In traffic congestions, the typical reaction of the drivers is to switch-on the recirculation mode of the vehicle's air conditioning system. In the summertime, in many cities with high air humidity and temperatures, people typically drive their cars in recirculation mode as well, to ensure the best cooling. However, the recirculation mode of the air in the cabin prevents O 2 from entering and leads to an increase in CO 2. In confined spaces (e.g., a vehicle cabin), the raised CO 2 concentration due to human exhalation and metabolism is associated with increased health symptoms, decreased concentration, and impaired performance. The paper presents an experimental study on the accumulation of carbon dioxide in a vehicle cabin from occupants breathing and metabolism. The concentration of CO 2 and O 2 were measured in terms of the number of occupants (1-4) in the car. The change in the indoor environmental parameters in the car cabin was also monitored. The results obtained show the increment of the CO 2 concentration at the expense of oxygen availability, together with the apparent impact of the number of people in the vehicle.

The study presents experiments, conducted with human subjects in an artificial cold chamber, assessing the influence of a cold environment on the temperature of the human body. Infrared thermography was applied as a non-invasive, contactless method for direct measurement of the temperature distribution of both clothed and uncovered parts of the body. Two subzero temperatures were applied and clothing ensembles with two different clothing insulation values were used to assess the effect of the clothing insulation of the torso on the temperature of clothed and uncovered parts of the body of the participants. The average temperature of the chest, back, upper arms, face and middle finger is presented and discussed in relation to the cold exposure duration and clothing insulation used. The results obtained showed the strong influence of the clothing insulation over the torso on skin and clothing temperatures of the body and overall cooling of the body in subzero temperatures.

The pyrolysis of wheat straw in order to produce biochar for soil amendment is a potential strategy for producing environmental friendly fertilizers capable of boosting soil fertility, increasing carbon storage, and lowering greenhouse gas emissions. However, straw biochar’s potential to influence these aspects may vary depending on its properties. Our study sought to investigate biochar from wheat straw from three different regions in Bulgaria. A specially designed set up was used for the biochar production. Three pyrolytic temperatures (300, 400, and 500 °C) were applied, resulting in nine biochar samples. The specific characteristics included moisture content, volatile substances content, ash content, fixed carbon content, and joint ash and carbon content, and they were determined for each sample. The chemical content, resulting in 17 chemical elements and compounds, was measured and analysed. The results obtained showed that the produced straw biochar has the potential to be used as a fertilizer and soil supplement.

The objective of the paper is to demonstrate the importance of the unsteady Computational Fluid Dynamics (CFD) simulations and long-term measurements for the reliable assessment of thermal comfort indoors, for proper categorization of the indoor thermal environment and for identifying the reasons for complaints due to draught discomfort. Numerical simulations and experimental measurements were applied in combination to study ventilation in a field laboratory, a university classroom with a controlled indoor environment. Strong unsteadiness of the airflow was registered both in the unsteady RANS results and the real-scale long-term velocity data measured with thermo anemometer. Low-frequency high-amplitude velocity fluctuations observed lead to substantial time variation of the draught rate. In case of categorization of a thermal environment, the point measurements or steady-state RANS computations would lead to wrong conclusions as well as they cannot be used for identification of the reasons for people’s complaints due to draught discomfort if strong unsteadiness of the airflow exists. It is demonstrated that the length of the time interval for draught rate (DR) assessment may not be universal if low-frequency high-amplitude pulsations are present in the room airflow.

People are the main reason for the deterioration of indoor air quality (IAQ) due to the continuous physiological metabolism processes in their bodies, including respiration. We present results from an investigation of the influence of indoor air temperature on the concentration of exhaled carbon dioxide (CO₂). The investigation was preconditioned by previous findings on the effect of air temperature on human metabolism. However, our literature survey showed a lack of studies on the influence of the indoor air temperature on the exhaled CO₂ (or metabolic CO₂), which leads to the novelty of our results. Our experiments had two phases: measurement in a university classroom with an installed heating, ventilation, and air-conditioning (HVAC) system during regular classes and measurement in a specially designed small climate chamber, where the time variations of the CO₂ concentrations, together with some physiological parameters, were measured. Two indoor air temperatures were set: 23 °C and 27 °C. The results obtained and their respective analyses show the strong effect of the two air temperatures on the CO₂ concentration due to exhalation. In the classroom, the CO₂ concentration at 27 °C was higher by 6.2% than at 23 °C. In the climate chamber, the CO₂ concentration at 27 °C was higher by 9.6% than at 23 °C. Physiological parameters (oxygen saturation pressure, pulse rate, end-tidal CO₂, and respiration rate) and their dependence on the air temperature were also measured in the climate chamber, establishing an effect of the temperature on the pulse rate.

Purpose: – The purpose of this paper is to integrate a thermophysiological human body model into a CFD simulation to predict the dry and latent body heat loss, the clothing, skin and core temperature, skin wettedness and periphery blood flow distribution. The integration of the model allows to generate more realistic boundary conditions for the CFD simulation and allows to predict the room distribution of temperature and humidity originating from the occupants. Design/methodology/approach: – A two-dimensional thermophysiological body model is integrated into a CFD simulation to predict the interaction between the human body and room environment. Parameters varied were clothing insulation and metabolic activity and supply air temperature. The body dry and latent heat loss, skin wettedness, skin and core temperatures were predicted together with the room air temperature and humidity. Findings: – Clothing and metabolic activity were found to have different level of impact on the dry and latent heat loss. Heat loss was more strongly affected by changes in the metabolic rate than in the clothing insulation. Latent heat loss was found to exhibit much larger variations compared to dry heat loss due to the high latent heat potential of water. Originality/value: – Unlike similar studies featuring naked human body, clothing characteristics like sensible resistance and vapor permeability were accommodated into the present study. A method to ensure numerical stability of the integrated simulation was developed and implemented to produce robust and reliable simulation performance.