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1

Impact of Clothing Size on Thermal Insulation – A Pilot Study

Młynarczyk Magdalena, Orysiak Joanna, Jankowski Jarosław, Prus Piotr

Fibres & Textiles in Eastern Europe

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2023

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Vol. 31, no. 1

1--8

EN

Thermal insulation may be influenced by the size of clothing and thus the volume of air gaps. The aim of this study was to determine the relationship between the size of outer wear clothing, and thus the indirect fit (the volume and size of air gaps), and thermal insulation in static and dynamic conditions. A set of underwear and two types of outerwear for workers of the energy sector and the chemical industry were selected for the study. Results showed that the value of thermal insulation (regardless of the type of outerwear) first increased with increasing clothing size.

2

Analysis of sound absorption performance of acoustic absorbers made of fibrous materials

Meissner Mirosław, Zieliński Tomasz G.

Vibrations in Physical Systems

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2022

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Vol. 33, nr 2

art. no. 2022205

EN

Absorbing properties of multi-layer acoustic absorbers were modeled using the impedance translation theorem and the Garai and Pompoli empirical model, which enables a determination of the characteristic impedance and propagation constant of fibrous sound-absorbing materials. The theoretical model was applied to the computational study of performance of single-layer acoustic absorber backed by a hard wall and the absorber consisting of one layer of absorbing material and an air gap between the rear of the material and a hard back wall. Simulation results have shown that a high thickness of absorbing material may cause wavy changes in the frequency relationship of the normal and random incidence absorption coefficients. It was also found that this effect is particularly noticeable for acoustic absorbers with a large thickness of air gap between the absorbing material and a hard back wall.

3

Influence of air gap on insulating properties of composite coatings on pipes for hot media transport

Posmyk Andrzej

Composites Theory and Practice

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2022

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R. 22, nr 1

54--57

EN

The shrinking resources of fossil fuels and the growing pollution of the environment have caused people to begin to search for possibilities of reducing energy losses. Vast possibilities in this area lie in industrial transport, called short distance transport, as well as in civil engineering. European Union authorities set limits for the emission of harmful pollutants and energy losses. That is why the laboratories of many research centres conduct research on composite insulating materials taking into account a nanotechnology and air gaps. The paper presents the results of research on steel pipelines used in the transport of hot media, insulated with PUR shaped materials covered with a composite coating with a polymer resin matrix containing an air gap between PUR and the pipe. Such a solution makes it possible to employ the reflective properties of selected materials, which, thanks to reflection of the heat flux, returns it to the source. An air gap with the thickness of 10 mm under the conditions of the conducted research, allows the heat losses of an steel industrial pipeline to be reduced by 7.6%.

PL

Kurczące się zasoby kopalnych surowców energetycznych oraz zwiększające się zanieczyszczenie środowiska sprawiły, że ludzie zaczęli szukać możliwości zmniejszenia strat energetycznych. Bardzo duże możliwości w tym zakresie tkwią w transporcie przemysłowym, nazywanym transportem krótkiego zasięgu, oraz w budownictwie. Organy Unii Europejskiej wprowadzają limity emisji szkodliwych zanieczyszczeń oraz strat energetycznych. Dlatego w laboratoriach wielu ośrodków naukowych są prowadzone badania kompozytowych materiałów izolacyjnych z uwzględnieniem nanotechnologii oraz szczelin powietrznych. W artykule przedstawiono wyniki badań stosowanych w transporcie gorących mediów izolowanych kształtkami PUR rur stalowych ze szczeliną powietrzną między rurą a PUR. Takie rozwiązanie pozwala wykorzystać zdolności refleksyjne wybranych materiałów, które dzięki odbijaniu strumienia ciepła zawracają go do źródła. Szczelina powietrzna o grubości 10 mm w warunkach przeprowadzonych badań pozwala zmniejszyć o 7,6% straty ciepła rurociągu przemysłowego.

