Thermal Insulation Value Research Articles

3D quantification of microclimate volume in layered clothing for the prediction of clothing insulation

Garment fit and resultant air volume is a crucial factor in thermal insulation, and yet, it has been difficult to quantify the air volume of clothing microclimate and relate it to the thermal insulation value just using the information on the size of clothing pattern without actual 3D volume measurement in wear condition. As earlier methods for the computation of air volume in clothing microclimate, vacuum over suit and circumference model have been used. However, these methods have inevitable disadvantages in terms of cost or accuracy due to the limitations of measurement equipments. In this paper, the phase-shifting moiré topography was introduced as one of the 3D scanning tools to measure the air volume of clothing microclimate quantitatively. The purpose of this research is to adopt a non-contact image scanning technology, phase-shifting moiré topography, to ascertain relationship between air volume and insulation value of layered clothing systems in wear situations where the 2D fabric creates new conditions in 3D spaces. The insulation of vests over shirts as a layered clothing system was measured with a thermal manikin in the environmental condition of 20 °C, 65% RH and air velocity of 0.79 m/s. As the pattern size increased, the insulation of the clothing system was increased. But beyond a certain limit, the insulation started to decrease due to convection and ventilation, which is more apparent when only the vest was worn over the torso of manikin. The relationship between clothing air volume and insulation was difficult to predict with a single vest due to the extreme openings which induced active ventilation. But when the vest was worn over the shirt, the effects of thickness of the fabrics on insulations were less pronounced compared with that of air volume. In conclusion, phase-shifting moiré topography was one of the efficient and accurate ways of quantifying air volume and its distribution across the clothing microclimate. It is also noted that air volume becomes more crucial factor in predicting thermal insulation when clothing is layered.

Test of Firefighter’s Turnout Gear in Hot and Humid Air Exposure

Five students of a rescue training school cycled at 50 W for 20 min at 20 °C before walking at 5 km/hr up to 30 min in a climatic chamber at 55 °C and 30% relative humidity. 4 different types of clothing ensembles differing in terms of thickness and thermal insulation value were tested on separate days. All subjects completed 28–30 min in light clothing, but quit after 20–27 min in 3 firefighter ensembles due to a rectal temperature of 39 °C or subjective fatigue. No difference in the evolution of mean skin or rectal temperature was seen for the 3 turnout ensembles. Sweat production amounted to about 1000 g in the turnout gears of which less than 20% evaporated. It was concluded that the small differences between the turnout gears in terms of design, thickness and insulation value had no effect on the resulting heat physiological strain for the given experimental conditions.

Determining localized garment insulation values from manikin studies: computational method and results

The localized thermal insulation value expresses a garment's thermal resistance over the region which is covered by the garment, rather than over the entire surface of a subject or manikin. The determination of localized garment insulation values is critical to the development of high-resolution models of sensible heat exchange. A method is presented for determining and validating localized garment insulation values, based on whole-body insulation values (clo units) and using computer-aided design and thermal analysis software. Localized insulation values are presented for a catalog consisting of 106 garments and verified using computer-generated models. The values presented are suitable for use on volume element-based or surface element-based models of heat transfer involving clothed subjects.

Production of Light Weight Ceramics Teils from Local Materials

This study covers the feasibility of production lightweight ceramics teils (light weight clay bricks) by adding local various types of combustible materials to the clay. It was found those substantial quantities of bagasse, sawdust, rice husks and straw are suitable for the production of lightweight bricks and distributed combustible materials finely was mixed with clay and molded into bricks. During firing in the kiln the combustible materials burnt out and leave air spaces, which contribute, to the high thermal insulation value of the bricks. It was possible to produce bricks with densities between 800 and 900 Kg m3 and thermal conductivity between 0.19 and 0.22 Kcal mh1

Evaluation of the validity of the UN SADT H.4 test for solid organic peroxides and self-reactive substances

