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Fine control over the growth of materials is required to precisely tailor their properties. Spatial atomic layer deposition (SALD) is a thin-film deposition technique that has recently attracted attention because it allows producing thin films with a precise number of deposited layers, while being vacuum-free and much faster than conventional atomic layer deposition. SALD can be used to grow films in the atomic layer deposition or chemical vapor deposition regimes, depending on the extent of precursor intermixing. Precursor intermixing is strongly influenced by the SALD head design and operating conditions, both of which affect film growth in complex ways, making it difficult to predict the growth regime prior to depositions. Here, we used numerical simulation to systematically study how to rationally design and operate SALD systems for growing thin films in different growth regimes. We developed design maps and a predictive equation allowing us to predict the growth regime as a function of the design parameters and operation conditions. The predicted growth regimes match those observed in depositions performed for various conditions. The developed design maps and predictive equation empower researchers in designing, operating, and optimizing SALD systems, while offering a convenient way to screen deposition parameters, prior to experimentation., The Journal of Physical Chemistry C, 127 (19), ISSN:1932-7455, ISSN:1932-7447

The European transportation sector employs 10 million people and accounts for 4.6 % of the European Union GDP. Due to climate change, this workforce is increasingly affected by high temperatures and radiant loads, particularly during summer. They rely on air conditioning (AC) to minimize heat inside the truck cabins, increasing fuel consumption and tailpipe emissions. Because sustainable transportation is crucial for climate change mitigation, we developed a numerical investigation on the dynamic thermal exchanges of cabins of heavy-duty trucks in realistic conditions of a summer workday, to quantify the potential impact of interventions in the glazing and paint optical properties, over the truck AC loads. We observed that the changes in air temperature and solar irradiation throughout the workday imply substantial variations in the truck���s AC loads and, consequently, in its fuel consumption and tailpipe emissions. Furthermore, windshields and side windows with transmissivity of 0.33 instead of typical 0.79 and 0.84, respectively, can reduce AC loads by up to 16 %. External paints with reflectivity of 0.70 instead of 0.04 can reduce the AC loads by up to 30 %, whereas cumulative changes to glazing and paint can reduce the AC load by up to 40 %. These interventions can lower fuel consumption and emissions by up to 0.4 %. These results show that important improvements in fuel efficiency and tailpipe emissions are possible, if the research community, policy makers and industry stakeholders successfully promote the adaptation of the European transportation fleet.

Objectives: To provide perspectives from the HEAT-SHIELD project (www.heat-shield.eu): a multinational, inter-sectoral, and cross-disciplinary initiative, incorporating twenty European research institutions, as well as occupational health and industrial partners, on solutions to combat negative health and productivity effects caused by working on a warmer world. Methods: In this invited review, we focus on the theoretical and methodological advancements developed to combat occupational heat stress during the last five years of operation. Results: We outline how we created climate forecast models to incorporate humidity, wind and solar radiation to the traditional temperature-based climate projections, providing the basis for timely, policy-relevant, industry-specific and individualized information. Further, we summarise the industry-specific guidelines we developed regarding technical and biophysical cooling solutions considering effectiveness, cost, sustainability, and the practical implementation potential in outdoor and indoor settings, in addition to field-testing of selected solutions with time-motion analyses and biophysical evaluations. All recommendations were adjusted following feedback from workshops with employers, employees, safety officers, and adjacent stakeholders such as local or national health policy makers. The cross-scientific approach was also used for providing policy-relevant information based on socioeconomic analyses and identification of vulnerable regions considered to be more relevant for political actions than average continental recommendations and interventions. Discussion: From the HEAT-SHIELD experiences developed within European settings, we discuss how this inter-sectoral approach may be adopted or translated into actionable knowledge across continents where workers and societies are affected by escalating environmental temperatures. The study has received funding from the European Union’s Horizon 2020 research and innovation program under the grant agreement No 668786

Thermal discomfort due to accumulated sweat increasing head skin wettedness may contribute to low wearing rates of bicycle helmets. Using curated data on human head sweating and helmet thermal properties, a modelling framework for the thermal comfort assessment of bicycle helmet use is proposed. Local sweat rates (LSR) at the head were predicted as the ratio to the gross sweat rate (GSR) of the whole body or by sudomotor sensitivity (SUD), the change in LSR per change in body core temperature (Delta tre). Combining those local models with Delta tre and GSR output from thermoregulation models, we simulated head sweating depending on the characteristics of the thermal environment, clothing, activity, and exposure duration. Local thermal comfort thresholds for head skin wettedness were derived in relation to thermal properties of bicycle helmets. The modelling framework was supplemented by regression equations predicting the wind-related reductions in thermal insulation and evapo-rative resistance of the headgear and boundary air layer, respectively. Comparing the predictions of local models coupled with different thermoregulation models to LSR measured at the frontal, lateral and medial head under bicycle helmet use revealed a large spread in LSR predictions predominantly determined by the local models and the considered head region. SUD tended to overestimate frontal LSR but performed better for lateral and medial head regions, whereas predictions by LSR/GSR ratios were lower and agreed better with measured frontal LSR. However, even for the best models root mean squared prediction errors exceeded experimental SD by 18-30%. From the high correlation (R > 0.9) of skin wettedness comfort thresholds with local sweating sensitivity re-ported for different body regions, we derived a threshold value of 0.37 for head skin wettedness. We illustrate the application of the modelling framework using a commuter-cycling scenario, and discuss its potential as well as the needs for further research.

