A heat exchanger system includes a heat exchanger having a body plate with a first side face and an opposing second side face, the body plate bounding a fluid channel disposed between the opposing side faces and extending between an inlet port and an outlet port, and a first side plate having an inside face. A flexible first bag includes of one or more sheets of polymeric material, the first bag bounding a fluid pathway that extends between a fluid inlet and a fluid outlet, the first bag being removably retained between the body plate and the first side plate so that at least a portion of the first bag rests against the first side face of the body plate when the fluid pathway of the first bag is filled with a fluid.