An HVAC system in compartment CFD simulation is a critical computer analysis for engineers designing vehicles and buildings. The goal is to ensure a comfortable and healthy environment for people inside. Using a compartment Thermal Comfort Fluent simulation with ANSYS Fluent, we can see exactly how conditioned air moves and how temperature is distributed. This Thermal Comfort CFD analysis is essential because it allows us to find and fix potential problems, like hot or cold spots, before construction begins.

This report details a Ventilation CFD study of an HVAC system within a passenger compartment. The analysis helps us predict the key factors for comfort, including air temperature and velocity. By testing the HVAC system CFD performance virtually, designers can optimize the placement of vents and airflow rates, ensuring the final design is both effective and energy-efficient. For more detailed HVAC CFD simulation tutorials and advanced thermal comfort studies, visit our comprehensive HVAC simulation collection.

• Reference [1]: Aliahmadipour, Mohammad, Morteza Abdolzadeh, and Khosro Lari. “Air flow simulation of HVAC system in compartment of a passenger coach.” Applied Thermal Engineering123 (2017): 973-990.

Figure 1: A diagram showing the key boundary conditions, including the main inlet and outlet locations, for the HVAC system CFD simulation.

Simulation process: Fluent-CFD Setup, Meshing and Boundary Conditions for HVAC Analysis

The simulation process for this HVAC system in compartment CFD study began with the creation of a detailed 3D geometry of the passenger compartment, which was based on a validated reference paper [1]. This model accurately includes the two main air inlets and the specific placement of several outlet vents. Using Fluent Meshing, a high-quality computational mesh composed of 1,516,733 polyhedral cells was generated. Polyhedral mesh was chosen because it provides a good balance of accuracy and computational efficiency, which is ideal for complex internal flow simulations. The key boundary condition was the air inlet, where the temperature was set to a cool 17°C (290 K) to represent the conditioned air supplied by the HVAC unit. The outlets were configured to maintain proper pressure and flow within the compartment.

Figure 2: The 3D geometry of the passenger compartment used for the Thermal Comfort CFD analysis.

Post-processing: CFD Analysis of Airflow and Thermal Performance

The simulation results provide a complete engineering analysis, proving that the HVAC design successfully creates a comfortable environment by using a smart airflow strategy. From an engineering viewpoint, the primary goal of any HVAC system is to mix conditioned air effectively without causing discomfort. The velocity streamlines in Figure 6 show that this design is highly successful. The placement of the inlets and outlets generates large, slow-moving, and organized circular flow patterns throughout the main cabin. This is a very deliberate and intelligent design. These large recirculation zones act like gentle, invisible fans, using the energy from the inlet jets to continuously stir the air in the entire compartment. The velocity contour in Figure 5 confirms this, showing that air speeds in the passenger areas are kept within a comfortable range of 0.35 to 0.70 m/s. This is fast enough for good mixing but slow enough to avoid creating any feeling of a cold draft, which is a common complaint in poorly designed systems.

Figure 3: Temperature streamlines from the Fluent simulation, visualizing the path of conditioned air and showing how it mixes effectively throughout the compartment.

Figure 4: Temperature contours from the Ventilation fluent analysis, illustrating the highly uniform thermal environment achieved in the main passenger zones.

This excellent airflow pattern is the direct cause of the outstanding thermal performance. The temperature contours in Figure 4 show a remarkably uniform thermal environment, with most of the passenger zone colored in a consistent green. This corresponds to a temperature range of 294-296 K (21-23°C). The final calculated average room temperature of 21.74°C is right in the ideal range for human comfort. The temperature streamlines in Figure 3 show exactly how this is achieved: the cool blue streams of air from the inlets are immediately caught up in the large circulation patterns and mix smoothly with the warmer room air. The absence of large blue (cold) or red (hot) spots proves the mixing is efficient and complete.

The most important achievement of this simulation is the clear, visual proof that the vent placement directly leads to superior thermal comfort. For an HVAC designer or manufacturer, this data is invaluable. It provides the confidence to move forward with manufacturing, knowing the design will perform as expected. This simulation confirms that the current number and location of vents are optimized for this specific compartment.

Figure 5: Velocity magnitude contours, showing the distribution of air speed and highlighting the gentle airflow in passenger areas.

Figure 6: Velocity streamlines from the HVAC CFD simulation, revealing the large, organized circulation patterns that drive air mixing.