Yehu Lu

Structure and performance ofBombyx mori silk modified with nano-TiO2 and chitosan

Bombyx mori (B. mori) silk was modified with the nano-TiO2 and chitosan dispersion system by the crosslinking reactions of citric acid (CA) and maleic anhydride (MA). The average size of the nano-TiO2 particles in the aqueous dispersion system was 36.7 nm. The scanning electron microscopy (SEM) micrographs showed that the nano-TiO2 particles were spherical and homogeneously dispersed in the dispersion system, and the surface ofB. mori silk fiber treated with the nano-TiO2 and chitosan dispersion system was rougher than that of the untreated one. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) Spectrometry indicated that the crystallinity of theB. mori silk fiber increased after treatment. It was also found that the nano-TiO2 and chitosan contributed to significantly enhance the mechanical properties including breaking strength, breaking elongation, initial modulus, rupture work, and elastic recovery property of theB. mori silk fiber. The wrinkle-resistant performance of the treatedB. mori silk fabrics was also greatly improved.

A novel personal cooling system (PCS) incorporated with phase change materials (PCMs) and ventilation fans: An investigation on its cooling efficiency.

Personal cooling systems (PCS) have been developed to mitigate the impact of severe heat stress for humans working in hot environments. It is still a great challenge to develop PCSs that are portable, inexpensive, and effective. We studied the performance of a new hybrid PCS incorporating both ventilation fans and phase change materials (PCMs). The cooling efficiency of the newly developed PCS was investigated on a sweating manikin in two hot conditions: hot humid (HH, 34°C, 75% RH) and hot dry (HD, 34°C, 28% RH). Four test scenarios were selected: fans off with no PCMs (i.e., Fan-off, the CONTROL), fans on with no PCMs (i.e., Fan-on), fans off with fully solidified PCMs (i.e., PCM+Fan-off), and fans on with fully solidified PCMs (i.e., PCM+Fan-on). It was found that the addition of PCMs provided a 54∼78min cooling in HH condition. In contrast, the PCMs only offered a 19-39min cooling in HD condition. In both conditions, the ventilation fans greatly enhanced the evaporative heat loss compared with Fan-off. The hybrid PCS (i.e., PCM+Fan-on) provided a continuous cooling effect during the three-hour test and the average cooling rate for the whole body was around 111 and 315W in HH and HD conditions, respectively. Overall, the new hybrid PCS may be an effective means of ameliorating symptoms of heat stress in both hot-humid and hot-dry environments.

Analysing Performance of Protective Clothing upon Hot Liquid Exposure Using Instrumented Spray Manikin

Hot liquid hazards existing in work environments present a common risk in workplace safety in numerous industries. In this study, a newly developed instrumented manikin system was used to assess the protective performance provided by protective clothing against hot liquid splash. The skin burn injury and its distribution for the selected clothing system were predicted and the effects of clothing design features (fabric properties and garment size) on protective performance were investigated. The air gap size and distribution existing between protective clothing and human skin were characterized using 3D body scanning, and their relation to skin burn injury was identified. The mechanism associated with heat and mass transfer under exposure to hot liquid splashes was discussed. The findings provided technical bases to improve the performance of protective clothing. For protective clothing design, minimizing mass transfer through clothing system is very important to provide high performance. Keeping the air gap between the garment and the human body is an essential approach to improve thermal performance. This can be achieved by proper design in size and fit, or applying functional textile materials.

A novel approach for fit analysis of thermal protective clothing using three-dimensional body scanning

The garment fit played an important role in protective performance, comfort and mobility. The purpose of this study is to quantify the air gap to quantitatively characterize a three-dimensional (3-D) garment fit using a 3-D body scanning technique. A method for processing of scanned data was developed to investigate the air gap size and distribution between the clothing and human body. The mesh model formed from nude and clothed body was aligned, superimposed and sectioned using Rapidform software. The air gap size and distribution over the body surface were analyzed. The total air volume was also calculated. The effects of fabric properties and garment size on air gap distribution were explored. The results indicated that average air gap of the fit clothing was around 25-30xa0mm and the overall air gap distribution was similar. The air gap was unevenly distributed over the body and it was strongly associated with the body parts, fabric properties and garment size. The research will help understand the overall clothing fit and its association with protection, thermal and movement comfort, and provide guidelines for clothing engineers to improve thermal performance and reduce physiological burden.

