Insulation Values Research Articles

Evaluation of a Coupled Model to Predict the Impact of Adaptive Behaviour in the Thermal Sensation of Occupants of Naturally Ventilated Buildings in Warm-Humid Regions

Improving indoor environment quality and making urban centres in tropical regions more sustainable has become a challenge for which computational models for the prediction of thermal sensation for naturally ventilated buildings (NVBs) have major role to play. This work performed analysis on thermal sensation for non-residential NVBs located in Brazilian tropical warm-humid climate and tested the effectiveness of suggested adaptive behaviours to mitigate warm thermal sensation. The research method utilized transient computational fluid dynamics models coupled with a dynamic model for human thermophysiology to predict thermal sensation. The calculated results were validated with comparison with benchmark values from questionnaires and from field measurements. The calculated results for dynamic thermal sensation (DTS) seven-point scale showed higher agreement with the thermal sensation vote than with the predicted mean vote. The test for the suggested adaptive behaviours considered reducing clothing insulation values from 0.18 to 0.32 clo (reducing DTS from 0.1 to 0.9), increasing the air speed in 0.9 m/s (reducing DTS from 0.1 to 0.9), and applying both suggestions together (reducing DTS from 0.1 to 1.3) for five scenarios with operative temperatures spanning 34.5–24.0 °C. Results quantified the tested adaptive behaviours’ efficiency showing applicability to improve thermal sensation from slightly-warm to neutral.

The estimation of ship cable condition by the means of measuring its insulation characteristics

Timely detection of defects in electrical equipment and cable network is required for the ensuring the fire safety of a modern marine vessel. The method of continuous monitoring of the resistance value of cable insulation is not very informative and is not applicable for assessing the service life of cables and predicting their replacement during operation and repair. Currently the problem of developing modern non-destructive methods of insulation control is very urgent in order to determine the operability of the cable, search for diagnostic parameters characterizing the state of insulation during prolonged aging, as well as the introduction of traditional methods of diagnostics of electrical equipment that have shown their effectiveness at the facilities of the coastal infrastructure. A promising solution for this problem is a method for monitoring the values of the tangent of the dielectric loss angle tgδ of cable insulation using devices that allow registering parameters with high accuracy. In this study the determination of changes in the parameters of a ship cable subjected to accelerated thermal aging at temperatures 120-130 °C has been made. The tgδ measurements of the cable sheath have been carried out using the Tangent-2000 insulation meter. The tests have shown that aging of cable hose insulation is accompanied by a non-linear change in tgδ; at certain values of the tangent of dielectric loss angle, visible cracks appear indicating the onset of an emergency condition of the cable. The nature of the change in the parameter tgδ is explained by the occurrence of reactions of oxidative dehydrochlorination of polychloroprene in the process of thermal aging of insulation and changes in its mass. Thus, the tangent of the dielectric loss angle can be one of the diagnostic parameters for assessing the state of the insulation of the ship's cable and predicting its service life.

Common clothing area factor estimation equations are inaccurate for highly insulating (Icl>2 clo) and non-western loose-fitting clothing ensembles.

The aim of this study was to evaluate the equations for calculating the clothing area factor (fcl) used in the standards based on data sets of clothing ensembles, that are meant to provide thermal comfort over a wide range of climatic conditions from hot summer days to extremely cold winter. Over 10 equations for fcl calculations were selected from the international standards and the literature. At first a theoretical comparison based on a range of insulation values was performed. Then the data sets were used to compare the equations and measurements on real clothing systems. Most of the fcl calculation equations do give reasonably good results for western type and industrial clothing with basic insulation (Icl) up to 1.5 clo. Above the Icl of 2 clo, the error in the calculations based on traditional equations increases considerably and they overestimate fcl. Some new equations were suggested for modern clothing systems. Oppositely, for non-western clothing (for hot climate), the available equations did give good match only for very light clothing sets and commonly underestimated the real fcl. For such sets and and fashion clothes their own equations maybe needed, that count for various design aspects, e.g. fit, draping etc.

