Anna Bogdan

Assessment of Thermal Comfort Using Personalized Ventilation

Personal ventilation (PV) is a solution that enables a user to attain full satisfaction from the indoor conditions. It is also a system that—if properly designed—can contribute to the energy efficiency in buildings (i.e., by supplying considerably lower amounts of fresh and treated air indoors). In order to test possible variants of local heating and cooling of a human body by the PV system, a series of tests was conducted. The tests were performed on a thermal manikin and aimed to determine which type of setting (i.e., direction of air supply and temperature of supplied air) causes required cooling/heating of the manikins surface. The tests were performed with a thermal manikin that helped to determine an equivalent temperature (teq ) of the environment shaped by the PV system. The results revealed that in tests with the nude manikin the PV system decreased the teq value, irrespective of the selected variant of the test. When the manikin was clothed, teq would fall or rise depending on the temperature of supplied air. Tests with a nude manikin demonstrated that the cooling effect was conditioned by the velocity of air supplied from the PV system, rather than by the temperature of the supplied air. In this study, the main parameters affecting teq were thermal insulation of clothing used on the manikin and velocity of air around the manikin.

Opportunities and constraints of presently used thermal manikins for thermo-physiological simulation of the human body

Combining the strengths of an advanced mathematical model of human physiology and a thermal manikin is a new paradigm for simulating thermal behaviour of humans. However, the forerunners of such adaptive manikins showed some substantial limitations. This project aimed to determine the opportunities and constraints of the existing thermal manikins when dynamically controlled by a mathematical model of human thermal physiology. Four thermal manikins were selected and evaluated for their heat flux measurement uncertainty including lateral heat flows between manikin body parts and the response of each sector to the frequent change of the set-point temperature typical when using a physiological model for control. In general, all evaluated manikins are suitable for coupling with a physiological model with some recommendations for further improvement of manikin dynamic performance. The proposed methodology is useful to improve the performance of the adaptive manikins and help to provide a reliable and versatile tool for the broad research and development domain of clothing, automotive and building engineering.

Comparison of fabric skins for the simulation of sweating on thermal manikins

Sweating is an important thermoregulatory process helping to dissipate heat and, thus, to prevent overheating of the human body. Simulations of human thermo-physiological responses in hot conditions or during exercising are helpful for assessing heat stress; however, realistic sweating simulation and evaporative cooling is needed. To this end, thermal manikins dressed with a tight fabric skin can be used, and the properties of this skin should help human-like sweat evaporation simulation. Four fabrics, i.e., cotton with elastane, polyester, polyamide with elastane, and a skin provided by a manikin manufacturer (Thermetrics) were compared in this study. The moisture management properties of the fabrics have been investigated in basic tests with regard to all phases of sweating relevant for simulating human thermo-physiological responses, namely, onset of sweating, fully developed sweating, and drying. The suitability of the fabrics for standard tests, such as clothing evaporative resistance measurements, was evaluated based on tests corresponding to the middle phase of sweating. Simulations with a head manikin coupled to a thermo-physiological model were performed to evaluate the overall performance of the skins. The results of the study showed that three out of four evaluated fabrics have adequate moisture management properties with regard to the simulation of sweating, which was confirmed in the coupled simulation with the head manikin. The presented tests are helpful for comparing the efficiency of different fabrics to simulate sweat-induced evaporative cooling on thermal manikins.

Impact of Clothing, Breathing and Body Posture on the Shaping of a Thermal Plume above a Human

Abstract The impact of clothing, breathing and body posture on the thermal plume above a thermal manikin was investigated. Measurements of air velocity and temperature above the manikin were performed at four different heights above a sitting and a lying manikin. The results obtained from tests above the sitting manikin show an inverse proportion between the thermal insulation of clothing and the air velocity in the thermal plume. Air velocity in the thermal plume with the breathing function switched on equalled 90–98% of the values obtained for non-breathing experiments. The use of the breathing function caused an asymmetry of the thermal plume above the manikin’s knees. The presence of an area of increased velocity and temperature originating from the breathing process was observed (“warm cloud”). Results obtained from the measurements above a lying manikin confirmed the impact of thermal insulation on the thermal plume, however a reverse relationship was observed at the lowest measurement height with the breathing function on. The existence of three areas influencing the thermal plume was revealed - head, torso, feet. For the lying manikin the air velocity increased by 6–13% when the breathing function was used in relation to non-breathing tests.

