Experimental study of heat and moisture transfer in vertical air gap under protective clothing against dry and wet heat exposures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yun Su ◽  
Miao Tian ◽  
Yunyi Wang ◽  
Xianghui Zhang ◽  
Jun Li
Keyword(s):  
Natural Convection ◽  
Protective Clothing ◽  
Moisture Transfer ◽  
Heat Exposure ◽  
Air Gap ◽  
Gap Size ◽  
Heat And Moisture Transfer ◽  
Content Type ◽  
Wet Heat ◽  
Heat And Moisture

PurposeThe 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/approachAn 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.FindingsThe 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/valueThis 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.

Effects of athletic T-shirt designs on natural ventilation

2016 ◽  
Vol 20 (2) ◽  
pp. 112-123 ◽  
Author(s):  
Chupo Ho ◽  
Jintu Fan ◽  
Edward Newton ◽  
Raymond Au
Keyword(s):  
Thermal Insulation ◽  
Moisture Transfer ◽  
Design Method ◽  
Air Gap ◽  
Thermal Manikin ◽  
Heat And Moisture Transfer ◽  
Content Type ◽  
Heat And Moisture ◽  
Air Circulation ◽  
Moisture Vapour

Purpose Maintaining air circulation between the wearer and garment layer is crucial for activating heat and moisture transfer from the body. If an air gap is trapped, air circulation may become ineffective and the ventilation of the garment is, thus, hindered. To maintain and extend the air gap, this study aims to propose a design method that involves placing spacer blocks underneath the garment to prevent the fabric from clinging directly to the skin. Design/methodology/approach To study the application of this design method, a series of T-shirts were produced and tested using a thermal manikin in standing and walking postures. All the T-shirts were made of fabric ostensibly manufactured to have high air permeability. Porous mesh fabric was used to construct the vented panels on the T-shirts. The test was conducted in a chamber with controlled temperature, relative humidity and wind velocity. Total thermal insulation (Rt) and moisture vapour resistance (Ret) were measured. Findings The test results showed that extension of the air gap between wearer and fabric provided higher ventilation to the wearer if the vented panels were also present on the T-shirts. Different placements of the vented panels on the T-shirts also affected the heat and moisture transfer from the thermal manikin. Research limitations/implications Due to limited resources, the evaluation of total thermal insulation and moisture vapour resistance was based on the testing result from a thermal manikin instead of any subjective wearer trial. Practical implications This research can contribute to the clothing designer who is developing function wear for a better ventilation. Social implications This research can contribute to the clothing designer who is developing function wear for a better ventilation. Originality/value This study aimed to further develop a new design concept in T-shirt design by improving the construction of the spacer blocks. Fabric with higher air and water vapour permeability was used to determine to what extent this design method is applicable to higher performance on heat and moisture transfer.

Design of polyester-elastane-cotton plated knitted components for hot and dry environment

2018 ◽  
Vol 30 (5) ◽  
pp. 657-667
Author(s):  
Varadaraju Ramakrishnan ◽  
Srinivasan Jagannathan
Keyword(s):  
Outer Layer ◽  
Linear Density ◽  
Moisture Transfer ◽  
Contact Layer ◽  
Cotton Yarn ◽  
Heat And Moisture Transfer ◽  
Polyester Yarn ◽  
Content Type ◽  
Skin Contact ◽  
Heat And Moisture

Purpose The purpose of this paper is to optimize the linear densities of polyester yarn and filament for inner layer and elastane for middle layer with cotton yarn outer layer in plain knitted plated structure for hot and dry environment clothing. Design/methodology/approach Three levels of polyester yarn linear densities (11.1, 8.4 and 5.6 Tex), filament linear densities (0.8, 1.55 and 2.3 Decitex) and elastane (0, 4 and 8 percent) with 14.75 Tex cotton yarn have been used to knit 15 single jersey plated fabrics based on Box and Benhens experimental design with same loop length. Three cotton–elastane core-spun fabrics were also produced. All the fabrics were analyzed for moisture and ergonomic comfort properties and wet fabric coefficient of friction. Findings The increase in elastane content and yarn linear density decreases water vapor and air permeability; the increase in filament linear density decreases wicking rate and water absorbency. The optimum solution is 5.55 Tex polyester yarn of 0.8 Decitex filament as inner layer and 14.75 Tex cotton yarn as outer layer which gives good heat and moisture transfer without stickiness. Research limitations/implications The implication of this paper is to study thinner polyester, polypropylene and polyethylene fabrics with more micro pores as skin contact layer for quicker heat and moisture transfer. Practical implications Outward wickability of sweat from the skin is the prime requirement of all skin contact layer fabrics. Social implications It shifts the social attitude of most comfortable fabric to polyester–cotton plated for hot and dry climate. Originality/value This paper employs a more practical method for the selection of fabric.