Validation of ISO 9920 clothing item insulation summation method based on an ambulance personnel clothing system.

This study aimed to validate the summation methods suggested by ISO 9920. Twenty seven items from an ambulance personnel clothing system were selected for testing. The basic insulation of each garment item (Iclu) was calculated based on the thermal manikin tests. More than 100 realistic clothing combinations were compiled and basic insulation (Icl) of these ensembles was calculated according to ISO 9920. These were ranked after the calculated insulation, and 14 sets covering insulation from 0.63 to 3.33 clo were measured on the thermal manikin for acquiring the basic clothing insulation (Icl). Regression analysis was used to compare the summed and measured Icl values. The difference between values varied from −18 to 12%. The highest percentual difference was for the lightest clothing sets, while the absolute differences were similar over the whole insulation range ranging between −0.17 to 0.18 clo with an average difference of 0.02 clo (−0.16%). All basic insulation values stayed very close to the line of identity (R2=0.98). The summation equation gave, in the case of this ambulance clothing system, very close results to the measured values. This encourages evaluating and selecting protective clothing combinations for thermal comfort based on individual item measurements.

Development of Recycled PET/comber Noil Nonwovens for Thermal Insulation Application

ABSTRACT In recent years, recycling has been an attractive issue for researchers considering the sustainability of the wastes arising from different engineering applications. In this scope, recycled PET fibers which are mechanically and chemically recycled from PET bottles can be reused in needle punched non-woven production technology. The usage of recycled PET fibers in nonwovens contributes to a decrease in environmental pollution, prevention of the decrease in petroleum supplies, and the decrease in raw material cost of nonwovens. In this work, recycled PET fibers were treated with sodium hydroxide to impart the surface roughness and reduce the fiber weight. The effect of alkali treatment was evaluated in terms of reduction in fiber weight and SEM images of the fibers. The nonwovens were developed from 100% recycled PET fibers and also by blending with comber noil by needle punching technique. The developed nonwovens were characterized for thermal insulation applications. It was found that nonwoven made from alkali-treated recycled PET fibers has a slightly higher thermal insulation value compared to nonwoven made from untreated recycled PET fibers. The increase in comber noil blend% reduces the thermal insulation of r-PET/comber noil nonwovens.

Methodology for calculating the ineffective diameter of thermal insulation

This article describes the results of energy efficiency analysis of various types of pipeline thermal insulation in a district heating system and equipment. The mathematical relations used in calculating the thickness of the thermal insulation for heat pipes and equipment are given. The concept of the critical value of the thermal insulation outside diameter of the heat pipe is described. An equation is presented that determines the ineffective thickness of the heat pipe insulation. A solution to this equation is proposed using numerical methods, namely, Newton’s method. The results of calculations of ineffective thermal insulation diameters for various parameters of the coolant, the diameters of the pipeline itself, and various heat-insulating materials are presented. The obtained data are analyzed. Recommendations are given for the correct selection and calculation of the thermal insulation thickness of district heating pipelines, as well as for the reconstruction of the existing ones.

Development and validation of an environmental heat strain risk assessment (EHSRA) index using structural equation modeling based on empirical relations

BackgroundNeed to a simple, available, accurate, comprehensive, and valid indicator is felt to assess thermal effects. Therefore, the present study was aimed to develop and validate the environmental heat strain risk assessment (EHSRA) index using structural equation modeling (SEM) based on empirical relations.MethodsThis cross-sectional study was performed on 201 male workers in environments with various climatic conditions. The heart rate and tympanic temperature of the individuals were monitored at times of 30, 60, and 90 min after beginning the work. At these times, values of dry temperature, wet temperature, globe temperature, and air velocity were also measured and metabolism rate and clothing thermal insulation value were estimated. At the end, a theoretical model was depicted in AMOS software and obtained coefficients were applied to develop a novel index. The scores of this indicator were categorized into four risk levels via ROC curves and validate using linear regression analysis.ResultsIndirect effect coefficients of the globe temperature, dry temperature, wet temperature, air velocity, metabolism, and clothing thermal insulation variables on the tympanic temperature were computed by 0.77, 0.75, 0.69, 0.24, 0.49, and 0.39, respectively. These coefficients were applied to develop the index. Optimal cut-off points of boundaries between risk levels included 12.02, 15.88, and 17.56. The results showed that the EHSRA index justified 75% of the variations of the tympanic temperature (R2 = 0.75).ConclusionsThe novel index possesses appropriate validity. It was suggested that this indicator is applied and validated in various environments in the next studies.

