The definition of a good indoor climate is important to the success of a passenger rail coach, not only because it will decide its energy consumption and thus influence its sustainability but also because good comfort for long journeys is essential. A survey in a coach investigating the thermal and air quality environment was undertaken. The intention is to use the results to optimise the control of the ventilation system to provide an indoor climate that passengers will find comfortable.
The term air conditioning not only prescribes comfort temperature and relative humidity, but also the quality of air inside the room. Indoor Air Quality (IAQ) has become a concomitant of air conditioning. The pollutants generated inside the room affect the quality of air inside the room. The major pollutants considered are occupant generated (carbon dioxide - CO2, odour), sulphur dioxide and toluene etc. The monitoring and controlling of all pollutants is cumbersome.
The term air conditioning not only prescribes comfort temperature and the relative humidity,but also the quality of air inside the room. Indoor air quality (IAQ) has become a concomitantof air conditioning. The pollutants generated inside the room affect the quality of air inside theroom. The major pollutants considered are CO2, sulfur dioxide, toluene, etc. Monitoring andcontrolling of all the pollutants is cumbersome. CO2 is considered as the surrogate index ofpollutants. Appendix D of the ASHRAE standards 62-1999 recommends a ventilation rate of15 cfm per person.
During the last 20 years, the humidity sensitive ventilation system evolved to products increasingly simplified thus standardised. At Aereco, there were 5 generations of extract units, each modification of product was due to a change in the acceptation criteria. In many countries, systems with variable airflows are accepted and recognised ; regulations moved. In other countries, the orthodoxy of the constant airflow of an air change per hour remains in force for simplifying reasons or by ignorance of the real interest.
The set points of supervisory control strategy are optimized with respect to energy use and thermal comfort for existing HVAC systems. The set point values of zone temperatures, supply duct static pressure, and supply air temperature are the problem variables, while energy use and thermal comfort are the objective functions. The HVAC system model includes all the individual component models developed and validated against the monitored data of an existing VAV system.
This paper proposes a space zone model for the calculation of all the airflow parameters based on tracer gas measurements, including flow rates of outdoor air, VAV supply. This approach gives a practical protocol for buildings managers to evaluate the performance of airside systems and determine air-conditioning and ventilation system performance parameters within acceptable errors.
The intent of this paper is to show that using Equation 6-1 from ASHRAE standard 62 based on occupancy is a non sense if used as a control algorithm in so far as up to now no sensors can physically count each individual in the space. Equation 6-1 describes how to calculate the amount of outdoor air required from an air-handling unit serving multiple spaces for system design purposes.
For the restoration of the historic fortress of Kufstein, the high humidity problems encountered have required special investigations : the capillary water up-take characteristics of the wall stones and identification of the ventilation deficiencies have been studied.
Results show that a controlled ventilation system may help to reduce the problems associated with humidity and condensation.
A number of computer simulation case studies have been conducted with the objective of investigating the potential for energy savings in buildings with variable air volume (VAV) systems and demand controlled ventilation (DCV), compared to buildings with conventional constant air volume (CAV) ventilation systems. The simulation systems have been modelled on a modular form, they are generally very detailed and comprehensive, and they have shown to be able to provide very realistic results compared to real world conditions.
A CO2 level of 1000 ppm is very often used as reference for control and design of ventilation flow rates in buildings. This level is well accepted in practice, and is thus normally not given any further considerations. To retain 1000 ppm CO2 in a room with fully mixed flow conditions, a flow rate of 7 liters/sec per person must be supplied. In many countries, national regulations and standards prescribe flow rates for comfort ventilation that are significantly higher than 7 l/s.
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