Effects of environmental temperature and humidity on evaporative heat loss through firefighter suit materials made with semi-permeable and microporous moisture barriers

2021 ◽  
pp. 004051752110265
Author(s):  
Huipu Gao ◽  
Anthoney Shawn Deaton ◽  
Xiaomeng Fang ◽  
Kyle Watson ◽  
Emiel A DenHartog ◽  
...  
Keyword(s):  
Heat Loss ◽  
Environmental Temperature ◽  
Moisture Absorption ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Evaporative Resistance ◽  
Environmental Testing ◽  
Permeable Barrier ◽  
Moisture Condensation ◽  
Moisture Barriers

The goal of this research was to understand how firefighter protective suits perform in different operational environments. This study used a sweating guarded hotplate to examine the effect of environmental temperature (20–45°C) and relative humidity (25–85% RH) on evaporative heat loss through firefighter turnout materials. Four firefighter turnout composites containing three different bi-component (semi-permeable) and one microporous moisture barriers were selected. The results showed that the evaporative resistance of microporous moisture barrier systems was independent of environmental testing conditions. However, absorbed moisture strongly affected evaporative heat loss through semi-permeable moisture barriers coated with a layer of nonporous hydrophilic polymer. Moisture absorption in mild environment (20–25°C) tests, or when testing at high humidity (>85% RH), significantly increased water vapor transmission in semi-permeable turnout systems. It was also found that environmental conditions used in the total heat loss (THL) test (25°C and 65% RH) produced moisture condensation in bi-component barrier systems, making them appear more breathable than could be expected when worn in hotter environments. Regression models successfully qualified the relationships between moisture uptake levels in semi-permeable barrier systems and evaporative resistance and THL. These findings reveal the limitations in relying on THL, the heat strain index currently called for by the NFPA 1971 Standard for Structural Firefighter personal protective equipment, and supports the need to measure turnout evaporative resistance at 35°C (Ret), in addition to THL at 25°C.

Evaluating turnout composite layering strategies for reducing thermal burden in structural firefighter protective clothing systems

2016 ◽  
Vol 87 (10) ◽  
pp. 1217-1225 ◽  
Author(s):  
Meredith McQuerry ◽  
Emiel DenHartog ◽  
Roger Barker
Keyword(s):  
Heat Loss ◽  
Protective Clothing ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Evaporative Resistance ◽  
Moisture Barrier ◽  
Dry Heat ◽  
Firefighter Protective Clothing ◽  
Base Composite ◽  
Specific Working

A modular approach for arranging the component layers used in the construction of structural firefighter turnout garments is explored as a strategy for reducing the thermal burden contributed by these protective garments to firefighter heat stress. An instrumented sweating manikin was used to measure the insulation, evaporative resistance and total heat loss through turnout systems configured to represent different layering strategies. The outer shell, moisture barrier and thermal liner layers of the structural turnout base composite were tested individually to determine each layer's thermal insulation and evaporative resistance. Multiple two- and three-layer combinations were analyzed for their application in specific working conditions. This study demonstrates that the moisture barrier layer contributes the most resistance to evaporative heat loss through the turnout system, while dry heat loss is most restricted by the thermal liner component. Removal of a single inner liner layer was equally beneficial for heat loss, regardless of material properties. It shows the potential benefit of turnout design strategy that utilizes a modular or adaptive layering approach to reduce turnout-related heat strain in conditions consistent with fire protection.

Respiratory water and heat loss of the black duck during flight at different ambient temperatures

1971 ◽  
Vol 49 (5) ◽  
pp. 767-774 ◽  
Author(s):  
M. Berger ◽  
J. S. Hart ◽  
O. Z. Roy
Keyword(s):  
Heat Loss ◽  
Water Loss ◽  
Pulmonary Ventilation ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Ambient Temperatures ◽  
Black Duck ◽  
Respiratory Heat Loss ◽  
Metabolic Water ◽  
Expired Air

Pulmonary ventilation and temperature of expired air and of the respiratory passages has been measured by telemetry during flight in the black duck (Anas rubripes) and the respiratory water and heat loss has been calculated.During flight, temperature of expired air was higher than at rest and decreased with decreasing ambient temperatures. Accordingly, respiratory water loss as well as evaporative heat loss decreased at low ambient temperatures, whereas heat loss by warming of the inspired air increased. The data indicated respiratory water loss exceeded metabolic water production except at very low ambient temperatures. In the range between −16 °C to +19 °C, the total respiratory heat loss was fairly constant and amounted to 19% of the heat production. Evidence for the independence of total heat loss and production from changes in ambient temperature during flight is discussed.

