Abstract
Microwave drying of suspensions of lignocellulosic fibers has the potential to produce porous foam materials that can replace materials such as expanded polystyrene, but the design and control of this drying method are not well understood. The main objective of this study was to develop a microwave drying model capable of predicting moisture loss regardless of the shape and microwave power input. A microwave heating model was developed by coupling electromagnetic and heat transfer physics using a commercial finite element code. The modeling results predicted heating time behavior consistent with experimental results as influenced by electromagnetic fields, waveguide size and microwave power absorption. The microwave heating modeling accurately predicted average temperature increase for 100 cm3 water domain at 360 and 840 W microwave power inputs. By dividing the energy absorption by the heat of vaporization, the amount of water evaporation in a specific time increment was predicted leading to a novel method to predict drying. Using this method, the best time increments, and other parameters were determined to predict drying. This novel method predicts the time to dry cellulose foams for a range of sample shapes, parameters, material parameters. The model was in agreement with the experimental results.
Highlights
Porous foam structures have been extensively used for a wide range of industrial applications including thermal insulation [1], packaging applications [2], energy storage [3] and biomedical applications [4]
This study focused on developing a modeling approach to predict the microwave drying for porous foam structures made from wood fibers and cellulose nanofibrils (CNF)
A 3D-finite element (FE) coupled electromagnetic and heat transfer analysis was developed for microwave heating of water for varying volumes under different power inputs
Summary
Porous foam structures have been extensively used for a wide range of industrial applications including thermal insulation [1], packaging applications [2], energy storage [3] and biomedical applications [4]. The binder applications of CNFs have recently attracted a lot of attention and various products such as paper laminates [9], particleboard [10], fiberboard [11] and wallboard [12] that take advantage of the impressive binder properties of CNF have been developed. These binder properties can be exploited to generate rigid foams if a method to produce them can be found
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