Nanoscience is one of the most developed fields in today's world. Its applications cover examples in natural, physical, pharmacological, and chemical sciences, with a high impact on human advancement in the present and the future. The application of nanotechnologies includes several advantages, for example, the decrease of manufacturing costs, the development of new technologies based on new properties, and the mitigation of side effects on human and environmental health. A stroke is a medical condition where poor blood flow causes the cell’s death because of a cerebrovascular or cardiovascular blockage. Strokes have been reported as one of the primary causes of death in 2019, with a 22% increase since the beginning of this century. This condition was responsible for 8.9 million deaths in 2019, with an expected increase, consequence of its relationship with the SARS-COV-2 (COVID19) virus1. Its high impact in human health has pushed scientists to develop and improve technologies for the study and treatment of strokes, as well as the relationship between stroke and viral diseases2-4. Current treatments for the disease have not overcome the medical limitations, where the administration times, drug efficiency, complex medical interventions, and secondary effects (such as haemorrhage) are liable for causing deaths among the treated people5. In this context, nanoscience concepts such as Lab-On-A-Chip technologies, controlled drug carrier transport, and micro-particle synthesis and manipulation can serve as a tool to overcome current challenges in stroke therapy. In this contribution, we will show how microfluidic technologies can have a great impact on this field enabling a controlled localization of clots as well as the study of their dissolution.

Background: Occupational heat exposure can provoke health problems that increase the risk of certain diseases and affect workers’ ability to maintain healthy and productive lives. This study investigates the effects of occupational heat stress on workers’ physiological strain and labor productivity, as well as examining multiple interventions to mitigate the problem. Methods: We monitored 518 full work-shifts obtained from 238 experienced and acclimatized individuals who work in key industrial sectors located in Cyprus, Greece, Qatar, and Spain. Continuous core body temperature, mean skin temperature, heart rate, and labor productivity were collected from the beginning to the end of all work-shifts. Results: In workplaces where self-pacing is not feasible or very limited, we found that occupational heat stress is associated with the heat strain experienced by workers. Strategies focusing on hydration, work-rest cycles, and ventilated clothing were able to mitigate the physiological heat strain experienced by workers. Increasing mechanization enhanced labor productivity without increasing workers’ physiological strain. Conclusions: Empowering laborers to self-pace is the basis of heat mitigation, while tailored strategies focusing on hydration, work-rest cycles, ventilated garments, and mechanization can further reduce the physiological heat strain experienced by workers under certain conditions.

Phase change materials are increasingly seen not only as a solution to reduce the mismatch between demand and supply of energy, but also as an adequate tool for heat management. Firefighters usually encounter high heat flux exposures, which can cause severe burns. The addition of a PCM layer into a typical firefighting garment ensemble can be used to mitigate this effect, increasing the time to second-degree burns. A numerical approach was used to investigate the effect of PCM latent heat, mass, melting temperature, and position within the garment ensemble, to assess the implications in terms of thermal performance and time to second-degree burns, under high-, medium- and low-intensity heat exposures. Guidelines for the specification of PCM characteristics are provided with respect to the heat exposure scenario considered, to enable informed decisions regarding the choice and features of the PCM, in function of the intended application and required time-windows without burns. The data discussed in this work provide insight on how a PCM layer influences the thermal burden on a firefighter, which enables the estimation of optimal PCM masses, and thus the minimization of the load to be carried by the firefighter, and the costs associated with the integration of high loads of PCM in a garment.

Clothing microclimates, i.e. the space between the skin and the clothing, can play a central role in the heat and mass exchanges from or to the body. This is especially true for protective clothing, where microclimates are generally thicker and natural convection is more likely to occur. We used a computational fluid dynamics approach to perform numerical studies of fluid flow and heat transfer across cylindrical clothing microclimates for Reynolds number of 3900. Transient simulations were performed for three different values of microclimate thickness to diameter ratio (0.05, 0.10 and 0.25), considering a two-dimensional cross-section of a human limb surrounded by a porous fabric and exposed to cool external air ( 10 ° C ). The obtained local heat transfer along the skin shows that increasing the microclimate thickness ratio from 0.05 to 0.25 decreases the convective heat fluxes by up to 100 % in the upstream regions of the microclimate, and increases them up to 190 % in the downstream regions. This asymmetry, which indicates an increasingly important role of natural convection as the microclimate thickness ratio is increased, is often overlooked in space-averaged approaches due to the opposite changes in the different regions of the microclimate. Local variations in temperature along the outer fabric and in convective fluxes along the skin were significant, reaching up to 14 K and 90%, respectively. The critical thickness ratio above which natural convection should not be ignored was found to be 0.1 (e.g. corresponding to a microclimate thicknesses of 11 mm or 8 mm, around an upper arm or forearm, respectively).