scholarly journals Protection against Cold in Prehospital Care: Evaporative Heat Loss Reduction by Wet Clothing Removal or the Addition of a Vapor Barrier—A Thermal Manikin Study

2012 ◽  
Vol 27 (1) ◽  
pp. 53-58 ◽  
Author(s):  
Otto Henriksson ◽  
Peter Lundgren ◽  
Kalev Kuklane ◽  
Ingvar Holmér ◽  
Peter Naredi ◽  
...  
Keyword(s):  
Heat Loss ◽  
Prehospital Care ◽  
Ambient Air ◽  
Total Heat ◽  
Thermal Manikin ◽  
Evaporative Heat Loss ◽  
Loss Reduction ◽  
Total Heat Loss ◽  
Cold Environments ◽  
Wet Heat

AbstractIntroduction: In the prehospital care of a cold and wet person, early application of adequate insulation is of utmost importance to reduce cold stress, limit body core cooling, and prevent deterioration of the patient’s condition. Most prehospital guidelines on protection against cold recommend the removal of wet clothing prior to insulation, and some also recommend the use of a waterproof vapor barrier to reduce evaporative heat loss. However, there is little scientific evidence of the effectiveness of these measures.Objective: Using a thermal manikin with wet clothing, this study was conducted to determine the effect of wet clothing removal or the addition of a vapor barrier on thermal insulation and evaporative heat loss using different amounts of insulation in both warm and cold ambient conditions.Methods: A thermal manikin dressed in wet clothing was set up in accordance with the European Standard for assessing requirements of sleeping bags, modified for wet heat loss determination, and the climatic chamber was set to -15 degrees Celsius (°C) for cold conditions and +10°C for warm conditions. Three different insulation ensembles, one, two or seven woollen blankets, were chosen to provide different levels of insulation. Five different test conditions were evaluated for all three levels of insulation ensembles: (1) dry underwear; (2) dry underwear with a vapor barrier; (3) wet underwear; (4) wet underwear with a vapor barrier; and (5) no underwear. Dry and wet heat loss and thermal resistance were determined from continuous monitoring of ambient air temperature, manikin surface temperature, heat flux and evaporative mass loss rate.Results: Independent of insulation thickness or ambient temperature, the removal of wet clothing or the addition of a vapor barrier resulted in a reduction in total heat loss of 19-42%. The absolute heat loss reduction was greater, however, and thus clinically more important in cold environments when little insulation is available. A similar reduction in total heat loss was also achieved by increasing the insulation from one to two blankets or from two to seven blankets.Conclusion: Wet clothing removal or the addition of a vapor barrier effectively reduced evaporative heat loss and might thus be of great importance in prehospital rescue scenarios in cold environments with limited insulation available, such as in mass-casualty situations or during protracted evacuations in harsh conditions.

Technical and Economic Performance Analysis of Utilization of Solar Energy in Indoor Swimming Pools, An Application

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Olcay Kincay ◽  
Zafer Utlu ◽  
Ugur Akbulut
Keyword(s):  
Solar Energy ◽  
Power Systems ◽  
Heat Loss ◽  
Economic Performance ◽  
Energy Demand ◽  
Reduction Rate ◽  
Energy Gain ◽  
Evaporative Heat Loss ◽  
Swimming Pools ◽  
Total Heat Loss

In this study, technical and economic performance analyses are conducted in order to determine the optimum collector surface area for indoor swimming pools. Required heat and economical conditions are taken into consideration while performing these evaluations. A brief summary of solar energy source and heat transfer equations for the Olympic pools are given. An Olympic swimming pool is assumed to be in different cities, and energy losses are calculated. For our sample Olympic pool, convective heat loss obtained is −3.86 kW and evaporative heat loss obtained is 265 kW. Total heat loss always maximum in January from 384 kW to 455.1 kW. Solar energy gain (assumption 1000 m2 collector area) and energy gain from boiler for different cities are calculated as maximum solar energy gain in July between 160 and 175 kW and minimum in January between 54.9 and 82 kW. High investment costs for solar power systems are responsible for low value of the reduction rate. Also, according to the energy demand and economical conditions, technical evaluations are performed in order to obtain optimum surface collector area, and economical analyses are conducted using unified cost method.

