Energy Efficiency Coefficients Research Articles

Operating characteristics and evaluation of air source heat pumps in cold regions during heating season in China

The mismatch between the actual heat production of an air source heat pump (ASHP) and the instantaneous load of the building it heats is a critical cause of low energy efficiency. Research on the measured heating effect provides an effective approach to improve the energy efficiency of an ASHP. This study therefore focused on two small office buildings to explore the operating data describing the ASHP system source and load sides during the heating season. A sensitivity analysis was employed to explore the actual operational effects of the ASHP. Common problems associated with system operation were comprehensively identified, including the operation characteristics, energy efficiency coefficients, load characteristics, and energy consumption characteristics of the transmission and distribution systems. The effects of these problems were evaluated from three perspectives: integrated part load value (IPLV), system performance loss, and indoor environmental parameters. The results shows that the highest coefficient of performance (COP) of the ASHP in Building A was 3.27 while the IPLV was 2.68, operating status reached the standard. The COP value of the ASHP in Building B was 1.55 while the IPLV was 2.45. Poor value shows the low performance in operating phase, which can be further optimised by matching the building instantaneous load to the heat production of the ASHP, improves the operating effect of two buildings comprehensively.

The effect of crop rotations and mineral fertilizers on economic and energy efficiency indicators when cultivating winter wheat in the Central Blackearth region

Economic efficiency is an integral method of analyzing agricultural technologies, especially against the rising prices for plant protection products, seeds, fertilizers, and fuels and lubricants. Identification and implementation of the most effective methods of field crops, growing using crop rotation and fertilizers remains an urgent task. The purpose of the current research was to study the effect of crop rotations and doses of mineral fertilizers on productivity of winter wheat grain, to analyze the economic and energy efficiency of its cultivation in the conditions of the Central Blackearth region. The study was carried out in the conditions of the experimental field of the Federal Agricultural Kursk Research Center in 2016, 2020. The soil of the experimental plot was typical medium-loamy, medium-humus blackearth (chernozem). The experimental scheme included such factors as grain-fallow-row crop, grain-grass-row crop, and grain-grass rotations; with doses of fertilizers or without fertilizers, N20P40K40 and N40P80K80. The weather conditions for the rotations of the studied crop rotations differed slightly. As a result of the study, there was found that winter wheat grain productivity in grain-grass and grain-grass-row crop rotations was 17.2 and 13.8 % lower than in grain-fallow-row crop rotation. When applying mineral fertilizers at a dose of N40P80K80, the largest winter wheat productivity was 4.52 t/ha. The lowest cost of grain was established in the grain-fallow-row crop rotation, which varied from 4.68 to 5.04 thousand rubles/t due to higher yields compared to other studied crop rotations and with a dose of N20P40K40 (4.68, 4.80 and 4.97 thousand rubles/t, respectively for crop rotations). A higher level of profitability of 113.7 % was observed in grain-fallow-row crop rotation with a dose of mineral fertilizers N20P40K40, a dose of N40P80K80 not allowing obtaining a high payback of fertilizers. The energy intensity of production increased with increasing doses of applied fertilizers; its minimum values were determined in grain-fallow-row crop rotation (1.35–2.77 GJ/t). Energy efficiency coefficients when applying a dose of N20P40K40 in crop rotations were higher than when applying N40P80K80.

Energy Efficiency Forecast as an Inverse Stochastic Problem: A Cross-Entropy Econometrics Approach

This paper forecasts the energy efficiency coefficients at the Polish province level (NUT-2), based on imperfect and contradictory knowledge. On the one hand, we have information on the aggregated national energy efficiency coefficients in the industrial, transport, household, and service sectors. On the other hand, we also have information on the energy intensity at the Polish province level. Since the two samples are of different natures and known with uncertainty, we are obviously dealing with an inverse stochastic problem whose solution requires particular statistical devices. The applied technique of non-extensive cross-entropy econometrics generalizes the Shannon-Kullback-Leibler approach based on the Gaussian assumptions. Its justification is explained throughout this paper from both methodological and empirical points of view. The model forecasts lead to the high-value energy efficiency estimates from quasi-unstructured sets of information. This constitutes the main contribution of this research. These outputs should provide energy policy units with valuable new devices for the optimization of the energy management processes on a disaggregated local level where, by contrast, different agents and households act decisively. On a global level, the proposed technique can be applied in different EU countries and elsewhere, in the context of experimental official statistics.

