Analysis of Drying Front Propagation and Coupled Heat and Mass Transfer During Evaporation From Additively Manufactured Porous Structures Under a Solar Flux.

Drying front propagation and coupled heat and mass transfer analysis from porous media is critical for soil-water dynamics, electronics cooling, and evaporative drying. In this study, de-ionized water was evaporated from three 3D printed porous structures (with 0.41 mm, 0.41 mm, and 0.16 mm effective radii, respectively) created out of acrylonitrile butadiene styrene (ABS) plastic using stereolithography technology. The structures were immersed in water until all the pores were invaded and then placed on the top of a sensitive scale to record evaporative mass loss. A 1000 W/m2 heat flux was applied with a solar simulator to the top of each structure to accelerate evaporation. The evaporative mass losses were recorded at 15 min time intervals and plotted against time to compare evaporation rates from the three structures. The evaporation phenomena were captured with a high-speed camera from the side of the structures to observe the drying front propagation during evaporation, and a high-resolution thermal camera was used to capture images to visualize the thermal gradients during evaporation. The 3D-structure with the smallest effective pore radius (i.e., 0.16 mm) experienced the sharpest decrease in the mass loss as the water evaporated from 0.8 g to 0.1 g within 180 min. The designed pore structures influenced hydraulic linkages, and therefore, evaporation processes. A coupled heat-and-mass-transfer model modeled constant rate evaporation, and the falling rate period was modeled through the normalized evaporation rate.

Flow condensation heat transfer coefficient and pressure drop data for R134a alternative refrigerants R513A and R450A in a 0.95-mm-diameter minichannel.

Flow condensation heat transfer coefficients and pressure drop data were collected in a small-scale vapor compression cycle. The test section consisted of seven parallel, 0.95-mm-diameter square channels which utilized a heat flux block to measure the temperature gradients of the heat leaving during the condensation process. Heat transfer coefficients and pressure drops were measured using the temperatures and pressures measured during experiments. Experimental flow condensation heat transfer coefficient and pressure drop data are tabulated for R134a, R513A, and R450A for a range of mass fluxes (i.e., 200 - 500 kg/m2s) and qualities (i.e., 0.2 - 0.8) at a saturation temperature of 40°C. The heat transfer coefficient uncertainties for all experiments were ± 6.3 - 21.2%, with an average uncertainty of ± 9.8%. Data include refrigerant saturation temperature, wall temperature, mass flux, quality, condensation heat transfer coefficient and its uncertainty, and pressure drop. The data tabulated are the raw data from the paper "Flow condensation heat transfer and pressure drop performance of R134a alternative refrigerants R513A and R450A in a 0.95-mm-diameter minichannel," published by the International Journal of Heat and Mass Transfer [1].