Criteria For Evaluation Of Efficiency Research Articles

A novel leaf bionic flow field with structured multi-level channel based on Murray's law in proton exchange membrane fuel cell for enhanced mass transfer

The design of flow field has a significant impact on the performance of proton exchange membrane fuel cells (PEMFCs). In this study, a novel leaf bionic flow field is designed and optimized based on Murray's law. The power consumption ratio is first used in the bionic PEMFC. Additionally, an evaluation criterion, the mass transfer efficiency evaluation criterion (MTEEC), is proposed to characterize mass transfer efficiency, and field synergy theory is used to analyze performance differences in mass transfer among various flow fields. The results demonstrate that adding multi-level channel and obstacles in the flow field significantly enhances cell output performance and reduces voltage losses in mass transfer regions. Applying Murray's law to distribute multi-level channel improves the uniformity of oxygen concentration distribution in the flow field and alleviates under-rib water accumulation. Compared to the secondary stream flow field (SSFF), the structure mesh of leaf bionic flow field (SMLBFF) demonstrates a nearly 19% increase in current density output at 0.45 V. SMLBFF exhibits an 81.51% increase in convective mass transfer rate compared to SSFF at 0.4 V. Moreover, the MTEEC of SMLBFF shows improvements of 179.68% at 0.5 A/cm2 and 135.43% at 1.0 A/cm2, compared to SSFF.

NH3 Synthesis from N1 Compounds by Photocatalytic Technology: Promotion Mechanism, Reaction Pathways, and Efficiency Evaluation Criteria

NH₃ Synthesis from N₁ Compounds by Photocatalytic Technology: Promotion Mechanism, Reaction Pathways, and Efficiency Evaluation Criteria

Evaluation of heat transfer enhancement effect at the hot/cold end of a Stirling engine using performance improvement factor

The driving force of a Stirling engine comes from the heating expansion and cooling compression of working medium. The enhancement of heat transfer capacity of the hot/cold end is the key to improve the Stirling engine performance, while how to objectively evaluate the heat transfer enhancement effect is a precondition. Herein, a polytropic model of a Stirling engine thermal cycle process was firstly established. A method for evaluating the heat transfer enhancement performance under oscillating flow was proposed based on the efficiency and power improvement of a Stirling engine. This method was further used to evaluate the heat transfer enhancement effect of a novel four-leaf helical heating tube under oscillating flow, the efficiency and power improvement factor of which was reached 13.5 % and 6.1 %, respectively. The results show that the efficiency and power improvement evaluation criterion was more comprehensive and intuitive in evaluating the heat transfer enhancement performance under oscillating flow compared with the conventional evaluation indictor like performance evaluation criterion and equivalent tube length and tube number criterion.

Optimal intensity measure for seismic performance assessment of shield tunnels in liquefiable and non-liquefiable soils

Relating the ground motion intensity measure (IM) and the structural engineering demand parameter is a crucial step in the performance-based earthquake engineering framework. This study investigates the selection of IM for development of probabilistic seismic demand model of urban shield tunnels subjected to earthquake ground motions in liquefiable and non-liquefiable soils. Nonlinear dynamic effective stress analyses are conducted to develop a database of the intensity measures and structural seismic responses exposed to ground shaking and soil liquefaction. Two advanced soil constitutive models (i.e., Pressure DependMultiYield03 and PressureIndependMultiYield for liquefiable and non-liquefiable soils, respectively) are employed to capture the nonlinear behavior. A suite of 23ground motion intensity measures is selected and assessed based on the evaluation criteria of correlation, efficiency, practicality and proficiency. Eventually, the multi-level fuzzy comprehensive evaluation method is employed to comprehensively consider the four evaluation criteria and establish the optimal ground motion IM suitable for probabilistic seismic demand analysis of shield tunnel structures. The obtained results show that the sustained maximum acceleration is the optimal IM for evaluating the structural seismic response, followed by the peak ground acceleration in both liquefiable and non-liquefiable soils. Peak pseudo velocity spectrum, displacement square integral and Housner spectral intensity are found to be not suitable for the probabilistic seismic demand analysis of shield tunnel structures.

