Adélio Rodrigues Gaspar

Measurements of clothing insulation with a thermal manikin operating under the thermal comfort regulation mode: comparative analysis of the calculation methods

The present work is dedicated to a comparative analysis of calculation methods about clothing insulation with a thermal manikin operating under the thermal comfort regulation mode. The serial, global, and parallel calculation methods are considered and the thermal insulation results for garments (30) and ensembles (9) are discussed. The serial and parallel methods presents the higher and lower values, respectively, and the differences were sometimes significant. Considering the results for the effective thermal insulation, the mean values of the relative differences between the serial and global methods were 25.7% for the daily wear garments, 45.2% for the cold protective garments and 38.5% for the ensembles. The corresponding mean values for the global and parallel methods were 8.7, 15.8, and 10.5%, respectively. Since any uneven clothing insulation is to be expected as a source of error, particular care must be required when the calculation methods deal with cold protective clothing.

Analysis of sensible heat exchanges from a thermal manikin

The present work is dedicated to the analysis of dry heat exchanges as measured by a thermal manikin placed in still air. We believe that the understanding of some fundamental aspects governing fluid flow and heat transfer around three-dimensional bodies such as human beings deserves appropriate attention. This should be of great significance for improving physiological models concerned with thermal exposures. The potential interest of such work can be directed towards quite distinct targets such as working conditions, sports, the military, or healthcare personnel and patients. In the present study, we made use of a climate chamber and an articulated thermal manikin of the Pernille type, with 16 body parts. The most common occidental postures (standing, sitting and lying) were studied. In order to separate heat losses due to radiation and convection, the radiative heat losses of the manikin were significantly reduced by means of a shiny aluminium coating, which was carefully applied to the artificial skin. The air temperature within the test chamber was varied between 13°C and 29°C. The corresponding mean differences between the skin and the operative temperatures changed from 3.8°C up to 15.8°C. The whole-body heat transfer coefficients by radiation and convection for both standing and sitting postures are in good agreement with those in the published literature. The lying posture appears to be more efficient for losing heat by convection. This is confirmed when the heat losses of each individual part are considered. The proposed correlations for the whole body suggest that natural convection is mainly laminar.

Dynamic clothing insulation. Measurements with a thermal manikin operating under the thermal comfort regulation mode.

The main objective of the present work is the assessment of the thermal insulation of clothing ensembles, both in static conditions and considering the effect of body movements. The different equations used to calculate the equivalent thermal resistance of the whole body, namely the serial, the global and the parallel methods, are considered and the results are presented and discussed for the basic, the effective and the total clothing insulations. The results show that the dynamic thermal insulation values are always lower than the corresponding static ones. The highest mean relative difference [(static-dynamic)/static] was obtained with the parallel method and the lowest with the serial. For I(cl) the mean relative differences varied from 0.5 to 13.4% with the serial method, from 5.6 to 14.6% with the global and from 7.2 to 17.7% with the parallel method. In addition, the dynamic tests presents the higher mean relative differences between the calculation methods. The results also show that the serial method always presents the higher values and the parallel method the lowest ones. The relative differences between the calculation methods {[(serial-global)/global] and [(parallel-global)/global]} were sometimes significant and associated to the non-uniform distribution of the clothing insulation. In fact, the ensembles with the highest thermal insulation values present the highest differences between the calculation methods.

Subjective analysis of cold thermal environments.

The present work is dedicated to the study of cold thermal environments in food distribution industrial units through a subjective assessment based on an individual questionnaire which aims to describe the working conditions of employees often exposed to cold. The survey was carried out in Portugal and the sample consists of 1575 valid responses obtained in 61 industrial units. The results show that the food distribution activity sector is characterized by a female population (78.1%) and by a young work force (63.4% of the workers are less than 35 years old). Despite the availability of cold protective clothing (52.8% of the workers indicate one garment) its characteristics require improvements. In addition almost 1/3 of the respondents consider the thermal environment cold and 79.6% of the workers report that working in the cold is harder in wintertime. The results also highlight that 37.3% of the workers report having health problems.

Evaluation of Occupational Cold Environments: Field Measurements and Subjective Analysis

The present work is dedicated to the study of occupational cold environments in food distribution industrial units. Field measurements and a subjective assessment based on an individual questionnaire were considered. The survey was carried out in 5 Portuguese companies. The field measurements include 26 workplaces, while a sample of 160 responses was considered for the subjective assessment. In order to characterize the level of cold exposure, the Required Clothing Insulation Index (IREQ) was adopted. The IREQ index highlights that in the majority of the workplaces the clothing ensembles worn are inadequate, namely in the freezing chambers where the protection provided by clothing is always insufficient. The questionnaires results show that the food distribution sector is characterized by a female population (70.6%), by a young work force (60.7% are less than 35 yr old) and by a population with a medium-length professional career (80.1% in this occupation for less than 10 yr). The incidence of health effects which is higher among women, the distribution of protective clothing (50.0% of the workers indicate one garment) and the significant percentage of workers (>75%) that has more difficulties in performing the activity during the winter represent other important results of the present study.

