ΣΧΟΛΙΟ "ΚΟΥΡΗΤΗΣ": ΕΠΕΙΔΗ ΠΟΛΛΟΙ ΔΗΜΟΣΙΟΓΡΑΦΟΙ ΑΛΛΑ ΚΑΙ ΠΥΡΟΣΒΕΣΤΕΣ ΣΕ ΔΗΛΩΣΕΙΣ ΤΟΥΣ ΜΙΛΗΣΑΝ ΓΙΑ ΘΕΡΜΟΤΗΤΑ ΠΟΥ ΥΠΕΡΕΒΑΙΝΕ ΤΟΥΣ 1000+ ΒΑΘΜΟΥΣ ΚΕΛΣΙΟΥ, ΜΟΥ ΕΚΑΝΕ ΕΝΤΥΠΩΣΗ ΚΑΙ ΕΙΠΑ ΝΑ ΤΟ ΨΑΞΩ ΛΙΓΟ. ΜΠΟΡΕΙ ΠΑΝΤΑ ΟΙ ΔΗΜΟΣΙΟΓΡΑΦΟΙ ΚΑΙ ΟΙ ΠΥΡΟΣΒΕΣΤΕΣ ΝΑ ΕΚΑΝΑΝ ΛΑΘΟΣ, ΔΕΔΟΜΕΝΟΥ ΠΩΣ ΔΕΝ ΚΥΚΛΟΦΟΡΟΥΝ ΜΕ ΕΝΑ ΘΕΡΜΟΜΕΤΡΟ ΑΝΑ ΧΕΙΡΑΣ.
ΑΥΤΟ ΠΟΥ ΕΜΕΝΑ ΜΟΥ ΚΙΝΗΣΕ ΤΗΝ ΠΕΡΙΕΡΓΕΙΑ ΕΙΝΑΙ ΤΟ ΠΩΣ ΕΝΑ ΑΠΟΨΙΛΩΜΕΝΟ ΚΑΙ ΑΡΑΙΟ ΔΑΣΟΣ, ΜΑΖΙ ΜΕ ΤΗΝ ΟΠΟΙΑ ΘΑΜΝΩΔΗ ΚΑΙ ΞΕΡΗ ΒΛΑΣΤΗΣΗ ΕΧΕΙ ΣΤΟ ΕΔΑΦΟΣ ΤΟΥ, ΤΡΟΦΟΔΟΤΟΥΣΕ ΤΕΤΟΙΕΣ ΦΛΟΓΕΣ (ΜΕΓΕΘΟΣ ΚΑΙ ΘΕΡΜΟΚΡΑΣΙΑ). ΑΚΟΜΗ ΚΑΙ Ο ΑΝΕΜΟΣ ΑΛΛΑ ΚΑΙ ΤΟ ΜΙΚΡΟΚΛΙΜΑ ΠΟΥ ΔΗΜΙΟΥΡΓΕΙ Η ΙΔΙΑ Η ΦΩΤΙΑ ΔΕΝ ΔΙΚΑΙΟΛΟΓΟΥΝ ΤΕΤΟΙΕΣ ΦΛΟΓΕΣ ΣΕ ΗΜΙΑΣΤΙΚΟ ΚΑΙ ΑΣΤΙΚΟ ΠΕΡΙΒΑΛΛΟΝ ΣΤΟ ΟΠΟΙΟ ΜΑΛΙΣΤΑ ΜΕΙΩΝΕΤΑΙ/ΕΚΛΕΙΠΕΙ ΤΟ ΚΥΡΙΩΣ "ΚΑΥΣΙΜΟ" ΠΟΥ ΤΙΣ ΤΡΟΦΟΔΟΤΕΙ.
ΠΕΡΑΙΤΕΡΩ ΣΧΟΛΙΟ ΔΕΝ ΘΑ ΚΑΝΩ ΟΥΤΕ ΚΑΙ ΘΑ ΑΠΑΝΤΗΣΩ, ΠΡΩΤΟΝ ΔΙΟΤΙ ΔΗΛΩΝΩ ΚΑΙ ΕΙΜΑΙ ΑΣΧΕΤΟΣ ΚΑΙ ΔΕΥΤΕΡΟΝ ΔΕΝ ΘΕΛΩ ΝΑ ΣΥΝΕΙΣΦΕΡΩ ΣΤΗΝ ΓΕΝΙΚΗ ΠΑΡΑΝΟΙΑ. ΕΧΩ ΟΜΩΣ ΒΓΑΛΕΙ ΤΟ ΔΙΚΟ ΜΟΥ ΑΝΤΙΕΠΙΣΤΗΜΟΝΙΚΟ ΚΑΙ ΕΝ ΠΑΡΑ ΠΟΛΛΟΙΣ ΑΥΘΑΙΡΕΤΟ ΣΥΜΠΕΡΑΣΜΑ ΜΟΥ. ΔΙΑΒΑΣΤΕ ΚΑΙ ΕΣΕΙΣ ΚΑΙ ΒΓΑΛΤΕ ΤΟ ΔΙΚΟ ΣΑΣ.