Building energy efficiency assessment base on predict-center criterion under diversified conditions

With the rapid expanding of urban economy and population, how to reduce the energy consumption and improve energy efficiency of public buildings has become a key issue for energy conservation and urban development. However, due to the diversity of building usage condition, energy consumption data often has problems with nonlinearity, outliers, and diversity, which greatly reduce the accuracy of energy consumption prediction and energy conservation assessment. To overcome the above drawbacks, a regression prediction model of building energy consumption is designed, which cluster the same type of data characteristics to form a subset of equipment through Gaussian mixture clustering, and design the specific normalized adaptive loss function to determine the optimal control parameters of regression model. Furthermore, a novel predict-center energy efficiency evaluation criterion is proposed, and the cumulative distribution pattern is further statistically analyzed. Finally, the energy benchmark evaluation framework is proposed to determine the energy efficiency evaluation grade. Through comparative experimental analysis, it can be seen that the proposed prediction model can adapt to different types of building data, and have better prediction accuracy and convergence speed. The consistency and robustness of the benchmark evaluation framework and method are optimal.

Optimal design and performance enhancement based on field synergy theory in a solid oxide electrolysis cell with blockage flow channel

The mass and heat transfer capability of the flow field greatly impact the performance of a solid oxide electrolysis cell (SOEC). In this study, rectangular and semicircular blockages are added to the flow channel to improve the heat and mass transfer process in the flow field. Additionally, the flow field synergy principle and the efficiency evaluation criterion (EEC) are used to evaluate the superiority of the flow field with additional blockages, respectively. The results show that the voltages of the flow channel with rectangular and semicircular blockages are reduced by 0.02 V and 0.015 V, respectively, at a current density of 10,000 A·m−2. Compared with semicircular blockages, the SOEC with rectangular blockages has a higher gas flow rate, lower thermal stress, and the EEC value increases by approximately 28 %. This indicates that the addition of the blockages can promotes the longitudinal gas flow for the improved gas diffusion; and enhance the synergy between the velocity and temperature gradient fields for the better heat transfer capacity.

Study on the efficient heat transfer mechanism of microchannel pin-fin arrays under low pumping power

The efficient heat transfer with low pressure loss has long been a critical challenge in the microchannel heat sinks (MCHS) design. Further study is required for the quantitative analysis of the longitudinal vortex heat transfer enhancement mechanism. In this research, a microchannel heat transfer experiment and corresponding simulations are conducted. Based on the common Reynolds number range in engineering applications of MCHS, the underlying causes of heat transfer enhancement and pressure loss increase in MCHS with respect to Reynolds numbers is clarified. The results show that when the Reynolds number is 400, the cylindrical wake reduces the synergistic angle between the velocity and the temperature gradient at the streamwise gap, which greatly enhances the heat transfer performance of MCHS. In addition, when the Reynolds number is 900, the early separation of the cylindrical wake vortex leads to a significant reflux near the center of the spanwise gap, which significantly increases the pressure loss. A Different Reynolds number Efficiency Evaluation Criterion (DEEC) is proposed for evaluating the performance of MCHS. It is found that the flow state of cylindrical wake with Reynolds number of 400 has the best heat transfer efficiency. The concept of introducing longitudinal vortices into the pin–fin array can serve as a key guideline in the heat transfer enhancement optimization design of MCHS.