Comparison of non-evaporative heat transfer in different cattle breeds

1985 ◽  
Vol 36 (3) ◽  
pp. 497 ◽  
Author(s):  
VA Finch
Keyword(s):  
Heat Loss ◽  
Air Temperature ◽  
Heat Storage ◽  
Absolute Humidity ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Excessive Sweating ◽  
Total Heat Loss ◽  
Evaporative Water ◽  
Rate Of Increase

Tissue conductance and non-evaporative heat loss from the skin were determined from measurements of body temperature, evaporative water loss, metabolic rate and heat storage in six steers in each of three breeds, Brahman (B), Brahman x Hereford-Shorthorn (BX) and Shorthorn (S). A group of six steers, two from each breed, remained in a climate room set at 25�C overnight, and during the following day all were exposed for 1 h to sequential increases in air temperature (28, 32, 37, 41, 43, 45�C). Each steer was measured at 25�C and after a 30-min exposure to each temperature. Tissue conductance increased with air temperature (Ta), reaching maximum values at 41�C, the rate of increase (W m-2 'C-I per degree rise in Ta) being for B 3.95, for BX 2.33 and for S 2,09. Between 41 and 45�C, tissue conductance remained constant in B but declined in BX and S with a concurrent increase in heat storage. Mean tissue conductance (W m-2 �C-1) of B was 63.5; BX, 56.1; and S, 47.8, values that were significantly different (P < 0.01). Expressed in terms of metabolic weight, the breed means of tissue conductance (litres O2 h-1 W-0.75 �C-1) were also significantly different: B, 0.56; BX, 0.43; and S, 0.33 (P < 0.005), with the relative differences similar to those calculated per unit area. Breed differences in tissue conductance may be related to variations in ability to redirect blood from the core to the skin. Non-evaporative heat loss comprised 55-65% of the total heat loss from the skin in all breeds at Ta of 25�C. The remaining heat was lost through sweating. As Ta increased and approached skin temperature, non-evaporative heat loss decreased but in B and BX remained 25% of the total heat loss from the skin. S steers, in contrast, sustained little non-evaporative heat loss as Ta increased because sweating rates increased 50% more than that required to dissipate the heat at the skin. The increase in absolute humidity of the chamber was associated with the excessive sweating in this breed.

scholarly journals Metabolic effects of altering the 24 h energy intake in man, using direct and indirect calorimetry

1980 ◽  
Vol 43 (2) ◽  
pp. 257-269 ◽  
Author(s):  
M. J. Dauncey
Keyword(s):  
Energy Expenditure ◽  
Metabolic Rate ◽  
Heat Loss ◽  
Energy Intake ◽  
Heat Production ◽  
Resting Metabolic Rate ◽  
Metabolic Effects ◽  
Evaporative Heat Loss ◽  
High Intake ◽  
Total Heat Loss

1. The metabolic effects of increasing or decreasing the usual energy intake for only 1 d were assessed in eight adult volunteers. Each subject lived for 28 h in a whole-body calorimeter at 26° on three separate occasions of high, medium or low energy intake. Intakes (mean±SEM) of 13830 ± 475 (high), 8400 ± 510 (medium) and 3700 ± 359 (low) kJ/24 h were eaten in three meals of identical nutrient composition.2. Energy expenditure was measured continuously by two methods: direct calorimetry, as total heat loss partitioned into its evaporative and sensible components; and indirect calorimetry, as heat production calculated from oxygen consumption and carbon dioxide production. For the twenty-four sessions there was a mean difference of only 1.2 ± 0.14 (SEM)% between the two estimates of 24 h energy expenditure, with heat loss being less than heat production. Since experimental error was involved in both estimates it would be wrong to ascribe greater accuracy to either one of the measures of energy expenditure.3. Despite the wide variation in the metabolic responses of the subjects to over-eating and under-eating, in comparison with the medium intake the 24 h heat production increased significantly by 10% on the high intake and decreased by 6% on the low intake. Mean (± SEM) values for 24 h heat production were 8770 ± 288, 7896 ± 297 and 7495 ± 253 kJ on the high, medium and low intakes respectively. The effects of over-eating were greatest at night and the resting metabolic rate remained elevated by 12% 14 h after the last meal. By contrast, during under-eating the metabolic rate at night decreased by only 1%.4. Evaporative heat loss accounted for an average of 25% of the total heat loss at each level of intake. Changes in evaporative heat loss were +14% on the high intake and −10% on the low intake. Sensible heat loss altered by +9% and −5% on the high and low intakes respectively.5. It is concluded that (a) the effects on 24 h energy expenditure of over-feeding for only 1 d do not differ markedly from those estimated by some other workers after several weeks of increasing the energy intake; (b) the resting metabolic rate, measured at least 14 h after the last meal, can be affected by the previous day's energy intake; (c) the zone of ambient temperature within which metabolism is minimal is probably altered by the level of energy intake.

