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Article

Tord af Klintberg, Gudni Johannesson and Folke Björk

Water damage is a severe problem in modern construction, causing economic loss and health implications. The patented Air Gap Method, which is a slight modification of the…

Abstract

Purpose

Water damage is a severe problem in modern construction, causing economic loss and health implications. The patented Air Gap Method, which is a slight modification of the common infill wall construction, provides means to build houses in a more robust way, minimizing the negative effects of water damage. This full‐scale study of the method aims to show how walls and floors may be built to create ventilation within the construction, with air gaps equipped with heating cables. The general hypothesis is that the patented Air Gap Method drains and evaporates dampness after water damage. The purpose of this study is to show how the method is built and how the method deals with water damage, such as a flooding, and with mould growth.

Design/methodology/approach

The Air Gap Method is based on a common timber‐framed construction and is completed by the provision of inlets, air gaps, slits, and outlets. The power for the convective airflow is given by an electrical heating cable. The study was carried out as a full‐scale experiment using a 24 m2 large apartment build by this method. This apartment was flooded with 120 litres of domestic wastewater and the drying period was compared when heating cables were switched on or not. Mould growth was also investigated.

Findings

The method dries out a flooded floor in nine days when two heating cables were switched on, in 13 days with one heating cable and 21 days when the heating cables were off. The method prevents all mould growth provided that the indoor RH is lower than 65 per cent.

Practical implications

The method provides means to build houses in a more robust way, minimizing the negative effects of water damage.

Originality/value

The issue of ventilated construction is rarely investigated in scientific research.

Details

Structural Survey, vol. 26 no. 3
Type: Research Article
ISSN: 0263-080X

Keywords

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Article

Tord af Klintberg and Folke Björk

The purpose of this paper is to report on a study which has been carried out on a timber floor construction above a ground‐supported concrete slab, which was used in small…

Abstract

Purpose

The purpose of this paper is to report on a study which has been carried out on a timber floor construction above a ground‐supported concrete slab, which was used in small detached houses built in Sweden during the period 1960‐1990. This method of building has turned out to be a risky construction nowadays, but there are 800,000 houses built this way in Sweden.

Design/methodology/approach

By using the patented Air Gap Method inside building constructions, harmful water can be dried out. The method ventilates air gaps inside walls and floors with an air flow driven by thermal buoyancy caused by a heating cable in the vertical air gaps. The drying out process has been studied both by measuring the moisture level in the slab and also by measuring the humidity transport and comparing this with air flow measurements.

Findings

The paper shows that the Air Gap Method manages to dry out water from both the slab and the overlaying wooden construction. The study shows also that the relative humidity (RH) levels in the air space below the floor are reduced in a significant way, thus minimizing mould growth. It is also shown that a thin layer of concrete upon floor beams prevents mould to grow even in a humid situation.

Research limitations/implications

The research reported in this paper is only concerned with timber‐framed small detached houses. Similar studies of apartment buildings are ongoing.

Practical implications

The Air Gap Method can thus be useful in the context of renovating a water damaged house of this type built during this 30‐year period. The method provides a possibility of drying out such damage without a separate drying period. The inhabitants could therefore be able to use a renovated water‐damaged kitchen six/eight weeks earlier compared to ordinary building methods.

Originality/value

The paper is useful because it provides better understanding of the mechanism of RH inside a building construction and how this parameter could be lowered. The paper is also useful in the context of renovating water‐damaged small detached houses built by the risky method of construction used in the last decades of the twentieth century.

Details

Structural Survey, vol. 28 no. 4
Type: Research Article
ISSN: 0263-080X

Keywords

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Article

Shitan Wang, Xiuhua Wang and Yunyi Wang

The purpose of this paper is to determine the effects of clothing ease and body postures on the size and distribution of the air gap as well as the body coverage with the clothing.

Abstract

Purpose

The purpose of this paper is to determine the effects of clothing ease and body postures on the size and distribution of the air gap as well as the body coverage with the clothing.

