Search results

The purpose of this paper is to prepare microencapsulated phase change materials (PCMs) and apply them to cotton and wool fabrics for developing thermo-regulating fabrics.

Microencapsulated n-hexadecane and n-octadecane with poly(methylmethacrylate-co-2-hydroxy ethyl methacrylate) shell was prepared. Microcapsules were fabricated using oil-in-water emulsion polymerization method. Their chemical structure, microstructure, thermal energy storage properties and thermal stability were analyzed by Fourier-transform infrared spectroscopy, polarized light microscope, differential scanning calorimeter and thermogravimetric analyzer, respectively. The mean particle size was tested by a particle sized instrument. The microcapsules were applied to the wool and cotton fabrics using pad-dry-cure method. The thermo-regulating property of the fabrics was evaluated using the T-History test. The distribution and durability of the microcapsules on the fabrics was investigated with scanning electron microscopy.

Spherical microcapsules with p(MMA-co-HEMA) shell and n-alkane core have been produced successfully. n-hexadecane in microcapsule solidifies at 14.8−15.6°C with the latent heat of 65.6−129.8 J/g and melts at 16.7−16.9°C with the latent heat of 67.6−136.9 J/g. Microencapsulated n-octadecane solidifies at 25.8−26.3°C with the latent heat of 74.1−106.2 J/g and melts at 26.8−27.4°C with the latent heat of 80.3−113.4 J/g. The microcapsules have enough thermal stability to the temperature of 150°C that was applied during the fixation of microcapsules on the fabric. The thermo-regulating effect of the microcapsule-incorporated fabrics has been proved by the T-history test.

PCM microcapsules with p(MMA-co-HEMA) shell and n-hexadecane and n-octadecane core have been produced and their usage to produce thermo-regulating textiles have been proved. To determine the thermo-regulating property of the fabrics treated with these new PCM microcapsules, a T-History system has been designed.

The purpose of this study was to investigate the heat and moisture transmission through different types of textile materials or material combinations used for male business clothing.

In this study, eight different material combinations, which simulate four‐layer male business clothing system were tested using the sweating cylinder under two environmental conditions (10°C/65% RH and 25°C/65% RH), and at two sweating levels (100 and 200 gm⁻²h⁻¹), in order to evaluate the heat and moisture transmission properties of material combinations.

The results show how combinations of clothing materials that simulate male business clothing system influence on the dry and evaporative heat loss between the cylinder surface and two different environment conditions as well as to different sweating levels.

The sweating cylinder can be used for measuring the heat and moisture transmission through clothing materials or material combinations in order to find out the best combination of textile materials, which simulate clothing system. Measured thermal comfort properties of material combinations evaluated with a sweating cylinder can provide valuable information for the textile and clothing industry by manufacturing/designing new textiles and clothing systems.

The paper investigated the heat and moisture transmission through combinations of clothing materials that simulate male business clothing system. In the past few years, clothing materials containing microencapsulated phase‐change materials (PCMs) have appeared in outdoor garments, particularly sportswear; therefore, we decided to investigate the combinations of standard used textile materials as well as of materials, containing PCMs, which simulate male business clothing system.

The purpose of this paper is to discuss the issue of relevance in full‐text patent document searches from the viewpoint of end‐users in science and technology. It aims to present three cases of patent document analysis for relevance, with an additional case of improved search profile with increased relevance, and to summarise the findings in the form of instructions for users.

Two methodological approaches were used for the analysis of patent documents: value‐added processing of the bibliographic part of patent documents for the identification of trends; and structuring of data into systems for the determination of patent relevance. Overall, four sets of full‐text patent documents were analysed, covering the topics of: microencapsulated phase change materials; digital photography and image sensors; patent document processing; and patent analysis.

Value‐added analysis of the bibliographic parts of patent documents is a quick and useful option for the recognition of research trends. However, where non‐relevant patent documents are present in a data set, automatic bibliographic analysis may lead to conclusions that are mathematically and statistically correct, but that are not reliable or may even be incorrect for the user's research. Non‐adequate terminology is one of the main obstacles to relevant patent searches, especially if well‐defined keywords are non‐existent, as with cases of newly emerging and fast developing scientific and technological fields.