Many self-accelerating decomposition temperatures (SADTs) of solid organic peroxides and self-reactive substances have been determined with the UN test method H.4, which is a scaled down test in a small Dewar vessel. For solid organic peroxides and solid self-reactive substances Fierz has questioned this procedure in a recent paper. Fierz concluded that the Dewar test results should not be extrapolated to beyond 8 l packages, owing to the thermal insulation value of solids. On the other hand, long term experience with the test, with a great variety of solid organic peroxides and self-reactive substances show about equal critical temperatures in the small Dewar vessel and on 50 kg scale. In the present work, we first checked, by numerical simulations, the Dewar scale versus the larger scale, in a way comparable with Fierz’ method: both scales are simulated by spheres, consisting of a number of annular layers, for the large scale the usual external heat loss term is used but for the small scale the outside heat transfer is strongly limited. The outcome of these simulations, covering a variety of physical parameters, supports the concerns expressed by Fierz. After this, we performed accurate cooling and heating experiments with solid organic peroxide in the usual Dewar vessel, provided with a large set of thermocouples. The results of these experiments showed that the simulation model for the Dewar vessel has to be changed from a spherical analogue to a short cylinder of solid material with heat exchange mainly via its top ( U top ∼ 3.5 W/(m 2 K), overall heat transfer coefficient) and some heat exchange ( U side ∼ 0.29 W/(m 2 K)) through its cylindrical and bottom part. With this “modified cylinder” model (being neither an infinitely long cylinder nor a slab) of the Dewar vessel, we found that the UN method H.4 enables an accurate prediction of the SADT, with small deviations of 0 ± 2.5 °C. Further, by performing a truly three-dimensional (3D) finite element calculation in FEMLAB, the new heat characteristics of the Dewar vessel as well as a 50 kg package of dilauroyl peroxide, a solid organic peroxide, were checked. The outcome was compared with the critical ambient temperatures known for various package sizes, which agreed well.

Manikin measurements versus wear trials of cold protective clothing (Subzero project).

The thermal insulation properties of clothing systems can be defined through physical measurements using thermal manikins or through wear trials using human test subjects. One objective of the European Subzero project was to define the relationship between physically measured thermal insulation values of cold-protective clothing and the corresponding physiological reactions on human test subjects. Four cold-protective clothing ensembles, intended for use in temperatures between 0 and -50 degrees C, were measured with manikins in eight European laboratories and on human test subjects in four of these laboratories. The results showed that reasonably good reproducible values from the manikin tests can be achieved (CV < 8%); however, the fit of the clothing on the manikin is a critical factor. There were greater individual differences in the wear trial results. Comparing the results from the manikin and the wear trials, good agreement in the thermal insulation values was shown if the amount of accumulated sweat was low. In these situations, which are normal when using cold protective clothing, the thermal comfort can also be determined with good accuracy by means of mathematical models based on manikin results. Special situations, e.g. for highly perspiring wearers, strong wind, or high friction between garment layers, need specific modelling; some suggestions have been made as a result of the Subzero project, but further research is required.

Thermal Insulation Value of Taiwan Traditional Clothes and Their Adaptable Climatic Zone

Thermal Insulation Value of Taiwan Traditional Clothes and Their Adaptable Climatic Zone

SHAPE MEMORY POLYURETHANE FOR SMART GARMENT

Thermal-responsive shape-memory polyurethane consists of two phases, a thermally reversible phase for maintaining a transient shape and fixed phase structure for recovering the original shape. The use of shape memory polyurethane in clothing is a novel concept. The aim of this paper is to introduce the application of shape memory polyurethane to smart clothing, whose thermal insulation value could be change depending on the change of temperature of the external environment to give comfort regardless of weather change. Thus a review on the shape memory polyurethane is introduced: the mechanism of the shape memory polyurethane is described; the difference between ordinary polyurethane and shape memory polyurethane, the research on shape memory polyurethane and its potential application to smart garment are summarized; the work being carried out in the Hong Kong Polytechnic University are also introduced.

Handle Characteristics of "Tatami" Surface Matting Made of Polyacrylonitrile Fiber.

Handle characteristics of “Tatami” surface matting made of polyacrylonitrile (=PAN) fiber were investigated by panels of women students using paired comparison and ranking methods. Basic thermal properties such as thermal insulation value, thermal conductivity, q-max and mechanical properties such as compressional and surface properties for the “Tatami” surface were measured precisely comparing with natural rush and polypropylene(=PP) “Tatami” surface. “Tatami” surface matting made of PAN showed higher thermal insulation value than those made of rush and PP. Apparent thermal conductivity and q-max of PAN showed smaller values than rush and PP. PAN showed softness in compression, however, recovered not enough. Good handle for “Tatami” surface was achieved by smooth and dry feeling. Handle characteristics of PAN “Tatami” surface is good as natural rush and may be used for winter season. “Tatami” surface is a good application of PAN fiber produced by successive polymerization and direct spinning method.