Numerical investigation of PV module cooling process by developing single-pass and doublepass PVT collectors

In this study, single-pass and double-pass photovoltaic thermal collectors were designed and analyzed numerically. Energy efficiency and heat transfer coefficients of the PV module were calculated in the study. For case studies two different meteorological conditions (winter and summer) choosed. Case studies were performed with three different Reynolds number (15059, 17805, 22061). Avarage thermal efficiencies obtained for single and double-pass PV-T calculated in winter 65.15% and 67.88% ; summer 56.09%, and 58.46% conditions, respectively. For double- as PV-T, these values are It has been determined that the temperature of the PV module decreases with the increase in flow rate. Avarage electrical efficiency for single pass PVT in winter condition determined as 13.68% where for summer it was calculated as 13.24%. For double pass PVT these values obtained as 14.40% and 13.94%, respectively.

Assessing the energy efficiency of irrigation pump systems

Abstract. The operating modes of pump units play a crucial role in determining the energy consumption of irrigation systems. Thus, the necessity of performing qualitative and quantitative assessments of the energy efficiency of such systems is of significant importance. This paper proposes a method, newly established by authors, for accomplishing such an assessment. Using dimensionless criteria from Dimensional Analysis (as outlined in earlier publications), we propose a method to determine the specific energy consumption (ev) for a given flow rate, regulated by either VFD or throttle flow control, which are commonly used in practice. The specific relative energy consumption is depicted as an exponential relationship with four other criteria, each expressed relatively. The exponents are determined depending on the type of pump system flow rate control method applied. This energy exponent is also expressed in the dimensionless form obtained depending on the main parameters of the pump and pipe system. In this regard, two energy efficiency coefficients are introduced – of the pump and pipe system . Results obtained after performing numerical studies of a pump system, consisting of Bulgarian double-suction pumps, are presented.

Energy efficiency of circulating pumps when using non-freezing heat transfer fluids

Introduction. The article considers the issues of operation of circulating pumps of autonomous heat supply systems when the heating circuit is filled with antifreezing coolants. It is possible to remotely start up a heating system cooled down to –15 °С. Ethylene glycol and propylene glycol antifreeze have been studied as antifreeze carriers. Flow-rate characteristics, power efficiency coefficients are studied for “wet rotor” circulation pumps in versions of electric motors of asynchronous type with constant rotor speed and energy-saving pumps on permanent magnets.
 Materials and methods. The research was carried out on test stands. Wall-mounted gas boilers and electric boilers witha rated capacity up to 24 kW were used as heat generators. Circulation motors, control hydraulic valves, part of the pipes with a length of 6 meters were located in a separate freezer. The pumps and parts of the heating circuit were kept at subzero temperatures for 2 hours before the system was started up
 Results. Pressure and flow characteristics of two types of pumps, energy efficiency coefficients were obtained, comparisons with water coolant are provided, the influence of electric network voltage on the investigated parameters was determined.
 Conclusions. The research has shown the possibility of starting circulating pumps in a refrigerated condition with a temperature of –15 °С. Remote start of the cooled heating system with circulation circuit filling with antifreeze when using hydrocarbon fuel boilers is not possible. Operation of heating systems with non-freezing coolants in the operation temperature ranges of 20–80 °C requires changing in settings of the combustion process and a significant increase inthe circulation pump head in comparison with the coolant water.

