Study of the water evaporation rate on stainless steel plate in controlled conditions

Abstract

The evaporation of water droplets is involved in many applications: fire extinction, building and greenhouse. On the equipment of a food plant (mostly made of stainless steel), bacterial contamination can cause the deterioration of food quality and safety. To avoid this problem, cleaning by water and subsequent drying are often performed. Water stagnation, however, is observed at certain positions if the ambient conditions during the drying process are not well-controlled. The water evaporation rate depends on the room conditions (temperature, velocity, humidity). It is thus necessary to understand the evaporation mechanism of water droplets on solid surfaces and the influence of the room conditions on the evaporation rate. Experiments were performed in a wind tunnel, in which the air velocity, temperature and relative humidity were controlled. Water droplets were deposited onto a stainless steel plate (15 cm × 15 cm × 0.1 cm). This plate, placed in a work zone, was exposed to several air velocities (0.5 m s−1 to 2.0 m s−1), relative humidities (50%–85%) and temperatures (4 °C–20 °C). The evolution of the wet surface on the plate was observed using a camera, and the evolution of the water weight was determined using a digital balance. The influence of the initial percentage of wet surface on the water evaporation rate was studied at various ambient conditions. It was observed that the air relative humidity is the factor that has the greatest influence on the evaporation rate.