 50 to 70 μm thickness prevents corrosion of the steel plates in contact with hot seawater-soaked fabrics.