Study of the efficiency of direct (no-till) sowing of grain crops in the Republic of Chuvashia

The current study was carried out in order to identify the efficiency of direct (no-till) sowing of grain crops after potatoes on medium loamy gray forest soils with 2.33 % of humus, 210 mg/kg of mobile phosphorus, 162 mg/kg of exchangeable potassium and 6.6 units of acidity. The objects of study were winter and spring wheat, spring barley for brewing and fodder, maize for grain and silage. The sowing complex ‘Amazone Primera DMC’ has carried out direct (no-till) sowing of disease-treated seeds with the simultaneous application of mineral fertilizers. Grain crop treatment to control weeds, pests, and diseases, as well as top dressing with macro- and micro-fertilizers were aimed at obtaining the maximum productivity of each grain crop. The hydrothermal coefficient in the 2020 growing year was 1.04, in 2021 it was 0.60 and in 2022 it was 1.05. Harvesting was carried out in the phase of full ripening of grain and milky-wax ripeness of cobs when laying maize silage. On average, the largest (3.85 t/ha) grain productivity when using direct (no-till) sowing was produced by maize, and the least yields (2.00 t/ha) were given by brewing barley. In the production of these crops, there have been identified maximum (2.72) and minimum (1.99) energy efficiency coefficients. An economic estimation has shown the feasibility of direct (no-till) sowing of winter wheat, where the maximum (68.4 %) level of profitability was established. The minimum (14.8 %) level of profitability was found in the cultivation of brewing barley, which could be explained by the high degree of material and labor costs and low productivity. The profitability of the production of other crops was lower in 1.21-3.39 times. In general, agroeconomic and energy analysis has proved a high efficiency of direct (no-till) sowing in the cultivation of winter wheat and maize after potatoes in the agro-climatic conditions of the Republic Chuvashia.

Improvement of thermal-hydraulic efficiency of mining power equipment through the application of porous freon steam generators with high heat conductivity

In the article, various areas of technical application of porous freon steam generators in mining power equipment are described, and explanations why freon coolants can provide a positive energy effect in such facilities are given. The paper presents results of calculations of thermal-hydraulic efficiency of the porous once-through tubular steam generators with freon-12 as a model working fluid in the the laminar flow area and with boundary conditions of the first kind. The smooth-wall cylindrical channels with different diameters were used as the reference surfaces to be compared. The following mode and design parameters were taken as a calculation base: the liquid temperature and pressure on the saturation line at the entry into the channel were: Ts0= 110 °С; P0s = 39,9·105 N/m2.; temperature heads, i.e. a difference between the wall temperature and temperature of the liquid at the entry into the channel were: ΔT=Tw-Ts0 = 1 °C; 2 °C; 3 °C; 4 °C; 5 °C; the Reynolds numbers at the entry into the channel were: Reo = 100; 200; 500; 1000; 2000; 2300; the channel porosities were: θ = 0.7; 0.75; 0.8; 0.85; 0.9. The porous material was metal felt with the copper fiber diameter of 200 microns. The channel diameters were: d =3·10-3 m; 4·10-3 m; 5·10-3 m; 6·10-3 m; 7·10-3 m. On the basis of the performed computational studies, it was concluded that for the conditions of the same mass flow rates of the coolant, with laminar flow, and the same channel diameters, it is possible to achieve a significant reduction in the length of the porous once-through steam generator in comparison with the length of the smooth-wall once-through steam generator. Due to the significantly shorter length, differential pressure for pumping the coolant can be several tens of percent less in porous evaporation channels than in the similar smooth-walled channels. This computational study also made it possible to establish main regularities in dynamics of the energy efficiency coefficients and their dependence on the model mode and design parameters. It was shown, that positive dynamics of the efficiency coefficients of porous steam generators occurs with decrease of the channel diameter and temperature head, as well as with increase of the Reynolds number in the investigated region of coolant laminar flow.