An average surface fire on the forest floor might have flames reaching 1 metre in height and can reach temperatures of 800°C (1,472°F) or more. Under extreme conditions a fire can give off 10,000 kilowatts or more per metre of fire front. This would mean flame heights of 50 metres or more and flame temperatures exceeding 1200°C (2,192°F). The flash point, or the temperature at which wood will burst into flame, is 572°F, according to HowStuffWorks.
Flames temperatures of open flames
For convenience, we can subdivide the turbulent diffusion flames from unwanted fires into two types: flames in the open, and room fires.
First we will consider open flames.
The starting point for discussing this topic can be the work of the late Dr. McCaffrey, who made extensive measurements [4] of temperatures in turbulent diffusion flames. He used gas burners in a "pool fire" mode (i.e., non-premixed) and studied various characteristics of such fire plumes. He described three different regimes in such a fire plume:
Slightly above the base of the fire begins the continuous flame region. Here the temperatures are constant and are slightly below 900°C.
Above the solid flame region is the intermittent flame region. Here the temperatures are continuously dropping as one moves up the plume. The visible flame tips correspond to a temperature of about 320°C.
Finally, beyond the flame tips is the thermal plume region, where no more flames are visible and temperature continually drop with height.
French researchers at the University of Poitiers recently made the same types of measurements and reported numerical values [5] indistinguishable from McCaffrey's. Cox and Chitty [6] measured similar plumes and obtained very similar results: a temperature of 900°C in the continuous flame region, and a temperature of around 340°C at the flame tips. The latter value does not appear to be a universal constant. Cox and Chitty later measured slightly higher heat release rate fires, and found a flame tip temperature of around 550°C. In a later paper [7], researchers from the same laboratory examined turbulent diffusion flames under slightly different conditions, and found peak values of 1150-1250°C for natural gas flames, which is rather higher than 900°C. The above results were from fires of circular or square fuel shape. Yuan and Cox [8] measured line-source type fires. They found a temperature of 898°C in the continuous flame region, and a flame tip temperature of around 340°C. This suggests that such results are not dependent on the shape of the fuel source.
In studying fires in a warehouse storage rack geometry, Ingason [9] found an average solid-flame temperature of 870°C. At the visible flame tips, the average temperature was 450°C, but the range was large, covering 300~600°C.
In a related study, Ingason and de Ris [10] found typical flame tip temperatures of 400°C for burner flames of propane, propylene, and carbon monoxide fuels.
Sullivan et al. [14] cite Australian studies on wildfire flames, finding that flame tip temperature corresponds to 300°C, while peak values around 927°C can be expected.
Heskestad [11] adopts a criterion of 500°C rise as defining the flame tip temperature, i.e. an actual temperature of about 520°C.
Taking all of the above information in account, it appears that flame tip temperatures for turbulent diffusion flames should be estimated as being around 320~400°C. For small flames (less than about 1 m base diameter), continuous flame region temperatures of around 900°C should be expected. For large pools, the latter value can rise to 1100~1200°C.
Flame temperatures in room fires
There is fairly broad agreement in the fire science community that flashover is reached when the average upper gas temperature in the room exceeds about 600°C. Prior to that point, no generalizations should be made: There will be zones of 900°C flame temperatures, but wide spatial variations will be seen. Of interest, however, is the peak fire temperature normally associated with room fires. The peak value is governed by ventilation and fuel supply characteristics [12] and so such values will form a wide frequency distribution. Of interest is the maximum value which is fairly regularly found. This value turns out to be around 1200°C, although a typical post-flashover room fire will more commonly be 900~1000°C. The time-temperature curve for the standard fire endurance test, ASTM E 119 [13] goes up to 1260°C, but this is reached only in 8 hr. In actual fact, no jurisdiction demands fire endurance periods for over 4 hr, at which point the curve only reaches 1093°C. The peak expected temperatures in room fires, then, are slightly greater than those found in free-burning fire plumes. This is to be expected. The amount that the fire plume's temperature drops below the adiabatic flame temperature is determined by the heat losses from the flame. When a flame is far away from any walls and does not heat up the enclosure, it radiates to surroundings which are essentially at 20°C. If the flame is big enough (or the room small enough) for the room walls to heat up substantially, then the flame exchanges radiation with a body that is several hundred °C; the consequence is smaller heat losses, and, therefore, a higher flame temperature.
