There are a few items I need to test before I start the design.

Testing items and results:

1. Verify the cooling effect:
   The cooling time is obviously decreased with the pump switched on. It will take  ~15 mins to have the cool feeling without the pump and ~5mins with the pump on.  However, the temp. different was around 1-2 degrees, and the cooling effect was not that obvious.
2. The required volume of water tank:
   The thermoelectric cooler was attached to a recycled box and half a bottle of water was enough to fill up  the insole
3. If additional cooling will be required:
   Basically, natural cooling was enough for this case
4. The workmanship of pipe bending:
   Dia 6 mm pipe was difficult to bend by bare hand. Even though the shape was alright, the insole would occupy a lot of space and the feet would not be able to fit in.

The experiment is shown below

Conclusion:

1. The cooling effect has to be enhanced 
2. The cooling pipe diameter has to be decreased