Sustainable Governance, Energy Security, and Energy Losses of Europe in Turbulent Times

The article aims to identify the relationship between energy efficiency and particular indicators of energy losses in Europe. The results of the bibliographic analysis showed a knowledge gap in energy losses in Europe regarding the new challenges of energy security. For the analysis, annual panel data from 32 European countries were collected from 1990 to 2019. The authors used the Jarque–Bera test to assess the normality of the residuals, utilized the Breush–Pagan test for heteroskedasticity check, and applied regression analysis to determine the relationship between energy efficiency and energy loss rates in Europe. To assess the effects of energy losses, the authors performed OLS modeling using the stats model’s package in Python. According to the modeling results, an increase in distribution losses (% of available energy from all sources) by 1% in Europe leads to an increase in energy consumption by 17.16% under other constant conditions. There is significant heterogeneity between European countries concerning energy efficiency and energy loss coefficients. Such a situation requires the development of new strategies and mechanisms to reduce energy losses, considering the challenges of energy security in Europe in turbulent times. Further research can be devoted to clustering European countries according to the main groups of energy losses: in the extraction, distribution, storage, and transformation of energy.

Impacts of industrial structure adjustment, upgrade and coordination on energy efficiency: Empirical research based on the extended STIRPAT model

This paper first estimates the energy efficiency of 13 cities and 30 key industries in the Beijing-Tianjin-Hebei (BTH) region between 2008 and 2017 using the super-efficiency slacks-based measure (SBM) model. Structural deviation, Moore index, and coupling coordination degree quantify the cities' industrial restructuring, upgrading, and coordination. Afterward, the extended STIRPAT model reveals the relationship between energy efficiency and industrial structure. Finally, a coupling coordination degree model measures the coupling between energy efficiency and industrial advanced development coefficients in key industries. The results show a wide variation in energy efficiency between cities, with most cities experiencing a decline in energy efficiency. Industrial structure adjustment and upgrading are on the rise, and coordination is on the wane, with the most significant changes occurring in the cities around Beijing. In most cities, industrial structure adjustment, upgrading, and coordination on energy efficiency are negative, positive, and negative. The coupling imbalance of energy efficiency and industrial advanced development coefficients is the most apparent feature of the key sectors, and this feature is not improving.

Alternate-day fasting, a high-sucrose/caloric diet and praziquantel treatment influence biochemical and behavioral parameters during Schistosoma mansoni infection in male BALB/c mice

Schistosoma mansoni-induced granulomas result in severe damage to the host's liver, as well as neurological and metabolic disorders. We evaluated the biochemical and behavioral changes during schistosomiasis under three diet protocols: ad libitum (AL), alternate-day fasting (ADF) and a high-sucrose/caloric diet (HSD). Healthy male BALB/c mice were divided into noninfected, matched infected and infected/treated [praziquantel (PZQ)] groups. Caloric intake and energy efficiency coefficients associated with diets were measured. Behavioral (exploratory and locomotor) and biochemical (glucose, triglycerides, total cholesterol, AST, ALT, ALP, and γ-GT) tests and histological analysis were performed. Fifteen weeks postinfection, HSD and PZQ promoted weight gain, with higher caloric consumption than ADF (p < 0.05), reflecting serum glucose levels and lipid profiles. HSD and PZQ prevented liver dysfunction (AST and ALT) and significantly prevented increases in granuloma area (p < 0.05). HSD and PZQ also significantly improved mouse physical performance in exploratory and locomotor behavior (p < 0.05), reversing the impaired motivation caused by infection. These findings showed that ADF worsened the course of S. mansoni infection, while HSD and PZQ, even with synergistic effects, prevented and/or attenuated biochemical and behavioral impairment from infection.

EXPERIMENTAL EVALUATION OF A CASCADE REFRIGERATION SYSTEM USING R-134a AND R-404a

Cascade refrigeration system is an attractive technology for low-temperature requirement, allowing operation under these conditions with positive suction pressures and a moderate condensation pressure at ambient temperature. This work describes a performance analysis of a cascade refrigeration prototype equipped with hermetic compressors working with R-134a and R-404a as refrigerants, thermally connected by a tube-in-tube-type cascade-condenser. Energy flows and performance parameters were evaluated under different evaporating temperature conditions of the low temperature cycle (LTC). The results showed an increase in energy efficiency ratio (EER) and coefficients of performance (COP) of cascade system as well as of each cycle with the increase of LTC evaporating temperature, even with a simultaneous increase of temperature difference in cascade-condenser.

