B737-800 Recirculation fans and packs
 

Question,

1. I do not know why a recirculation fan(s) affects operation of packs?

2. and Are packs operation only limited on the ground
(because there is only OAT)

Please respond to my question.

MEL say :

Left fan may be inoperative provided the left pack
is operating when OAT is above 100 degrees F (38
degrees C).

Right fan may be inoperative provided:
a) The left pack is operating when OAT is above
100 degrees F (38 degrees C), and
b) Flight is conducted pressurized.

both fans may be inoperative provided:
a) OAT remains below 100 degrees F (38
degrees C), and
b) Flight is conducted pressurized.