Adiabatic flame temperature
https://www.doctorfire.com/flametmp.html
ΑΥΤΟ ΠΟΥ ΕΜΕΝΑ ΜΟΥ ΚΙΝΗΣΕ ΤΗΝ ΠΕΡΙΕΡΓΕΙΑ ΕΙΝΑΙ ΤΟ ΠΩΣ ΕΝΑ ΑΠΟΨΙΛΩΜΕΝΟ ΚΑΙ ΑΡΑΙΟ ΔΑΣΟΣ, ΜΑΖΙ ΜΕ ΤΗΝ ΟΠΟΙΑ ΘΑΜΝΩΔΗ ΚΑΙ ΞΕΡΗ ΒΛΑΣΤΗΣΗ ΕΧΕΙ ΣΤΟ ΕΔΑΦΟΣ ΤΟΥ, ΤΡΟΦΟΔΟΤΟΥΣΕ ΤΕΤΟΙΕΣ ΦΛΟΓΕΣ (ΜΕΓΕΘΟΣ ΚΑΙ ΘΕΡΜΟΚΡΑΣΙΑ). ΑΚΟΜΗ ΚΑΙ Ο ΑΝΕΜΟΣ ΑΛΛΑ ΚΑΙ ΤΟ ΜΙΚΡΟΚΛΙΜΑ ΠΟΥ ΔΗΜΙΟΥΡΓΕΙ Η ΙΔΙΑ Η ΦΩΤΙΑ ΔΕΝ ΔΙΚΑΙΟΛΟΓΟΥΝ ΤΕΤΟΙΕΣ ΦΛΟΓΕΣ ΣΕ ΗΜΙΑΣΤΙΚΟ ΚΑΙ ΑΣΤΙΚΟ ΠΕΡΙΒΑΛΛΟΝ ΣΤΟ ΟΠΟΙΟ ΜΑΛΙΣΤΑ ΜΕΙΩΝΕΤΑΙ/ΕΚΛΕΙΠΕΙ ΤΟ ΚΥΡΙΩΣ "ΚΑΥΣΙΜΟ" ΠΟΥ ΤΙΣ ΤΡΟΦΟΔΟΤΕΙ.
ΠΕΡΑΙΤΕΡΩ ΣΧΟΛΙΟ ΔΕΝ ΘΑ ΚΑΝΩ ΟΥΤΕ ΚΑΙ ΘΑ ΑΠΑΝΤΗΣΩ, ΠΡΩΤΟΝ ΔΙΟΤΙ ΔΗΛΩΝΩ ΚΑΙ ΕΙΜΑΙ ΑΣΧΕΤΟΣ ΚΑΙ ΔΕΥΤΕΡΟΝ ΔΕΝ ΘΕΛΩ ΝΑ ΣΥΝΕΙΣΦΕΡΩ ΣΤΗΝ ΓΕΝΙΚΗ ΠΑΡΑΝΟΙΑ. ΕΧΩ ΟΜΩΣ ΒΓΑΛΕΙ ΤΟ ΔΙΚΟ ΜΟΥ ΑΝΤΙΕΠΙΣΤΗΜΟΝΙΚΟ ΚΑΙ ΕΝ ΠΑΡΑ ΠΟΛΛΟΙΣ ΑΥΘΑΙΡΕΤΟ ΣΥΜΠΕΡΑΣΜΑ ΜΟΥ. ΔΙΑΒΑΣΤΕ ΚΑΙ ΕΣΕΙΣ ΚΑΙ ΒΓΑΛΤΕ ΤΟ ΔΙΚΟ ΣΑΣ.
An average surface fire on the forest floor might have flames reaching 1 metre in height and can reach temperatures of 800°C (1,472°F) or more. Under extreme conditions a fire can give off 10,000 kilowatts or more per metre of fire front. This would mean flame heights of 50 metres or more and flame temperatures exceeding 1200°C (2,192°F). The flash point, or the temperature at which wood will burst into flame, is 572°F, according to HowStuffWorks.
