Modelling of two-component turbulent mass and heat transfer in air-fed pressurised suits

This article has been accepted for publication in the Flow, Turbulence and Combustion journal.In this paper the modelling of an important industrial problem is addressed, which involves the two-component turbulent flow with heat transfer that takes place inside protective clothing. The geometry of the flow boundaries is reconstructed in a CAD system from photogrammetry scan data. The overall model is sufficiently realistic to allow, after validation, design improvements to be tested. Those presented here allow the reduction of hot spots over the worker’s body surface and increase thermal comfort.This project is funded by the Engineering and Physical Sciences Research Council and the UK Atomic Energy Authority

Oral application of L-menthol in the heat: From pleasure to performance

When menthol is applied to the oral cavity it presents with a familiar refreshing sensation and cooling mint flavour. This may be deemed hedonic in some individuals, but may cause irritation in others. This variation in response is likely dependent upon trigeminal sensitivity toward cold stimuli, suggesting a need for a menthol solution that can be easily personalised. Menthol’s characteristics can also be enhanced by matching colour to qualitative outcomes; a factor which can easily be manipulated by practitioners working in athletic or occupational settings to potentially enhance intervention efficacy. This presentation will outline the efficacy of oral menthol application for improving time trial performance to date, either via swilling or via co-ingestion with other cooling strategies, with an emphasis upon how menthol can be applied in ecologically valid scenarios. Situations in which performance is not expected to be enhanced will also be discussed. An updated model by which menthol may prove hedonic, satiate thirst and affect ventilation will also be presented, with the potential performance implications of these findings discussed and modelled. Qualitative reflections from athletes that have implemented menthol mouth swilling in competition, training and maximal exercise will also be included

The effect of air gap entrapped in firefighter protective garment on thermal behaviour

Mestrado de dupla diplomação com a Hassiba Benbouali University of ChlefThe main objective of this work is to investigate the thermal protective performance (TPP) of firefighter’s garments under 10s/20s of various thermal exposures, shedding light on the effect of the air gap, the effect of fabric thickness and the radiant heat intensity (using Kevlar/PBI and Nomex fabrics) on skin burn predictions. The numerical simulations were performed using the ANSYS software in accordance with the temperature-dependent thermal properties of the materials. A numerical calculation model by finite elements is developed considering the blood perfusion rate. The model is validated against experimental tests and against numerical results from other authors. A parametric analysis was developed upon a set of 500 simulations. The results obtained are treated to evaluate and study the effect of the above-mentioned factors on TPP of firefighter’s garments and skin burn predictions. Finally, based on the numerical results determined for high flash fire and for high exposure time (20 s), a new proposal is presented to determine the time to reach the first, second and third-degree skin burn.O principal objetivo deste trabalho é investigar o desempenho de proteção térmica (TPP) de vestuário de bombeiros quando exposto durante 10s/20s a várias solicitações térmicas, analisando o efeito da camada de ar, o efeito da espessura do tecido e a intensidade de calor radiante (utilizando tecidos Kevlar/PBI e NOMEX) na previsão de queimadura da pele. As simulações numéricas foram realizadas utilizando o programa ANSYS, de acordo com as propriedades térmicas dependentes da temperatura dos materiais. Foi desenvolvido um modelo de cálculo numérico por elementos finitos, considerando a taxa de perfusão sanguínea. O modelo é validado em relação a testes experimentais e em relação a resultados numéricos de outros autores. Foi desenvolvido um estudo paramétrico, com base num conjunto de 500 simulações. Os resultados obtidos são tratados para avaliar e estudar o efeito dos fatores acima mencionados sobre o desempenho TPP do vestuário de bombeiros e previsões de queimaduras da pele. Finalmente, com base nos resultados numéricos determinados para exposições a elevados valores de radiação e para tempos de exposição elevados (20 s), é apresentada uma nova proposta para determinar o tempo para atingir queimaduras de primeiro, segundo e terceiro grau na pele

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

Development of a numerical model to predict physiological strain of firefighter in fire hazard