Clothing plays a key role in the capacity of the body to adapt to the surrounding thermal environments. Thus, it is critically important to have a solid understanding of the effects of clothing and fibres properties on the body exchange rates. To this end, a detailed transfer model was implemented to analyse the effect of several textiles characteristics (outer surface emissivity, tortuosity, and fraction of fibre) and fibre properties (affinity with water, coefficient of water diffusion in the fibres, thermal conductivity, density, and specific heat), on the heat and mass transfer through multilayer clothing, for different intensities of heat/sweat release. The temperature and humidity predictions were validated with experimental data obtained during measurements of textile evaporative resistance. The results obtained for the multilayer clothing during an energy-demanding activity (i.e. metabolic heat production of 300 W m(-2) and sweating of 240 g m(-3) h(-1)) show that a decrease in the emissivity of the outer surface (0.9 - 0.1), and an increase in the coefficient of water diffusion in the fibres of the inner layer (4 x 10(-16) - 4 x 10(-11)), induce an increase in the maximum skin temperature (of 4.5 degrees C and 6.8 degrees C, respectively). Moreover, the water trapped inside clothing is significantly increased by augmenting the fraction of fibre (0.07 - 0.4), the density of the fibre (910 - 7850 kg m(3)), the fibre affinity with water (i.e. regains of 0.07 - 0.3), and the coefficient of water diffusion in the fibres (4 x 10(-16) - 4 x 10(-11)). During the post-exercise phase (with metabolic heat production of 65 W m(-2) and perspiration of 9 g m(-3) h(-1)), the parameters affecting significantly the Water content of the inner layer are the fraction of fibre, its density, and its affinity with water. The proposed numerical approach allows the study of strategies to optimise heat/mass transport rates through materials surrounding the body (e.g. in clothing applications, automotive environments or work-place microclimates) in order to minimise thermal discomfort and/or problems of high water content (e.g. friction burns and/or growth of fungi and bacteria).

Design strategies for sustainable buildings, that improve building performance and avoid extensive resource utilization, should also promote healthy indoor environments. The following paper contains a review of the couplings between (1) building design, (2) indoor environmental quality and (3) occupant behavior. The paper focuses on defining the limits of adaptation on the three aforementioned levels to ensure the energy eciency of the whole system and healthy environments. The adaptation limits are described for measurable physical parameters and the relevant responsible human sensory systems, evaluating thermal comfort, visual comfort, indoor air quality and acoustical quality. The goal is to describe the interactions between the three levels where none is a passive participant, but rather an active agent of a wider human-built environment system. The conclusions are drawn in regard to the comfort of the occupant. The study reviews more than 300 sources, ranging from journals, books, conference proceedings, and reports complemented by a review of standards and directives.

White adipose tissue (WAT) thermogenic activity may play a role in whole-body energy balance and two of its main regulators are thought to be environmental temperature (Tenv) and exercise. Low Tenv may increase uncoupling protein one (UCP1; the main biomarker of thermogenic activity) in WAT to regulate body temperature. On the other hand, exercise may stimulate UCP1 in WAT, which is thought to alter body weight regulation. However, our understanding of the roles (if any) of Tenv and exercise in WAT thermogenic activity remains incomplete. Our aim was to examine the impacts of low Tenv and exercise on WAT thermogenic activity, which may alter energy homeostasis and body weight regulation. We conducted a series of four experimental studies, supported by two systematic reviews and meta-analyses. We found increased UCP1 mRNA (p = 0.03; but not protein level) in human WAT biopsy samples collected during the cold part of the year, a finding supported by a systematic review and meta-analysis (PROSPERO review protocol: CRD42019120116). Additional clinical trials (NCT04037371; NCT04037410) using Positron Emission Tomography/Computed Tomography (PET/CT) revealed no impact of low Tenv on human WAT thermogenic activity (p > 0.05). Furthermore, we found no effects of exercise on UCP1 mRNA or protein levels (p > 0.05) in WAT biopsy samples from a human randomized controlled trial (Clinical trial: NCT04039685), a finding supported by systematic review and meta-analytic data (PROSPERO review protocol: CRD42019120213). Taken together, the present experimental and meta-analytic findings of UCP1 and SUVmax, demonstrate that cold and exercise may play insignificant roles in human WAT thermogenic activity. Abbreviations: WAT:White adipose tissue; Tenv: Environmental temperature; UCP1: Uncoupling protein one; BAT: Brown adipose tissue; BMI:Body mass index; mRNA: Messenger ribonucleic acid; RCT: Randomized controlled trial; WHR: Waist-to-hip ratio; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-analyses; PET/CT: Positron Emission Tomography and Computed Tomography; REE: Resting energy expenditure; 18F-FDG: F18 fludeoxyglucose; VO2peak:Peak oxygen consumption; 1RM: One repetition maximum; SUVmax: Maximum standardized uptake value; Std: Standardized mean difference