Calculation of view factors for complex geometries using Stokes’ theorem

This paper presents an algorithm that calculates the radiative view factors based on Stokes’ theorem. The authors propose a formulation where the original surfaces are divided into a grid of elementary areas and Stokes’ theorem is applied for the determination of the view factors between these elementary areas. With this approach, the account of the shading effect of obstructions is significantly improved. The capabilities of the proposed formulation were tested with the calculation of radiative view factors between flat and curved surfaces. The results obtained showed a good agreement with the corresponding analytical solutions, with relative errors (REs) lower than 2%. The proposed methodology was also compared with the application of the double integral area formulation and a better agreement was found, between RE and the CPU, using the present formulation.

The impact of electrochromic windows on the energy performance of buildings in Mediterranean climates: a case study

Abstract The process of building rehabilitation is usually strongly constrained regarding morphological changes, particularly in the cases of historic or classified buildings. Therefore, in the present chapter the emerging technology of electrochromic (EC) windows is studied, using building energy simulation to assess the effects on energy efficiency in buildings. The phenomena associated with the current state of EC device technology are described, and their potential future trends are discussed. The validation of control procedures for commercially available EC windows is carried out using the ESP-r simulator, using a case study building to be rehabilitated (Faculty of Arts and Humanities, University of Coimbra) through the analysis of the impact of EC technology on energy consumption and thermal comfort. The methodology designed to assess the use of EC windows begins with the calculation, through simulation for a reference case with single glazing windows, of the solar gains and the internal gains of each space, for both heating and cooling seasons, followed by the estimation of the energy savings that result from the application of EC windows. From the results it is concluded that EC windows are an effective solution to the problems associated with the control of solar gain in the east and west facades. The use of EC windows will reduce the annual energy needs, which is clearly an advantage in the cooling season. Generally, it is concluded that the use of EC windows must be defined according to the type of building, or even space, particularly depending on the occupation and the overall internal gains, on the facade characteristics, orientation, and the shading influence of neighboring buildings.

Thermal conditions in freezing chambers and prediction of the thermophysiological responses of workers

The present work is dedicated to the assessment of the cold thermal strain of human beings working within freezing chambers. To obtain the present results, both field measurements and a numerical procedure based on a modified version of the Stolwijk thermoregulation model were used. Eighteen freezing chambers were considered. A wide range of physical parameters of the cold stores, the workers clothing insulation, and the working and recovering periods were observed. The combination of these environmental and individual parameters lead to different levels of thermal stress, which were grouped under three categories. Some good practices were observed in the field evaluations, namely situations with appropriate level of clothing protection and limited duration of exposure to cold avoiding unacceptable level of hypothermia. However, the clothing ensembles normally used by the workers do not provide the minimum required insulation, which suggests the possibility of the whole body cooling for levels higher than admissible. The numerical predictions corroborate the main conclusions of the field survey. The results obtained with both methodologies clearly show that, for the low temperature of the freezing chambers, the clothing insulation is insufficient, the exposure periods are too long, and the recovering periods are inadequate. Thus, high levels of physiological strain can indeed be reached by human beings under such working environments.

On the measurement of globe temperatures: analysis of the influence of different parameters

The assessment of thermal stress, either due to heat or cold, requires the measurement of different physical parameters. Budd [1] states that such assessments are difficult, expensive and time-consuming. The accurate evaluation of the physical parameters is recognized as one of the most important reasons for this statement. When heat stress is considered, the Wet Bulb Globe Temperature index (WBGT) [2] is probably the most common index used throughout the world. Its assessment requires the measurement of the globe temperature, an important issue that is addressed in the present paper.

Assessment of thermal environments: working conditions in the portuguese glass industry

The objective of the present contribution is to assess the exposure to hot thermal environments in the Portuguese glass industry. For this purpose a field survey was carried out and the measurements took place in industrial units - five industries and nineteen workplaces were considered–so all the results are based on real working conditions. In order to assess the level of heat exposure the Wet Bulb Globe Temperature (WBGT) index and the Predicted Heat Strain (PHS) model, defined in ISO Standards 7243 (1989) and 7933 (2004), respectively, were used. According to the WBGT index, the results show that almost 80% of the workplaces under analysis are prone to heat stress conditions. If the PHS model is considered, the results highlight that the predicted and the maximum sweat rates present equal values in about 40% of the workplaces. In addition, in almost 25% of the workplaces the estimated rectal temperature was higher than 38°C, just for an exposure period of one hour. Thus, the present study brings to light the characteristics of the glass industry in terms of the occupational exposure to hot environments and places this activity sector as one of the most difficult to deal with.