Hello, I made an experiment. On the bigger surface of the sample of porous material (size 0,5 m x 0,5 m x 0,1 m) thin layer of water was sprayed (25 g). After that the sample was sealed and the moistened surface was cooled to the temperature about 268 K (-5 C). I think most of water stayed at the surface where it was sprayed during the experiment. Measuring the heat flux trough the cooled surface we realized that freezing of water occured at the temperature about 270 K (-3 C). Does anyone has an explanation for that? Where can I find something more about that? It is very urgent. Thanks for your help.