Bison (<i>Bison bison</i>) activity fragments subnivean tunnels of small mammals

Ecological interactions between ungulates and small mammals are generally not well understood. Here, we report an observation of unusually extensive small mammal (likely Meadow Vole [Microtus pennsylvanicus] or Tundra Vole [Microtus oeconomus]) tracks above the snow, exiting from trails and bed sites created by Bison (Bison bison) in northern Canada. We believe that weather and snow conditions were optimal for this observation. Although alteration of above-snow activity of small mammals in response to snow compaction by ungulates is probably not a rare event, it is not often reported. The effect on voles of exiting their subnivean tunnels as a result of Bison activity is unclear, but may be detrimental to their overwinter survival. Ungulate activity compacts snow, fragmenting small mammal tunnels resulting in loss of their insulative value for voles, and making it harder for them to dig new tunnels. Clearly, determining the effect of snow disturbance by gregarious ungulates on voles or other microtines, particularly regarding their overwinter survival, requires detailed investigation. Nevertheless, this observation provides new information on the ecological interactions between ungulates and small mammals, particularly from the boreal forest, where such information is largely lacking.

The Study on Effects of Walking on the Thermal Properties of Clothing and Subjective Comfort

Abstract Former studies done by other authors investigated the first- and second-layered air gaps beneath the clothing garments. None of the previous studies reported multidisciplinary clothing design testing approach linking both the objective measuring methods and subjective responses, while testing the thermal properties linked to a microclimatic volume formed between the layers of garments forming the ensemble. Neither was determined the limiting value of the microclimatic volume for outerwear garments, after which the thermal insulation will start to decrease due to convection. By taking the advantage of the precise three-dimensional (3D) body scanning technology and reverse engineering 3D CAD tool, the volume of the microclimatic air layers formed under outerwear garments was determined to study the impact of the ensemble’s microclimatic volume on the overall insulation value, measured by means of the thermal manikin. The jacket with the smaller microclimatic volume provided 5.2–13.5% less insulation than wider jackets, while the ensembles with tighter jackets showed 0.74–1.9% less insulation in static and 0.9–2.7% more insulation in dynamic conditions, thus proving that the limiting value of the microclimatic volume is greater than previously reported for three-layered ensembles. The effective thermal insulation value was reduced in average by 20.98–25.34% between standing and moving manikins. The thermal manikins are designed for steady-state measurements and do not work well under transient conditions, so three human subjects were employed as evaluators of the clothing thermal quality. In cooler climatic conditions, the measured physiological parameters and subjects’ grades pointed to discomfort while wearing ensembles with tighter jackets.

The Effects of the Dynamic Thermophysical Properties of Clothing and the Walking Speed Input Parameter on the Heat Strain of a Human Body Predicted by the PHS Model

The prediction accuracy of the Predicted Heat Strain (PHS) model is affected by the correction approaches of static thermophysical properties of clothing considering the pumping effects of wind and body movement. In this study, a comparison of different correction algorithms for three types of clothing and their influence on the heat strain predicted by the PHS model was carried out with experimental data obtained from the literature. Results show that the dynamic insulation values calculated by ISO 9920 corrections are larger than those obtained by ISO 7933 when the static insulation values are higher than 0.4 clo, but when the static values are lower than 0.4 clo, it varies contrarily. The dynamic evaporative resistance values calculated with ISO 9920 equations are larger than those with ISO 7933. The prediction accuracy of the PHS model with ISO 9920 corrections and the addition of the walking speed input parameter can be improved for normal clothing (NC) in a hot environment and high clothing insulation. For specialized, insulating, cold weather clothing (SC), ISO 7933 corrections with an added walking speed input parameter to the PHS model have a good prediction precision.