Thermal Sensations of Surgeons During Work in Surgical Gowns

Standards for surgical procedures and medical clothing, designed for use in the operating theatre, have been gradually developed with the progress in science and technology. Standard No. EN 13795:2011, determining the requirements concerning materials for production of surgical gowns, was introduced in 2003. It concerns, e.g., resistance to microbial penetration. Little attention is given to thermal comfort, even though it is well known that thermal discomfort can have an adverse effect on the quality and efficiency of work. During a real-life test and laboratory tests, 2 male surgeons and 8 male volunteers were asked to describe their subjective sensations before and after work. The results of the real-life test and the laboratory tests are comparable. They show a clear lack of thermal comfort when medical clothing designed for the operating theatre is used.

Case Study Assessment of Local and General Thermal Comfort by Means of Local Skin Temperature

Abstract The temperature of human skin is determined by the human thermoregulatory system which reacts to changes in the thermal balance between a human body and the environment. For this reason, skin temperature can be used as the quickest predictor for the assessment of local comfort or discomfort. This paper presents the outcome of case study experiments carried out to determine which of the skin temperature measurement points (specified in accordance with the ISO 9886 standard) can be used to determine local and general thermal comfort. To this end, experiments were conducted using 14 volunteers who were asked to wear the following three types of clothing ensembles: winter clothing, summer clothing and underwear only (i.e. semi-nude). Thermal conditions were achieved using a climatic chamber over the temperature range between 15 and 35 oC. On the basis of the conducted experiments it was determined that the highest correlation between thermal sensation and skin temperature occurs for measurements on the forehead, chest and abdomen (R2>0.9). Moreover, the results provided the basis for deriving linear equations characterizing a relationship between thermal sensation responses and skin temperature. The results of these experiments will help in the setting for optimum performance of ventilation and air-conditioning systems.

The Effect of Personalized Ventilation on Work Productivity

Abstract As compared to mixing ventilation systems, the personalized ventilation system (PV) can help to create a healthy and comfortable working environment with a simultaneous reduction of energy consumption. This latter aspect should be of particular significance for employers and investors who bear responsibility for office space conditions. The parameter which is of paramount interest for this group of people is productivity as it translates into a company’s revenue. Hence, the objective of the study presented in this article was to determine which conditions of air supply, supply temperature and room temperature would have optimum impact on an occupant’s ability to work most productively. These parameters were assessed by the means of an objective concentration test, a subjective test for diagnosing mental fatigue and mood, and a subjective test to assess work productivity. The results of the tests showed that for optimum user comfort and productivity, the air supplied from a PV system should be directed towards the face, both in the case of space heating and cooling. For winter conditions, the greatest number of positive responses, given by volunteers with regard to fatigue, mood and work productivity was a PV supply of air to the face or ankles at a temperature of 22 oC, combined with an ambient room temperature of 20 oC. For summer the largest number of positive responses concerning fatigue and mood as well as work productivity was for air supplied at face level at a temperature of 24 oC and at an ambient room temperature of 26 oC.

Methods of Estimating the Effect of Integral Motorcycle Helmets on Physiological and Psychological Performance

Abstract This article proposes a method for a comprehensive assessment of the effect of integral motorcycle helmets on physiological and cognitive responses of motorcyclists. To verify the reliability of commonly used tests, we conducted experiments with 5 motorcyclists. We recorded changes in physiological parameters (heart rate, local skin temperature, core temperature, air temperature, relative humidity in the space between the helmet and the surface of the head, and the concentration of O2 and CO2 under the helmet) and in psychological parameters (motorcyclists ‘ reflexes, fatigue, perceptiveness and mood). We also studied changes in the motorcyclists’ subjective sensation of thermal comfort. The results made it possible to identify reliable parameters for assessing the effect of integral helmets on performance, i.e., physiological factors (head skin temperature, internal temperature and concentration of O2 and CO2 under the helmet) and on psychomotor factors (reaction time, attention and vigilance, work performance, concentration and a subjective feeling of mood and fatigue).