Research on textile-vamp punching based on punching point gradient phase and edge significance

A visual technology to identify the punching points of a textile vamp to replace manual punching by machinery is proposed in this paper. This could solve several problems relating to the manual punching of textile vamp, such as high manual-punching strength, low efficiency, and poor punching accuracy. Unsharp mask guided filtering was adopted, to enhance the details of the textile-vamp punching points, considering the edge point position, gradient phase, and edge significance of the punching points, in building the template matching similarity measure function. A partial Hausdorff distance was proposed to sum and average values, to improve the degree of matching of punching point shape defects. A local search area of punching points to improve identification efficiency and punching evaluation criteria was established to evaluate the punching effects. The results showed that the matching similarity of the complete boundary was above 0.9. Positioning accuracy was 0.43 mm in the x-direction, 0.38 mm in the y-direction, and repeat positioning accuracy was 0.09 mm. The center average relative error was 5.03% and the relative error of the radius was 7.81%. Identification timeliness increased with the rotation angle, template size, and the number of punching points. When the rotation angle was between –180° and 180° and the number of punching points was 24, identification timeliness was 830 ms, which met productivity requirements. Textile-vamp punching grades A to D qualified, however, grades E and F were unqualified for punching.

Summative evaluation of implementation of Jordan's national anti‐corruption strategy, 2013–2017, in the perspective of public choice theory

AbstractThis summative evaluation's objective is to evaluate the degree to which Jordan's National Anti‐corruption Strategy (JNACS) effectively and sustainably achieves its objectives in the war against corruption, with particular reference to the Anti‐corruption Commission (JACC). This evaluation analyzes certain indicators and methods used to combat corruption in the public service. This evaluation considers the before and after approach. Pre‐implementation and post‐implementation periods were compared using trend analysis to show the difference between pre‐implementation and post‐implementation of JNACS from 2013 to 2017. A line chart and interrupted time series were used to display trends over time, and the Wilcoxon signed test was utilized. Our summative evaluation findings are mainly structured by the evaluation criteria of effectiveness, efficiency, and relevance. These findings illustrate the difficulty and challenge of making progress in the war against corruption in Jordan. This evaluation has indicated that JNACS (2013–2017) was ineffective in strengthening the capacity of the JACC; promoting investigation, prosecution, and court proceedings of corruption; and enhancing international cooperation in the anti‐corruption field. The task of this agency is challenging due to the broad definition of corruption and the increasing demand for its services within a very complicated operational environment. As a result, our summative evaluation makes some policy recommendations after numerous arguments regarding the subject matter.

Prospects for hydrogen production by the method of gasification of MSW at operating TPPs

The work is devoted to the development of a thermal scheme for the conversion of a cogeneration power plant to threegeneration with the production of hydrogen as a new product.The purpose of the work is to assess the possibility and potential of hydrogen production from MSW at the existing thermal power plants of St. Petersburg.To achieve this goal, it is necessary to develop a methodology for selecting the site of an existing thermal power plant in order to integrate a hydrogen production complex by the MSW gasification method, as well as a methodology for estimating the amount of hydrogen that can potentially be obtained from a given amount of MSW. The research methods include simulation of the thermal circuit of a steam power plant in the United Cycle program.The paper proposes an algorithm for selecting the site of an operating thermal power plant for the integration of a complex for the production of hydrogen by the method of MSW gasification. The algorithm can be applied to any subjects of the Russian Federation, and its relevance is confirmed by strategic documents. Potential locations for the new TPP are being considered in the territories of TPP-21 and TPP-22, which have the necessary resources and good infrastructure. As a result of the study, the site of TPP-22 was selected as the most suitable for the placement of new facilities.A new thermal scheme of a threegeneration power plant has been developed, including a hydrogen generation unit by the MSW gasification method. This allows the production of hydrogen in parallel with the production of electricity and heat. The efficiency evaluation criterion is the fuel heat utilization factor (FHUF). Regardless of the hydrogen content in the generated synthesis gas, the integration of the synthesis gas cooler into the thermal circuit of the TPP leads to an increase in the FHUF and an additional energy effect. This scheme increases the efficiency of existing TPP plants, regardless of the morphological composition of municipal solid waste.