The Use of Pentanes as Blowing Agent in Rigid Polyurethane Foam

The overall performance of pentane blown rigid polyurethane foams in terms of insulation value and mechanical properties is demonstrated. The low vapor pressure of both normal-pentane and cyclopentane is shown to induce condensation effects. The consequences of condensation in terms of thermal conductivity and dimensional stability are discussed. The effects on the cell gas pressure of the pentane solubility in the polymer matrix are demonstrated and compared with sorption measurements. The solubility is shown not to deteriorate the foam mechanical properties as a function of time. The ageing characteristics of normal -and cyclopentane blown laminates in terms of the thermal insulation value are discussed. Mixtures of normal- and cyclopentane are suggested to be advantageous in view of their ageing profile.

Silicone Surfactants for Pentane Blown Rigid Foam

Auxiliary blowing agents are utilized in most polyurethane applications. However, the impact of these blowing agents on final foam properties is most critical in the rigid foam area. In most rigid applications the blowing agent serves a dual role in both generating the foam volume, and, in addition, the residual gas remaining within the cells functions to reduce the rate of heat transfer and improve the insulation properties of the foam. Traditionally CFCs have been used as the preferred blowing agent within the polyurethane industry due to their excellent volatility, low flammability, and thermal characteristics. Within the last few years the use of many grades of CFCs have come under restriction due to their implication in depleting atmospheric ozone levels, and these products will ultimately be banned according to the Montreal Protocol. Other types of halogen containing replacements such as HCFCs and HFAs are being examined as potential replacements for the CFCs. However, the future viability of these types of materials is in question, as their toxicological, environmental and economic impact are still under examination. One of the most viable alternatives to replace CFCs as a blowing agent in rigid foam formulations is n-pentane or one of the isomers of pentane. These materials are considered to be excellent replacement candidates due to their availability, low pricing, and most importantly, zero ozone depleting potential(ODP). The use of pentane in rigid continuous laminate boardstock foam has already been initiated, with commercial utilization anticipated in other rigid applications within the next 12 to 18 months. Pentane is the most non polar of the auxiliary blowing agents used in polyurethane foam applications. As a result of the chemical and physical characteristics of pentane, the solubility and compatibility with the polyurethane raw materials and developing foam mixture are completely different compared to all other blowing technologies. This low solubility of pentane in the final polyurethane foam matrix results in very low diffusion rates of pentane. Therefore, initially obtained thermal insulation values are maintained with minimal drift. Due to the inflammable nature of pentane, new processing and handling procedures are required in addition to modifications to the foam formulations. Considering the potential flammability and explosion hazards, minimizing pentane emissions during production is an absolute requirement to safely utilize this new technology. The current and proposed environmental legislations on organic emissions is another reason to ensure minimal levels of VOCs when using pentane as a blowing agent in the production of rigid foams. One of the primary applications for panels produced by the continuous lamination process is in the construction industry, where the flammability rating is one of the most important properties of these materials. The use of an inflammable liquid as a blowing agent, where most of the residual material is retained within the foam cells, requires further formulation modifications to maintain the flame retardancy characteristic of the foams. System modifications, such as incorporating flame retardant additives and water as a co-blowing agent, further increases the polarity of the resultant polyol preblend. The increased polarity of this preblend accompanied by the very low polarity of the pentane puts further limitations on the total system solubility. To improve the solubilization/compatibilization of pentane into these systems, new surfactant technology is required. The primary role of a silicone surfactant in a rigid polyurethane system is to emulsify the incompatible reactants of the preblend and phases that occur during the reaction. In order to achieve similar processing performance and final foam physical properties with these modified formulations containing pentane, new specially designed silicone surfactant molecules are required. In order to investigate the silicone surfactant structure/foam performance relationship, a design study was initiated in a variety of formulations. In addition to the standard performance evaluations, special techniques were developed and effected to understand the solubility, emulsification and compatibility characteristics of pentane during the production and aging of the foam. This paper will discuss the influence of different silicone surfactants on the emulsification and stabilization of pentane in polyol premixes, reaction mixtures and during foam formation. The influence of the silicone surfactants on the physical properties of the final foam will also be discussed.