Influence of air humidity on the partition of heat exchanges of cattle

1972 ◽  
Vol 78 (2) ◽  
pp. 303-307 ◽  
Author(s):  
J. A. McLean ◽  
D. T. Calvert
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Air Temperature ◽  
Heat Production ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Air Humidity ◽  
Total Heat Loss ◽  
Air Temperatures ◽  
Heat Exchanges

SUMMARYThe balance between heat production and heat loss and the partition of heat exchanges of cattle in relation to air humidity has been studied at two different air temperatures using a direct (gradient-layer) calorimeter.Increasing humidity at 35 °C air temperature caused no significant change in heat production or in the level of total heat loss finally attained, but body temperature and respiratory activity were both increased.Increasing humidity at 15 °C air temperature caused a small reduction in heat loss by evaporation but had no effect on sensible heat loss, body temperature or respiratory frequency.Heat loss by evaporation amounted to 18% of the total heat loss at 15 °C and to 84% at 35 °C.Heat loss by respiratory evaporation amounted to 54% of the total evaporative heat loss at 15 °C and to 38% at 35 °C.

scholarly journals Thermal comfort properties of bifacial fabrics

2017 ◽  
Vol 89 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Licheng Zhu ◽  
Xungai Wang ◽  
Ian Blanchonette ◽  
Maryam Naebe
Keyword(s):  
Thermal Comfort ◽  
Heat Loss ◽  
Air Permeability ◽  
Total Heat ◽  
Loop Length ◽  
Permeability Index ◽  
Total Heat Loss ◽  
Knitted Fabrics ◽  
Evaporative Resistance ◽  
Thermal Comfort Properties

Bifacial fabrics, with a single jersey on one face and a plain weave on the other, were produced on a purpose-built machine. Thermal comfort properties of bifacial fabrics were compared with conventional woven and knitted fabrics and the effect of weft density and loop length of bifacial fabrics on their thermal comfort properties was investigated. While different fabric structures were produced with the same wool, acrylic, and polyester yarns, the findings confirmed that the bifacial fabric is warmer (lower total heat loss) and more breathable (higher permeability index ( im)) than the corresponding woven and knitted fabrics. Increasing the loop length of bifacial fabrics enhanced evaporative resistance, air permeability, warm feeling, thermal resistance, and water vapor permeability index, yet reduced total heat loss. An increase in the weft density of bifacial fabrics led to higher evaporative resistance, warmer feeling, higher thermal resistance, lower air permeability, and total heat loss. However, the permeability index did not change with an increase in weft density. This study suggests that thermal comfort properties of bifacial fabrics can be optimized by modifying structural parameters to engineer high-performance textiles.

Cutaneous heat loss shortly after burn injury in children

1992 ◽  
Vol 83 (1) ◽  
pp. 117-126 ◽  
Author(s):  
Charmaine Childs ◽  
H. B. Stoner ◽  
R. A. Little
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Burn Injury ◽  
Heat Content ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Healthy Children ◽  
Total Heat Loss ◽  
Control Subjects ◽  
Injured Patients

1. Total heat loss and its components have been studied in cool (20°C) and warm (30°C) environments in 30 healthy children and 21 children who had been burned (10-17% body surface area) 0.5-29 h previously. 2. In healthy naked children at 20°C, the partition of total heat loss was: radiation, 64%; convection, 32%; evaporation, 4%. On transfer to the warm, total heat loss was reduced by approximately 50%, with disproportionate reductions in the contributions from radiation and convection being offset, to some extent, by an increase in evaporative heat loss. 3. In patients during the first 5.5 h after injury, the magnitude and pattern of heat loss at 20°C and 30°C were similar to those in control subjects and were unaffected by bandaging. 4. Ten to twenty-nine hours after injury, when the patients were bandaged and body temperature and heat content were significantly higher than in control subjects, radiant and convective heat losses were increased, but as evaporative heat loss tended to be reduced; total heat loss in the warm was unchanged. However, at this time at 20°C, total heat loss was reduced compared with healthy children at the same ambient temperature. 5. The findings of unchanged or reduced total heat loss and reduced evaporative heat loss in injured patients are interpreted as inappropriate responses to an increased body temperature and heat content in children after burn injury.

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