The main objective of the study was to investigate the thermal performance of five (open and closed) bicycle helmets for convective and evaporative heat transfer using a nine-zone thermal manikin. The shape of the thermal manikin was obtained by averaging the 3D-point coordinates of the head over a sample of 85 head scans of human subjects, obtained through magnetic resonance imaging (MRI) and 3D-printed. Experiments were carried out in two stages, (i) a convective test and (ii) an evaporative test, with ambient temperature maintained at 20.5 &plusmn, 0.5 &deg, C and manikin skin temperature at 30.5 &plusmn, C for both the tests. Results showed that the evaporative heat transfer contributed up to 51%&ndash, 53% of the total heat loss from the nude head. For the convective tests, the open helmet A1 having the highest number of vents among tested helmets showed the highest cooling efficiency at 3 m/s (100.9%) and at 6 m/s (101.6%) and the closed helmet (A2) with fewer inlets and outlets and limited internal channels showed the lowest cooling efficiency at 3 m/s (75.6%) and at 6 m/s (84.4%). For the evaporative tests, the open helmet A1 showed the highest cooling efficiency at 3 m/s (97.8%), the open helmet A4 showed the highest cooling efficiency at 6 m/s (96.7%) and the closed helmet A2 showed the lowest cooling efficiency at 3 m/s (79.8%) and at 6 m/s (89.9%). Two-way analysis of variance (ANOVA) showed that the zonal heat-flux values for the two tested velocities were significantly different (p &lt, 0.05) for both the modes of heat transfer. For the convective tests, at 3 m/s, the frontal zone (256&ndash, 283 W/m2) recorded the highest heat flux for open helmets, the facial zone (210&ndash, 212 W/m2) recorded the highest heat flux for closed helmets and the parietal zone (54&ndash, 123 W/m2) recorded the lowest heat flux values for all helmets. At 6 m/s, the frontal zone (233&ndash, 310 W/m2) recorded the highest heat flux for open helmets and the closed helmet H1, the facial zone (266 W/m2) recorded the highest heat flux for the closed helmet A2 and the parietal zone (65&ndash, 123 W/m2) recorded the lowest heat flux for all the helmets. For evaporative tests, at 3 m/s, the frontal zone (547&ndash, 615 W/m2) recorded the highest heat flux for all open helmets and the closed helmet H1, the facial zone (469 W/m2) recorded the highest heat flux for the closed helmet A2 and the parietal zone (61&ndash, 204 W/m2) recorded the lowest heat flux for all helmets. At 6 m/s, the frontal zone (564&ndash, 621 W/m2) recorded highest heat flux for all the helmets and the parietal zone (97&ndash, 260 W/m2) recorded the lowest heat flux for all helmets.

AIM: Cold exposure and exercise may increase thermogenic capacity of white adipose tissue (WAT), which could subsequently enhance energy expenditure and body weight loss. We aimed to identify possible alterations in uncoupling protein 1 (UCP1)—the main biomarker of thermogenic activation—in human WAT due to both cold exposure and exercise, as well as the link between environmental temperature and thermogenic capacity of human WAT. MATERIAL & METHOD: We conducted four human experimental studies and two systematic reviews and meta-analyses—PROSPERO registration CRD42019120116, CRD42019120213. RESULTS: UCP1 mRNA was higher in winter than in summer [t(30) = 2.232, p = 0.03] in human WAT and our meta-analysis showed a main effect of cold exposure on human UCP1 mRNA [standard mean difference (Std-md) = 1.81, confidence interval (CI) = 0.50–3.13, p = 0.007]. However, UCP1 mRNA/protein expressions displayed no associations with %fat mass or BMI (p > 0.05, Cohen’s f2 < 0.20). Both a 2-hour cooling and a non-cooling protocol preceding the positron emission tomography/computed tomography (PET/CT) measurements revealed no association between environmental temperature and standardised uptake value (SUVmax) of human WAT, as well as no mean differences in SUVmax-WAT-activity between winter and summer. An 8-week exercise program had no effect on UCP1 of human WAT or on body composition. Our meta-analysis also revealed: (a) no effect of chronic exercise on human UCP1 mRNA, (b) a main effect of chronic exercise on UCP1 protein concentrations (Std-md = 0.59, CI = 0.03–1.16, p = 0.04) and UCP1 mRNA (Std-md = 1.76, CI = 0.48–3.04, p = 0.007) in WAT of normal diet animals, c) a main effect of chronic exercise on UCP1 mRNA (Std-md = 2.94, CI = 0.24–5.65, p = 0.03) and UCP1 protein concentrations (Std-md = 2.06, CI = 0.07–4.05, p = 0.04) of high-fat diet animals. CONCLUSIONS: Cold exposure represents a main stimulus for increased thermogenic capacity in human white adipocytes; however, this may have no impact on body weight loss. Chronic exercise may represent no major stimulus for UCP1 induced in human white adipocytes, while in animals it increases UCP1 gene independently of their diet. Therefore, evidence from animal studies regarding UCP1 gene activation in white adipocytes may not be applicable in humans. Finally, the identification of human WAT thermogenic capacity via PET/CT examination may be optimal with both a cooling and a non-cooling protocol.

Bicyclists can be subjected to crashes, which can cause injuries over the whole body, especially the head. Head injuries can be prevented by wearing bicycle helmets, however, bicycle helmets are frequently not worn due to a variety of reasons. One of the most common complaints about wearing bicycle helmets relates to thermal discomfort. So far, insufficient attention has been given to the thermal performance of helmets. This paper aimed to introduce and develop an adaptive model for the online monitoring of head thermal comfort based on easily measured variables, which can be measured continuously using impeded sensors in the helmet. During the course of this work, 22 participants in total were subjected to different levels of environmental conditions (air temperature, air velocity, mechanical work and helmet thermal resistance) to develop a general model to predict head thermal comfort. A reduced-order general linear regression model with three input variables, namely, temperature difference between ambient temperature and average under-helmet temperature, cyclist&rsquo, s heart rate and the interaction between ambient temperature and helmet thermal resistance, was the most suitable to predict the cyclist&rsquo, s head thermal comfort and showed maximum mean absolute percentage error (MAPE) of 8.4%. Based on the selected model variables, a smart helmet prototype (SmartHelmet) was developed using impeded sensing technology, which was used to validate the developed general model. Finally, we introduced a framework of calculation for an adaptive personalised model to predict head thermal comfort based on streaming data from the SmartHelmet prototype.

