A new blood unit cooling system was designed to cool blood rapidly to about 22° C. and maintain it at about that temperature, even in ambient temperature extremes, for several hours. The system incorporating a preferred eutectic solution including 98% 1-dodecanol, 1.5% myristyl alcohol and 0.5% 1-decanol (having a melting point of about 23° C.) contained in a sealed flexible polymer layer, was used to cool whole blood-filled bags. The preferred design used double-layered transparent polyethylene, with two sealed compartments filled with the solution, separated by a flattened and sealed portion between them. One of the two sealed compartments contacts one side of the blood bag and the other compartment is folded over to contact the other side of the blood bag. The transparent compartments allows an operator to verify at any time whether the solution is in a solid state, and the flexibility of the compartments eases the proper positioning of them around a blood bag.