Flames temperatures of open flames
For convenience, we can subdivide the turbulent diffusion flames from unwanted fires into two types: flames in the open, and room fires.
First we will consider open flames.
The starting point for discussing this topic can be the work of the late Dr. McCaffrey, who made extensive measurements [4] of temperatures in turbulent diffusion flames. He used gas burners in a "pool fire" mode (i.e., non-premixed) and studied various characteristics of such fire plumes. He described three different regimes in such a fire plume:
Slightly above the base of the fire begins the continuous flame region. Here the temperatures are constant and are slightly below 900°C.
Above the solid flame region is the intermittent flame region. Here the temperatures are continuously dropping as one moves up the plume. The visible flame tips correspond to a temperature of about 320°C.
Finally, beyond the flame tips is the thermal plume region, where no more flames are visible and temperature continually drop with height.
French researchers at the University of Poitiers recently made the same types of measurements and reported numerical values [5] indistinguishable from McCaffrey's. Cox and Chitty [6] measured similar plumes and obtained very similar results: a temperature of 900°C in the continuous flame region, and a temperature of around 340°C at the flame tips. The latter value does not appear to be a universal constant. Cox and Chitty later measured slightly higher heat release rate fires, and found a flame tip temperature of around 550°C. In a later paper [7], researchers from the same laboratory examined turbulent diffusion flames under slightly different conditions, and found peak values of 1150-1250°C for natural gas flames, which is rather higher than 900°C. The above results were from fires of circular or square fuel shape. Yuan and Cox [8] measured line-source type fires. They found a temperature of 898°C in the continuous flame region, and a flame tip temperature of around 340°C. This suggests that such results are not dependent on the shape of the fuel source.
In studying fires in a warehouse storage rack geometry, Ingason [9] found an average solid-flame temperature of 870°C. At the visible flame tips, the average temperature was 450°C, but the range was large, covering 300~600°C.
In a related study, Ingason and de Ris [10] found typical flame tip temperatures of 400°C for burner flames of propane, propylene, and carbon monoxide fuels.
Sullivan et al. [14] cite Australian studies on wildfire flames, finding that flame tip temperature corresponds to 300°C, while peak values around 927°C can be expected.
Heskestad [11] adopts a criterion of 500°C rise as defining the flame tip temperature, i.e. an actual temperature of about 520°C.
Taking all of the above information in account, it appears that flame tip temperatures for turbulent diffusion flames should be estimated as being around 320~400°C. For small flames (less than about 1 m base diameter), continuous flame region temperatures of around 900°C should be expected. For large pools, the latter value can rise to 1100~1200°C.
Flame temperatures in room fires
There is fairly broad agreement in the fire science community that flashover is reached when the average upper gas temperature in the room exceeds about 600°C. Prior to that point, no generalizations should be made: There will be zones of 900°C flame temperatures, but wide spatial variations will be seen. Of interest, however, is the peak fire temperature normally associated with room fires. The peak value is governed by ventilation and fuel supply characteristics [12] and so such values will form a wide frequency distribution. Of interest is the maximum value which is fairly regularly found. This value turns out to be around 1200°C, although a typical post-flashover room fire will more commonly be 900~1000°C. The time-temperature curve for the standard fire endurance test, ASTM E 119 [13] goes up to 1260°C, but this is reached only in 8 hr. In actual fact, no jurisdiction demands fire endurance periods for over 4 hr, at which point the curve only reaches 1093°C. The peak expected temperatures in room fires, then, are slightly greater than those found in free-burning fire plumes. This is to be expected. The amount that the fire plume's temperature drops below the adiabatic flame temperature is determined by the heat losses from the flame. When a flame is far away from any walls and does not heat up the enclosure, it radiates to surroundings which are essentially at 20°C. If the flame is big enough (or the room small enough) for the room walls to heat up substantially, then the flame exchanges radiation with a body that is several hundred °C; the consequence is smaller heat losses, and, therefore, a higher flame temperature.
Adiabatic flame temperature
https://www.doctorfire.com/flametmp.html
Ανά σημεία αναπτύχθηκαν έως και 1.600 βαθμοί Κελσίου κυριολεκτικά λιώνοντας τα μέταλλα. Σε αυτή την αποκάλυψη προχώρησε ανώτατος αξιωματικός της Πυροσβεστικής υπηρεσίας.
ReplyDeletehttps://www.stoxos.gr/2018/07/1600_26.html