Optimization Control And Software Development For Air Handling Subsystem In The Heating Ventilating And Air-conditioning System

In the heating ventilating and air-conditioning (HVAC) system, the energy cost of the air handling subsystem is about 35 percent of the whole system. Because of the fix set-point working mode, the air handling subsystem usually works at the conditions of large flow and small temperature difference, which results in low energy efficiency ratio and serious energy waste. Thus, the research focus on the on-line optimization of air handling subsystem to make the system working at the optimal work points within the entire load range. It can efficiently reduce the energy consumption of the HVAC system.This thesis analyzes the operating process and the energy consumption characteristics of various links in the HVAC system. And the modeling method of the major devices in this subsystem is studied. According to heat transfer theory and energy balance theory, the traditional mechanistic analysis method is used to establish the model of cooling coil. Based on the experimental data, polynomial method is used to identify the static model of the fan and pump.Based on understanding the characteristics of the practical HVAC system, the cost function and constraints of the air handling subsystem are determined. The optimization problem of this subsystem is a multivariable nonlinear optimization problem with equation and inequality constraints. The sequential quadratic programming (SQP) is used to solve the optimization problem. The variable metric method is used to construct and develop the Hess matrix of the SQP method, which is characterized by better numerical stability and linear convergence. Using this optimizing method on air handling subsystem, the supply temperature and the supply airflow rate etc. can be obtained, which can be used to optimize the system. In order to verify the performance of this method, the simulation is used to analyze and contrast the energy consumption of fix set-point and optimal set-point in different working conditions. The result shows that the method of on-line optimization can efficiently reduce the energy consumption of the HVAC system. In order to apply the on-line optimization to engineering, Visual C++ is used for the primary design of optimization software. The software module of devices data maintenance, which includes device parameters and engineering condition etc., is achieved. It can be used for man-machine interaction and modifying the system data quickly and accurately.