How to add shrinkage model for a given problem?

i am currently working on "convective drying of carrot" model in comsol,and i am able to get results of heat and mass transfer for a given model by applying heat and mass transfer equations. but now i want to study shrinkage effect ,so please anyone tell me which model i should use in order to get the results and also also how to couple heat and mass transfer model with shrinage model