Design/methodology/approach

Visual and quantitative analyses were conducted using a 3D body scanner and Geomagic Software. The air gap size and clothing area factor (fcl) in three test coverall and seven selected postures were calculated and compared.

Findings

The results indicated that both the clothing ease and body postures had a strong effect on the air gap and clothing coverage, especially the more complex the postures, the wider the range of influence. Nevertheless, these effects varied over body regions, being stronger at the lower body than the upper body. The air gap size at the left side of the body was generally larger than the right side. It was also found that the clothing coverage was linearly correlated with the air gap size and could be employed as an indicator to evaluate clothing protective capabilities.

Practical implications

The findings suggested that greater attention should be paid to the protection and flexibility at the lower body and asymmetrical distribution of the air gap should be considered in the future air gap modeling.

Originality/value

The outcomes provided useful information to improve the protective clothing and develop more realistic air gap models to simulate the heat and mass transfer.

Details

International Journal of Clothing Science and Technology, vol. 31 no. 4
Type: Research Article
ISSN: 0955-6222

Keywords

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Article

Yun Su, Miao Tian, Yunyi Wang, Xianghui Zhang and Jun Li

The purpose of this paper is to study heat and steam transfer in a vertical air gap and improve thermal protective performance of protective clothing under thermal…

Abstract

Purpose

The purpose of this paper is to study heat and steam transfer in a vertical air gap and improve thermal protective performance of protective clothing under thermal radiation and hot steam.

Design/methodology/approach

An experiment-based model was introduced to analyze heat and moisture transfer in the vertical air gap between the protective clothing and human body. A developed test apparatus was used to simulate different air gap sizes (3, 6, 9, 12, 15, 18, 21 and 24 mm). The protective clothing with different air gap sizes was subjected to dry and wet heat exposures.

Findings

The increase of the air gap size reduced the heat and moisture transfer from the protective clothing to the skin surface under both heat exposures. The minimum air gap size for the initiation of natural convection in the dry heat exposure was between 6 and 9 mm, while the air gap size for the occurrence of natural convection was increased in the wet heat exposure. In addition, the steam mass flux presented a sharp decrease with the rising of the air gap size, followed by a stable state, mainly depending on the molecular diffusion and the convection mass transfer.

Originality/value

This research provides a better understanding of the optimum air gap under the protective clothing, which contributes to the design of optimum air gap size that provided higher thermal protection against dry and wet heat exposures.

Details

International Journal of Clothing Science and Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0955-6222

Keywords

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Article

Norman Borchardt and Roland Kasper

This study aims to present a parametric model of a novel electrical machine, based on a slotless air gap winding, allowing for fast and precise magnetic circuit calculations.

Abstract

Purpose

This study aims to present a parametric model of a novel electrical machine, based on a slotless air gap winding, allowing for fast and precise magnetic circuit calculations.

Design/methodology/approach

Approximations of Fourier coefficients through an exponential function deliver the required nonlinear air gap flux density and inductance. Accordingly, major machine characteristics, such as back-EMF and torque, can be calculated analytically with high speed and precision. A physical model of the electrical machine with air gap windings is given. It is based on a finite element analysis of the air gap magnetic flux density and inductance. The air gap height and the permanent magnetic height are considered as magnetic circuit parameters.

Findings

In total, 11 Fourier coefficient matrixes with 65 sampling points each were generated. From each, matrix a two-dimensional surface function was approximated by using exponentials. Optimal parameters were calculated by the least-squares method. Comparison with the finite element model demonstrates a very low error of the analytical approximation for all Fourier coefficients considered. Finally, the dynamics of an electrical machine, modeled using the preceding magnetic flux density approximation, are analyzed in MATLAB Simulink. Required approximations of the phase self-inductance and mutual inductance were given. Accordingly, the effects of the two magnetic circuit parameters on the dynamics of electrical machine current as well as the electrical machine torque are explained.