Experimental study of replacement of cement with ground granulated blast furnace slag

This research investigates and assesses the effects of substituting fly ash and ground-granulated blast-furnace slag for cement on the compressive energy and break-up tensile strength of a concrete mixture after 28 days. It is not intended to be all-encompassing. With the M40 concrete grade in mind, it was decided to explore and evaluate the compressive strength of concrete generated by substituting GGBS for cement at different percentages of 0, 10, 20, 30, and 40% of total cement content, respectively. When building a concrete structure, it is vital to keep the energy efficiency coefficients for GGBS at different percentages of 0, 10, 20, 30, and 40 for concrete with the M40 strength grade in mind. When the experimental usefulness was changed from liquid to solid, it was necessary to inspect the cubes in order to learn about compressive strength in order to achieve the research goals and finish the study objectives, rather than doing so as soon as expected at the start.

Determining the Energy Efficiency of Corn, Sun-flower and Soybean Cultivation with the Use of Ridge Technology

The article presents the developed energy-saving, resource-saving ridge technology for cultivating row crops and means of mechanization for its implementation allows increasing the yield of row crops on average in 5 years up to 38% without the use of environmentally unsafe herbicides. The implementation of ridge technology to cultivate corn for grain, sunflower and soybeans, the energy efficiency coefficients, respectively, amounted to 15.54; 9.71 and 3.43 units, which is by 0.6; 3.81 and 4.41 units more in comparison with the traditional technology of cultivation of the aforesaid crops on a flat surface of the field.

Calculation of thermohydraulic effectiveness of the porous once-through water steam generators in laminar flow region with boundary conditions of the first kind

The paper presents results of calculations of thermohydraulic efficiency of the porous once-through steam generators with water as a model working fluid in the region of the heat-transfer agent laminar motion and with boundary conditions of the first kind. The smooth-wall cylindrical channels with different diameters were used as the reference surfaces to be compared. The following operating and design parameters were taken as a calculation base: temperature of the liquid on the saturation line at entry into the channel was: Tso = 280 °C, 300 °C, 320 °C, 340 °C, 360 °C. Temperature head, i.e. a difference between the wall temperature and temperature of the liquid at entry into the channel was: ΔT=Tw-To = 1 °C; 2 °C; 3 °C; 4 °C; 5 °C. The Reynolds number at entry into the channel was: Reo = 700; 1000; 1200; 1500; 1700; 2000; 2300. The channel porosity was: θ = 0.7; 0.75; 0.8; 0.85; 0.9. The porous material was metal felt with the copper fiber diameter of 200 microns. The channel diameter was: d =3·10-3 m; 4·10-3 m; 5·10-3 m; 6·10-3 m; 7·10-3m; 10·10-3 m. On the basis of the performed computational studies, it was concluded that for the conditions of the same mass flow rates of the coolant, with laminar mode of motion, and the same channel diameters, it is possible to achieve a significant reduction in the length of the porous once-through steam generator in comparison with the length of the smooth-wall once-through steam generator; however, under these conditions it is not possible to reduce pressure drop in the channels and, accordingly, to reduce power consumption needed for heat-transfer agent pumping. This computational study also made it possible to establish main regularities in behavior of the energy efficiency coefficients and their dependence on the model operating and design parameters. Keywords: thermo-hydraulic efficiency; porous steam-generating channels; heat-transfer agent, water; boundary conditions of the first kind; laminar flow regime.

