HVAC System AHU Simulation Model

The AHU (Air Handling Unit) simulation model serves as a critical research tool in HVAC (Heating, Ventilation, and Air Conditioning) systems, designed to simulate the behavior of key components during air handling processes. This simulation model typically incorporates core modules such as valve models, cooling coil models, heater models, humidifier models, and sensor models. Through mathematical modeling and numerical computations, it predicts the system's dynamic responses and energy consumption characteristics. In code implementation, these models often utilize differential equations and state-space representations solved with numerical methods like Runge-Kutta or Euler integration.

Valve Model: Valves primarily regulate water or airflow in AHU systems. The simulation commonly employs flow coefficients (Cv values) or opening-flow characteristic curves to describe their dynamic behavior. The valve model can simulate flow variations under different control strategies, thereby affecting the overall heat exchange efficiency. Code implementation typically involves piecewise linear interpolation or polynomial fitting of valve characteristics, with PID controllers adjusting the opening degree based on setpoints.

Cooling Coil Model: As a crucial heat exchange component for air cooling, the cooling coil model is based on energy conservation and heat transfer equations. It considers heat exchange processes on both air and water sides, incorporating enthalpy changes of moist air to simulate cooling effects. Implementation often uses NTU-effectiveness method or logarithmic mean temperature difference (LMTD) approach with iterative calculations for moisture condensation effects.

Heater Model: The heater model, used for raising air temperature, applies thermodynamic principles to calculate the heat transfer efficiency of heating elements (such as electric coils or hot water coils). It analyzes the relationship between air temperature rise and energy consumption. Code implementation typically involves resistance heat calculations or heat exchanger efficiency maps with real-time power modulation algorithms.

Humidifier Model: Humidifiers function in scenarios requiring air humidity adjustment. Their simulation models employ mass transfer and energy balance equations to simulate humidity changes during steam or spray humidification processes. Implementation often uses psychrometric calculations with mass diffusion equations and adiabatic saturation assumptions for different humidifier types.

Sensor Model: Sensors monitor parameters like temperature, humidity, and pressure in AHU systems. The simulation model replicates sensor dynamic response characteristics including delays and noise to enhance system realism and control algorithm verification accuracy. Code implementation typically incorporates first-order lag filters, Gaussian noise injection, and calibration offset simulations using time-domain response functions.

By integrating these sub-models, the AHU simulation system provides a reliable testing platform for optimizing control strategies, energy-efficient design, and fault diagnosis. The complete system architecture often follows modular programming principles with standardized data interfaces between components, enabling flexible configuration and co-simulation with building automation systems.