On the features of production, design and reliability assessment of enclosing composite structures with effective thermal insulation

The article gives priority results on the production, design and assessment of the reliability of composite structures made of materials with energy-saving thermal insulation, physical heterogeneity of the parameters and the adhesion strength of the thermal insulation to the metal finishes. Addresses experimental results of changes in bulk mass, tensile and compressive strength, elastic properties in tension and compression along the thickness of the products perpendicular (⊥) and parallel to (ǁ) the product plane. Establishes the parameters of adhesion to the upper and lower finishes and their probability distributions according to Gauss, Gram-Charles, Pearson, Weibull and the log-normal law. This allows to set the standard values of thermal insulation. The article is aimed at the maximum use in buildings of sandwich panels of full factory production.

The Effect of Finishing Treatment by Aqueus Ginger Solution on Electrostatic and Thermal Insulation properties of Medical Bandages

This research aims to study the effect of ginger solutionin reducing the electrostatic property and increasing the thermal insulation of the bandage while maintaining the functional properties of the bandage fabric.To achieve this goal, bandage fabrics consisting of 70% cotton and 30% polyamide were treated with ginger in different concentrations, (25 - 50 - 100%), There are some variables such as ginger solution concentration and number of bandage layers (1, 2 and 3) whose effect on the performance properties of bandage has been studied. Several tests were performed for these samples before and after treatment such as electrostatic charge value, thermal insulation value, air permeability, water permeability and square meter weight. The results showed that with an increase in the concentration of the treatment material and the number of layers, the value of thermal insulation increased and the value of the electrostatic charge decreased, with an unnoticeable effect on the other properties of the bandage. Thus the ginger-treated bandage can be used to treat patients with arthritis.

Typical winter clothing characteristics and thermal insulation of ensembles for older people in China

Clothing plays an essential role in maintaining heat balance and thermal comfort for older people but varies with climate conditions and costume culture. The recommended clothing insulation in ISO 7730 and ASHRAE Standard 55 lack information on typical clothing ensemble and local insulation values for older people. To investigate the winter clothing characteristics of older people living in Shanghai, a field survey involving 342 healthy subjects from 12 aged-care homes and a lab study conducted with a 22-segment thermal manikin were performed. Subjects' typical clothing ensembles were summarized based on the survey. The local clothing insulation of 34 typical garments and 35 clothing ensembles were measured in the lab experiment. Results show that most older people in winter worn 7 pieces of clothes (excluding underpants, socks and shoes). The frequencies of typical upper and lower garments/ensembles were reported. Through manikin tests, the whole and local insulation of those typical garments and ensembles were presented. By comparison, the insulation values of garments in ISO 7730 were found to be inconsistent with tested garments’ results for older people. Further, linear regression models were built to link relationships of the insulation of multiple garments and ensembles. Through running an older people-based thermoregulation model, it was found an incorrect estimation of typical winter clothing insulation for older people could lead around 1.3 °C deviation on predicted mean skin temperature or around 26% deviation on heat loss.

Microstructure, Compressive Strength and Sound Insulation Property of Fly Ash-Based Geopolymeric Foams with Silica Fume as Foaming Agent

Geopolymer as an alternative to cement has gained increasing attention. The aim of this article is to study the influence of the silica fume content and activator type on the porous fly ash-based geopolymer with silica fume as foaming agent. Geopolymeric foams were fabricated using low-calcium fly ash, silica fume, and sodium-based alkaline activator as initial materials. The designed silica fume contents were 0, 15, 30, and 45 wt % and two kinds of activators of water glass and sodium hydroxide were used for comparison. Phase composition, microstructure, mechanical properties and sound insulation properties of as-prepared bulks were systematically investigated. It was found that, with increasing silica fume content, the density and compressive strength decreased simultaneously, whereas the porosity and sound insulation performance were effectively enhanced. At the silica fume content of 45% with sodium hydroxide as activator, the porosity was increased 3.02 times, and, at the silica fume content of 45% with water glass as activator, the mean sound insulation value of 43.74 dB was obtained.