© 2019 by the authors. Design strategies for sustainable buildings, that improve building performance and avoid extensive resource utilization, should also promote healthy indoor environments. The following paper contains a review of the couplings between (1) building design, (2) indoor environmental quality and (3) occupant behavior. The paper focuses on defining the limits of adaptation on the three aforementioned levels to ensure the energy efficiency of the whole system and healthy environments. The adaptation limits are described for measurable physical parameters and the relevant responsible human sensory systems, evaluating thermal comfort, visual comfort, indoor air quality and acoustical quality. The goal is to describe the interactions between the three levels where none is a passive participant, but rather an active agent of a wider human-built environment system. The conclusions are drawn in regard to the comfort of the occupant. The study reviews more than 300 sources, ranging from journals, books, conference proceedings, and reports complemented by a review of standards and directives. ispartof: ENERGIES vol:12 issue:8 status: published

To date, crystallization studies conducted in space laboratories, which are prohibitively costly and unsuitable to most research laboratories, have shown the valuable effects of microgravity during crystal growth and morphogenesis. Herein, an easy and highly efficient method is shown to achieve space-like experimentation conditions on Earth employing custom-made microfluidic devices to fabricate 2D porous crystalline molecular frameworks. It is confirmed that experimentation under these simulated microgravity conditions has unprecedented effects on the orientation, compactness and crack-free generation of 2D porous crystalline molecular frameworks as well as in their integration and crystal morphogenesis. It is believed that this work will provide a new "playground" to chemists, physicists, and materials scientists that desire to process unprecedented 2D functional materials and devices., Advanced Materials, 33 (30), ISSN:0935-9648, ISSN:1521-4095

Thermal performance of three bicycle helmets for radiative and convective heat loss was evaluated through heat loss experiments in a wind tunnel. A 3D printed thermal manikin head of a 50th percentile western male population was developed. Thermal performance of a helmet was quantified by comparing the manikin head heat losses with and without helmet. Experiments were performed for two air velocities: 1.6 m/s and 6 m/s. An infrared heat lamp positioned above the manikin simulated the effect of solar load. The results from the experiments showed a convective cooling efficiency between 89% and 96% for open helmets and between 78% and 83% for closed helmets. The radiative heat gain ranged from 3.5 W to 4.5 W for open helmets and 5 W to 8 W for closed helmets.

The ability of clothing to provide protection against external environments is critical for wearer's safety and thermal comfort. It is a function of several factors, such as external environmental conditions, clothing properties and activity level.Thesefactorsdeterminethecharacteristicsofthedifferent microclimates existing inside the clothing which, ultimately, have a key role in the transport processes occurring across clothing. As an effort to understand the effect of transport phe- nomena in clothing microclimates on the overall heat transport across clothing structures, a numerical approach was used to study the buoyancy-driven heat transfer across horizontal air layers trapped inside air impermeable clothing. The study in- cluded both the internal flow occurring inside the microclimate and the external flow occurring outside the clothing layer, in order to analyze the interdependency of these flows in the way heat is transported to/from the body. Two-dimensional simula- tions were conducted considering different values of microcli- mate thickness (8, 25 and 52 mm), external air temperature (10, 20 and 30 °C), external air velocity (0.5, 1 and 3 m s −1 )a nd emissivity of the clothing inner surface (0.05 and 0.95), which implied Rayleigh numbers in the microclimate spanning 4 or- ders of magnitude (9×10 2 -3×10 5 ). The convective heat trans- fer coefficients obtained along the clothing were found to strongly depend on the transport phenomena in the microclimate, in particular when natural convection is the most important transport mechanism. In such scenario, convective coefficients were found to vary in wavy-like manner, depend- ing on the position of the flow vortices in the microclimate. These observations clearly differ from data in the literature for the case of air flow over flat-heated surfaces with constant temperature (which shows monotonic variations of the convec- tive heat transfer coefficients, along the length of the surface). The flow patterns and temperature fields in the microclimates were found to strongly depend on the characteristics of the external boundary layer forming along the clothing and on the distribution of temperature in the clothing. The local heat transfer rates obtained in the microclimate are in marked con- trast with those found in the literature for enclosures with constant-temperature active walls. These results stress the im- portance of coupling the calculation of the internal and the external flows and of the heat transfer convective and radiative components, when analyzing the way heat is transported to/from the body.

