The analysis of controllability of a heat exchanger operating under two-phase conditions is performed. An evaporator operating in a vapor compression system is chosen for the analysis. A moving-boundary model is used to simulate the dynamic behavior of the evaporator. First, the controllability of the linearized model is verified. Then, it is shown that the nonlinear model can be classified as a control-affine system with drift. Short-term local controllability of the nonlinear model is shown using Lie algebras. A linear quadratic (LQ) controller is developed for the linearized system and numerical simulations are provided that show a strong coupling between the variables of the model. (c) 2007 Elsevier Ltd. All rights reserved.