Based on the bibliographic and content analyses of patent documents, the paper provides instructions for users in the form of ten general rules for increasing the relevance of full‐text patent document searches.

This study aims to explore the infrared imaging effect of fabrics coated with phase change material microcapsules (PCM-MCs), which are prepared by the initiation of ultraviolet (UV) light.

PCM-MCs were prepared by UV polymerization using paraffin (PA) as core material, polymethyl methacrylate as wall material and ferric chloride as photoinitiator. The effects of emulsifier dosage and emulsification temperature on the properties of PA emulsion were investigated. Scanning electron microscopy, particle size analysis, infrared spectroscopy, differential scanning calorimetry and infrared imaging test were used to characterize the properties of microcapsules.

The PCM-MCs with good morphology and particle size were prepared with 25 cm of the distance between light source and the liquid. The average particle size was 1.066 µm and the latent heat of phase transition was 19.96 J/g. After 100 accelerated thermal cycles, the latent heat only decreased by 1.8%. It had good heat storage stability and thermal stability. The fabric coated by the microcapsules exhibited a variable temperature hysteresis effect when placed in the sun, and presented a color close to the infrared images of the human palm under the external environment temperature close to the human body temperature.

The PCM-MCs prepared based on UV light initiation showed good thermal properties and its coated fabrics had an infrared decoy effect below the temperature of the human body.

This study explored the application of microcapsules in textiles.

The microcapsules had a certain application potential in infrared decoy effect.

Heat capacity enhancement is important for variety of applications, including microchannel cooling and solar thermal energy conversion. A promising method to enhance heat capacity of a fluid is by introducing phase change particles in a flow system. The purpose of this paper is to investigate heat capacity enhancement in a microchannel flow with the presence of phase change material (PCM) particles.

Discrete phase model (DPM) and homogeneous model have been compared in this study. Water is used as the carrier fluid and lauric acid as the PCM particles with different volume concentrations, ranging from 0 to 10%. Both the models neglect the particle‐particle interaction effects of PCM particles.

The DPM indicates that presence of 10% volume concentration of PCM particles does not cause an increase in the pressure drop along the channel length. However, prediction from the homogeneous model shows an increase in the pressure drop due to the addition of nanoparticles in such a way that 10% volume concentration of particles causes 34.4% increase in pressure drop.

The study covers only 10% volume concentration of PCM particles; however, the model may be modified to include higher volume concentrations. The laminar flow is considered; it may be extended to study the turbulence effects.

This work provides a starting framework for the practical use of different PCM particles, carrier fluid properties, and different particle volume concentrations in electronic cooling applications.

The work presented is original and the findings will be very useful for researchers and engineers working in microchannel flow in cooling and thermal storage applications.

In order to characterize the temperature regulating ability of fabrics containing phase change material (PCM), the test instrument has been designed and built.

To assess temperature regulating ability, temperature regulating factor (TRF) is determined. TRF is defined by Hittle as a quotient of the amplitude of the temperature variation of the hot plate and the amplitude of the heat flux variation divided by the steady state heat resistance of the fabric.

The test instrument presented here is intended to be used for testing steady state and transient state characteristics of the apparel fabrics containing the PCMs.

This test instrument can be used in quality control during the manufacture of fabrics containing PCMs. TRF can be used in clothing industry to establish the criteria for comfort parameters of textiles.

The instrument can provide information for the fabric and garment designers and be useful in quality control during the manufacture of fabrics with the microPCMs. The TRF can be used in the clothing industry to establish the criteria for the comfort parameters of textiles.

The paper aims to investigate thermal comfort properties, such as heat and moisture transmission through male business clothing systems, by using a sweating thermal manikin Coppelius that simulates heat and moisture production in a similar way to the human body and measures the influence of clothing on heat exchange in different environmental and sweating conditions.

Ten different combination of male business clothing systems were measured using the sweating manikin, under three environmental conditions (10°C/50 per cent RH, 25°C/50 per cent RH and −5°C), and at 0 and 50 gm⁻² h⁻¹ sweating levels, in order to evaluate the influence of environmental and sweating conditions on thermal comfort properties of clothing systems.

The results show how business clothing systems influence on the dry and evaporative heat loss between the manikin surface and environment in different environmental and sweating conditions.