The aim of this study was to develop methodologies and experimental procedures to determine textile parameters required in numerical approaches of heat and mass transfer through textiles. Privileging techniques usually available in textile/clothing laboratories, experimental approaches were defined that allow to estimate all required parameters, while taking into consideration water presence in the fibres and hence the effect of fibres hygroscopic properties. Numerical models usually require values of textile thickness, fibre fraction, and tortuosity, as well as knowledge of the boundary conditions, e.g. convective heat and mass transfer coefficients. To calculate these parameters, thickness, weight, and volume of textile samples were measured, whereas convective and textile evaporative resistances were determined by indirect measurements. Results were obtained for four distinct textile samples (made of wool, cotton, and a mixture of materials), of different hydrophilic nature. When the obtained parameters were incorporated in a numerical model and numerical predictions of temperature and humidity were compared with experimental data obtained during measurements of fabric evaporative resistance, it was shown that the predictions were accurate; this lends support to the developed methods and approaches. Since an uncertainty in the measured parameters can compromise the accuracy of numerical predictions, a sensitivity analysis was conducted to study the influence of deviations in the model input parameters and of assumptions regarding water presence in the fibres, on the predictions of heat and mass transfer rates. The results show that a deviation in textile weight and thickness as well as the assumption of no water retained in fibres during their characterisation, have a significant effect on the predicted heat transfer and water distribution over time. Moreover, a deviation in the total evaporative resistance, convective evaporative resistance, and sorption rate factor has great influence on the heat flux obtained in the initial period of testing.

PurposeThe purpose of this paper is to investigate the heat transfer on an alpine‐climbing mitt featuring an electrical heating multilayer, in order to provide information for the optimization of its thermal performance.Design/methodology/approachA numerical model was developed to simulate the heat transfer across an electrical‐heated alpine mitt. The model was used to study the heat losses as a function of the environmental conditions, to optimise the positioning of the heating elements, to determine the optimal power input to the heating system, to estimate the battery capacity requirements and to assess the effect of low‐emissivity surfaces.FindingsThe results show that: the heating elements assure approximately constant temperatures across the skin provided they are not more than 6‐7 mm apart; the use of low‐emissivity surfaces facing the skin can reduce the total heat loss by 8‐36 per cent (for air layer thicknesses in the range 10−3 to 10−2 m) and to increase the skin temperature during the transient operation of the heating multilayer; the heat losses from the mitt are practically independent of the chosen heating power; and a battery capacity of 4 A h assures active temperature regulation for more than 18‐23 h.Practical implicationsBy enhancing the thermal performance of an electrical heating mitt, the use of low‐emissivity surfaces (facing the skin) can favour the thermal comfort perception of its user.Originality/valueThe influence of several parameters on the thermal performance of an electrical‐heated mitt is analysed and discussed. The findings are relevant for improving the performance of existing electrical heating garments.

An experimental study on free-bubbling gas–liquid (air–water) vertical slug flow was developed using a non-intrusive image analysis technique. The flow pattern in the near-wake of the bubbles and in the main liquid between bubbles was turbulent. A single correlation for the bubble-to-bubble interaction is proposed, relating the trailing bubble velocity to the length of the liquid slug ahead of the bubble. The proposed correlation is shown to be independent of column diameter, column vertical coordinate, superficial liquid and gas velocities and the velocity and length of the leading bubble. Frequency distribution curves, averages, modes and standard deviations are reported, for distributions of bubble velocity, bubble length and liquid slug length, for each experimental condition studied. Good agreement was found between theoretical predictions and experimental results regarding the upward velocity of undisturbed bubbles, in a 0.032 m internal diameter column. A considerable discrepancy was found, though, for a 0.052 m internal diameter column. The acquired experimental data are crucial for the development and validation of a robust slug flow simulator.

New experimental data for air–water flow in a horizontal square cross-section channel (H = 24.25 mm) is presented, including data on liquid hold-up, gas and liquid velocities, and wave velocities and frequencies. For the majority of gas and liquid flow rates studied, the regime observed was pseudo-slug. Using visualization studies it was possible to identify wavy-stratified and pseudo-slug flows. For the pseudo-slug regime new correlations were obtained for liquid hold-up, for gas and liquid velocities as a function of the ratio between gas and liquid mass flow rates, and for the frequency of roll-waves as a function of gas and liquid mass flow rates.

An experimental and simulation study on free bubbling vertical slug flow in laminar regime in the main liquid and turbulent regime in the near-wake bubble region is reported. A non-intrusive image analysis technique and a previously developed slug flow simulator (SFS) were used. Two aqueous glycerol solutions (0.012–0.013 and 0.022 Pa s) were studied. A single bubble-to-bubble interaction curve was obtained. Strong interaction was found for bubbles flowing less than 3–4D apart, with slight interaction persisting for longer distances. The shape of the interaction curve bridges those for fully turbulent and fully laminar regimes. The experimental average bubble velocity in undisturbed conditions was shown not to follow the correlation-based predictions for laminar regime in the liquid. Alternative fitting coefficients are proposed. An entrance length of 50–80D (or 90–170D) was obtained for normal inlet slug length distributions centred on 2–5D (or 2–6 D ), for superficial gas and liquid velocities up to 0.40 and 0.30 m/s, respectively. More contrasting inlet slug length distributions were found not to converge within the length of the column (6.5 m). An overall comparison between the three regimes is presented.

