a tubing having a central lumen, a middle lumen surrounding said central lumen and an outer lumen surrounding said middle lumen a supply fitting connected to one end of said tubing, said supply fitting having a proximal port, an inlet and an outlet, said supply fitting configured to connect said proximal port to said middle lumen, said inlet to said central lumen and said outlet to said outer lumen a return fitting connected to other end of said tubing, said return fitting having a distal port and an internal orifice, said return fitting configured to connect said middle lumen to said distal port so that a through passage is established between said proximal port and said distal port, said return fitting further configured to establish a passage between said central lumen and said outer lumen via said internal orifice wherein a fluid input to said inlet at said supply fitting flows from said supply fitting to said central lumen and is rerouted through said internal orifice to said outer lumen for circulation to said outlet at said supply fitting.
