{"id":19481,"date":"2020-10-12T06:28:05","date_gmt":"2020-10-12T10:28:05","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/simcenter\/?p=19481"},"modified":"2026-03-26T06:10:54","modified_gmt":"2026-03-26T10:10:54","slug":"assess-the-thermal-comfort-in-a-city-bus-with-a-multi-zone-modeling-approach","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/simcenter\/assess-the-thermal-comfort-in-a-city-bus-with-a-multi-zone-modeling-approach\/","title":{"rendered":"Assess the thermal comfort in a city bus with a multi-zone modeling approach"},"content":{"rendered":"\n

Let’s see how the last version of Simcenter Amesim Embedded CFD can help you through a smart combination of 1D and 3D simulation environments.<\/h2>\n\n\n\n
\"Thermal<\/figure>\n\n\n\n

Vehicle thermal comfort challenges<\/strong><\/h3>\n\n\n\n

The need to assess thermal comfort in all kind of vehicles is constantly increasing due to climate changes but also to the resulting energy savings objectives. Especially to assess the thermal comfort in a city bus.<\/p>\n\n\n\n

The electrification of vehicles also drives these energy saving. In these vehicles, heating is not “free” anymore, as it was for internal combustion powered vehicles, getting similarly to cooling its energy from the batteries, thus impacting the vehicle range.<\/p>\n\n\n\n

In the transport sector consequently, OEMs as well as suppliers are facing the challenge of handling thermal comfort very early in the design cycle to make quickly the best decision in order to avoid inefficient late iterations.<\/p>\n\n\n\n

Introducing thermal comfort assessment in early design should give the correct trends, quickly and easily, not going into too many details since all the system components are not finalized. It should be logically assessed for a large variety of configurations and realistic conditions, i.e. during transient scenarios.<\/p>\n\n\n\n

To answer this challenge, we often use system simulation without offering however a sufficient level of fidelity, due to the 3D nature of air flow phenomena.<\/p>\n\n\n\n

The classical alternative in doing it with a full 3D CFD approach is also not optimal since CAD needs to be fully available and number of configurations that can be quickly handled is limited.<\/p>\n\n\n\n

Overview of Simcenter Amesim Embedded CFD 2020.2<\/strong><\/h3>\n\n\n\n

Considering the above-mentioned challenges, the Embedded CFD approach of Simcenter Amesim is de facto a good compromise combining the system simulation approach together with Simcenter STAR-CCM+ 3D CFD approach. Described as a hybrid tool between 1D and 3D CFD simulation environments, this tool benefits from both technologies. It offers the fidelity of 3D resolution together with close-to 1D simulation times, all encapsulated into an easy-to-use specific GUI.<\/p>\n\n\n\n

The new 2020.2 version of Simcenter Amesim Embedded CFD for cabin comfort widens the possibilities. It can handle any type of cabin, ranging from a 2-seater car up to an entire commercial plane.<\/p>\n\n\n\n

The user can now define its own geometry, the number of air zones, the location of air vents, the type of material (either opaque or transparent) and much more.<\/p>\n\n\n\n

In addition to this important enhancement, we upgraded the compatibility with Simcenter STAR-CCM+ to additional versions (up to 2020.1).<\/p>\n\n\n\n

\"Cabin<\/figure>\n\n\n\n

Application to a city bus cooldown scenario with doors opening<\/strong><\/h3>\n\n\n\n

A concrete scenario to assess the thermal comfort in a city bus with a multi-zone modeling approach will hereafter illustrate the usage of Simcenter Amesim Embedded CFD. Let’s simulate an entire bus cooldown in a first phase, followed by 2 consecutive bus stops during which both front and mid doors open.<\/p>\n\n\n\n

Simcenter Amesim model<\/strong><\/h4>\n\n\n\n

The figure below illustrates the HEAT library containing the Cabin component.<\/p>\n\n\n\n

This component has 3 external ports by default to connect on the left side the air vents boundary conditions in terms of air mass flow, temperature, pressure and humidity and on the right side the vehicle velocity and ambient air temperature.<\/p>\n\n\n\n

\"Simcenter
Simcenter Amesim cabin thermal model with connected air vents<\/figcaption><\/figure>\n\n\n\n

Build 3D geometry<\/strong><\/h4>\n\n\n\n

To build the 3D geometry from the above Simcenter Amesim model, we launch the Simcenter Amesim Embedded CFD app from the cabin component.<\/p>\n\n\n\n

The step-by-step GUI guides the user towards the completion of the 1D-3D coupled simulation.<\/p>\n\n\n\n

Let’s start with the 3D geometry building.<\/p>\n\n\n\n

\"3D
Simcenter Amesim Embedded CFD geometry step<\/figcaption><\/figure>\n\n\n\n

The 3D geometry is built with XYZ coordinates and dimensions of elementary blocks such as boxes, cylinders, 3D polygons, etc. \u2026  Elements can be of 3 types:<\/p>\n\n\n\n