Unsteady Interior Climate Simulation of Electric Buses
Typ
Examensarbete för masterexamen
Program
Applied mechanics (MPAME), MSc
Publicerad
2020
Författare
Ravindra, Nithin Bharadwaj
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In today’s world buses are one of the most popular means of transport for commuters in an urban setting. To
maintain the thermal comfort of passengers inside the bus the heating, ventilation and air condition (HVAC)
systems are used. These systems consume a large part of the total power consumption in the bus especially
when working in extreme weather conditions. In urban areas, the energy lost to the external atmosphere is
not only through the walls of the bus but also when the doors are opened for passengers to board or depart.
The recent shift towards electrification of buses, especially in cities, makes analysing and reducing the power
consumption of HVAC system ever so important.
This study uses Computational Fluid Dynamics(CFD) to frame a methodology for simulating the interior
climate of bus. Simulations offer a way to test various cases at relatively lower cost and faster rate when
compared to experiments. In this study initially a steady state model is built using Reynolds Averaged Navier
Stokes(RANS) equations and realizable k turbulence model with all the necessary HVAC system boundary
conditions. The model is calibrated against the experiments by sweeping a scaling factor to find the heat
transfer coefficient(HTC) of the exterior parts of the bus such as floor, roof, windows, walls etc. The calibrated
model is then converted into an unsteady model using steady state simulation results as an initial solution. The
unsteady model is built to simulate one standard door opening cycle, i.e, 20 seconds of opened door followed by
2 minutes of closed door simulation. The motion of the doors in the simulation is obtained by using overset
mesh methodology. The model is built with one extreme weather condition of -8.3 C. The results from steady
state describing the flow behaviour of the interior climate and the effect of door opening cycle on the interior
climate from unsteady simulation are discussed in this study.
Beskrivning
Ämne/nyckelord
Interior Climate , HVAC , CFD , Overset mesh , Electric bus , Unsteady simulation