Passive Ventilation CFD Simulation Training Package, ANSYS Fluent
In this CFD simulation training package, we have studied various methods for different Passive Ventilation systems. There are 10 CFD projects, including a windcatcher, atrium, turbo ventilator, solar chimney, facade, balcony, wind tower, PCM application, and wind tower with qanat.
This training package includes 10 Passive Ventilation CFD simulation projects using ANSYS Fluent software. MR-CFD suggests this package to those interested in the passive ventilation engineering field. This package introduces you to various passive ventilation systems’ performance principles and how to simulate them numerically. This package presents 10 different Passive Ventilation systems appropriate for all Beginner, Intermediate, and Advanced users.
Passive Ventilation supplies air to and removes air from an indoor space without using mechanical systems. There are two types of natural ventilation occurring in buildings: wind-driven Ventilation and buoyancy-driven Ventilation.
Wind-driven Passive Ventilation arises from the different pressures created by wind around a building or structure and openings formed on the perimeter, which then permit flow through the building.
However, Buoyancy-driven Passive Ventilation occurs due to the directional buoyancy force that results from temperature differences between the interior and exterior.
Wind-Driven Passive Ventilation
A clear example of wind-driven passive ventilation systems is the windcatcher, which project no. 1 presented. A windcatcher is a tower for Ventilation and cooling the building’s interior on the roof.
The windcatcher transfers air into the building by suction to drive warm and polluted air out. The internal structure is such that air enters and traps between the walls. As a result, air moves downward from its outlet panels to the building’s interior.
In another example of the wind-driven passive ventilation system, project no. 2 investigated the airflow inside the atrium.
This atrium has a glass roof and a set of windows that usually are located immediately after the main entrances of the buildings. This part of the building is used to provide the necessary light for the interior and building Ventilation.
Sometimes in a ventilation system, there is also a mechanical device. However, this mechanical device does not consume energy and works without the intervention of an external agent. The turbo ventilator is a sample of this group.
A rotating turbine is placed on the ceiling of the room. It receives the energy of the air inside, and as a result, it rotates. Due to the rotation of the blades, air suction is created to enhance the ventilation process. Project no. 3 has investigated the performance of this system.
Buoyancy-Driven Passive Ventilation
A clear example of buoyancy-driven passive ventilation systems is the facade, which project no. 4 presented. Double skin facades consist of two skin (mainly glass layers), and the space between these two shells is a channel or holes for airflow.
In the hot seasons, the air sucked from the bottom into the interior space of the two-layer facade can repel the heat absorbed by the sun’s heat to the interior space between the two skins upwards. As a result, rejecting the heat from the walls of the building, it cools the interior space of the building.
In the cold seasons, the same heat absorbed from the sunlight on the facade skins is transferred to the interior of the building through conduction and radiation.
Project no. 5 has also presented the simulation of another example of a facade. We modeled a simple facade in the previous project, but the facade also has shading devices in the present project. To increase the efficiency of the cooling and heating process in this system, you can use shading devices with the ability to adjust the angle.
The placement angle of these shading devices in the hot seasons is such that it blocks the sunlight and causes the sunlight to be reflected in the outside environment after hitting its surfaces.
The angle of these shading devices in the cold seasons is such that it allows the solar rays to shine directly on the glass surface of the building and, as a result, heat the walls of the building.
Project no. 6 presents a simpler model of a solar chimney. In this project, the effect of the solar chimney on the air ventilation inside the room has been investigated.
This model consists of two main parts, including the interior of the room and a sloping solar chimney on the room’s ceiling. The solar chimney consists of glass plates in contact with the environment and receives solar energy as a transparent medium.
Project no. 7 investigates the air conditioning of a room with a balcony. The use of any ventilation system depends on the location of the building and the climatic zone of the desired location. Sunlight plays an important role in the temperature of the walls and the air temperature inside the building.
The balcony has a glass roof and one glass wall. Due to the radiation of sunlight, both room and balcony become warmer, and natural convection plays an important role in circulating the flow inside these spaces.
Project no. 8 is related to an air tower. This project investigates the conjugate heat transfer of airflow in a simplified 4-story wind tower. Turbulent airflow enters the domain from the top left region.
Due to heat transfer to air from the right diagonal wall under solar radiation, conjugate heat transfer leads to buoyancy, which helps airflow exit the domain from the top right region. This process creates steady airflow in all four stories of the building.
PCM for Passive Ventilation
Phase change materials (PCM) are one of the new methods in air conditioning. Phase change materials can generally absorb and store large amounts of latent thermal energy. PCMs can cause cooling, heating, and thermal storage in the environment by changing the phase between solid and liquid.
In project no. 9, We first simulated a simple room. One of the room’s walls produces heat under the influence of solar radiation and the heat of the outside environment.
We applied a PCM layer on the same heating wall in the next step. The presence of PCM causes the thermal energy of the wall. So Passive Ventilation takes place in the room.
Hybrid Passive Ventilation
Wind Tower with Qanat
Some passive ventilation systems work in combination. This means that both pressure differences and temperature changes cause air conditioning.
Pay attention to project number 10. We design a wind tower with an underground cooling system. We use the qanat as a cooling system.
The outside air enters the qanat and gets cold from the water surface inside the channel. On the other hand, the wind tower is designed to have a pressure difference between the outer and inner parts. So the air suction causes the old air to come out.