Influence of different intensity methods of basic processing of podzolized chernozem on the state of fertility and productivity of crops

Relevance . In the conditions of the Ryazan region, a significant part of the soil cover has not quite favorable properties (high equilibrium density and low water resistance), so the choice of the optimal cultivation system for a certain type of soil is one of the main conditions for increasing fertility, as well as a guarantee of obtaining high yields of cultivated crops. Material and methods . The article presents the results of studies for three crop rotation rotations (1992-2017) to study the effect of soil cultivation systems on the agrophysical properties of podzolized chernozem (degraded) and crop productivity in the conditions of the south of the Central Non-Black Earth Region using generally accepted agricultural techniques for this zone. The duration of the studies made it possible to cover periods different in meteorological conditions. Results . A comparative analysis of the effectiveness of five options for mechanical tillage systems has been carried out, the use of which contributes to the softening of the soil and increase its porosity to 51.9-53.9% compared with the initial rate of 48.3-48.7%. The number of water-resistant units increased by 17.2-19.8% compared with the initial data. Over the years of the experiment, the ability of the soil to retain moisture has increased, the lowest moisture capacity, which has increased from 26.1% to 32.0% during three rotation of the crop rotation. The productivity of cultivated crops was determined, which, depending on the applied treatment systems, increased by 10.2-22.7%. The strengths and weaknesses of each of the five main soil tillage systems presented were identified and energy efficiency coefficients (CEE) were calculated.

FEATURES OF ANALYTICAL SYNCHRONIZATION OF DATA OF WORKING PROCESS MONITORING IN TRANSPORT DIESEL ENGINES UNDER OPERATION

The article discusses methods for determining top dead center, based on the analysis of pressure diagrams of a marine engine. The advantages and disadvantages of different methods are shown. Diagnostics of marine engines during operation and selection of optimal operating modes are based on the analysis of pressure diagrams, as well as fuel supply and gas distribution diagrams. As a result of the analysis of the pressure diagrams, the indicator engine power is calculated, which is further used in the control of engine operation modes, in the calculation of specific indicators, as well as in the calculation of energy efficiency coefficients of marine vessels according to IMO recommendations. The influence of the accuracy of determining the position of the top dead center on the calculation of the mean indicated pressure and indicated power is shown. Solving the problem of synchronization of data of working process monitoring using hardware sensors is unacceptable due to the complexity, and sometimes the impossibility of installing hardware sensors for the position of the top dead center of the piston, in addition to the standard sensors. This also leads to a more complex measurement pattern, combined with high accuracy, which is dependent on the load mode. In addition, the installation of hardware sensors is time-consuming and involves organizational problems, as it is necessary to temporarily disable the engine. The mentioned problems are absent in case of analytical data synchronization. It is shown that the existing methods of analytical synchronization are not effective enough for the operating conditions of transport engines. This is mainly due to the complexity of the formulation of the synchronization criteria or their lack of precision due to the impact of noise in the output data. In portable diagnostic systems, the top dead center determination is best done immediately by the analytical method. Principally, there are inconveniences during the diagnosis of engines, because additional pickup sensors and their cables must be used. Before installing the sensors, it is necessary to take the engine out of operation. The installed sensors must be calibrated, which is associated with a significant investment of time. All portable systems for parametric engine diagnostics measure the pressure in the working cylinder through the channel of the indicator valve. In this regard, in portable systems, in addition to the aforementioned errors, errors occur such as throttling and delay of the signal, which leads to an additional shift of the top dead center position. Thus, recently, most modern portable systems for diagnosing marine diesel engines do not use pickup sensors, but use different variants of the analytical determination of top dead center. Diagnostics of marine engines during operating and the selection of optimal operating conditions is based on the analysis of gas pressure diagrams, as well as fuel supply and gas distribution diagrams. As a result of the analysis of the pressure diagrams, the indicator engine power is calculated, which is further used in the management of engine operation modes, in the calculation of specific indicators, as well as in the calculation of energy efficiency coefficients of marine vessels according to International maritime organization recommendations. The authors claimed a method for determining the top dead center, based on solving the equation of equality to zero the first derivative of the gas pressure under compression, which provides the required accuracy in calculating the average indicated pressure and indicator power of the engine during operation. It is shown that the method can be applicable in marine engine working process monitoring systems as an alternative to hardware methods for determining the top dead center.

