Combustion Evolution of Aviation Kerosene Pools in Confined Spaces Under Mechanical Negative Pressure

Fires and vibrations can occur simultaneously. Two obvious examples are ship fires and fires during earthquakes. One previous study has investigated the horizontal seismic effect on pool fires, showing higher heat release rate (HRR), shorter and wider flames. This study experimentally explored the effects of vertical vibrations on the structure and behavior of free-burning pool fires. The experimental set-up and design were similar to the previous study, i.e. burning wood cribs on a vibrator under an ISO 9705 hood. The preparation of wood-cribs and the ignition method followed ISO 15779. Moreover, the wood sticks were connected by nails and the wood cribs were fixed on the vibrator to avoid the influence of collapse of wood cribs. The vibrator can generate vertical vibrations, and different scales of seismic conditions, calculated by vibration amplitude and frequency, were applied. The parameters measured included flame height, flame diameter, flame frequency, flame temperature, air entrainment velocity and HRR. The experimental results showed that the flame were higher with the vibration scale, and the flame diameter did not change. The vertical vibration lengthened the flames, while some discontinuity was observed. This discontinuity was even enhanced with the increased vibration scale. Additionally, the flame frequency and the air entrainment velocity was increased due to the vertical vibrations. The air entrainment and the mixing of fuel volatiles and oxygen were enhanced. This argument can be proved by increased HRR. The HRR was increased with the increased vibration scale, but with an exception of the 6-Upper scale (the highest scale herein). This exception may be caused by decreased heat feedback in the test of 6-Upper scale. More discontinuity of flames and further distance between the flame (particularly the upper part flames) and the wood cribs due to lengthened flames decreased the heat feedback to the wood cribs.

Oxygen concentration effects on the burning behavior of small scale pool fires

Experimental study of the burning behavior of small-scale n-heptane pool fires enhanced by use of immersed thermally conductive thin plates

The influence of a plate obstacle on the burning behavior of small scale pool fires: An experimental study

The ventilation equipment for enclosed spaces or office rooms is specified according National Building Code of India published by the Bureau of Indian Standards. Natural ventilation peri-odically together with mechanical ventilation is recommended to remove pollutants. The need to study fire and smoke behavior inside a completely closed room with air intake and exhaust vents becomes important in case of low or no mechanical ventilation service. An experimental study on unsteady heptane pool fires of different sizes in their initial stages was conducted in a cubical fire test chamber of 27 m3 inside dimensions. The compartment was naturally ventilated with a typical configuration of a vertical intake on a side wall and an exhaust vent at the ceiling leading into a duct. Three circular pans of diameters 0.34, 0.47 and 0.61 m were employed to generate the fire with n-heptane as fuel on a bed of water. Temperatures, wall heat fluxes and mass loss rate were measured. The flame was visualized using a video camera through a tempered view glass. The total heat transfer to the ceiling and wall increased with the increase in fire size as the flames became taller in the initial stages (3-4 minutes) with sig-nificant increase in case of 500 kW fire. The smoke layer was observed at about mid height (1.5 m) above floor. The leaning behavior of flames was seen due to naturally induced air inflow. The wall heat flux of about 50 kW/m2 obtained indicate hazardous environment for further flame spread. A fourfold increase in mass loss rate was observed with just 2.5 times increase in fire size inside the ceiling vented compartment.

O-29A6-1 Background/Aims: The Netherlands is situated in a moderate maritime climate in Western Europe, where most houses today are built with thermal insulation and mechanical ventilation. Mechanical ventilation can be subdivided in systems which combine natural supply and mechanical exhaust and systems with mechanical supply and exhaust with heat recovery. In 2007, a Municipal Health Service reported health complaints of residents in dwellings with the latter type of mechanical ventilation system. Residents reported nonspecific health complaints such as respiratory, nose, and eye complaints; fatigue; and sleep problems attributed to the ventilation system. As stricter requirements for energy performance are expected in the future, mechanical ventilation with heat recovery will become more common. Therefore, understanding the relationship of mechanical ventilation and health complaints is needed. This study aimed to investigate the relationship between the quality of mechanical ventilation systems and health complaints and wellbeing in private homes. Methods: One hundred fifty newly built houses with natural supply and mechanical exhaust ventilation and 150 newly built houses with mechanical supply and exhaust with heat recovery throughout the Netherlands were selected from an existing database. A structured home inspection by trained surveyors aimed at the ventilation system was combined with a questionnaire survey among the 300 residents. The ventilation system was checked for ventilation capacity, noise levels, construction flaws, internal cleanliness, and maintenance state, etc. The questionnaire contained questions about nonspecific health complaints, sleep quality, noise annoyance, thermal comfort, environmental sensitivity, and coping strategies. Results: This paper will present results about the association of different mechanical ventilation systems with health complains and well-being. The role of perceptions and environmental sensitivity will be discussed. Conclusion: Home inspection reveals that a priori 20% of both types of ventilation systems have insufficient ventilation capacity. In working conditions, an additional 60% does not have a sufficient ventilation capacity and might result in adverse health effects.