Comparison of traditional and manufactured cold weather ensembles

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 05:83-90 (1995) - DOI: https://doi.org/10.3354/cr005083 Comparison of traditional and manufactured cold weather ensembles Oakes J, Wilkins H, Riewe R, Kelker D, Forest T ABSTRACT: Inuit elders stress the importance of wearing caribou skin clothing for winter trips. Although laboratory tests for thermal insulation values of clothing are extensive, caribou skin clothing is rarely tested. The purpose of this research was to compare the thermal comfort of caribou skin clothing, military winter issue clothing, and northern expedition clothing using experimental and ethnographic methods. To collect the experimental data, each subject wore the ensembles in an environmental chamber designed to simulate travelling on a sled pulled by a snowmobile in the Arctic winter. Skin temperatures and comfort ratings were analyzed using analysis of variance and multiple regression methods. Ethnographic methods were used to collect 'traditional' knowledge from Inuit elders. Findings indicate that the average skin temperature and comfort ratings dropped significantly less (p < 0.05) when wearing the caribou skin ensemble compared to changes observed when wearing the military or expedition clothing ensembles. There were no significant differences between the military and expedition clothing ensembles. Inuit elders use years of field experiences as a base for their recommendations to use caribou skin clothing for long-term protection for sedentary individuals exposed to a cold winter climate. They also point out the advantages of specific style features and materials for cold weather clothing. In conclusion, the combination of laboratory tests and traditional knowledge has given 2 distinct perspectives which provide a more holistic answer to cold weather clothing needs for people travelling during the Arctic winter. KEY WORDS: Cold weather clothing · Inuit clothing · Skin clothing . Caribou clothing · Contemporary cold weather fabrics · Scientific and traditional knowledge · Thermal comfort Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 05, No. 1. Publication date: February 23, 1995 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 1995 Inter-Research.

Plasma-sprayed yttria-stabilized zirconia coatings: Structure-property relationships

A number of plasma-sprayed yttria-stabilized zirconia coatings were prepared representing a combination of significantly different starting powders and different plasma torch designs. The coatings had densities in the range 85%–91% of the theoretical. Coating hardness, particle erosion resistance and cohesive strength were proportional to density. The thermal fatigue resistance of zirconia coatings, 1.3 mm (0.05 in) thick, increased with increasing density, but their thermal insulation value was inversely proportional to density. In general, the coatings exhibited a number of properties related to density without separate regard to process.

In Vivo Cutaneous and Perceived Comfort Response to Fabric

We report on the perceived comfort data collected while ten female subjects exercised in the hot, humid environment ( 29.4°C, 75% RH) wearing garments made from the three experimental knit fabrics. These findings are related to the fabric thermophys iological comfort data reported in Part I, the mechanical and surface related comfort data in Part II, and the skin alteration data in Part III of this series. At four times during the wear protocol (after acclimation, after 10 minutes of wear, after 40 minutes of exercise, and after 20 minutes of rest following exercise), subjects were asked to indicate overall comfort and thermal, wetness, and contact sensations. There was no difference between the fabrics for wetness or thermal sensation, a result explainable in terms of the extremely small differences in water and heat transport data reported in Part I. The thermal insulation, permeability index, and comfort limit values we calculated predict that differences in perceived thermal and wetness sensation should be minimal. Skin temperature was a significant determinant of perceived thermal comfort in our regression model, but capillary blood flow was not. The regression model for wetness sensation showed that stratum corneum water content and evaporative water loss were statistically significant determinants. Use of wetness-related and contact sensation descriptors differed for the three experimental fabrics. Differences in the wetness-related descriptors appear related to the percent water uptake of the fabrics during exercise. Fiber denier and fabric mechanical and surface feature data were useful in explaining the difference in contact sensations. The fabrics differed in perceived overall comfort. In the regression analysis, capillary blood flow was the only physio logical factor with a statistically significant effect on overall comfort. We suspect a link between the mechanical and surface features and capillary blood flow.

Design of functional work clothing for meat-cutters

The aim of this study was to design new functional work clothing for meat-cutters, paying particular attention to the metabolic requirements of the work and the thermal and general working conditions in slaughterhouses. On the basis of the results of the pilot study (review of the literature, questionnaires and interviews, work analysis, physiological measurements) different types of work clothing were designed for prolonged used during normal work in meat cutting. Physical material tests and measurements of thermal insulation values (l cl), and the follow-up of clothing maintenance were carried out. Further modifications and evaluations of work clothing were based on the opinions of meat-cutters and on the physiological trials in slaughterhouses. The final assembly of work clothing consists of three pieces (cotton/polyester): an apron, trousers with extra insulation in the lower back, and a work coat with extra insulation in the neck and shoulders, and at the wrists. The sleeves are protected against moisture by special textile material. The thermal insulation of this new set of work clothing together with long sleeved and legged underwear is 1·3 clo and it proved to be sufficient for thermal comfort in moderate work in an air temperature of 10°C.

