Presentation on theme: "Thermal comfort of football dresses in dry and wet state Lubos Hes Technical University of Liberec Czech Republic"— Presentation transcript:
Thermal comfort of football dresses in dry and wet state Lubos Hes Technical University of Liberec Czech Republic e-mail: firstname.lastname@example.org
Football dresses history Since 1908: football belongs to an official Olympic sport Today: considered the most popular sport at all, due to its good financial accessibility There are 207 football associations in the World under the umbrella of FIFA Football empire: empire of peace, even in the period of wars and political disharmony Football dresses: serve to distin- guish the rival teams and empha- sise the team images. Fig. 2 Dress of L. Andrade during the match with Buenos Aires, 1910
Football dresses - composition Today, with so many football teams: it is not easy do design an original dress, especially when the dress structure is clearly defined and compulsory. Originally: all dresses made of cotton – see the national dress Uruguay of José Leandro Andrede from the twen- ties of 20. century. Onset of synthetic materials: at seventies of the last century Fig. 3 Permitted modern dresses should involve long sleeves
Primary positive property of cotton : pleasant handle, but did not compensate: the exceeding sweat sorption permanent cooling effect long time of drying high mass of the wet dress and increase of the dress dimensions.
At the beginning: polyamide (PAD) was used, but later was replaced by polyester (PES), due to its hydrophobicity, UV + abrasion resistance, high tenacity, excellent coloration etc. First PES coarse fibres: quite unpleasant in hand, causing skin irritation due to high bending rigidity (10 times higher then for same fineness cotton fibres). Sportsmen complained on allergy and had to use fine underwear. Today: prevailing PES microfibers knits exhibit good softness, no underwear is necessary. Modern dresses consist of different parts, where each satisfies specific function, according to its location on the body.
Modern design of performance garments (sport dresses): Higher price of garments with high added value, made of performance or smart fabrics, should be based on higher protection and comfort properties. Garment prototypes should be tested in terms of their protection and comfort parameters by means of new testing instruments, Testing of comfort properties of final products (dresses) should be non-destructive, to enable economical comparison of various products, here dresses
The biggest problem of known measuring methods: requirement on cutting of samples of given dimensions, which results in destruction of the garment. Strategy of the Dept. of textile Marketing of TU Liberec: to promote and in some cases to develop relatively cheap and user-friendly instruments, which measure the garment comfort properties without the necessity to destroy the garments. Also smaller dimensions of specimens reduce the testing costs.
Such instruments, in fu- ture, can be used also in large shopping centers and specialised shops, to enable the testing the basic comfort characteristics in front of the customer. As an example of such simple user friendly instrument, serves the PERMETEST instrument (by SENSORA)
Survey of comfort characteristics of fabrics and garments, which are tested Properties of textile fabrics and garments embrace both purely mechanical properties and heat / moisture transfer properties. Complex effect of these properties characterise comfort properties of fabrics. Properties, which involve the effect of fabric humidity on selected mechanical parameters along with the effect of deformation properties and contact force of garments on the users perception during the garment wearing we call sensorial properties.
More simple is the fabric hand or handle, generally perceived by hands, where from transfer properties just warm-cool feeling is involved. Heat/moisture transfer properties involve steady state and transient properties, which contribute to thermal equilibrium of human thermal engine - our body.
. Tactile (hand) characteristics of fabrics: Friction + profile Thickness + compressibility Bending + shearing stiffness (at low and large deformations) Elasticity, tenacity Warm-cool feeling (transient contact heat transfer)
Thermo-physiological comfort characteristics of fabrics+ garments: Steady-state local thermal insulation parameters (thermal resistance and conductivity) Steady-state total thermal resistance (including ventilation effects) Steady-state local and total moisture transfer parameters (evaporation resistance) Transient moisture transfer (moisture absorbtivity)
Determination of Water vapour permeability by means of the PERMETESTinstrument (non-gravimetric method with electric output) This instrument is the so called skin model, which simulates dry and wet human skin in terms of its thermal feeling and serves for determination of water vapour and thermal resistance of fabrics. If the instrument is used in laboratories with standard air conditions, then it offers reasonable precision of measurement. Results of measurement are expressed in units defined in the ISO Standard 11092. The instrument principle is following :
Slightly curved porous surface is moistened and exposed in a wind channel to parallel air flow of adjustable velocity. A tested sample is located on the wetted area of diameter about 80 mm. The amount of evaporation heat taken away from the active porous surface is measured by a special power sensing integrated system. The measurement time is very short – full signal is achieved within several minutes. The instrument body can be heated above the room temperature or kept at the room temperature to maintain the isothermal working conditions.
At the beginning of the measurement, the measuring head is covered by semi-permeable foil to keep the measured garment dry. Then, heat flow value q o without a sample is registered. In the next step, the full-size garment is inserted (without being cut to special shape) between the head and the orifice in the bottom of the channel. When the signal gets steady, the level of q s, which quantifies heat loses of wet measuring head covered by a sample, is registered. Both values then serve for calculation (made by a micro-PC) of the following parameters of garment water vapour permeability:
Relative water vapour permeability P is a non- standardized, but practical parameter (P = 100% presents the permeability of free measuring surface). It is given by the relationship P = 100 ( q s / q o ) [ % ] Water vapour resistance R et (as defined in ISO 11092) expresses the equation R et = (P m – P a ) (q v -1 - q o -1 ) [ m 2 Pa/W] The values P m and P a in this equation represent the water vapour saturate partial pressure in Pascals valid for ambient temperature t a and actual partial water vapour pressure in a laboratory.