When using sweating thermal manikin Coppelius, water vapour transmission (WVT) through and water condensation on the clothing can be determined simultaneously with the thermal insulation (I_t) of clothing system. Measured thermal comfort properties of clothing systems evaluated with a sweating thermal manikin can provide valuable information for the clothing industry by manufacturing/designing new clothing systems.

In this investigation, the heat and moisture transmission properties of male business clothing systems were measured in different environmental and sweating conditions. In the past few years, clothing materials containing microencapsulated phase‐change materials (PCMs) have appeared in outdoor garments, particularly sportswear; therefore, we decided to investigate the thermal comfort properties of different standard male business apparel, as well as male business clothing that contain PCMs used as liner and outerwear material.

The paper aims to provide an overview of the area of smart textiles.

The paper describes and discusses new and developing materials and technologies used in the textile industries.

Significant progress has been achieved in the area of technical textiles. Fibres, yarns, fabrics and other structures with added‐value functionality have been successfully developed for technical and/or high performance end‐uses. The basic building blocks are already in place in the field of smart textiles and clothing.

As progress in science and engineering research advances, and as the gap between designers and scientists narrows, the area of smart clothing is likely to keep on expanding for the foreseeable future. Growth is predicted to occur in two distinct directions: performance‐driven smart clothing and fashion‐driven smart clothing. There are challenges that have to be addressed.

The paper provides information of value to those interested in the future directions of the textile industry.

To examine the heat transfer characteristics of soild‐liquid phase change material (PCM) suspensions in a rectangular natural circulation loop.

A continuum mixture flow model is used for the buoyancy‐driven circulation flow of the PCM suspensions together with an approximate enthalpy model to describe the solid‐liquid phase change (melting/freezing) process of the PC particles in the loop. Numerical simulations via a finite difference method have been conducted for the pertinent physical parameters of a loop with fixed geometrical configuration in the following ranges: the modified Rayleigh number Ra*=10⁹‐10¹³, the modified Stefan number Ste*=0.05‐0.5, the particle volumetric fraction C_v=0‐20 percent and the modified subcooling factor Sb*=0‐2.0.

The melting/freezing processes of the PCM particles at the heated/cooled sections of the loop are closely interrelated in their inlet conditions of the suspension. The influences of the modified Rayleigh number, the particle fraction, the modified Stefan number, and the modified subcooling factor on the heat transfer behavior, as well as the thermal efficacy of the PCM suspensions are elucidated. There could be a flow regime in the parametirc domain where heat transfer performance of the suspension circulation loop is significantly enhanced, due to contribution of the latent heat transport associated with melting/freezing of PCM particles.

Future work to address effects of the geometric parameters such as the aspect ratio; the lengths and locations of, as well as the relative height between the heated and cooled sections is definitely needed, which are necessary steps towards developing more reliable predictive tools for system design of a circulation loop containing PCM suspension.

This work has explored the feasibility and quantified the efficacy of incorporating the PC suspensions as the heat transfer enhancement medium in a natural circulation loop, which has not been examined previously.

The purpose of this paper is to first present the key features of hybrid numerical methods that enable cost-effective simulations of complex thermofluid systems, and then demonstrate the formulation and application of such a method.

A hybrid numerical method is formulated for simulations of a closed-loop thermosyphon operating with slurries of a micro-encapsulated phase-change material suspended in distilled water. The slurries are modeled as homogeneous mixtures, with inputs of effective properties and overall heat-loss coefficients. Combinations of an axisymmetric two-dimensional (2D) control-volume finite-element method and a segmented-quasi-one-dimensional (1D) model are used to achieve cost-effective simulations. Proper matching of the solutions at the interfaces between adjacent axisymmetric 2D and quasi-1D zones is ensured by incorporating and heuristically determining suitable lengths of pre- and post-heating (and also pre- and post-cooling) sections.

In the demonstration problem, which would strictly require full three-dimensional simulations of the fluid flow and heat transfer phenomena, the proposed hybrid 1D/2D numerical method produces results that are in very good agreement with those obtained in a complementary experimental investigation.

The hybrid numerical methods discussed in this paper allow cost-effective computer simulations of complex thermofluid systems. These methods can therefore serve as very useful tools for the design, parametric studies, and optimization of such systems.