Originality/value

The presented model offers high accuracy comparable to FE-models, needing only very limited computational complexity.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Meng Deng, Yunyi Wang and Peijing Li

The purpose of this paper is to provide the details of developments to research works in the distribution characteristics of the air gaps within firefighters’ clothing and…

Abstract

Purpose

The purpose of this paper is to provide the details of developments to research works in the distribution characteristics of the air gaps within firefighters’ clothing and research methods to evaluate the effect of air gaps on the thermal protective performance of firefighters’ clothing.

Design/methodology/approach

In this paper, the distribution of air gaps within firefighters’ clothing was first analyzed, and the air gaps characteristics were summarized as thickness, location, heterogeneity, orientation and dynamics. Then, the evaluation of the air gap on the thermal protective performance of fighters’ clothing was reviewed for both experimental and numerical studies.

Findings

The air gaps within clothing layers and between clothing and skin play an important role in determining the thermal protective performance of firefighters’ protective clothing. It is obvious that research works on the effects of actual air gaps entrapped in firefighters’ clothing on thermal protection are comparatively few in number, primarily focusing on static and uniform air gaps at the fabric level. Further studies should be conducted to define the characteristic of air gap, deepen the understand of mechanism of heat transfer and numerically simulate the 3D dynamic heat transfer in clothing to improve the evaluation of thermal protective performance provided by the firefighters’ clothing.

Practical implications

Air gaps within thermal protective clothing play a crucial role in the protective performance of clothing and provide an efficient way to provide fire-fighting occupational safety. To accurately characterize the distribution of air gaps in firefighters’ clothing under high heat exposure, the paper will provide guidelines for clothing engineers to design clothing for fighters and optimize the clothing performance.

Originality/value

This paper is offered as a concise reference for researchers’ further research in the area of the effect of air gaps within firefighters’ clothing under thermal exposure.

Details

International Journal of Clothing Science and Technology, vol. 30 no. 2
Type: Research Article
ISSN: 0955-6222

Keywords

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Article

Ming Fu, Wenguo Weng and Hongyong Yuan

– The purpose of this paper is to measure the thermal insulation of protective clothing with multilayer gaps in low-level heat exposures.

Abstract

Purpose

The purpose of this paper is to measure the thermal insulation of protective clothing with multilayer gaps in low-level heat exposures.

Design/methodology/approach

Nine different combinations of protective clothing systems with multiple air gaps are used to measure the thermal insulation by a self-designed bench-scale test apparatus in different levels of an external thermal radiation of 2-10 kW/m2. The outside and inside surface temperatures of each fabric layer are also measured to calculate the local thermal insulation of each fabric layer and each air gap.

Findings

The results show that the total thermal insulation of protective clothing under thermal radiation is less than that in normal environments, and the exposed thermal radiation will worsen the total thermal insulation of the multilayer fabric systems. Air gap plays a positive role in the total thermal insulation, and thus provides the enhanced thermal protection. It is also suggested that the local resistance of the air gap closer to the external thermal radiation is more easily affected by the thermal radiation, due to the different heat transfer ways in the fabric system and the external thermal radiation.

Originality/value

Effects of air gap on the thermal insulation of protective clothing, and contribution of the local thermal resistance of each fabric layer and each air gap to the total thermal insulation.

Details

International Journal of Clothing Science and Technology, vol. 26 no. 5
Type: Research Article
ISSN: 0955-6222

Keywords

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Article

Tord af Klintberg and Folke Björk

Water damage is a severe problem in modern construction, causing economic loss and health implications. By using the patented Air Gap Method inside building constructions…

Abstract

Purpose

Water damage is a severe problem in modern construction, causing economic loss and health implications. By using the patented Air Gap Method inside building constructions, harmful water in the construction can be dried out. The method drains and ventilates air gaps inside walls and floors with an airflow driven by thermal buoyancy caused by a heating cable in vertical air gaps. This paper aims to investigate this method and measurements of airflow inside air gaps of walls.

Design/methodology/approach

This study investigates the measured correlation between the power of the heating cable, the difference of temperature inside and outside the air gap, and the airflow. Data are collected by experimentation with a full‐scale constructed wall.

