Chandra is the moon. In chandra bhedhana pranayama, all inhalations are done through the left nostril and all exhalations through the right nostril. Pranic energy in all inhalations is channeled through the ida or chandra nadi. All exhalations pass through the pingala or surya nadi.
Follow the same techniqueu given for Surya Bhedana, reading the word 'Right' for left and vice versa.
The chandra bhedana pranayama is similar to that of Surya bhedana pranayama except that this pranayama cools the system.