4

Numerical Investigation of Heat Transfer in Garment Air Gap

Zhang Yijie, Jia Juhong

Autex Research Journal

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2022

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Vol. 22, no. 1

89--95

EN

This article aimed to study the characteristics and mechanisms of 3D heat transfer through clothing involving the air gap. A three-dimensional finite volume method is used to obtain the coupled conductive, convective, and radiative heat transfer in a body-air-cloth microclimate system. The flow contours and characteristics of temperature, heat flux, and velocity have been obtained. The reason for the high flux and temperature regions was analyzed. Computational results show that the coupled effect of the air gap and the airflow between the skin and garment strongly influences the temperature and heat flux distribution. There are several high-temperature regions on the clothing and high heat flux regions on the body skin because the conductive heat flux can cross through the narrow air gap and reach the cloth surface easily. The high-speed cooling airflow brings about high forced convective heat flux, which will result in the temperature increase on the upper cloth surface. The radiative heat flux has a strong correlation with the temperature gradient between the body and clothing. But its proportion in the total heat flux is relatively small.

5

Coupled circuit method applied to the detection of defects in a conductive multilayer device

Bouali Ferroudja, Mohellebi Hassane, Yousfi Ghania

Przegląd Elektrotechniczny

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2021

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R. 97, nr 3

106--112

EN

The work present the coupled circuit method applied to an eddy current nondestructive testing (EC-NDT) problems. The device is consisting on a conductive multilayer structure having an air gap (delamination), or a physical defect (lack of material). The purpose of the study is to identify the presence of the delamination when a physical defect can occur simultaneously. The use of Coupled Circuits Method permits to reduce the discretization to only the active parts without mesh air gap. The results obtained are compared to finite elements ones. A good agreement is observed between results. Interesting and useful conclusions are made.

PL

W pracy przedstawiono metodę obwodów sprzężonych zastosowaną do badań nieniszczących prądów wirowych (EC-NDT). Urządzenie składa się z przewodzącej konstrukcji ze szczeliną powietrzną (rozwarstwieniem) lub wadą fizyczną (brak materiału). Celem badania jest identyfikacja obecności rozwarstwienia, gdy jednocześnie może wystąpić wada fizyczna. Zastosowanie metody obwodów sprzężonych pozwala zredukować dyskretyzację tylko do aktywnych części bez siatkowej szczeliny powietrznej. Uzyskane wyniki porównuje się z wynikami elementów skończonych. Obserwuje się dobrą zgodność wyników.

6

Numerical Investigation of the Air Gap Distribution of Jackets with Different Fits and its Influence on Human Temperature

Awais Muhammad, Krzywinski Sybille, Kyosev Yordan

Fibres & Textiles in Eastern Europe

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2021

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Vol. 29, no. 6 (150)

77--86

EN

The air gaps underneath clothing have a great influence on the thermal regulation of the human body. The distribution of the air gaps depends on the shape of the human body as well as on clothing style, fit, and deformation properties. This paper reports on the influence of clothing fit on thermophysiological parameters of the human body through thermal simulation. Four different fits of jacket and a test person were considered for the investigation and for simulation purposes. The results of the simulation concluded that different thermal regulations of the human body were exhibited for different fits of the jacket, which is due to distinct air gaps between the human body and clothing for each fit of the jacket. This research work presents a fast method to predict the influence of clothing fit on thermal comfort, which is usually studied by a time-consuming, laborious method – the wear trial.

7

Experimental characterization of heat transfer coefficients for hot stamping AA7075 sheets with an air gap

Xiao Wenchao, Zheng Kailun, Wang Baoyu, Yang Xiaoming

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

429--438

EN

The heat transfer coefficient (HTC) is critical for hot stamping and in-die quenching. The air gap at interface is a dominant factor affecting the HTC, which is normally resulted from initial tooling clearance and thinning of deformed aluminum sheet. To precisely determine the HTCs under different air gaps, this research performed a comprehensive investigation on determining HTCs between an AA7075 blank and H13 tool steel. Hot stamping experiments were performed with different air gaps enabling HTC values were determined. Using the experimentally calibrated HTC, a finite-element model for hot stamping a door beam was established, which was successfully verified using the experimentation. The good predictions showed the reliability of the HTC values under different air gap conditions.