The instrument also measures thermal resistance R et [m 2 K/W] of garments, similarly as given by the ISO standard 11092. How the sample dimensions affect the measurement precision? Is here any effect of moisture conduction along the sample surface resulting in (incorrectly) higher water vapourpermeability, then in case of the cut sample? Systematic measurements of relative water vapour permeability on samples with varying dimensions proved, that the effect of sample dimensions (diameter) is not very strong - Variation coefficients in most cases did not exceed 5%, which confirms good measurement precision for this kind of measurement.
Warm - cool feeling and Moisture absorbtivity evaluation by means of the ALAMBETA tester The apparatus used in this study enables the measurement of thermal conductivity, thermal absorbtivity, thermal resistance and sample thickness.
Thermal absorbtivity b of fabrics was introduced by L. Hes (1987) to characterise thermal feeling (heat flow level) during short time contactof human skin with the fabric surface. For time of thermal contact τ between the human skin and the fabric shorter then several seconds, the measured fabric can be simplified into semi-infinite homogenous mass with thermal capacity ρc [J/m 3 ] and initial temperature t 2. Unsteady temperature field between the human skin (with temperature t 1 ) and fabric with respect to of boundary conditions offers a relationship, which enables to determine the heat flow q [W/m2] course passing through the fabric: q = b (t 1 – t 2 ) / (π τ ) 1/2, b = ( λρc ) 1/2 [Ws 1/2 /m 2 K] where ρc [J/m3] is thermal capacity of the fabric and the term b presents thermal absorbtivity of fabrics.
The higher is thermal absorbtivity of the fabric, the cooler is its feeling. In the textile praxis this parameter ranges from 20 Ws 1/2 /m 2 K for fine nonwoven webs to 600 Ws 1/2 /m 2 K for heavy wet fabrics. Thermal resistance R depends on fabric thickness h and thermal conductivity λ: R = h/λ [m 2 K/W]
Computer-controlled instrument ALAMBETA for fast measurement of thermal insulation and thermal-contact properties of compressible materials like textile fabrics
Experimental part There are 4 manufacturers of football dresses in Czech Republics : Alea Sportswear, (Písek), Jadberg (Napajedla), LoMa sport (Broumov), Panartex (Prague). In this research 6 dresses of different design and composition were studied: Manchester United- chest +armpit + belly Munique dress 1860 of 1988 Czech National dress Red dress Sport Club Kladno, Czech Republic Blue dress
Testing procedure and experimental results The dresses were measured 4 times in dry state and thermal absorbtivity was measured at the next to skin surface in wet state also. The wet measurement simulated the so called sweating impulse, depending in application of 0,3 water with 1% of detergent in to the measuring area centre. The proper measurement was carried out after 1 minute delay, to get rid of the effect of moistening heat. After 1 minute also the wet spot diameter was determined.
Thermal conductivity λ 53,3 52,1 45,5 44,8 39,439,338,5 36,8 25 30 35 40 45 50 55 60 65 λ [mW/m.K] Red dress of 1988 Blue Dress of 1970 Munique of 1999 Manchest. U.(chest) SC Kladno of 2006 Manch. U. (armpit) Czech nat. dress Manchester U.(belly)
r [m 2 K/W] Thermal resistance r 18,3 15 11,1 10,810,7 9,4 8,2 7,1 0 2 4 6 8 10 12 14 16 18 20 r Red dress of 1988 Blue dress of 1970 Munique dress of 1999 Manchester U.(belly) SC Kladno of 2006 Czech Rep. training Manchester U. armpit Manchester U. chest
MUC CZN MUA MUB MUN RED SCK BLU Thermal absorbtivity values b [Ws 1/2 /m 2 K] in dry state (blue) and wet state (red)
Diameter of the wetted area (mm) 29 25 21 18 16 15 10 8 SC Kladno Blue dress of 1970 Manchester U.(belly ) Manchester U.(chest) Czech rep.training Red dress of 1988 Manch. U. armpit Munique 1860
Evaluation of results The oldest cotton dresses with highest thickness exhi- bits highest thermal resistance, but with the disadvan- tage of high square mass. High thermal insulation is here also the disadvantage. The lowest thermal insulation exhibits the Manchester United dress. As regards the water vapour permeability, the highest levels ofers the Manchster United dress made of Coolmax (PES), whereas the lowest levels exhibit the two old cotton dresses.
Thermal absorbtivity The MU PES dress exhibited at some body parts (chest, armpit) the required coolest feeling, provided that after the cooling period the fabric gets dry rapidly and protects the body against post treatment chill. Unfortunately, the cooling effect on the back has not been measured. Thanks to the rib structure, the warmest feeling showed the cotton dresses, despite the reduced distribution of moisture along the fabric plane. However, cotton fabrics turn dry after quite a long time, which is one of their most serious disadvantages.
Conclusions This study presents the first part of the systematic experimental research of comfort properties of football dresses, focused on determination of their dry thermal properties and thermal absorbtivity after single sweating impulse. From the presented results follows, that thermal comfort properties of the dresses both in dry state (thermal resistance) and wet state (thermal absorbtivity) vary substantially according to dress composition and structure (design). Also water vapour permeability of the studied dresses depends strongly on their composition. In the next step, also the effect of moisture on thermal insulation properties and water vapour permeability will be systematically investigated.
Acknowledgements The Czech Ministry of Education Supported Mr. Paul Smith, designer MU partially this study within the Grant of SPECIFIC RESEARCH and the author also thanks to Mr. Lukáš Killar for his experimental work (BSc, 2007)