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

Effects of internal/external EGR and combustion phase on gasoline compression ignition at low-load condition

A single-cylinder test engine model was built by GT-Power software, and the effects of internal exhaust gas recirculation (i-EGR), external EGR (e-EGR), i-EGR/e-EGR coupling and the crank angle degree at which 50% of total heat loss has taken place (CA50) on combustion and emission characteristics of gasoline compression ignition at low-load condition were analysed. The results show that the ignition delay period with e-EGR was extended slightly with the increased EGR ratio, while that with i-EGR strategy first shortened and then extended, and that the optimised indicated thermal efficiency could be achieved using a small amount of i-EGR. With the same EGR ratio, nitrogen oxide (NO X ) emission is more likely to be suppressed by i-EGR, while soot emission was more deteriorated, and the superior trade-off relationship between carbon monoxide (CO)/hydrocarbon (HC) emissions and NO X emission was attained by the combination of lower i-EGR ratios and CA50 closed to top dead centre. When using i-EGR/e-EGR coupling with total EGR ratio being fixed, the indicated thermal efficiency was decreased by increasing i-EGR ratio, while the lower NO X , CO and HC emissions could be realised, but only with the consequence that soot emission increased.

Nordic Seas Heat Loss, Atlantic Inflow, and Arctic Sea Ice cover over the last century

<p>Poleward ocean heat transport is a key process in the earth system. Here we detail the changing northward Atlantic Water (AW) flow in the Nordic Seas and the associated Arctic Ocean heat transport and heat loss to the atmosphere since 1900, in relation to the sea ice cover. Our synthesis is largely based on a sea ice-ocean model forced by a reanalysis atmosphere (1900-2018) corroborated by a comprehensive hydrographic database (1950-), measurements of AW inflow (1996-), and other key long-term regional time series. Since the 1970s, ocean temperatures have increased in the Nordic, Barents and Polar Seas, in particular on the shelves. The AW loses heat to the atmosphere as it travels poleward, mostly in  the Nordic Seas, where ~60% of the Arctic Ocean total heat loss resides. Nordic Seas heat loss variability is large, but the long-term positive trend is small. The Barents Sea heat loss is ~30% of the total, but has larger consistently positive trends, related to AW heat transport and sea ice loss. The Arctic seas farther north see only ~10% of the  total heat loss, but show a consistently large increase in heat loss as well as decrease in sea ice since 1900. The AW inflow, the cooling of this water mass as it travels poleward, and the dense outflow have thus all increased since 1900, and they are consistently related through theoretical scaling. Some of the increased AW inflow is wind-driven, and much of the heat loss variability is linked to Cold Air Outbreaks and cyclones in the Nordic and Barents Seas. The oceanic warming is congruent with increased ocean heat transport and a loss of sea ice, and has contributed to the retreat of marine terminating glaciers on Greenland. After 2000, the warming has accelerated, creating a “new normal” that appears to also affect deep water volumes and temperature. The 20th century average Nordic, Barents and Polar Seas CO2 uptake constitutes ~8% of the global ocean, and is almost entirely driven by heat loss to the atmosphere as the AW transforms from inflow to overflow water. The total Arctic Ocean CO2 uptake has increased by ~30% since 1900, which is closely linked to the loss of sea ice in the Barents and Polar Seas.</p>

Mathematical Modeling and Optimization of Vanadium-Titanium Black Ceramic Solar Collectors

The vanadium-titanium black ceramic (VTBC) coating on all-ceramic solar collectors has both high absorptance (0.94) and high emissivity (90%). However, the thermal conductivity of ceramic is very low (1.256 W/mK). To improve the heat collection efficiency of VTBC solar collectors, this paper establishes a mathematical model based on the energy-conservation relationships under steady-state conditions and creates a corresponding computer program. Key parameters for VTBC solar collectors include the heat-removal factor, effective transmittance-absorptance product for the absorber, total heat loss coefficient, etc. Then, via experimental testing, this study proposes a reference model for domestic VTBC solar collectors in a cold location (η = 0.89 − 2.20Tm*). Last, this work analyzes the influences of fin design and transparent cover design on VTBC solar collectors individually, using the created computer program. Results show that the most effective optimization method is to increase the transmittance of the transparent cover. By increasing the transmittance from 0.93 to 0.96, this study creates an optimized VTBC solar collector theoretical model (η = 0.92 − 2.20Tm*).