This paper aims to develop a numerical model to predict heat stress of frefghter under low-level thermal radiation. The model integrated a modifed multi-layer clothing model with a human thermoregulation model. We took the coupled radiative and conductive heat transfer in the clothing, the size-dependent heat transfer in the air gaps, and the controlling active and controlled passive thermal regulation in human body into consideration. The predicted core temperature and mean skin temperature from the model showed a good agreement with the experimental results. Parametric study was conducted and the result demonstrated that the radiative intensity had a signifcant infuence on the physiological heat strain. The existence of air gap showed positive efect on the physiological heat strain when air gap size is small. However, when the size of air gap exceeds 6mm, a diferent trend was observed due to the occurrence of natural convection. Additionally, the time length for the existence of the physiological heat strain was greater than the existence of the skin burn under various heat exposures. The fndings obtained in this study provide a better understanding of the physiological strain of frefghter and shed light on textile material engineering for achieving higher protective performance

Moisture in clothing and its transient influence on human thermal responses through clothing microenvironment in cold environments in winter

Air humidity produces conditions of varying moisture contents in clothing, which affects the heat and moisture transfer between human body, clothing and environment, as well as the wearers’ comfort. This study was designed to evaluate the moisture effects in clothing in cold environments. A series of wearing experiments were conducted in a climate chamber, simulating transient moisture absorption and desorption in experimental clothes. Totally 20 subjects were involved in three temperature levels (16 oC/20 oC/24 oC) and two relative humidity levels (15% RH/85% RH) during winter, with physiological measurement and subjective evaluation. The results showed that moisture in clothing under 85% RH significantly reduced subject mean skin temperatures(MST) and increased the local blood flow, due to enhanced heat loss by vapour evaporation. The initial skin wettedness was approximately 0.7 at 85% RH and stabilised at 0.33 after 90min exposure. The skin heat loss (Qskin) at 85% RH was almost twice as high as that at 15% RH under the same temperature conditions, owing to larger sensible and evaporative heat loss caused by moist clothing. The inner clothing effective temperature Teff was proposed to relate to TSV that the TSV increased by 1.12 units with an increase of 1 oC of Teff, which quantified the coupled effects of air temperature and humidity in clothing microenvironment on human thermal comfort. The findings address the negative effect of clothing absorbing a large amount of moisture, which should be considered for indoor heating temperature designs in cold-humid environments

EVALUATION OF THE THERMAL PERFORMANCE OF FIRE FIGHTER PROTECTIVE CLOTHING WITH THE ADDITION OF PHASE CHANGE MATERIAL

Fire fighters rely on fire fighter protective clothing (FFPC) to provide adequate protection in the various hazardous environments they may encounter during operations. FFPC has seen significant advancement in technology over the past few decades. The addition of phase change material (PCM) to FFPC is a new technology with potential to enhance the thermal protection provided by the FFPC. To explore this technology, data from bench-scale experiments involving FFPC with PCMs are compared with a theoretical finite difference heat transfer model. The results demonstrate an effective method to mathematically model the heat transfer and provide insight into the effectiveness of improving the thermal protection of FFPC. The experiments confirm that the latent heat absorbed during the phase change reduces temperatures that might be experienced at the fire fighter's skin surface, advancing the high temperature performance of FFPC

Modeling Thermoregulatory Responses to Cold Environments

The ability to model and simulate the rise and fall of core body temperature is of significant interest to a broad spectrum of organizations. These organizations include the military, as well as both public and private health and medical groups. To effectively use cold models, it is useful to understand the first principles of heat transfer within a given environment as well as have an understanding of the underlying physiology, including the thermoregulatory responses to various conditions and activities. The combination of both rational or first principles and empirical approaches to modeling allow for the development of practical models that can predict and simulate core body temperature changes for a given individual and ultimately provide protection from injury or death. The ability to predict these maximal potentials within complex and extreme environments is difficult. The present work outlines biomedical modeling techniques to simulate and predict cold-related injuries, and discusses current and legacy models and methods