Achievable optimal superheat temperature control in evaporators of HVAC systems

In this paper a novel approach to minimize superheat temperature of an evaporator in real-time operation of a Heating Ventilation Air Conditioning (HVAC)-Refrigeration system is presented. Two approaches for optimal control of an evaporator superheat are presented in this paper. Both approaches use the second derivative of superheat (Tgh), w.r.t. mass flow rate of refrigerant at the outlet of an evaporator for the purpose of controfling the superheat to its near optimal value. The first approach is based on an analytical formulation of the second derivative and employs gradient descent method to drive the Ts h to its optimal point. The second approach utilizes an extremum seeking control (ESC) for optimizing higher order derivatives to drive and maintain the Ts h at its minimum stable level. The proposed approaches have been validated through simulation studies in MATLAB/Simulink environment.