8

Determination of mineral surface energy using impact of rough topography

Can Muhammed Fatih, Çiftçi Caner

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 4

1002--1013

EN

While some of the studies on the functionalization of surfaces are still in theoretical phase, it is not possible to apply them on natural surfaces which already contain some irregularities. However, progress can be made with a mineral having significant purity, crystal homogeneity, and controllable surface workability for surface treatment operations. Therefore, in this study the effects of roughness on the surface energies of natural stones were investigated by selecting a sample with a distinctive color and metamorphic origin from Mugla, Turkey. First, sample surfaces were prepared using a polishing line with five different abrasives. Three-dimensional surface scans were then performed with ZYGONewView7100 optical-profilometer and ParkSystemAFM to identify the 3D roughness of the surfaces on two different scales (micro and nano) with SPIP-software. The micro average heights (S) of the produced surfaces ranged between 0.423-1.127 µm, nano-scale 0.0806-0.173 µm, while the surface roughness ratio (S_dr) between 33.7%-40.1%, and nano-scale 5.19%-18.5%. The contact angles of the samples were measured in the presence of pure water, formamide, and diiodomethane using AttensionTheta-tensiometer. Changes in surface energy were followed by Van Oss, Good-Chaudrey approach. Young, Wenzel, Cassie-Baxter contact angle theories were tested within these calculations. It was revealed that the inconsistency in solid phase energy could not be determined at this stage, but it could be regulated by modifying the Cassie-Baxter approach. Furthermore, the percentage of air packs likely to be below the water droplet not foreseen by the previous studies was calculated as 26% up to 35% air gap on the solid/water interface.

9

Effect of Air Gap Entrapped in Firefighter Protective Clothing on Thermal Resistance and Evaporative Resistance

He H., Yu Z.

Autex Research Journal

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2018

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Vol. 18, no. 1

28--34

EN

Heat and water vapor transfer behavior of thermal protective clothing is greatly influenced by the air gap entrapped in multilayer fabric system. In this study, a sweating hot plate method was used to investigate the effect of air gap position and size on thermal resistance and evaporative resistance of firefighter clothing under a range of ambient temperature and humidity. Results indicated that the presence of air gap in multilayer fabric system decreased heat and water vapor transfer abilities under normal wear. Moreover, the air gap position slightly influenced the thermal and evaporative performances of the firefighter clothing. In this study, the multilayer fabric system obtained the highest thermal resistance, when the air space was located at position B. Furthermore, the effect of ambient temperature on heat and water vapor transfer properties of the multilayer fabric system was also investigated in the presence of a specific air gap. It was indicated that ambient temperature did not influence the evaporative resistance of thermal protective clothing. A thermographic image was used to test the surface temperature of multilayer fabric system when an air gap was incorporated. These results suggested that a certain air gap entrapped in thermal protective clothing system could affect wear comfort.

10

Improvement of solenoid valve performance by axial slots inserted in the armature

Goraj R.

Engineering Transactions

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2017

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Vol. 65, iss. 2

269--287

EN

The article presents numerical investigations of the influence of axial slots inserted in the armature of a solenoid valve (SV) on the magnetic and frictional force acting on the armature during its movement. The numerical computations were performed using the method of finite differences. The computational room of the magnetic solution was the radial air gap of a SV. In the case of the fluid mechanical solution the computation room was the oil film. Both of these rooms were functions of the circumferential position of the armature. These computational rooms were transformed to the co-ordinate system in each they get a rectangle. This transformation was performed by means of the Laplace operator derived using a function shoal and the differential geometry. The computed distributions of magnetic energy density in the radial air gap and the magnitude of the magnetic flux density on the side surface of the eccentrically positioned armature in the magnet yoke were presented and discussed. These distributions in the case of both slotted and non-slotted armature were visualised in the transformed co-ordinate systems and compared to one another. Also the distribution of the oil velocity in the oil film and the distribution of the shear stress vector at two different temperatures were shown in figures.