In this work, the cooling performance of night ventilation systems and different earth heat exchange technologies were experimentally analysed in three office buildings in Southern Germany. One of the first passive energy standard office buildings in Europe was extensively monitored over a three year period to analyse the summer performance of a highly insulated and well shaded building in which night cooling ventilation was based on stack effect and cross ventilation. This was combined with a mechanical ventilation system incorporating a ground coupled heat exchanger to supply daytime fresh air.For comparison, an energy analysis was made of a mechanically driven exhaust air night ventilation system and a supply and exhaust air system in the other two buildings. The first of these was a passively cooled refurbished building in Tübingen which utilises mechanical night ventilation to effectively discharge ceilings with phase change material. In addition, fresh air cooling is achieved using a horizontal brine-earth heat exchanger. The second comparison building was a low energy office building in Freiburg which uses water based ground coupled heat exchangers for fresh air cooling and an exhaust air ventilation system for night cooling.During a typical German summer, in which the number of hours that the ambient air temperature exceeds 25°C is less than 160, the passively ventilated building performed excellently, even with relatively high internal heat loads of 200 to 400 Wh.m−2.day−1. However, when the ambient air temperature was significantly higher, such as in the summer of 2003 (i.e. 3 K higher than the average summer temperature), nearly 10% of all office hours recorded room air temperatures above 26 °C. In the case of the two buildings that were night cooled by mechanical ventilation, cooling performance was limited by the rather low air exchange rate of 2 h−1. This resulted in overnight room temperature reductions of just 2–3 K during hot summer nights. Also the coefficient of performance (COP) was relatively low for this approach at between 4 to 6.All the earth heat exchangers showed excellent energy performances with COP's between 20 and 50. However, due to the limited fresh air volume flow in such buildings, the earth heat exchanger only removed a small part of the total load.

The purpose of this research is to understand the fire behavior expected in a mechanically ventilated compartment. To date, some experimental studies have been conducted for investigation of fire behavior under mechanical forced ventilation; however, it might be not enough to understand everything. We therefore carried out a series of experiments on fire behavior focused on the effect of air inlet position in a compartment with same size as an ISO 9705 room (width 2.4 m × length 3.6 m × height 2.4 m) under conditions of mechanical ventilation using a pool fire. In this paper, the effects of ventilation conditions such as air inlet position and flow rate were studied. We found that differences in the air inlet position and flow rate were one of the principal factors for determining the burning behavior.

The behavior of pool fires: State of the art and new insights

Quantitative investigation of the gravity effect was performed for small-sized acetone and kerosene pool fires. Several investigations on the behavior of pool fires have been conducted to understand the physical model. In their primary papers, it was mentioned that the buoyancy effect on the motion of pool fires was significant to understand the characteristics such as flame height, oscillatory frequency, and so on. Under these circumstances, in this investigation, a centrifuge was used to create elevated gravity fields and to examine the gravity effect. Small-scale pool fires were observed under various high gravity fields. Regions of stable flame, puffing flame and irregular oscillatory flame were categorized to make a map related with the gravity level and pool diameter. Flame height decreased and oscillatory frequency increased with an increase in the gravity level. Behavior of the flame height was agreed quantitatively with the scaling prediction presented by Orloff and Heskestad. Puffing phenomena observed under various gravity fields were summarized with the relationship between Strouhal and Froude number. As the result, an empirical equation expressed by St = 0.517Fr -0.502 could be obtained. From this equation, puffing frequency could be estimated for a flame of various pool diameters varying from 0.01 to 50m.

Under certain circumstances, the water on which a burning pool of liquid fuel is supported may begin to boil. The water vapor that is released and escapes through the fuel surface tends to atomize the oil, which results in an emulsive-droplet flame above the fuel surface. This phenomenon, called boilover, has been observed for large scale pool fires, but the mechanism causing it to occur has not been fully investigated yet. This paper describes fundamental aspects of the effect of a boiling water sublayer on the behavior of pool fires. A burner system in which the burning surface of the fuel can be fed into the flame so that the fuel/water interface with respect to the edge of the container remains fixed was used. Ten different single-component and six different multicomponent fuels were tested. Conventional flow visualization techniques were applied to study the liquid motion, and results for an ethylbcnzene pool in a 4.8cm diameter pan are presented. Data obtained include temperatures and mass ...

