Hygienic Assessment of Risks of Thermal Balance Disruption in Medical Laboratory Workers Using Personal Protective Equipment for Biohazards

Introduction: Specifics of activities of medical personnel in different types of laboratories can potentially create working conditions that violate occupational safety and health regulations. Objective: The study aimed to assess health risks of thermal balance disruption in PCR laboratory staff wearing personal protective equipment for biohazards in the context of the COVID-19 pandemic. Materials and methods: The study was conducted in winter 2020–2021 in PCR laboratories of the Volgograd Region. It included measurements of laboratory microclimate parameters, such as relative humidity, air temperature and velocity, used to estimate the heat load index. An observation cohort of 31 female medical laboratory workers aged 32.48 ± 1.45 years with a three to nine months experience of work in the PCR laboratory was formed to monitor the thermal state at the start and end of the work shift by measuring skin temperature at five points, sublingual temperature, and heat sensation. The results of measurements were used to estimate the mean skin temperature and heart rate while the dynamics of work ability was assessed by the results of contact tremorometry. Results: We established a significant increase in all measured values. The mean skin temperature at the end of the shift reached 33.85 ± 0.24 °C, thus exceeding the upper limit of the permissible value. The heart rate and heat sensation parameters approached the upper values of the maximum permissible thermal state of a person. Contact tremorometry results indicated a decrease in the performance by the end of the work shift. The findings gave evidence of tension of thermoregulatory reactions and the risk of thermal balance disruption posed by the use of a specific type of personal protective equipment in the PCR laboratory. Conclusion: The research results provide strong support for the conclusion that the use of PPE for biohazards poses a risk of thermal balance disruption in medical laboratory personnel. The severity of stress of thermoregulatory reactions depends on technical and design characteristics of the PPE used. The necessity of a physiological and hygienic substantiation of acceptable duration of work of medical workers wearing various types of PPE for biohazards in PCR laboratories justifies the importance of further studies.

Research methods in the study of heat transfer coefficient during flow in minichannels

The paper presents the specification of research methods commonly encountered in the studies of heat transfer processes in minichannels. In particular the following methods have been emphasized: electrochemical limiting current method as well as the thermal balance method. In thermal balance method the mean heat transfer coefficient is determined by the set of experimental thermal measurements of the investigated heat exchanger. In turn, limiting current method is based on heat and mass transfer analogy. The discussed research methods have been implemented on two specially designed and constructed test facilities with compact minichannel heat exchangers, which have been presented and described in details. In order to validate the designed setup, the preliminary experimental measurements of two minichannel heat exchangers with hydraulic diameter of 2 mm and rectangular cross sections during single-phase liquid flows have been carried out. In further perspective it is planned to extend the experimental studies of minichannel heat exchangers and to compare the results obtained by both methods described.

METHODOLOGY FOR DETERMINING THE MAIN INDICATORS OF THE TEMPERATURE AND DYNAMIC CHARACTERISTICS OF THE COOLING SYSTEM OF AN ENERGY VEHICLE DURING OPERATION

The efficiency of internal combustion engines of energy facilities operating in the conditions of enterprises of the agro-industrial complex depends on the stability of the thermal regime of the engine. Its provision is entrusted to the cooling system, in this article which is a radiator with a polyurethane core. The temperature regime of the engine operation affecting a number of factors is given and described - these are design parameters (design features of the radiator and the features of the working process of the radiator, taking into account the operating conditions of the tractor) and operational, which take into account the operating mode of the tractor and natural and climatic conditions. According to the research results during the operation of the tractor in steady conditions, the temperature of the coolant in the system is stable, respectively, the temperature field of the air flow at the inlet and outlet of the radiator with a polyurethane core also stabilizes. To take them into account, the coefficient of thermal properties of the radiator is introduced, which depends on the external and internal temperature-dynamic effects of the environment, and a diagram is constructed that shows the dependence of the temperature of the coolant flowing in the radiator on the generated load of the tractor during operation in the field. At the same time, the temperature-dynamic characteristic of the tractor does not depend on the design features of the engine, but on the power developed by the engine. Therefore, the heat removed from the engine into the coolant is calculated by us through the engine power. Based on this, the characteristic of the thermal balance of the engine and the heat transfer of the radiator during the operation of the tractor at full load are considered, taking into account the change in gears within the speed limits, a graph of the thermal balance of the engine and radiator versus speed is built. Based on the calculations, it was concluded that the use of the characteristics of the traction-dynamic balance of the tractor can serve as the basis for the general analysis and calculated and experimental operating modes of the automotive polymer radiator and the cooling system as a whole, taking into account the loads, climatic conditions and operating parameters of the cooling system

Influence of low temperatures on heat balance in easily assembled premises of different types

The purpose of this work was to analyze the thermal balance of easily assembled premises of different types and sizes during the periods of low average daily temperatures. The research was conducted during the winter period of 2020–2021 in the Kyiv region. The used material was easily assembled premises of different types and sizes: easily assembled ones without insulation elements; with elements of warming and premises with deep-litter. In each of the studied premises were kept 400 dairy cows. The studies were performed during two periods: the first period had ambient temperatures from -10 to -14.9 °C and the second one from -15.0 °C and below. In our studies, the average daily temperature (during the ambient temperature from -10 to 14.9 °C) in easily assembled premises with the use of insulation elements was 6.20 and 5.31 °C higher than in premises without insulation and deep-litter. A similar trend was observed during the period of lowering the ambient temperature up to 15 °C and below. Thus, the advantage of the premises without insulation constituted 6.28 °C, and of the premises with deep-litter per 5.84 °C, respectively. It was found that keeping in easy-to-assemble premises with insulation elements, the consumption of free thermal energy from the whole herd during the experimental periods was lower compared to the keeping in a boxing cowshed and a cowshed with deep litter. This is due to the smaller range of fluctuations in the average daily temperature in a room with insulation elements. A similar trend was observed for energy consumption through enclosing structures and for moisture evaporation and, accordingly, total heat consumption. In general, heat deficiency was observed during the keeping of cows in the investigated premises of easily assembled type at negative temperatures (-10–14.9 and -15 °С and above). Accordingly, the thermal balance of the premises was negative. The highest values of heat balance among easily assembled premises in both research periods were observed for keeping in rooms that used insulation elements.