A study on the gas phase expansion and gas hold-up occurring in free bubbling vertical slug flow is reported. A slug flow simulator (SFS) supported by air–water experimental data was used for this purpose. The study was accomplished by implementing in the simulator the gas phase expansion along the column. Effects over bubble lengths and bubble velocities were considered. The flow in 6.5 and 20 m long columns with internal diameter of 0.032 m was simulated. Expansion of gas phase along the column is shown to slightly decrease the occurrence of bubble coalescence. Liquid free surface oscillations (due to bubble burst events and continuous inlet of liquid and gas in the column) were found to affect the expansion of the gas phase, especially for high gas flow rates. The gas phase expansion for different outlet column configurations was studied. The use of a high and large cross sectional tank (to dampen free surface oscillations) is shown not to assure a permanent expansion rate of the gas phase. Simulations with and without gas expansion along the column were compared for the computation of average flow parameters. Approximate approaches (with constant UG, corrected for the mid-column pressure) were found suitable for the prediction of the average slug length and gas hold-up. Those approaches are, however, inadequate for the computation of the average bubble length and velocity along the vertical coordinate of the column.

A methodology that can be efficiently used to synthesize, isolate, and study out-of-equilibrium crystal structures employing controlled and diffusion-limited microfluidic environments is demonstrated. Unlike studies conducted with conventional mixing procedures in a flask, it is proven experimentally and with numerical simulations that microfluidic technologies can undoubtedly fine-tune reaction times and reagents concentration profiles; factors that enable out-of-equilibrium crystal forms to be obtained., The authors acknowledge the financial support from MINECO-Spain, under projects MAT2012-30994 and CTQ2011-16009-E, the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement no 615954 and from the Swiss National Science Foundation (SNF) through the project no 200021_160174. The authors thank the Microscopy Service of the UAB. M.R.-M. and C.C. thank the ICN2 for their research fellowship, I.I., N.D., and J.P.-L. thank the MINECO for RyC contracts. ICN2 acknowledges the support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program, under Grant SEV-2013-0295.

The optimisation of the performance of products with smart/active functionalities (e. g. in protective clothing, home textiles products, automotive seats, etc.) is still a challenge for manufacturers and developers. The aim of this study was to optimise the thermal performance of a heating product by a numerical approach, by analysing several opposing requirements and defining solutions for the identified limitations, before the construction of the first prototype. A transfer model was developed to investigate the transport of heat from the skin to the environment, across a heating blanket with an embedded smart heating system. Several parameters of the textile material and of the heating system were studied, in order to optimise the thermal performance of the heating blanket. Focus was put on the effects of thickness and thermal conductivity of each layer, and on parameters associated with the heating elements, e.g. position of the heating wires relative to the skin, distance between heating wires, applied heating power, and temperature range for operation of the heating system. Furthermore, several configurations of the blanket (and corresponding heating powers) were analysed in order to minimise the heat loss from the body to the environment, and the temperature distribution along the skin. The results show that, to ensure an optimal compromise between the thermal performance of the product and the temperature oscillation along its surface, the distance between the wires should be small (and not bigger than 50 mm), and each layer of the heating blanket should have a specific thermal resistance, based on the expected external conditions during use and the requirements of the heating system (i.e. requirements regarding energy consumption/efficiency and capacity to effectively regulate body exchanges with surrounding environment). The heating system should operate in an ON/OFF mode based on the body heating needs and within a temperature range specified based on the blanket total thermal resistance, external temperature during use, and observed temperature on the blanket outer surface (safety and energy efficiency aspects). The approach described in this work enabled the definition of the textile properties, the features of the embedded heating system, and the overall design of the system thus reducing substantially the number of prototypes needed for the final performance optimisation and fine-tuning.

The previous round-robin (RR) study on clothing evaporative resistance (Ret) has shown that the repeatability and reproducibility of clothing Ret measurements on sweating manikins were rather low. To further examine and enhance the measurement accuracy, a new strict but feasible test protocol was proposed and thoroughly examined in a new round-robin test. Eight laboratories participated in this study and three types of sweating manikins were used. Six clothing ensembles including body mapping cycling wear, light summer workwear, typical spring and autumn clothing for people living in subtropical regions, cold protective clothing and functional Gore-Tex coverall were selected. The measurement repeatability and reproducibility are analysed. The ultimate goal of the RR study is to provide solid support for amending ASTM F2370 standard and/or drafting a new ISO/EN standard.

Evaporative resistance is an important parameter to characterise clothing thermal comfort. However, previous work has focused mainly on either total static or dynamic evaporative resistance. There is a lack of investigation of localised clothing evaporative resistance. The objective of this study was to study localised evaporative resistance using sweating thermal manikins. The individual and interaction effects of air and body movements on localised resultant evaporative resistance were examined in a strict protocol. The boundary air layer's localised evaporative resistance was investigated on nude sweating manikins at three different air velocity levels (0.18, 0.48 and 0.78 m/s) and three different walking speeds (0, 0.96 and 1.17 m/s). Similarly, localised clothing evaporative resistance was measured on sweating manikins at three different air velocities (0.13, 0.48 and 0.70 m/s) and three walking speeds (0, 0.96 and 1.17 m/s). Results showed that the wind speed has distinct effects on local body segments. In contrast, walking speed brought much more effect on the limbs, such as thigh and forearm, than on body torso, such as back and waist. In addition, the combined effect of body and air movement on localised evaporative resistance demonstrated that the walking effect has more influence on the extremities than on the torso. Therefore, localised evaporative resistance values should be provided when reporting test results in order to clearly describe clothing local moisture transfer characteristics.Localised boundary air layer and clothing evaporative resistances are essential data for clothing design and assessment of thermal comfort. A comprehensive understanding of the effects of air and body movement on localised evaporative resistance is also necessary by both textile and apparel researchers and industry.