Findings

The study finds that airflow increases with raised temperature difference between the air gap and room and with raised power of the heating cable. The measured airflow reaches values up to 140 m3/metre wall and day for one cable. A small increase in temperature, between 0.2 and 0.3 oC inside the vertical air gap results in an air flow of approximately 60 m3/metre wall and day. The air change rate per hour for the air inside the wall construction varies between 15 times for a 6 W/m cable and 37 times for a 16 W/m cable.

Practical implications

The method provides the means to build houses in a more robust way, minimising the negative effects of water damage. This investigation provides an understanding of how temperature and ventilation are related in this method of construction.

Originality/value

The issue of ventilated construction is rarely investigated in scientific research.

Details

Structural Survey, vol. 26 no. 4
Type: Research Article
ISSN: 0263-080X

Keywords

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Article

D.A. PARKER and G.M. DONNISON

The concept of an airgap insulated piston has been explored using bolted and welded/roll bonded designs. Pistons with bolted‐on crowns demonstrated the effectiveness of…

Abstract

The concept of an airgap insulated piston has been explored using bolted and welded/roll bonded designs. Pistons with bolted‐on crowns demonstrated the effectiveness of air gap insulation, but roll bonded and welded designs were found to be more robust and to provide the complete sealing of the air gap necessary for continued insulation. Evolution of the design to combine high insulation with adequate durability is discussed. Engine running times of up to 200 hours at full load have been achieved for an air gap piston which reduces heat flow to the crown by 33 per cent. An improved design giving 41 per cent reduction of heat flow has been tested for 78 hours at full engine load with no evident deterioration. Development is continuing to provide a fully durable piston achieving up to 50 per cent reduction in heat flow.

Details

Industrial Lubrication and Tribology, vol. 39 no. 4
Type: Research Article
ISSN: 0036-8792

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Article

Piotr Lapka, Piotr Furmanski and Tomasz Wisniewski

The paper aims to present the advanced mathematical and numerical models of conjugated heat and mass transfer in a multi-layer protective clothing, human skin and muscle…

Abstract

Purpose

The paper aims to present the advanced mathematical and numerical models of conjugated heat and mass transfer in a multi-layer protective clothing, human skin and muscle subjected to incident external radiative heat flux.

Design/methodology/approach

The garment was made of three layers of porous fabric separated by the air gaps, whereas in the tissue, four skin sublayers and muscle layer were distinguished. The mathematical model accounted for the coupled heat transfer by conduction and thermal radiation with the associated phase transition of the bound water in the fabric fibres and diffusion of the water vapour in the clothing layers and air gaps. The skin and muscle were modelled with two equation model which accounted for heat transfer in the tissue and arterial blood. Complex thermal and mass transfer conditions at the internal or external boundaries between the fabric layers, air gaps and skin were assumed. Special attention was paid to modelling of thermal radiation emitted by external heat source, for example, a fire, penetrating through the protective clothing and being absorbed by the skin and muscle.

Findings

Temporal and spatial variations of temperature in the protective garment, skin and muscle, as well as volume fractions of the water vapour and bound water in the clothing, were calculated for various intensity of incident radiative heat flux. The results of numerical simulation were used to estimate the risk of the first-, second- and third-degree burns.

Research limitations/implications

Because of the small thickness of the considered system in comparison to its lateral dimensions, the presented model was limited to 1D heat and moisture transfer. The convective heat transfer through the clothing was neglected.

Practical implications

The model may be applied for design of the new protective clothing and for assessment of thermal performance of the various types of protective garments. Additionally, the proposed approach may be used in the medicine for estimation of degree of thermal destruction of the tissue during treatment of burns.

Originality/value

The novel advanced thermal model of the multi-layer protective garment, skin and muscle layer was developed. For the first time, non-grey optical properties and various optical phenomena at the internal or external boundaries between the fabric layers, air gaps and skin were accounted for during simulation of thermal interactions between the external heat source (e.g. a fire), protective clothing and human skin.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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