11

Computer Simulation of the Solidification Process Including Air Gap Formation

Skrzypczak T., Węgrzyn-Skrzypczak E., Sowa L.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 4

147--150

EN

The paper presents an approach of numerical modelling of alloy solidification in permanent mold and transient heat transport between the casting and the mold in two-dimensional space. The gap of time-dependent width called "air gap", filled with heat conducting gaseous medium is included in the model. The coefficient of thermal conductivity of the gas filling the space between the casting and the mold is small enough to introduce significant thermal resistance into the heat transport process. The mathematical model of heat transport is based on the partial differential equation of heat conduction written independently for the solidifying region and the mold. Appropriate solidification model based on the latent heat of solidification is also included in the mathematical description. These equations are supplemented by appropriate initial and boundary conditions. The formation process of air gap depends on the thermal deformations of the mold and the casting. The numerical model is based on the finite element method (FEM) with independent spatial discretization of interacting regions. It results in multi-mesh problem because the considered regions are disconnected.

12

Measurement of the dielectric strength of air in the non uniform field

Fedorowicz P.

Zeszyty Naukowe. Elektryka / Politechnika Opolska

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2014

|

z. 70

19-20

EN

This paper presents a typical power setup and obtained results of the corona inception voltage, spark discharge voltage and breakdown voltage measurements using three different air gap arrangements characterized by a strong non uniform field.

13

The Influence of the Air Gap on the Characteristics of the Double-Shielded Microstrip Delay Devices

Mikucionis S., Urbanavicius V., Gurskas A., Krukonis A.

Przegląd Elektrotechniczny

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2014

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R. 90, nr 6

275--279

EN

A double-shielded microstrip (DSM) device is made of conventional microstrip device and by mounting additional shielded dielectric plate on top of it. The resulting structure is similar to the strip line, but there is a significant difference – a thin air gap that is equal to the thickness of the microstrip. The thickness of this air gap can become uncontrollable in the device manufacture process. In this paper the influence of thin air gap on the electrical parameters of DSM devices such as: microstrip line, coupled lines, multiconductor line, and meander delay line is investigated.

PL

W podwójnie ekranowanym mikropasku (DSM) układu opóźniającego DDs dodano dodatkową warstwę dielektryczną. Cienka szczelina powietrzna ma grubość paska. Ta szczelina może być trudna do kontrolowania w procesie produkcji. W artykule analizowano wpływ szczeliny powietrznej na parametry układu DSM.

14

Cylindrical double air gap motor for aerial applications

Kowalczyk M., Vezzini A., Grzesiak L.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 1a

25--28

EN

The authors describe various constructions of high torque density motors for electrical drive system to small airplane. There were also proposed projects of motors with dual stator and dual rotor for aerial applications. Further, there was also presented the comparison of parameters between motors with dual air-gap, with inner stator and with outer stator.

PL

Autorzy opisują konstrukcje silników o wysokej gęstości momentu dla elektrycznego systemu napędu do małego samolotu. Zamieszczono przykładowe projekty silników z podwójnym statorem i podwójnym rotorem dla zastosowań lotniczych. Porównano parametry silników z podówjną szczeliną z silnikami w wykonaniu z zewnętrznym oraz wewnętrznym stojanem.

15

Wpływ braku współosiowości części czynnej i biernej sprzęgła magnetycznego na obciążenia wału i łożyskowania

Pilch Z., Kowol P., Bizoń K., Sochacki P.

