Diffusion igennem granulært medie opløst i vand - Kaffebrygning i stempelkande: Diffusion through granular media suspended in water - Coffee brewing in a press pot

Daniel Abildgaard Rasmussen & Anna Tang Nielsen

Student thesis: Termpaper


In this experimental project a physical model is presented, which decribes the extraction of among other things oils, taste- and aromasubstances during coffee brewing in a press pot. The model is based upon the physical theory about diffusion in spherical geometry. One fundamental assumption is that the growth of the concentration is similar in all directions. Another is that all particles in the granulate are homogeneous round spheres. The model decribes diffusion of matter from an inner volume to an outer volume, where the rate of diffusion is governed by the material dependend diffusioncoefficent and the flux. Furthermore, we assume that the concentration of matter on the boundary between the inner and outer volume is equal to the concentration in the outer volume, and this concentration is only dependend on time and no longer position. In circumstances of the coffee brewing the inner volume is equivalent to the coffee granular, and the outer volume is equivalent to the boiling water. This model is compared, through simulations in MATLAB, with data achieved by own experiments done in a laboratory, where the change in the concentration with respect to time, c(t ), in the outer volume is measured for varying size of the granular. The concentration are in the series of experiments measured by the dry matter percentage. The size of the granular are divided into three intervals, which are achieved by filtration of the coffee granular. Through this project it has been observed that the developed model can describe the dynamics of the coffee brewing process with minimal deviations and that the brewing time is strongly dependent on the size of the coffee granular.

EducationsPhysics, (Bachelor/Graduate Programme) Undergraduate or graduate
Publication date23 Jan 2015
SupervisorsBo Jakobsen


  • Kaffe
  • Kuglegeometri
  • Eksperimental
  • Experimental
  • Kaffebrygning
  • Stempelkande
  • Dry matter percentage
  • Dimensionsløse variable
  • Diffusionskoefficient
  • Tørstofprocent
  • Spherical geometry
  • Coffee
  • Dimensionless variables
  • Press pot
  • Fysisk modellering
  • Diffusion
  • Diffusion coefficient
  • Physical modelling
  • Coffee brewing