Clothing resultant thermal insulation determined on a movable thermal manikin. Part II: effects of wind and body movement on local insulation

Part II of this two-part series study was focused on examining the effects of wind and body movement on local clothing thermal insulation. Seventeen clothing ensembles with different layers (i.e., 1, 2, or 3 layers) were selected for this study. Local thermal insulation with different air velocities (0.15, 1.55, and 4.0xa0m/s) and walking speeds (0, 0.75, and 1.17xa0m/s) were investigated on a thermal manikin. Empirical equations for estimating local resultant clothing insulation as a function of local insulation, air velocity, and walking speed were developed. The results showed that the effects of wind and body movement on local resultant thermal resistance are complex and differ distinctively among different body parts. In general, the reductions of local insulation with wind at the chest, abdomen, and pelvis were greater than those at the lower leg and back, and the changes at the body extremity such as the forearm, thigh, and lower leg were higher than such immobile body parts as the chest and back. In addition, the wind effect interacted with the walking effect. This study may have important applications in human local thermal comfort modeling and functional clothing design.

Effects of moisture content and clothing fit on clothing apparent ‘wet’ thermal insulation: A thermal manikin study

‘Wet’ thermal insulation, defined as the thermal insulation when clothing gets partially or fully wet, is an important physical parameter to quantify clothing thermal comfort. As the water/sweat gradually occupies the intra-yarn and inter-yarn air voids of the clothing material, the clothing intrinsic thermal insulation will be diminished and, hence, contribute to the loss of total insulation. In cold conditions, a loss in total thermal insulation caused by sweating may result in an inadequate thermal insulation to keep thermal balance and eventually leads to the development of hypothermia and cold injuries. Therefore, it is imperative to investigate the effect of clothing fit and moisture content on clothing ‘wet’ insulation. In this study, the ‘wet’ thermal insulation of three two-layer clothing ensembles was determined using a Newton thermal manikin. Four levels of moisture content were added to the underwear: 100, 200, 500 and 700u2009g. The clothing apparent ‘wet’ thermal insulation under different testing scenarios was calculated and compared. A third-degree polynomial relationship between the reduction in ‘wet’ thermal insulation and the moisture content added to underwear was obtained. Further, it was evident that the clothing fit has a minimal effect on the apparent ‘wet’ thermal insulation. The findings may have important applications in designing and engineering functional cold weather clothing and immersion suits.

Effect of sweating set rate on clothing real evaporative resistance determined on a sweating thermal manikin in a so-called isothermal condition ( T manikin = T a = T r )

The ASTM F2370 (2010) is the only standard with regard to measurement of clothing real evaporative resistance by means of a sweating manikin. However, the sweating set-point is not recommended in the standard. In this study, the effect of sweating rate on clothing real evaporative resistance was investigated on a 34-zone “Newton” sweating thermal manikin in a so-called isothermal condition (Tmanikinu2009=u2009Tau2009=u2009Tr). Four different sweating set rates (i.e., all segments had a sweating rate of 400, 800, 1200xa0ml/hr∙m2, respectively, and different sweating rates were assigned to different segments) were applied to determine the clothing real evaporative resistance of five clothing ensembles and the boundary air layer. The results indicated that the sweating rate did not affect the real evaporative resistance of clothing ensembles with the absence of strong moisture absorbent layers. For the clothing ensemble with tight cotton underwear, a sweating rate of lower than 400xa0ml/hr∙m2 is not recommended. This is mainly because the wet fabric “skin” might not be fully saturated and thus led to a lower evaporative heat loss and thereby a higher real evaporative resistance. For vapor permeable clothing, the real evaporative resistance determined in the so-called isothermal condition should be corrected before being used in thermal comfort or heat strain models. However, the reduction of wet thermal insulation due to moisture absorption in different test scenarios had a limited contribution to the effect of sweating rate on the real evaporative resistance.