Study on Winter Indoor Thermal Environment of Temporary Shelters Built in Nepal After Massive Earthquake 2015

Natural disasters and wars are main reasons that force people to leave their homes and consequently require urgent needs including temporary shelters. After massive earthquake 2015, thousands of Nepalese who lost their home were doomed to live in temporary shelters, mostly self-built by using zinc/tarpaulin sheets which can hardly provide sufficient thermal comfort. We need to analyze the thermal characteristics of the temporary shelters for creating a better environment for their own sake. Thus, this study tries to evaluate the winter indoor thermal environment of different types of local materials used for insulation in these investigated shelters. The indoor and outdoor thermal environment was measured by digital data loggers at the 10-minute intervals for winter in thirteen different shaped shelters in main three earthquake affected districts: Gorkha, Sindhupalchowk and Lalitpur. The mean indoor and mean outdoor air temperatures were found 12.3°C and 10.1°C. The total heat loss coefficient estimated in thirteen shelters ranges from 74.8 to 325.9 W/K and their specific values with respect to the ranges from 8.1 to 20.4 W/ (m2.K). These values are very large in comparison to those in ordinary houses; this is the major reason of low indoor air temperature especially during nighttime. This suggests that some insulating materials need to be added or replaced with the materials used for the improvement for better indoor thermal environment.

A Comparative Numerical Study on Conjugate Natural Convection From Vertical Hollow Cylinder With Finite Thickness Placed on Ground and in Air

The present work reports a comparative analysis of natural convection heat transfer from a thick hollow vertical cylinder either placed on the ground or suspended in the air. The numerical simulations have been performed by varying the cylinder length to its outer diameter (L/Do) in the range of 0.2–20, the thickness ratio (Di/Do) in a range of 0.5–0.9, and Rayleigh number (Ra) from 104 to 108. The flow and heat transfer characteristics have been delineated precisely with the presentation of the thermal plume and flow field in the vicinity of the cylinder. The variation of average Nusselt number (Nu), local Nu, and contribution to total heat loss from different surfaces with the pertinent parameters have been elucidated graphically. The average Nu is always more for the cylinder in the air compared with the case when it is on the ground. However, the difference between the Nu for these two cases diminishes, as the L/Do increases. It has also been found that the contribution to total heat loss from the inner surface of the hollow cylinder suspended in air increases with L/Do, attains a peak, and decreases sharply. Cooling time curves for the cylinder placed in air or on the ground have been described precisely. Finally, a correlation for the average Nusselt number as a function of all the pertinent parameters has been proposed that can be useful for industrial and academic purposes.

The contribution of the mouse tail to thermoregulation is modest

Understanding mouse thermal physiology informs the usefulness of mice as models of human disease. It is widely assumed that the mouse tail contributes greatly to heat loss (as it does in rat), but this has not been quantitated. We studied C57BL/6J mice after tail amputation. Tailless mice housed at 22°C did not differ from littermate controls in body weight, lean or fat content, or energy expenditure. With acute changes in ambient temperature from 19 to 39°C, tailless and control mice demonstrated similar body temperatures (Tb), metabolic rates, and heat conductances and no difference in thermoneutral point. Treatment with prazosin, an α1-adrenergic antagonist and vasodilator, increased tail temperature in control mice by up to 4.8 ± 0.8°C. Comparing prazosin treatment in tailless and control mice suggested that the tail’s contribution to total heat loss was a nonsignificant 3.4%. Major heat stress produced by treatment at 30°C with CL316243, a β3-adrenergic agonist, increased metabolic rate and Tb and, at a matched increase in metabolic rate, the tailless mice showed a 0.72 ± 0.14°C greater Tb increase and 7.6% lower whole body heat conductance. Thus, the mouse tail is a useful biomarker of vasodilation and thermoregulation, but in our experiments contributes only 5–8% of whole body heat dissipation, less than the 17% reported for rat. Heat dissipation through the tail is important under extreme scenarios such as pharmacological activation of brown adipose tissue; however, non-tail contributions to heat loss may have been underestimated in the mouse.

Analysis of solutions of the Muskat — Leverett non-isothermal model for different types of oils

In this article, numerical methods are used to analyze the features of solutions to the non-isothermal Muskat — Leverett two-phase filtration model. The structure of solutions to thermal waterflooding problems for low-viscosity and high viscosity types of oil is considered. Typical solutions for different types of functional parameters of the model are shown. The simulations show that hot water displacement of high-viscosity oil is an effective method of increasing oil recovery. In particular, if in the case of thermal flooding the reservoir with low-viscosity oil, recovery increases by only a few percent, then for a field with high viscosity oil, thermal flooding increases oil recovery by tens of percent. It is shown that in order to increase the efficiency of the thermal flooding it is necessary to pump hot water with the minimum possible capillary parameter. High total filtration rate reduces total heat loss through the roof and sole of the formation. Numerical experiments have shown that for an adequate simulation of thermal flooding, in addition to taking into account changes in oil viscosity, it is necessary to take into account the action of capillary forces and the variation of relative phase permeability during the operation of the oil field.