António M. Raimundo

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.

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.

Heat transfer measurements in a rotor–stator system with three-dimensional non-axisymmetric flow conditions

Abstract In this work, the results of an experimental investigation on the heat transfer associated with steady, three-dimensional, non-axisymmetric flows confined in a rotor–stator system with a disk rotating around its vertical axis are presented and analysed. A detailed description of the laboratory installation, including the heat, rotation and throughflow generation devices is presented. The measuring, acquisition and processing systems are described together with their calibration procedure. An analysis of the probable uncertainty associated to the experimental measurements is reported. The flow structure in the region that is more directly affected by the inlet jet is characterized. Finally, the dependence of the different heat fluxes, as well as the global thermal energy removed by the flow, upon the inlet mass flow rate and the angular velocity of the rotating walls is systematically analysed. The Rossby number ( Ro ) appears to be an important parameter that can be taken as a criterion reference to balance the relative importance between the inlet mass flow rate and the angular velocity. A value of Ro ≈0.01 defines a clear boundary between a rotation dominated regime (for Ro Ro >0.01). In general, the global transfer of heat increases with increasing rotation, decreases with growing inlet jet throughflow and reaches minimum values for Ro ≈0.01.

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.

Numerical evaluation of a radiant panel system for heating a high-ceiling room

It is common to assess the level of wasted energy due to the inappropriate selection of HVAC systems (Heating, Ventilation and Air Conditioning) that are regularly used to control temperature in man-made environments. The present work investigates the use of radiant panels as alternative method for controlling the thermal environment and aims to contribute to the characterization of the performance of these devices. It is a technology that has already proven its effectiveness in terms of cooling, however, still little explored for heating, particularly in spaces with high ceilings.

Replacement costs of cold storage equipment for medical products of public healthcare establishments of European Union countries

This study presents a quantification of the financial needs to maintain the stock of cold equipment for the preservation of medical products in public health care establishments of European Union (EU) countries. The conditions that must be guaranteed, the types of equipment used, the installed capacity, the total annual financial needs and the estimate of its evolution in the near future are addressed. A field survey involving Portuguese establishments of various types and dimensions was performed in order to assess the currently installed volume by type of equipment. Through an analysis based on possible scenarios and using a methodology considered adequate, the financial needs to maintain such equipment in operation was estimated for Portugal, for each EU country and for the EU as a whole. The economic value of these amounts in 2017 and following years was obtained assuming the average price of each type of equipment and considering an expected evolution of its value.

Assessment of thermal environments: Working conditions in the Portuguese ceramic industry in 1994 and 2012

BACKGROUND The assessment of heat stress in the ceramic industry is a matter of great concern for safety and health of workers. For this purpose working conditions in the last two decades are analysed. OBJECTIVE To study occupational hot thermal environments in the Portuguese ceramic activity sector in 8 industrial units and 21 workplaces. METHODS In order to characterise the level of heat exposure, the method proposed by ISO 7243 (1989) based on the Wet-Bulb Globe Temperature (WBGT) index was adopted. RESULTS Two field surveys, one carried out in 1994 and the other in 2012 are considered. The WBGT mean values varied between 23.7 and 37.8°C in the 1994 survey while in 2012 those values ranged from 21.5 to 30.5°C. In the 1994 evaluations 5 out of 8 (62.5%) of the workplaces present heat stress conditions whereas in the 2012 assessments the corresponding value is 46.2% (6 out of 13 workplaces). CONCLUSIONS Despite two decades between the two surveys, the results highlight that the overall thermal conditions of the workplaces in the ceramic sector are still quite similar, suggesting that the working conditions have not changed enough, a conclusion that asks for further analysis and improvements.

Development and validation of a computer program for simulation of the human body thermophysiological response

The purpose of this work is the development and the validation of an accurate computer program for modeling of the thermal, the respiratory and the cardiovascular responses of a live or dead person exposed to any kind of environment while wearing different kinds of clothing and at rest or doing a moderate or intensive activity. The range of possible utilization is extensive, e.g., the optimization of sportive performance, the quantification of the thermal comfort achieved on exposition to moderate thermal environments, the evaluation of thermal stress and the risk of collapse in the execution of tasks in very hot or very cold situations or requiring high levels of effort and as support for medical activities. This manuscript describes the research efforts performed at the Mechanical Engineering Department of the Faculty of Sciences and Technology of University of Coimbra (DEM-FCTUC) in order to achieve mathematical and computational models suitable for the prediction of human body thermophysiological behavior.