Somil,
all these answers from other people are correct.. you can set the model to null or empty object to clear our the data... the reason you may not be seeing the refresh on your data may be if the model is only one way.. or you may need to do the model.refresh() operation so that the changes are propagated to your UI.
alternatively, please debug and make sure that after you set the model to null or empty object, there is no other place where the model gets set.
hope this works and good luck