Comfort study for the numerical validation of the air conditioning strategy. Through the simulation of fluids, the most extreme operating conditions have been reproduced, as well as the real validation tests. In this work the results are presented for the case of heating, where the external temperature is -10 ºC. The total heating power is 23.5 kW, and the flow rate is 2000 m3/h.
The visualization of the fluid field, in addition to the ability to measure and monitor any parameter of interest, allows us to ensure both the quality of the air and the stratification of temperatures according to the norm. It is also a calculation tool to be able to validate the power specified in the HVAC equipment, as well as the ducting system and the air outlets.
The study focuses on one of the central cars, where the hot air supply is carried out at ground level and the return of air to the HVAC equipment is conducted through various openings in the ceiling.
Average thickness and conductivity values are available for each of the surfaces that delimit the interior volume of air; being 3.1 W/m2K the total average.
The ducting system has been studied independently, obtaining as a result the values of flow rate and supply temperature for each of the air outlets. The average outlet temperature is 31 ºC and the flow rate, adjusted for pressure drops, is reduced to 1770 m3/h.
The objective of any comfort study is to ensure indoor air conditions in accordance with the norm, ensuring correct stratification and air quality. In this case, the measurements corresponding to the validation tests of the air conditioning system for the railway sector have also been reproduced.
Below are results that start from the thermal equilibrium condition. That is, a first stationary study has been carried out, around the equilibrium point, from which a time-dependent solution can be obtained. Also note that for the stationary solution averaged turbulence models (RANS) have been used, while for the transient case the turbulence has been calculated (LES).
To ensure compliance with the standard, in addition to evaluating the interior conditions, it is necessary to obtain the specific values of temperature and speed at the specified measurement points for the validation tests.
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