Cost and Energy Reduction of a New nZEB Wooden Building

The current study demonstrates the possibilities of reducing energy use and construction costs and provides evidence that wooden nearly-zero-energy buildings (nZEB) are technically possible at affordable construction costs by using novel design processes and procurement models that enable scalable and modular production. The energy efficiency solutions were derived by increasing/decreasing the insulation value of the building envelope in successive steps. Financial calculations were based on the investment needed to achieve the nearly-zero-energy levels. Overall, many opportunities exist to decrease the cost and energy use compared to the current (pre-nZEB) practice because the net present value can change up to 150 €/m² on the same energy performance indicator (EPI) level. The EPI in the cost-even range was reached by combining a ground-source heat pump (between 115 and 128 kWh/(m2·a)) and efficient district heating (between 106 and 124 kWh/(m2·a)). As energy efficiency decreases, improving energy efficiency becomes more expensive by insulation measures. Throughout the EPI range the most cost efficient was investment in the improvement of the thermal transmittance of windows (3–13 €/(kWh/(m2·a))) while investments in other building envelope parts were less effective (4–80 €/(kWh/(m2·a))). If these were possible to install, photovoltaic (PV) panels installed to the roof would be the cheapest solution to improve the energy performance. Integrated project delivery procurement (design and construction together) and the use of prefabricated wooden structures reduced the constructing cost by half (from ~2700 €/net m2 to 1390 €/net m2) and helped to keep the budget within limits.

Quality Improvement of Dumba Fleece Using Dehairing Technique and Value Addition of Recovered Wool

ABSTRACT The wool of Dumba fleece is an admixture of fine wool and coarse hairy fibers. (Tomer, 2018) The use of the slow speed carding machinerecovers fine wool fibers accounts 19.6% of fleece weight. The mean fiber diameter and medullation of recovered wool are 23.2 µm and 14.0%, respectively. The recovered wool fibers are able to spin into yarn of 20.7 Nm with the use of carrier fiber only. Nylon staple fiber of 2.5 denier and fine crossbred wool are mixed to spin yarn on semi-worsted spinning system. The fabric was woven with prepared yarn on handloom. The fabric has found the harsh feel due to available medullated fibers even after the removal of hairy fibers. The surface properties of the fabric were improved through enzyme treatment followed by softener application. The fabrics were evaluated for thermal insulation and surface smoothness. The thermal insulation value is found to improve from 2.03 to 2.18 for enzyme and softener treated fabric, respectively. The chemical treatment improves the fabric smoothness/softness, i.e, frictional properties viz. dynamic and static frictional resistance by 12.4% and 7.0%, respectively.

Thermal Performance of a Massive Wall in the Mediterranean Climate: Experimental and Analytical Research

In the Mediterranean climate, indoor overheating and, thus, excessive use of cooling systems represents one of the main problems both for the occupants’ health and energy consumption. In order to limit this problem, an appropriate design or energy retrofitting of the building envelope is of utmost importance. The predominance of massive buildings in the Italian territory and the need to comply with Italian regulations often leads technicians to not optimal energy saving solutions. To this purpose, this experimental research was conducted on a mockup building, located in Fabriano and characterized by high thermal mass walls (W0) and two different external insulating systems: Cork based lightweight plaster (W1) and Extruded polystyrene foam panel (XPS) (W2). Furthermore, a virtual model in TRNSYS, a transient simulation software, was used to compare analytical and simulated values. Results show that W2 undergoes a higher level of thermal stress than W1, due to higher peaks in the external surface temperature and larger fluctuations in daily temperature. Therefore, a high value of thermal resistance of the external insulation and low value of external areal heat capacity on a massive building causes external surface overheating problems, thus, not representing the optimal construction solution.