Modelowanie Inżynierskie

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2013

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T. 18, nr 49

52--57

PL

Sprzęgła stanowią jeden z istotnych elementów układów przeniesienia napędu. W najprostszych rozwiązaniach spełniają tylko funkcję łączenia elementów układów napędowych. Osiągnięcia inżynierii sprawiły, że na przestrzeni dziesięcioleci opracowano wiele rozwiązań sprzęgieł o bardziej złożonych konstrukcjach i bardziej rozbudowanych cechach funkcjonalnych. Aktualnie niektóre rozwiązania sprzęgieł są nie mniej złożone niż łączone przez nie elementy systemu przeniesienia momentu i źródeł tegoż momentu. W artykule przedstawiono wyniki symulacji komputerowych dla układu przeniesienia napędu ze sprzęgłem magnetycznym (sprzęgłem z magnesami trwałymi). Charakterystyki kątowe momentu oraz sił promieniowych, będących efektem niewyosiowania części czynnej i biernej sprzęgła wyznaczono na drodze obliczeń polowych i częściowo zweryfikowano poprzez pomiary na stanowisku badawczym.

EN

In the paper the magnetic clutch with permanent magnets is described. The magnetic field model of the clutch and the calculations made using the model are presented. The calculations take into account the misalignment of driving and driven members of the clutch. The results of the calculations are the characteristics of clutching torque and radial force vs. angle of rotation. The results of calculations are compared with measurement results. At the end of the paper the analysis of influence of described radial force on the shaft and bearing system is carried out.

16

Problemy z wyliczaniem momentu obrotowego w szczelinie powietrznej przy wykorzystaniu metody elementów skończonych

Szewczyk K.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 12b

87-88

PL

Artykuł przedstawia problemy związane ze stosowaniem gotowego oprogramowania do obliczeń zagadnień związanych z silnikami elektrycznymi z użyciem Metody Elementów Skończonych. Na przykładzie oprogramowania Ansys, Flux, FEMM można wykazać, że przy wyborze niewłaściwych dróg całkowania oraz opcji programu można uzyskać różne wyniki. Autorzy dokonali obliczeń momentu silnika z magnesami stałymi. Różne drogi całkowania momentu statycznego silnika pokazały różnice obliczanych wielkości. Wyniki przedstawiono w artykule.

EN

In the paper some problems with computing of rotating torque in any motor with an air gap has been presented. It is very important the path of integration. It is possible to show that choosing different path we can have many different results. In the simulations for peramnent magnet motor static torque was dependent on the path of integration. All simulations for computing flux density, forces and torques have been peformed by the programs Ansys Maxwell, Flux 2D and FEMM. The result are presented as a diagram variability of results depending on the path of integration.

17

Wpływ grubości szczeliny powietrznej na charakterystyki statyczne silnika SRM

Bogusz P., Korkosz M., Prokop J.

Napędy i Sterowanie

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2011

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R. 13, nr 6

116-121

PL

Współczesne układy napędowe przeznaczone do sprzętu AGD wymagają stosowania silników elektrycznych umożliwiających regulację prędkości obrotowej w szerokim zakresie i pracujących jednocześnie z jak największą sprawnością. Dodatkowym kryterium jest minimalizacja kosztów takiego układu napędowego. Wiele obecnie produkowanych układów napędowych spełnia częściowo te wymagania. Klasyczne silniki komutatorowe powszechnie stosowane w sprzęcie AGD umożliwiają regulację prędkości obrotowej w szerokim zakresie, są relatywnie w miarę tanie w produkcji masowej, ale są stosunkowo zawodne i sprawność takich napędów jest niezadowalająca. Silniki z magnesami trwałymi (BLDC) oferują znacznie większą sprawność przetwarzania energii w szerokim zakresie zmian prędkości. Trwałość takiego rozwiązania znacznie przewyższa maszynę komutatorową, w której zawsze po pewnym czasie następuje zużycie szczotek lub uszkodzenie zestyku szczotka-komutator. Natomiast wadą układów napędowych z silnikami z magnesami trwałymi jest zmiana właściwości silnika związana z procesem tzw. starzenia się magnesu trwałego oraz stosunkowo duża cena z uwagi na konieczność zastosowania magnesów stałych.