Energy conservation and its implication for architectural design and town planning in the hot-arid areas of Saudi Arabia and the Gulf states

Abstract The energy crisis has had adverse effects on the national development plans of Saudi Arabia and the Gulf States, even though they are oil-rich countries. Sooner or later fossil fuels will be in short supply. At the moment they are abundant and will still be the main source of national income for the foreseeable future so they should be used wisely and not wastefully. These fossil fuels must be used economically and skillfully and only for the progress and development of the nations dependent on them. The whole of the energy needs should be examined with a view to reducing the demand on oil and making better use of solar energy. Can we reduce the demand for oil in transport and for air-conditioning in the cities? Can we create an awareness that fossil fuels are not renewable and that solar energy is free? A better understanding of our climatic conditions and the use of passive solar energy in building techniques by simply grouping buildings better would save energy. We need to do research into building materials with a higher thermal capacity and insulation value that are durable and maintenance free. Our towns and communities should be so laid out that travel requirements are reduced to a minimum. Transport modes should be suitable and efficient. Hopefully a pleasant living environment can be created for the people of the Arab Gulf despite the harshness of the climate while at the same time conserving their national wealth.

Insulation haracteristics of Outdoor Garments and Fabric Systems

The thermal insulation (clo) values of different combinations of shell fabrics, linings, and filling materials were measured using a guarded hot plate. The same fabric systems were constructed into long and short coats, and an electrically heated manikin was used to measure the insulation provided by each coat worn with a standard set of indoor garments. The type of fabric and/or filling material significantly affected the insulation provided by fabric systems and coat ensem bles. The long coats were significantly warmer than their shorter counterparts, and the sensitivity of garment clo to fabric clo was greater for the long coats than for the short coats. It appears that small differences in the thermal insulation of fabric systems become more important when most of the body is covered with a given fabric system. However, when an outdoor garment covers only part of the body and is worn over garments with less thermal resistance, the garment's contribution to total body insulation is lessened.

Static method for determining the R value of thermal insulation

A steady-state technique for finding the thermal resistance of rigid thermal insulation is discussed. The method, which is suitable for use in the general physics laboratory, can be understood in terms of a simple electrical analogy.

Development of light-weight insulating clay products from the clay-sawdust-glass system

Employing a simple dry-pressing and sintering process, lightweight clay products with various physical, mechanical and thermal properties have been fabricated from mixtures of maplewood sawdust, clay and soda-lime glass grains prepared from recycled waste glass. Studies showed that thermal conductivity, compressive strength, and cold water absorption of the sintered sawdust-clay products are significantly modified by the addition of sawdust particles to the clay mixes. Studies also showed that portions of the clay particles can be replaced with soda-lime glass grains of similar sizes. These light-weight composite clay products have compressive strength in excess of 31 MN/m 2, thermal conductivity value in the range 0.21–0.39 W/m, °C and water saturation coefficient of about o.72. The fabricated clay products exhibit attractive characteristics as building materials and could contribute to energy conservation because of their high thermal insulation value.

Heat Transfer on Cylinder Covered with Close-fitting Fabrics : Part II. Heat Transfer on the Stagnation Point

The objective of investigation is to get a clear idea of the nature of wind penetration effects in clothing. The preceding study of wind penetration through fabric is extended, in this paper, to determine the heat transfer of fabric system. With the aid of heat transfer equation of porous media, the thermal insulation value of fabric layer can be described as a function of such arguments as α*, some pertinent properties of fabric and wind velocity, where α* is the characteristic number of contact layer referring to the manner of contact between fabric and cylinder. Quantitative agreement' between the theory and experimental data is considerably good. Then it is seen that the dynamic pressure of wind sets up penetration, and thereby augments heat transfer process. The insulation value decreases with an increasing wind velocity and the behaviour of the decreasing depends largely on α*. Therefore α* is an essential factor for assessing the value of a sample fabric in wind.