Using a Thermal Camera to Measure Heat Loss Through Bird Feather Coats.

Feathers are essential to insulation, and therefore to the cost of thermoregulation,in birds. There is robust literature on the energetic cost of thermoregulation in birds across a variety of ecological circumstances. However, few studies characterize the contribution of the feathers alone to thermoregulation. Several previous studies have established methods for measuring the insulation value of animal pelts, but they require destructive sampling methods that are problematic for birds, whose feathers are not distributed evenly across the skin. More information is needed about 1) how the contribution of feathers to thermoregulation varies both across and within species and 2) how feather coats may change over space and time. Reported here is a method for rapidly and directly measuring the thermal performance of feather coats and the skin using dried whole skin specimens, without the need to destroy the skin specimen. This method isolates and measures the thermal gradient across a feather coat in a way that measurements of heat loss and metabolic cost in live birds, which use behavioral and physiological strategies to thermoregulate, cannot. The method employs a thermal camera, which allows the rapid collection of quantitative thermal data to measure heat loss from a stable source through the skin. This protocol can easily be applied to various research questions, is applicable to any avian taxa, and does not require destruction of the skin specimen. Finally, it will further the understanding of the importance of passive thermoregulation in birds by simplifying and accelerating the collection of quantitative data.

Development of a personal heat strain risk assessment (PHSRA) index in workplaces and its validation

BackgroundThere is not a comprehensive heat stress index to screen the people susceptible to heat disorders and illnesses in hot workplaces. The present study was aimed to develop a personal heat strain risk assessment (PHSRA) index in workplaces and validate it.MethodsThis cross-sectional study was carried out on 201 Iranian male employees under various thermal conditions. At first, the demographical data of participants were gathered. After that, the heart rate and tympanic temperature of the subjects were carefully measured at times of 30, 60, and 90 min of starting the work. Environmental factors were measured simultaneously. The metabolism rate and insulation value of clothes were also estimated. At the end, a novel index of the heat strain was developed using structural equation modeling in AMOS and validated using linear regression analysis in SPSS.ResultsIndirect effect coefficients of personal factors including age, body mass index, maximum aerobic capacity, and body surface area were equal to 0.031, 0.145, − 0.064, and 0.106, respectively. The coefficients of main factors including dry temperature, wet temperature, globe temperature, wind speed, metabolism, and clothing thermal insulation were obtained as 0.739, 0.688, 0.765, 0.245, 0.482, and 0.383, respectively. These coefficients and normalized values of the factors were used to develop a novel index. The total score of the index was categorized into four levels by optimal cut-off points of 12.93, 16.48, and 18.87. Based on the results of regression analysis, this index justifies 77% of the tympanic temperature as a dependent variable (R2 = 0.77).ConclusionsIn general, the results indicated that the novel index developed by the personal and main factors had proper validity in the prediction of thermal strain.

Warm insulation of exhaust pipe when taking gas from the “dome - separator” installation from large depths

The article describes the impact of the use of polyurethane insulation on the tubes sclerosis by hydrate when gas is taken from the “dome-separator”, installation that designed for emergency hydrocarbon collection at the bottom of the ocean. Such an installation collects hydrocarbons directly above the breakthrough point at the bottom of the ocean, and their transportation is carried out through pipes to the collecting vessel. Currently, in the conditions of the development of the Arctic shelf in order to increase the level of oil production, such breakthroughs can cause enormous damage to the ecosystem, in particular, in the Arctic Ocean, since living organisms that exists in the harsh conditions of these latitudes are more sensitive to changes in the environment. But during the passage of gas through the exhaust pipe in the presence of moisture and corresponding thermodynamic conditions, a hydrate formation process occurs. This phenomenon can cause the pipeline to overlap and impede the normal operation of the selection of hydrocarbons from great depths. To prevent these consequences, work suggests possible options for warming the pipeline. It is shown that sclerosis of a pipe extending to great depths can be prevented even with small values of polyurethane foam insulation.