Kurzes Lehrbuch der Physikalischen Chemie

Ulich, H.; Cruse, K.

doi:10.1007/978-3-642-87258-7

Cited by 20 publications

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“…This formula is known as Richmann's mixing rule [23]. The formula directly derives from the first law of thermodynamics [24].…”

Section: Numerical Simulationmentioning

confidence: 99%

Injury Threshold of Oral Contact with Hot Foods and Method for Its Sensory Evaluation

Lachenmeier

2018

Safety

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Epidemiological studies indicate an increased risk of esophageal cancer from the consumption of very hot foods and beverages. The contact time and the contact temperature are decisive for the risk of injury. However, measuring the contact temperature is not easy in practice. In the present study, a numerical simulation based on the solution of the heat conduction equation was initially used to investigate whether and for what period of time a constant contact temperature is to be expected under oral conditions. For small food samples (e.g., cooked potatoes) in contact with the tongue, the simulation results in constant contact temperatures of up to 10 s before cooling depending on thickness. Hot beverages, which spread as a thin film and thereby increase their surface area, can therefore be consumed at higher temperatures than solid foods. Furthermore, orientating measurements with a “measuring spoon” determined the contact temperature of 46.5 °C considered to be just comfortable for any period >10 s and about 48 °C for periods of less than 10 s The course of the contact temperatures determined in the experiment over time allows the corresponding threshold values of consumption temperatures for various hot foods to be calculated. In view of the fact that the contact temperature is obviously the determining factor for the risk of injury from burns in the oral cavity in addition to the contact time, it makes sense to reference threshold values to the contact temperature rather than to the surface or consumption temperature of a food product, which is current customary practice. If this contact temperature is defined as a threshold value, the surface or consumption temperature for any other food can be calculated.

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“…This formula is known as Richmann's mixing rule [23]. The formula directly derives from the first law of thermodynamics [24].…”

Section: Numerical Simulationmentioning

confidence: 99%

Injury Threshold of Oral Contact with Hot Foods and Method for Its Sensory Evaluation

Lachenmeier

2018

Safety

View full text Add to dashboard Cite

show abstract

“…This formula is known as Richmann's mixing rule [23]. The formula directly derives from the first law of thermodynamics [24].…”

Section: Numerical Simulationmentioning

confidence: 99%

Injury Threshold of Mouth Contact with Hot Solid or Paste-Like Foods and Sensory Evaluation of Consumption Temperatures

Lachenmeier¹,

Lachenmeier²

2018

Preprint

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Epidemiological studies indicate an increased risk of cancer from the consumption of very hot foods and beverages. The International Agency for Research on Cancer (IARC) has already recommended threshold values for the maximum drinking temperature of very hot beverages. The contact time and the contact temperature are decisive for the risk of injury when hot media come into contact with human skin. However, measuring the contact temperature is not easily possible in practice. In the present study, a numerical simulation based on the solution of the heat conduction equation was initially used to investigate whether and for what period of time a constant contact temperature is to be expected under oral conditions. For small circular 3-cm food samples (e.g., cooked potatoes) with 2.5 mm thickness in contact with the tongue, the simulation results in a constant contact temperature of 10 s before cooling. With a thickness of 0.5 mm, the contact temperature is only maintained 1 s. Hot drinks, which spread as a thin film and thereby increase their surface area, can therefore be consumed at higher temperatures than solid foods. Furthermore, a simple test technique with a "measuring spoon" was developed. A hot sample is placed on the tongue. Orientating measurements were used to determine which contact temperature was considered to be just comfortable for any period > 10 s and for which period of less than 10 s it was still just bearable. The contact temperature, which was still perceived as tolerable for periods > 10 s, was 46.5 °C. The time spans for the higher contact temperature 48 °C were between 2 and 4 s and for 49 °C between 1 and 2 s. The course of the contact temperatures determined in the experiment over the contact time allows to calculate the corresponding threshold values of consumption temperatures for various foods such as potatoes, vegetables, cheese or fish. Consumption temperatures of about 56 °C for potatoes and 60 °C for cheese are still perceived as tolerable. In view of the fact that the contact temperature is obviously the determining factor for the risk of injury from burns in the oral cavity in addition to the contact time, it makes sense to reference threshold values to the contact temperature rather than to the surface or consumption temperature of a food product, which is the customary practice up to now. If this contact temperature is defined as a threshold value, the surface or consumption temperature for any other food can be calculated.

