Calculating Water Evaporation from Clay Pots

[KeKe29]

hello, i am crowed and i need help,
first of all i am thankful for every help,
terms are : i have 2 clay pot 1 small and 1 big one, on picture black sticks are pot, the small one is inside the big one and empty space is filled with sand, i am making this sand wet and after some minutes next temperature inside small pot is going down, i have to explain this effect why this happens and make some calculations.
i have formed explanation that : water molecules have different speed and some of them has enough energy to evaporate and leave sand, after this sand is getting cold because high energy molecules are leaving sand. this is general explanation but how i told i am crowed in calculation, i want to calculate T(t)=? T-temperature inside small pot and t - time after making sand wet,
i have way but i have no enough knowledge to calculate it, first of all we have to calculate chance of speed distribution (maxwell-boltzman distribution) integral from this function will be chance of speed distribution, but we have to calculate speed for Z vector, after this we have to multiplication chance on number of water molecules which are able to leave sand and they have on this distance l=VevaporationXt V-speed for evaporation and t - time, after this i can't resume if u can help me to calculate T(t) we have any information about sand, water, pots and everything what you need, maybe i am wrong and please help me to calculate this, anyway i am thankful for every help.

and sorry for my bad english. thanks

 

[KeKe29]

basic picture

i miss one thing that small pot has no thermocontact with air