Coupled transient heat and moisture transfer investigation of facade panel connections

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Bahram Abediniangerabi ◽  
Mohsen Shahandashti ◽  
Atefe Makhmalbaf
Keyword(s):  
Moisture Transfer ◽  
The Other ◽  
Heat Transfer Analysis ◽  
Thermal Resistivity ◽  
Heat And Moisture Transfer ◽  
Maximum Heat ◽  
Content Type ◽  
Hygrothermal Performance ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture

Purpose The purpose of this study is to investigate the effect of panel connections on the hygrothermal performance of facade panels using a coupled, transient heat and moisture transfer analysis. Design/methodology/approach A coupled, transient heat and moisture transfer analysis has been conducted to investigate the effect of panel connections in the hygrothermal behavior of facade panels. Governing partial differential equations for the coupled heat and moisture transfer were formulated. Four panel connections proposed by pre-cast/pre-stressed concrete institute were modeled for the ultra-high performance fiber-reinforced concrete facade panel as illustrations and a finite element method was used to solve the numerical models. Findings The results of heat transfer analysis showed that steel connections could significantly reduce the thermal resistivity of facade panels by converging heat fluxes and acting as thermal bridges within facade panels. The results also showed that the maximum heat flux in the steel connector of the panel to foundation connection was 10 times higher compared to the other connections. Also, the results of moisture transfer showed that air gaps between the panels had higher moisture flux compared to the other layers in the models. The results show the significant importance of panel connections in the energy performance analysis of facade systems. They also highlight the importance of devising novel connection designs and materials that consider the transient, coupled heat and moisture transfer in the connections to effectively exploit the potential opportunities provided by innovative facade systems to improve building energy efficiency. Originality/value This paper, for the first time, investigates the effect of panel connections in the hygrothermal performance of building facade systems using a coupled, transient heat and moisture transfer analysis.

scholarly journals The interaction of clothing ventilation with dry and evaporative heat transfer of jackets

2016 ◽  
Vol 28 (5) ◽  
pp. 570-581 ◽  
Author(s):  
Xiao-Qun Dai ◽  
George Havenith
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Moisture Transfer ◽  
Heat Diffusion ◽  
Vapor Permeability ◽  
Heat And Moisture Transfer ◽  
Content Type ◽  
Dry Heat ◽  
Evaporative Heat Transfer ◽  
Heat And Moisture

Purpose The purpose of this paper is to investigate the effect of air and vapor permeability of jacket materials on ventilation, heat and moisture transfer. Design/methodology/approach Clothing ventilation (V), thermal insulation (I) and vapor resistance (R e ) of three jackets made of different materials (normal textile, PVC and “breathable” membrane coated textile), worn on an articulated thermal manikin in a controlled climate chamber, were measured under various conditions, respectively. The various conditions of microenvironment ventilation were created by making the manikin stand and walk, combined with three wind speeds of <0.2, 0.4 and 2.0 m/s, respectively. Findings In the condition without any forced convection, the air permeability makes no big difference to dry and evaporative heat transfer among the jackets, while the vapor permeability plays a big role in the evaporative heat loss. In the condition with forced convection, the dry heat diffusion is strongly coupled to the evaporative heat transfer in air and vapor permeable textile material. Research limitations/implications The effects of ventilation on heat and moisture transfer varies because of different ways of ventilation arising: penetration through the fabric is proven to be the most effective way in vapor transfer although it does not seem as helpful for dry heat diffusion. Originality/value The achievements in this paper deepens the understanding of the process of the dry and evaporative heat transfer through clothing, provides clothing designer guidance to choose proper materials for a garment, especially work clothing.

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