Wind has a significant effect on pool fire behavior, which is relevant to many fire conditions, such as wildfires, building fires, and oil transportation fires. Although fire behavior and morphology changes have received considerable attention and been widely researched, there are few works concerning the flow and flam dynamics of pool fire. A large eddy simulation model is adopted to investigate the flow and flame dynamics of a rectangular pool fire considering the combined effects of wind and slope. The results show that, with a wind speed of 0.5 m/s, a flame develops immediately downstream of the fire source and sustains two flanks of plume. Further downstream, the plume starts to rise due to buoyant force. Temperature, velocity, and vorticity distributions show significantly different shapes at different streamwise locations. Near the fire source, the flame is confined to a small region around the fire source. The air circulation downstream shows a cylindrical spiring pattern. When the wind speed increases, the temperature and velocity become more parallel to the surface and their maximum values increase. On the contrary, the temperature fluctuations and turbulent kinetic energy decrease with the wind speed, and they are more frequent near the flame tails.

Experimental and numerical investigation into burning rate and fire plume characteristic of pool fire with plate obstacle

MONICAIR - MONItoring & Control of Air quality in Individual Rooms - is a pre-competitive field research project of a broad consortium of Dutch ventilation unit manufacturers and research institutes, supported by the Dutch government. The first aim of the project is to investigate and compare the indoor air quality (IAQ) performance and energy characteristics during the heating season of ten different mechanical ventilation solutions in dwellings that meet strict air-tightness standards and comply with current building regulations. The second goal is to further improve the ventilation systems on their IAQ-performance while minimizing their energy consumption.Over a full year 62 residential dwellings were monitored with, in each habitable room, sensors for occupancy, CO2, relative humidity and air temperature. Power consumption of the mechanical ventilation units was also continuously monitored. The ventilation solutions included traditional mechanical exhaust ventilation or MEV systems (systems with mechanical exhaust in the wet rooms), state-of-the-art MEV systems (systems with mechanical exhaust in all rooms), as well as local and central balanced systems with heat recovery (MVHR-systems), with various types of controls. Although all systems under investigation comply with building codes, the data show that huge differences occur in both the IAQ and energy performance. CO2 excess dose (above 1200 ppm) may vary per dwelling from 10 to 850 kppmh per person per heating season, resulting in a situation in which respectively 1 to approximately 85% of the time spent at home, the ventilation is not sufficient in the room that one occupies. Real life primary energy consumption varies from 23 MJ/m2 for centralized ventilation systems with heat recovery to 144 MJ/m2 for traditional MEV-systems.

