Abstract
A fivefold-effect still with 5 mm vapor-diffusion distances between evaporating and condensing surfaces was examined experimentally. Evaporating wicks were glued to metal plates, and concentrate was collected by gutters at the lower ends of the wicks. The still was tilted at a 45° degree angle, and heated on the 1×1.6 m2 bottom area and cooled on the top by means of forced convection. The experimental results were compared to theoretical ones based on a two-dimensional steady-state model. The findings are summarized as （1）Gluing wicks to metal plates with double-sided adhesive tape prevents the appearance of air bubbles under evaporating wicks, keeping hydrophilicity of the wick high enough for evaporation. （2）The experimental evaporation rates from inner wicks are smaller than the theoretical ones, suggesting that part of the condensate comes down from upper plates and mixes with concentrate. （3）Experimental total evaporation rates are smaller than the theoretical ones by 12 ％ on average. （4）Experimental heat ratios of total evaporation to condensation on the first plate are smaller than theoretical ones by 13 ％ on average.