Energy efficiency analysis of a rotating-drum dryer using hot steel balls for converter sludge

We proposed a novel rotating-drum technology for drying converter sludge with high efficiency and low cost. This study aimed to investigate the drying energy efficiency of our technology and the effect of sludge treatment mass (ms0 = 3.0–9.0 kg), steel ball temperature (Tb0 = 300–500 °C), steel ball diameter (d = 20–40 mm), and drum rotating speed (n = 1–7 rpm). The evaluation criteria of energy efficiency included energy utilization rate (ηb), specific energy consumption (SEC), drying rate (DR), etc. Results showed that appropriately increasing ms0 and decreasing Tb0 can increase ηb and reduce SEC, but also reduced DR. Selecting appropriate d and n can not only increase ηb and DR, but also reduce SEC. Under our experimental conditions, ηb is 50–95%, SEC is 0.8–1.5 kW·h/kgw, and DR is 1.0 × 10−4–1.8 × 10−3 g/(g·s). The improved self-scaling method was used to evaluate the energy efficiency under the studied working conditions, and the comprehensive optimal combination of operating parameters was obtained in our experiments, which can be achieved ηb > 78%, SEC < 1.0 kW·h/kgw, and DR > 9.9 × 10−4 g/(g·s).

Nanofluid turbulent flow in parabolic trough collector: Insulator roof, acentric absorber tube and SiC nanoparticles effects

The key purpose of the current study is to design a parabolic trough collector (PTC) having insulator roof and an acentric absorber tube, with nanofluid using single-phase and two-phase mixture models (TPM and SPM). The effects of employing the SPM and TPM on the fluid field and heat transfer of nanofluid (SiC nanoparticles (16–90 nm) and volume fraction (0–4%) to the water and EG-water) in the absorber tube is studied. Results of present investigation shown that for both proposed (novel) and conventional PTC arrangements, the pressure drop (3%), Nusselt number (5%), friction factor (3%), energy efficiency (3%), and performance evaluation criteria (PEC) (3%) employing the TPM are greater than that of SPM. In addition, it is shown that employing the novel PTC presents greater Nusselt number (25%), energy efficiency (30%), and PEC (50%). Temperature field inside the absorber tube and heat transfer fluid zone employing the TPM are greater than that of SPM. Maximum PEC for SiC/EG-water and EG-water nanofluid are 1.67 and 1.70, respectively, for sinusoidal-wavy minichannel having a nanoparticle volume fraction of 4%, nanoparticles diameter of 90 nm, and Reynolds number of 15,001.3. Furthermore, EG-water as base fluid with a nanoparticle diameter of 90 nm presents greater energy efficiency than water.

An emergency observation method for space debris dangerous conjunction events based on nanosatellite constellation

The amount of space debris is rising rapidly, and the number of satellites launched by humans is also growing. This poses a serious threat to the security of many important space assets including the International Space Station and the China Space Station. Due to the frequent occurrence of hazardous space conjunction (potential collisions) events, we aim to use a constellation composed of a few optical satellites to observe these space dangerous conjunction events, thereby improving the observation accuracy and timeliness of key conjunction events. We consider a variety of factors to establish an optical nanosatellite constellation design model, develop constellation observation efficiency evaluation criteria, construct a constellation configuration evaluation function, and design the performance parameters of space-based optical telescopes. The optimal orbit parameters and constellation configuration are obtained by using the genetic algorithm for optimization calculation. It is determined that a constellation of 6 satellites can track and observe more than 96% of potentially dangerous conjunction objects 24–48 h before a dangerous conjunction occurs. According to the observation data, high-precision orbit information of space objects can be obtained, which can reduce the collision false alarm rate by 99%. As a result, operators are notified to take collision avoidance measures only when the space object is truly in danger. This approach greatly reduces the number of avoidance operations caused by false early warnings, lowers the operating cost of space assets, and ensures the safety of space assets.