An experimental and simulation study on free-bubbling vertical slug flow in the laminar regime was developed. A non-intrusive image analysis technique and a developed simulation code (SFS, slug flow simulator) were used for the purpose. A single correlation was obtained for the prediction of the bubble velocity as a function of the length of the liquid slug ahead of the bubble. Strong bubble interaction was found for liquid slugs shorter than 2D, with weak and decreasing interaction persisting for longer liquid slugs. Coalescence, though sparse, was found to occur along the whole column length (6.5 m). These observations differ from the findings regarding turbulent regime (bubble interaction for liquid slugs shorter than 8-10D and coalescence mainly in the lower part of the column). A slug flow entrance length of 70-100D was obtained for inlet slug length distributions centered on 2-4D, for the ranges of superficial gas and liquid velocities studied (0.05-0.20 m/s). Different inlet slug length distributions (for instance centered on 2D and 5D) were found not to evolve to a single flow pattern within the 6.5 m length of the column. General expressions were proposed to predict the evolution of the mode and standard deviation of bubble velocity, bubble length, and liquid slug length distributions as a function of the vertical column coordinate and superficial gas and liquid velocities. Bubble coalescence was found to govern the evolution of the liquid slug length along the column. Gas expansion and bubble coalescence were found to play important roles in the evolution of bubble length and velocity.

An image analysis technique for the study of continuous co-current gas–liquid slug flow, in vertical columns, is reported. The technique comprises the automatic analysis of a sequence of video frames with the purpose of object (bubbles) tracking and characterization (dimension, velocity, distance). Its applicability to continuous slug flow conditions (even for very large number of bubbles) and the high accuracy of the results are the main added value of the proposed technique. The evaluation of the uncertainty associated with the parameters measured is performed (following the general uncertainty analysis approach ). Partial uncertainties are acknowledged in bubble boundary definition, time measurement and calibration procedure. Expressions are derived for the computation of the overall uncertainty of bubble velocity, bubble length and liquid slug length. Global relative uncertainties of 5%, 2.5% and 7%, were found, for these parameters. The uncertainty estimation supports the ongoing trend for the implementation of image analysis techniques for the study of slug flow patterns.

The thermal effects related to wearing headgear are complex and different studies have investigated single parts of this topic. This review aims at summarizing the different findings to give a complete overview on this topic as well as to suggest new perspectives. Headgear increases head insulation and therefore is mainly problematic under warm conditions, which is the focus of this review. Helmets do not affect physiological parameters other than the local skin temperature and sweat rate. However, the head is among the most sensitive body parts related to thermal comfort, thereby directly affecting the willingness to wear headgear. Several methods have been used to study thermal aspects of headgear, which could be categorized as (i) numerical, (ii) biophysical, (iii) combined numerical and biophysical, and (iv) user trials. The application of these methods established that heat transfer mainly takes place through radiation and convection. Headgear parameters relevant to these heat transfer pathways, are reviewed and suggestions are provided for improving existing headgear concepts and developing new concepts, ultimately leading to more accepted headgear. Relevance to industry This review provides a sound basis for improving existing headgear concepts. Firstly, a concise overview of headgear research related to thermal effects is given, leading to empirically based improvement suggestions and identification of research fields with a high potential. Finally, relevant research methods are described facilitating evaluation in R&D processes. Keywords Headgear; Helmets; Ergonomics; Thermal physiology; Mass transfer; Heat transfer; Comfort; Heat loss; Ventilation; CFD; Manikins; Review; Temperature

Tese de doutoramento. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2007

Only 1% to 40% of adult cyclists in European countries make use of bicycle helmets. This may be partly attributable to impaired thermal comfort associated with helmet use, which can lead to locally accumulated sweat and increased skin wettedness [1]. Local sweat rates (LSR) can be modelled by sudomotor sensitivities (SUD) relating the change in LSR to the change in body core temperature (TC) [2], or by the ratio of LSR to gross sweat rate (GSR) of the whole body [3]. Coupling those local models with models of thermoregulation predicting TC and GSR provides a framework for predicting head sweat rates in response to the characteristics of the thermal environment, clothing, level of activity and exposure time. This paper studies the influence of different local and whole-body models on predictive accuracy.

Humans depend on clothing protection to minimize the thermal burden imposed on the body by the surrounding environments to which they may be exposed ([1]). The ability of clothing to offer protection depends on multiple factors, from properties of its materials to geometrical aspects influencing the shape of the clothing elements and the way they fit the body. The latter is particularly relevant for the case of loose garments (e.g. CBRN), where relatively thick microclimates exist between the skin and the clothing, which may originate internal buoyancy-driven flows (i.e. natural convection) and substantially alter the way heat is transported to/from the body. Recent literature ([2-4]) report relevant changes in the local heat transport along the skin, in horizontal clothing microclimates, stressing the need for analyses of other geometrical arrangements occurring within clothing.