Evaluation of a hybrid personal cooling system using a manikin operated in constant temperature mode and thermoregulatory model control mode in warm conditions

In this study, the cooling effect of a portable hybrid personal cooling system (PCS) was investigated on a sweating manikin operated in the constant temperature (CT) mode and the thermoregulatory model control (TMC) mode. Both dry (i.e., no sweating) and wet manikin tests (i.e., sweating) were performed in the CT mode in a warm condition (30℃, 47% relative humidity (RH), air velocity vau2009=u20090.4u2009m/s). For the TMC mode, two case studies were simulated: light work condition (30℃, 47% RH, air velocity vau2009=u20090.15u2009m/s, duration: 60u2009min, metabolic rate: 1.5 METs) and construction work condition (30℃, 47% RH, vau2009=u20091.0u2009m/s, 40u2009min exercise [5.5 METs] and 20u2009min rest [1.2 METs]). Four test scenarios were selected: fans off with no phase change materials (PCMs) (i.e., Fan-off, the Control), fans on with no PCMs (i.e., Fan-on), fans off with fully solidified PCMs (i.e., PCM+Fan-off) and fans on with fully solidified PCMs (i.e., PCM+Fan-on). Under the dry condition, the cooling rate in PCM+Fan-off during the initial stage (e.g., 55 and 50u2009W for the first 15u2009min and 20u2009min, respectively) was higher than that in Fan-on (i.e., 45u2009±u20091u2009W); under the wet condition, the cooling rate in PCM+Fan-off (e.g., 45u2009W for 10u2009min) was much lower than that in Fan-on (i.e., 282u2009±u20091u2009W). The hybrid PCS (i.e., PCM+Fan-on) provided a continuous strong cooling effect. Simulation results indicated that ventilation fans or PCMs alone could provide sufficient cooling while doing light work. For the intensive work condition, the PCS in all three scenarios (i.e., PCM+Fan-off, Fan-on and PCM+Fan-on) exhibited beneficial cooling, and the hybrid PCS showed an optimized performance in alleviating heat strain during both exercise and recovery periods. It was thus concluded that the PCS could effectively remove body heat in warm conditions for moderate intensive activities.

Correction of the heat loss method for calculating clothing real evaporative resistance

In the so-called isothermal condition (i.e., Tair [air temperature]=Tmanikin [manikin temperature]=Tr [radiant temperature]), the actual energy used for moisture evaporation detected by most sweating manikins was underestimated due to the uncontrolled fabric skin temperature Tsk,fxa0(i.e., Tsk,f<Tmanikin). Thus, it must be corrected before being used to compute the clothing real evaporative resistance. In this study, correction of the real evaporative heat loss from the wet fabric skin-clothing system was proposed and experimentally validated on a Newton sweating manikin. The real evaporative resistance of five clothing ensembles and the nude fabric skin calculated by the corrected heat loss method was also reported and compared with that by the mass loss method. Results revealed that, depending on the types of tested clothing, different amounts of heat were drawn from the ambient environment. In general, a greater amount of heat was drawn from the ambient environment by the wet fabric skin-clothing system in lower thermal insulation clothing than that in higher insulation clothing. There were no significant differences between clothing real evaporative resistances calculated by the corrected heat loss method and those by the mass loss method. It was therefore concluded that the correction method proposed in this study has been successfully validated.

Effect of two sweating simulation methods on clothing evaporative resistance in a so-called isothermal condition

AbstractThe effect of sweating simulation methods on clothing evaporative resistance was investigated in a so-called isothermal condition (Tmanikinu2009n =u2009Tau2009=u2009Tr). Two sweating simulation methods, namely, the pre-wetted fabric “skin” (PW) and the water supplied sweating (WS), were applied to determine clothing evaporative resistance on a “Newton” thermal manikin. Results indicated that the clothing evaporative resistance determined by the WS method was significantly lower than that measured by the PW method. In addition, the evaporative resistances measured by the two methods were correlated and exhibited a linear relationship. Validation experiments demonstrated that the empirical regression equation showed highly acceptable estimations. The study contributes to improving the accuracy of measurements of clothing evaporative resistance by means of a sweating manikin.