Assessment of the Space Heating and Domestic Hot Water Market in Europe—Open Data and Results

The paper investigates the European space heating (SH) and domestic hot water (DHW) market in order to close knowledge gaps concerning its size. The stimulus for this research arises from incongruences found in SH and DHW market’s data in spite of over two decades of scientific research. The given investigation has been carried out in the framework of the Hotmaps project (Horizon 2020—H2020), which aims at designing an open source toolbox to support urban planners, energy agencies, and public authorities in heating and cooling (H&amp;C) planning on country, regional, and local levels. Our research collects and analyzes SH and DHW market data in the European Union (EU), specifically the amount of operative units, installed capacities, energy efficiency coefficients as well as equivalent full-load hours per equipment type and country, with a bottom-up approach. The analysis indicates that SH and DHW account for a significant portion of the total EU energy utilization (more than 20%), amounting to almost 3900 TWh/y. At the same time, the energy consumption provided by district heating (DH) systems exceeds the one of condensing boilers. While DH systems applications are growing throughout the EU, the replacement of elderly, conventional boilers progresses at a slower pace.

A comparative study on electric and gas engine heat pump

The paper compares heat pumps driven by electric motors (EHP) with heat pumps driven by gas engines (GEHP). GEHPs are still a novelty on the Polish HVACR market - therefore, the subject of the study is to indicate whether in Polish climatic conditions their use is profitable. A thorough analysis of the energy consumption of selected devices was carried out due to the consumption of utilities needed for their propulsion and the related costs. This has been done by calculating seasonal efficiency coefficients and using an innovative method of comparative modifiers allowing for unification of the performance of EHP and GEHP pumps. The results obtained include average energy efficiency coefficients, operating costs and payback times. Discussion of the calculation results proved that under certain assumptions GEHP pumps may be competitive with EHP heat pumps due to the possibility of managing waste heat at high temperatures.

Combined experimental and computational investigations of a device for respiratory organs protection at low air temperatures

Investigation of the Arctic region is a crucial task and comprises various geopolitical, economical, technological and ecological activities at a global scale. In the course of intensification of the geopolitical struggle for resources usage, the Arctic region has now brought under new scrutiny. The known development strategies for the Arctic zone of the Russian Federation are based on the usage of advanced technologies. They are aimed at the creation of supply systems for emergency-rescue and other urgent works at specific severe conditions and critically important objects, including oil and gas production, power and communal facilities. These tasks might be accomplished using modern heat-protective devices, which provide effective and sustainable usage of human energy resources. Among the vast variety of individual safety gear for workers, there are some devices which are highly-efficient at extremely low-temperature conditions. These devices are based on thermal energy regeneration process of the exhaled air. Air temperature under the mask is increased driven by the heat of expired air and heating of incoming cold air while passing through the regenerative heat exchange unit. This heat-exchange unit was previously heated during expiration. This paper presents a survey concerning the following themes: a review of scientific researches, concerning tools for human respiratory organs protection at low air temperatures, patent documents and commercially-viable technical devices used for this purpose, as well as mathematical models of regenerative heat exchange. The devices and methods were compared, their advantages and disadvantages were revealed. It was stated that the most effective heat-exchange device is not that made of tissue material, but that is a solid-state composite construction of an irregular shape with internal channels for air transport. The presented thermal mask cap is designed so that vertically oriented channel rows do not connect with each other. The developed mathematical model is based on Newton-Richmann law. This model includes equations with efficiency coefficients for regenerative cap material at accumulation and regeneration heat stages. For various external air temperatures, we have calculated temperature oscillations between regenerative heat exchange unit input and output. These values were plotted together with the experimental temperature values and compared. Mathematical model adequacy and energy efficiency coefficients for thermal masks were determined. An engineering technique for device efficiency determination was proposed. The conducted combined experimental and computational investigations allowed us to carry out the efficiency analysis of the existing heat-protective masks which are based on thermal energy regeneration process of the exhaled air for inhaled air heating. The numerical values for the efficiency coefficients were obtained, and we made some conclusions concerning further device improvements on behalf of the Arctic region development.