Analysis of efficiency and performance evaluation criterion of nanofluid flow within a tube enhanced with perforated triple twisted tape: A two-phase analysis

In this work, a two-phase simulation is used to examine the flow of nanofluid and hydraulic-thermal analysis in a tube with triple-perforated twisted tape (TT). Water-MWCNT NF is used as the heat transfer fluid (HTF) in a variety of volume concentrations (φ). The fluid enters the tube at Tin = 300 K at different velocities corresponding to Reynolds numbers 6000, 12000, 18000, and 24000. The 2L inlet-to-length section is intended to confirm that the inlet flow is entirely developed. In this work, various geometrical factors of TT are investigated. The optimization is carried out to achieve the utmost PEC. According to the results, the use of TT has a profound effect on the H-T features of the channel and causes undulating flow, which increases the heat transfer (HT) coefficient and the pressure drop (Δp). Besides, it is recognized that the PEC values are always greater than 1.10, indicating that the utilization of these turbulators (TRBs) is H-T efficient. The perforated pattern (Case E and N = 4) is presented as the best pattern in this study, and its PEC amounts for NF in φ = 0.8% at Re = 6000, 12000, 18000, and 24000 are 1.38, 1.60, 1.77, and 1.92, respectively.

Scaling analysis of diffusion–reaction process in proton exchange membrane fuel cell with the second Damköhler number

Diffusion-reaction coupling process in flow fields dominates the performance of proton exchange membrane fuel cell. This paper defined a new second mechanistic Damköhler number (DaII,mech) to compare the similarity and efficiency between different flow fields. Dimensionless model and numerical model were combined together to analyze the single channels, parallel and single-serpentine channels. According to trends of DaII,mech curves over current density, the diffusion–reaction interaction can be divided into three states: reaction-enhanced (DaII,mech ∼ 1000), transition and diffusion-limited states (DaII,mech ∼ 100). With the enlargement of active area, almost the same Damköhler curves and contours demonstrate the similarity of diffusion–reaction process in single channel and parallel channels. But there is no obvious scaling invariance over active area for single-serpentine channels due to its asymmetric structure. A new efficiency evaluation criterion (EEC) based on Damköhler number and Euler number is proposed to comprehensively compare the fuel cell performance. The EEC curves also present three-state characteristics. And the EEC values of parallel channels are several orders of magnitude higher than that of single-serpentine channels. This scaling method is expected to be further generalized to other flow fields and operating conditions to accelerate the fuel cell design and optimization.

Design and optimization study of discrete inclined ribs enhanced bend tube based on “Diamond” active cooling thermal protection systems of hypersonic aircraft

When the hypersonic aircraft cruises, the surface will generate huge aerodynamic heating. Aiming at the thermal protection of hypersonic aircraft, this paper presented a study on the thermal–hydraulic and thermodynamic performance of discrete inclined ribs enhanced bend tube based on the designed “Diamond” channel. Meanwhile, a comprehensive numerical investigation was carried out for different models. The fluid velocity was found to vary in the range of 0.1–3.5 m·s−1, with the corresponding Reynolds number ranging from 3600 to 127000. The inlet temperature of heat transfer fluid was set to 253 K. It was visible that double–symmetrical longitudinal swirl was generated under a single upper and lower arrangement (Model D), which led to the best cooling performance on the inner wall. The performance evaluation criteria (PEC) and efficiency evaluation criterion (EEC) reached 0.99–1.18 and 0.66–1.00, respectively. The effect of four geometrical parameters (height–width ratio(H/d), length–width ratio (L/d), group number of ribs (n), and tilt angle (α)) of which the ranges are 0.5–2.5, 1.0–4.0,6–15 and 0°–90°, separately, was explored. The results showed that the inner wall temperature decreased up to 4.4 K when the Reynolds number was 72000. The Nusselt number and friction factor increased about 9.9 %–28.8 % and 16.5 %–111.5 %. Efficiency evaluation criterion reached 0.43–0.96. It was found that the combination of parameters would significantly affect the distribution of longitudinal swirls under the influence of secondary circulation in the bend tube. Moreover, many pairs of small vortices near the wall could improve active thermal protection performance. After obtaining the fitting function through the artificial neural network (ANN), the genetic algorithm (GA) was applied to obtain the Pareto front. The design variable for the L/d = 3.19, n = 11, and α = 14.3° was selected as the optimal solution by the TOPSIS method. When Reynolds number is 72000, the corresponding Tin and ΔP were 261.86 K and 2471.2 Pa. The performance evaluation criteria and efficiency evaluation criterion reached 1.02 and 1.09, respectively. Furthermore, a design variable for the L/d = 3.0, n = 11, and α = 15° was given for ease of engineering. The present work verified the feasibility of realizing heat transfer enhancement by combining the secondary circulation with longitudinal swirls formed by bend tube and discrete inclined ribs and proposed a new design scheme of active cooling thermal protection systems (ACTPS).

