Indoor Climate Analysis for Urban Mobility Buses: a CFD Model for the Evaluation of thermal Comfort
International Journal of Environmental Protection and Policy
Volume 1, Issue 1, May 2013, Pages: 1-8
Received: Apr. 11, 2013;
Published: May 2, 2013
Views 3413 Downloads 303
Roberto de Lieto Vollaro, Dept. Engineering of University of Rome 3, Via della Vasca Navale 79 – 00146 Rome, Italy
The aim of this work is to analyze the indoor climate in city buses; the study was developed by numerical simulation and experimental validation carried out on the urban mobility buses of the city of Rome (Italy). Several factors have contributed to increase the concern about the comfort evaluation in vehicles and particularly in city buses. Due to the rising of the mobility needs, time that people spend in vehicles has grown substantially. The thermal environment in urban buses also varies greatly: passengers are exposed to local heating and/or cooling due to vertical temperature gradients, radiant asymmetry and local unexpected airflow. The interaction of the cabin thermal environment, created by the HVAC-system, the outdoor conditions as well as the occupants is rather complex. At the moment no standards exist for assessment and classification of the thermal environment quality in vehicles. To obtain some evidences, in order to enhance the indoor climate for a city bus and to improve occupants’ comfort monitoring local temperature and air distribution around passengers, we have developed a mathematical model. The numerical model was implemented with Computational Fluid Dynamic software (CFD, Fluent Inc.): it permits the evaluation of the thermal and fluid-dynamic performances of the air conditioning system and diffusers’ distribution. To gain a deeper understanding of the local climate comfort, the numerical simulation results were experimentally validated by several measurements inside the urban buses performed under real operative conditions during the summer season.The experimental results are in good agreement with the CFD evidences. This shows that the model developed can give reliable results to optimize and locally modify the air diffusers distribution inside cabin spaces. These evidences can help to improve the air conditioning distribution as a function of the obstructions’ typical for a city bus vehicle and to reduce the draught risk related to the bus stop door apertures. One of the most important reasons of local temperature differences and unexpected air velocity gradients is due to the multi-door system apertures at each bus stop. This situation is particularly recurrent in a city area where an urban bus can afford several stops during his programmed route. For this reason it’s important to get more information about this transient localized load for the climate conditions and about the time needed to reach again the steady conditions. To avoid or, at least, reduce this kind of problem it is proposed an air knife screened doors system bus. The thermo fluid dynamic results obtained show a significant improvement in the indoor climate comfort.
Roberto de Lieto Vollaro,
Indoor Climate Analysis for Urban Mobility Buses: a CFD Model for the Evaluation of thermal Comfort, International Journal of Environmental Protection and Policy.
Vol. 1, No. 1,
2013, pp. 1-8.
Bruun H.H. 1995. Hot-wire anemometry. Principles and signal analysis. Oxford University Press, New York.
Chen Q., Moser A. 1991. Simulation of a multiple nozzle diffuser. Proceedings of the 12th AIVC Conference, Vol.2, pp.1-14.
De Lieto Vollaro R. 2011. Numerical analysis and measures for the evaluation of comfort inside buses used for public transport. In: Technical paper session 9, Montreal, July 1-2, pp.26
Chow W.K., Wong L.T. 1997. Design of Air Diffusion Ter-minal Devices in Passenger Train Vehicle. Journal of Envi-ronmental Engineering, Vol.123, Issue 12, pp.1203-1207.
Etheridge D., Sandberg M. 1996. Building Ventilation. Theory and Measurements. John Wiley & Sons, Chichester, pp.391-446.
Fanger P.O., Melikov A.K., Hanzawa H., Ring J. 1998. Air Turbulence and Sensation of Draught. Energy and Buildings, vol. 12, pp. 21-39
ISO Standard No.7730, 1997. Moderate thermal environ-ments-determination of the PMV and PPD indices and spe-cification of the conditions for thermal comfort. International Standards Organization (ISO)
Hanzawa H., Melikow A. K., Fanger P.O. 1987. Airflow characteristics in the occupied zone of ventilated spaces. ASHRAE Transactions, Vol.93, pp.524-539.
Patankar S.V. 1980. Numerical Heat transfer and fluid flow. Hemisphere Publishing Corporation, Washington.
Thorshauge J. 1982. Air velocity fluctuations in the occupied zone of ventilated space. ASHRAE Transactions 88, pp.753-763.
Taniguchi Y, Aoki H., Fujikake K., Tanaka H., Kitada M. 1992. Study on car air conditioning system controlled by car occupants' skin temperatures-part 1: Research on a method of quantitative evaluation of car occupants' thermal sensations by skin temperatures. SAE Paper Ser 920169, pp.13–19.
Daniels R., Henser D. 2000. Valuation of environmental impacts of transport projects. Journal of transport economics and policy, Vol.34, issue 2, pp.189-214.
UNI EN 27726. 1997. Thermal environments-Instruments and methods for measuring physical quantities.
UNI EN 13182. 2002. Ventilation for buildings – Instru-mentation requirements for air velocity measurements in ventilated spaces.
Zhivov A.M., Zhang J.S., Christianson L.L. 1993. Characte-ristics of diffuser air jets and airflow in the occupied regions of mechanically ventilated rooms-a literature review. ASHRAE Transactions, Vol.99, issue 1, pp.1119-1127.
EN 14750-1. 2006. Railway applications - Air conditioning for urban and suburban rolling stock - Part 1: Comfort parameters
Khamis Mansour M., Musa Md Nor, Wan Hassan Mat Nawi, Saqr Khalid M. 2008. Development of novel control strategy for multiple circuit, roof top bus air conditioning system in hot humid countries. Energy Conversion and Management, Vol.49, issue 6, pp.1455-1468.
Miyata Etsuji, Takeuchi Hirotsugu, Imazu Masataka 1996. Development of De-misting Techniques for Bus Air Condi-tioning - Dehumidification Control at Outside Temperature Below Freezing Point. JSAE Review, Vol.17, Issue 4, pp. 455-456.
Eriksson P., Friberg O. 2000. Ride comfort optimization of a city bus - Structural and multidisciplinary optimization. Structural and Multidisciplinary Optimization Journal, Volume 20, Issue 1 , pp 67-75
De Lieto Vollaro R,, Grignaffini S., Vallati A. 2008. Numerical analysis and measures, for the evaluation of comfort – inside buses used for public transportation. In: Urban Transport XIV: Urban Transport and the Environment in the 21st Century WIT Press Malta, September 1-3, 2008, pp763
Posner J.D., Buchanan C.R., Dunn-Rankin D. 2003. Mea-surement and prediction of indoor air flow in a model room. Energy and Buildings, Vol.35, Issue 5, pp.515–526.
Gatski T.B., Hussaini M.Y., Lumley J.L. 1996. Simulation and Modeling of Turbulent Flows, Oxford University Press, New York, USA.
Baldocchi, D. (2005), Lecture 18, Wind and Turbulence, Part 1, Surface Boundary Layer: Theory and Principles , Ecosystem Science Division, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA: USA.