A heat exchanger system includes a heat exchanger having a body with a first side face and an opposing second side face, the body bounding a fluid channel disposed between the opposing side faces and extending between an inlet port and an outlet port. A flexible first bag has of one or more sheet of polymeric material and bounds a fluid pathway that extends between a fluid inlet and a fluid outlet. The first bag is removably retained against the first side face of the body of the heat exchanger, the fluid channel of the body of the heat exchanger being sealed from fluid communication with the fluid pathway of the first bag.