In this paper, we apply a turn over method for distributed parameter systems to a widely used heatexchanger system. The control law has both desirable properties of a pole assignment and an optimal control law, and the feedback gain is obtained without solving an infinite dimensional Riccati type differential equation. By this method, open loop poles existing in the right hand side of the turn over line are moved to the axial symmetry positions respecting to the turn over line drawn parallel to the imaginary axis, thus all closed loop poles are located in the specified region with desired degree of exponential stability. The distributed feedback law for a distributed heatexchanger system is proposed by using the technique without any approximation. We confirm by experiments that the constructed system has a short rise time and a short settling time. The state variables needed in the feedback law is estimated by a distributed observer. The distributed parameter observer is approximated by the method of weighted residuals and gives a good estimated value with only four sensors in the experiment.