Does your home have a mechanical ventilation system? If not, does this mean that your home is naturally ventilated? Probably not. Several studies have compared the effects of naturally versus mechanically ventilated buildings on indoor air quality. However, these comparisons may be unfair to some naturally ventilated buildings. Let's discover why. Ventilation is the process of supplying air to and/or removing air from a space for the purpose of controlling air contaminant concentrations, humidity, or temperature within the space (ASHRAE, 2013). Buildings are usually classified according to their ventilation system as mechanically, naturally, or mixed (hybrid) ventilated. In a mechanically ventilated building, ventilation is provided by powered equipment, such as motor-driven fans and blowers. In a naturally ventilated building, ventilation is provided by natural forces such as wind-induced pressure differences or temperature-induced differences in air density. In natural ventilation, air is introduced into the ventilated space through intentional openings in the building envelope. In the third mode, mixed or hybrid ventilation (Heiselberg, 2002), the two strategies are alternated spatially or temporally. ASHRAE Standard 62.1-2013 (ASHRAE, 2013) specifies that a natural ventilation system should be ‘designed.’ This specification implies that there should be a professional who takes responsibility for designing openings and methods for their control according to standards or best practices, for example CIBSE AM 10 (CIBSE, 2010). The designer may take into consideration parameters that affect the performance of the natural ventilation system, such as wind speed and direction, indoor and outdoor temperatures, and location and size of the designed and controlled openings. So, here is a key question to consider. Should buildings without a mechanical ventilation system automatically be classified as naturally ventilated? In my view, the proper answer is ‘no.’ It is reasonable to assume that—for a significant part of the world's building stock—no one designed a ventilation system according to pertinent best practices. In the absence of appropriate design, it seems wrong for the default building classification to be ‘naturally ventilated.’ If buildings without designed ventilation should not be classified as ‘naturally ventilated,’ then how should we classify them? How should we refer to this case? One option would be ‘noncompliant ventilation.’ However, this name may be too ambiguous. The ventilation system may not comply with a specific standard or a version of a standard, but it may comply with other guidelines or standards. This name does not shed light on the fact that the no one deliberately designed the system. Another name might be ‘unknown ventilation’ or, to draw on a classical Greek root, we might refer to such circumstances as possessing ‘agnostic ventilation’ [from ‘agnōstos’ in classical Greek: ‘άγνωστος’, ‘not (to be) known’]. This nomenclature, too, presents problems. One could argue that even for designed mechanical or natural ventilation systems, the actual or average outdoor airflow rate is uncertain in operation. Moreover, in English usage, the term agnostic is commonly associated with people who believe that the existence or nature of God is not known or cannot be known. In reflecting about this problem, I found myself stuck on these terms, when Bill Nazaroff happened to stop by my desk and suggested the term ‘adventitious ventilation.’ It took me some minutes to learn how to spell it, and it is not yet easy to pronounce, but regardless of these difficulties, this was exactly the term I was looking for. In fact, the Oxford English Dictionary defines adventitious as ‘ …occurring as a result of an external factor or of chance, rather than by design….’ The term ‘adventitious ventilation’ is not new. It has been used, mainly in the seventies and for residential buildings, as synonymous of infiltration and natural ventilation (Harris-Bass et al., 1974). This interchangeable use of the terms ‘natural’ and ‘adventitious’ ventilation underlines the negative prejudice about the unpredictability and randomness of natural ventilation. Since then, we have learned much about natural ventilation, and it now seems worthwhile to distinguish natural ventilation from adventitious ventilation. Now that we have a name, let's try to develop a definition. In an adventitiously ventilated building, ventilation is incidental, and the ventilation system has not been taken into account and designed to achieve any particular code, standard or best practice. This definition does not exclude that sufficient or abundant outdoor airflow rate could occur or that adventitiously ventilated buildings have higher, equal, or lower performance compared to naturally ventilated buildings (i.e., buildings provided with a designed system). There are examples of vernacular architecture that are proven to work well. Those buildings have embedded centuries of empirical design that can be considered a best practice. This definition does not guarantee that the natural ventilation performs well either. To do that, an assessment should be carried out. The definition underlines the point that, for an adventitiously ventilated building, the issue of ventilation was not considered by the designers and builders. If a researcher, engineer, or architect does not find reasonable evidence to show that a natural ventilation system was designed, then he/she should classify the building as adventitiously ventilated. Is this new classification needed? In an ideal world, we would not need to distinguish naturally and adventitiously ventilated buildings because we would classify ventilation systems based on their measured performance (e.g., outdoor airflow rate, ventilation effectiveness, pollutant concentrations, etc.). Until then, it seems manifestly unfair for well-designed naturally ventilated buildings (examples are described in Lomas, 2007) to be included in the same group of buildings for which ventilation occurs incidentally, rather than intentionally. For the same wind conditions and air temperature differences between indoors and outdoors, it is possible that the outdoor airflow rate, where air enters the indoor space, and how air is distributed throughout the building could be substantially different between superficially clustered naturally and adventitiously ventilated buildings. Seppänen and Fisk (2002) published a literature review on the associations of ventilation and air-conditioning system types in office buildings with sick building syndrome (SBS) symptoms. They classified buildings into five main categories (natural ventilation, mechanical exhaust, mechanical ventilation, and air-conditioned with and without humidification). They followed a similar classification used by Mendell and Smith (1990). They concluded that: ‘relative to natural ventilation, air-conditioning, with or without humidification, was consistently associated with a statistically significant increase in the prevalence of one or more SBS symptoms, by approximately 30–200%.’ We do not know exactly what proportions of the buildings they studied were naturally or adventitiously ventilated. How different would the prevalence of SBS symptoms be in air-conditioned buildings compared to naturally or adventitiously ventilated buildings? Finding an answer would be interesting and potentially important for ongoing efforts to improve ventilation design and practice. Why has this category not been introduced before? A possible answer comes from the introduction of natural ventilation design methods into code and standards. Decades ago, it was unlikely to find buildings in which natural ventilation was explicitly designed. Today, the absence of design may still be common, but an increasing number of buildings have been designed for natural ventilation according to appropriate guidelines. This effort and the potential for improved performance should be acknowledged in our studies when we compare different ventilation systems. So, are your home and workspace mechanically, naturally, or adventitiously ventilated? Let me know the answer at http://bit.ly/Adventitious. This work was supported by SinBerBEST (Singapore-Berkeley Building Efficiency and Sustainability in the Tropics) Research Program. The idea described here was inspired by the discussions on residential ventilation systems with Prof. Roberto Zecchin and Dr. Valentina Raisa.