EN

In the article we discuss the influence of an air-gap thickness on the switched reluctance motor with 6/4 configuration static characteristics. This motor has been projected for household equipment purpose and it is characterized by non-symmetrical construction of magnetic circuit. In the work we present field computation results of motor magnetic circuit tor particular changes of air-gap thickness range for two different (because of non-symmetrical construction) motor phases. There is also presented dependences of mean value of motor torque versus current on air-gap thickness changes for two different phases. We present laboratory research results of self-inductances windings profile estimation versus rotor angle tor few cases of motor air-gap thickness.

18

Model for Predicting the Effect of an Air Gap on the Heat Transfer of a Clothed Human Body

Zhang Z. X., Wang Y., Li J.

Fibres & Textiles in Eastern Europe

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2011

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Vol. 19, no. 4 (87)

105--110

EN

Considering a clothing system consists of the human body, an air gap layer under the clothing as well as a fabric layer and boundary layer adjacent to the fabric, heat transfer from the skin to the environment is influenced by human body thermoregulation, the air gap, the fabric and environmental conditions. Based on Stolwijk’s 25-node thermoregulatory model, a new mathematical model was developed to include the sensible and latent heat transfer through the air gap, fabric layer and boundary layer adjacent to the fabric. To quantify the effect of the air gap on human body heat transfer, a 3D human body scanner was utilised to measure the air gap thickness of five experimental garments of increasing chest circumference. The model can be used to predict the apparent clothing temperature and heat loss from the human body when people are dressed in differently sized clothing.

PL

Analizowano model ubioru, w którym znajduje się warstwa powietrza pomiędzy ciałem a kolejnymi warstwami ubioru. Analizowano przepływ strumienia ciepła z ciała człowieka do otoczenia uzależnionego od przemiany energetycznej oraz warunków otoczenia. W oparciu o model Stolwijk 25 opracowano nowy model matematyczny określający przepływ ciepła przez warstwy powietrza oraz graniczne warstwy odzieży. Dla ilościowego określenia strumienia ciepła przepływającego przez szczelinę powietrzną oceniono jej rozmiary i konfiguracje za pomocą systemu skanującego 3D dla określonego typu odzieży. Model może być zastosowany dla przewidywania strat ciepła i temperatury zewnętrznej ubioru.

19

Study of heat transfer through multilayer clothing assemblies: a theoretical prediction

Das A., Alagirusamy R., Kumar P.

Autex Research Journal

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2011

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Vol. 11, no. 2

54--60

EN

It has long been recognised that heat transfer through clothing is a main constraint to the comfort properties of clothing. The present work relates to the development of a mathematical model for the prediction of heat transmission through multilayer clothing with air in between two successive layers of fabric in a multilayered clothing assembly. A mathematical model was developed using general equations of heat transfer through porous media and was validated using experimental results. A series of multilayered fabric assemblies were created with different combinations of fabric layers and air gaps of different thicknesses. The predicted total thermal resistance of these fabric assemblies was obtained from the model and the values were compared with experimental results. The total thermal resistance of these fabric assemblies were measured using a guarded hot plate for validating the model. Fairly good correlations between the predicted and experimental values of thermal resistance were observed.

20

A Study of Interaction of Ultrasonic and Optical Wave in Optical Fiber Using the Air Gap

Gudra T., Muc S.

Archives of Acoustics

|

2011

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Vol. 36, No. 3

613-628

EN

There exist some possibilities for simultaneous delivery of laser radiation and ultrasounds of low frequency and high intensity: introducing ultrasound oscillations in the optical fiber by the rigid connection of the fiber to the vibrating element and non-contact influence of the ultrasonic wave on the laser beam. The article presents the results of Matlab simulations and experimental studies of influence of the ultrasonic wave on the laser beam. A role of the air gap, and its influence on laser- ultrasonic transmission in optical fiber was examined. Advantages and disadvantages of both solutions of interaction of ultrasonic and optical waves in, e.g., surgical applications are discussed.