Evaporation of ethanol films wicking on structured, porous coatings deposited on copper plates. (June 2019)

• Record Type: Journal Article
• Authors: Feng, Chen; Chandra, Sanjeev
• Is Part Of: International journal of heat and mass transfer. Volume 136(2019)
• Page Start: 821
• Page End: 831
• Publication Date: 2019-06
• Subjects: Porous coatings -- Capillarity -- Evaporative cooling -- Analytical model -- Film thickness; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2019.03.045
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Coatings deposited by flame spraying were made porous and had channels. Capillary forces caused ethanol to rise on coatings and evaporate, cooling the strips. Increasing porosity enhanced mass flow rate and raised dry-out heat flux. Analytical model was created to predict film height, thickness and evaporation rate. Abstract: Porous copper coatings were deposited on copper plates by flame spraying. Wire mesh masks were placed on the substrate while spraying to create channels in the coatings. Pores increased the capillary pressure of liquid flowing through the coating while channels increased permeability. Coated copper strips were suspended vertically with their bottom edges touching an ethanol reservoir so that liquid wicked upwards due to capillary force and evaporated. The copper strips were heated electrically and their temperature recorded as the heater power was varied. The rate of ethanol evaporation was measured by recording the change in weight of the liquid reservoir and the height of the liquid film measured from photographs. Raising surface temperature increased liquid evaporation rate and reduced the film height. Surface dry-out occurred when the mass evaporation rate became greater than the maximum wicking rate for a given surface. Increasing the effective porosity of the coating enhanced the maximum mass flow rate through it. For high porosity surfaces the liquid began to boil before dry-out occurred. An analytical model of liquid film rise was developed to predict film height, film thickness, and the rate of evaporative cooling as a function of surface temperature.