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“…Interessant ist weiterhin, dal3 die in der Pyrolyseformel auftretende Energiekonstante E, = 3,2 . los J/mol in der GroDenordnung der Dissoziationsenergie einer C-C-Bindung mit etwa 3,6. lo5 J/mol [13] liegt.…”

Section: Kohlendioxidunclassified

“…Fur die Ortsabhangigkeit der Streuungen a,(x) von RUB, CO, und 0, wurde, ahnlich wie in der Immissionsberechnung luftfremder Stoffe [ 12,22,23], folgender Potenzansatz ver- Am Beispiel der gemessenen RuB-Konzentrationsverteilungen (siehe Abb. 9 und 11) im Gebiet der Flammenfahne der untersuchten Tankflammen sollen aus der Kenntnis der Streuungen a,(x) nach Gleichung (13) die Linien konstanter RuBkonzentrationen (RUB-Isoplethen), axiale RuDkonzentrationen (siehe Abschnitt 4.4.2) sowie turbulente, ortsabhangige AustauschgroDen (siehe Abschnitt 4.5) berechnet werden.…”

Section: Abb 24 Streuungen Uy(x) Der Gauo-konzentrations-querverteilunclassified

Der konvektive Stofftransport als geschwindigkeitsbestimmender Schritt in Tankflammen und seine Analogie zur Ausbreitung luftfremder Stoffe in der Atmosphäre)

Brötz

Schönbucher

1978

Ber Bunsenges Phys Chem

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Der Stofftransport in n‐Hexan‐ und n‐Butan‐Tankflammen wurde aus gemessenen Konzentrationsverteilungen von Ruß. Brennstoff. Sauerstoff und Kohlendioxid ermittelt unter Beachtung der aus Langzeitaufnahmen erhaltenen Flammenkontur. – Die Verbrennungsvorgänge in Tankflammen laufen vorwiegend in einer dünnen Mantelzone des Flammenhalses ab, wobei der effektive Transport des Brennstoffes in diese Zone der geschwindigkeitsbestimmende Schritt ist. – In dem Flammenhals entsteht im wesentlichen durch thermische Crackung eines geringen Anteils des Brennstoffs Ruß, dessen Konzentration mit einer empirisch ermittelten Pyrolyseformel berechnet wird. Der größte Anteil des Brennstoffs n‐Butan wird im Flammenhals entsprechend dem 2. Fickschen Gesetz zu der Mantelzone transportiert, jedoch mit einem effektiven Diffusionskoeffizienten von Deff = 1,1 · 10−3 m2/s, der etwa um den Faktor 10 größer ist als der molekulare Diffusionskoeffizient. – In dem turbulenten Gebiet über dem Flammenhals (Flammenfahne), das etwa 2/3 der gesamten sichtbaren Flammenerscheinung ausmacht, läßt sich von den eingesetzten Brennstoffen n‐Butan und n‐Hexan praktisch nichts mehr nachweisen. Hier findet ein turbulenter Stofftransport von Ruß, Kohlendioxid und Sauerstoff statt, deren Konzentrationsfelder sich mit einem statistischen Gauß‐Ausbreitungsmodell berechnen lassen. Es wurden ortsabhängige, turbulente Stoffaustauschgrößen Ky(x) berechnet, die für die n‐Butan‐Tankflamme bis um den Faktor 5 größer sind als der effektive Diffusionskoeffizient Deff im Flammenhals. Der für den turbulenten Stofftransport maßgebende Ausbreitungsparameter f ist für die drei genannten Stoffe ähnlich und größenordnungsmäßig gleich dem entsprechenden Ausbreitungsparameter luftfremder Stoffe in der Atmosphäre. Schließlich wurden die ortsabhängigen Stoffaustauschgrößen dadurch erklärt, daß die Abmessungen der Wirbel in derselben Größenordnung liegen wie die momentanen Flammenbreiten.

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Kurzes Lehrbuch der Physikalischen Chemie

Cited by 20 publications

References 0 publications

Injury Threshold of Oral Contact with Hot Foods and Method for Its Sensory Evaluation

Injury Threshold of Oral Contact with Hot Foods and Method for Its Sensory Evaluation

Injury Threshold of Mouth Contact with Hot Solid or Paste-Like Foods and Sensory Evaluation of Consumption Temperatures

Der konvektive Stofftransport als geschwindigkeitsbestimmender Schritt in Tankflammen und seine Analogie zur Ausbreitung luftfremder Stoffe in der Atmosphäre)

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