The Purpose and Efficiency of State Governance in the Area of Protection and Use of the Animal World: Legal Values of Administrative Law

Introduction . In accordance with the Russian Federation state policy on environmental development, the preservation of biodiversity is declared one of the conditions for ensuring environmental protection and environmental safety. The animal world is an integral part of biological diversity and, accordingly, is one of the essentials for solving the tasks and achieving the goals of pro-ecological development. At the same time, according to the basic principles of the national economic policy, the establishment of excessive environmental requirements is determined as the risk for the economic progress. Thus, environmental protection is not an ultimate value and environmental requirements should be set at the level that does not hinder the economic growth. The study aims to analyse the objective and subjective nature of the purpose of legal regulation and the administrative law efficiency in the area of protection and use of the animal world objects. To reach the above aim the definition of concept and distinguishing the features of the purposes of legal regulation, as the legal value of the administrative law, was made; the same as the specification of the legal support efficiency criteria of the animal world objects’ protection and use. Materials and Methods. The methodological framework used in the article includes a set of philosophical, general scientific and specific scientific methods of cognition (analysis, synthesis, concrete historical, logical method, etc.). Results . The main result of the study is provision of the doctrinal definition of the purpose of legal regulation of faunal legal relationships and the evaluation criteria of the state governance efficiency in the area of protection and use of the animal world objects. Discussion and Conclusions. The article is useful for educational activity of law universities and faculties and for the activity of executive authorities of the subjects of the Russian Federation. The proposals and recommendations developed by the author in the course of research are advised to be used as the theoretical basis for conducting and organising the scientific projects on the topic of state governance in the area of protection and use of the animal world.

Experimental performance of proton exchange membrane fuel cell with novel flow fields and numerical investigation of water-gas transport enhancement

The performance of the proton exchange membrane fuel cell (PEMFC) depends on the water-gas transport capacity of flow fields. In this paper, the performance of the designed PEMFC with novel flow fields is tested by experimental methods. The experimental results show that the PEMFC with opposite sinusoidal wave flow field (OSWFF) and intercepted flow field (ICFF) are improved compared to the parallel flow field. The PEMFC with single-inlet OSWFF and ICFF show 19% and 11% performance enhancement at 2.0 A cm−2, respectively. A 3D numerical model for the validation experiment is established to analyze the water-gas transport characteristics of the flow field. The mass transfer performance of ICFF with 3D structural optimization is much better than that of OSWFF with 2D structural optimization, and the effective mass transfer coefficient and efficiency evaluation criterion are improved by 106% and 258%, respectively. The 7% improvement in oxygen uniformity in the dual-inlet mode compared to the single-inlet mode enhances the stability of the electrochemical reaction and the 28% improvement in velocity uniformity, which contributes to the uniform distribution and discharge of liquid water, which in turn enhances the PEMFC performance.

RESEARCH ON THE PRINCIPLES OF ARTIFICIAL NEURAL NETWORK CONSTRUCTION AND PARAMETER MODELING

Studies show that neural networks with multilayer direct propagation have be-come more widespread, which is due to the simplicity of their implementation, the availability of advanced learning methods, and the parallel execution of calculations. In these networks, the computational complexity increases proportionally to the square of the data size, which leads to a decrease in performance and an increase in hardware costs. The main problems of synthesis of artificial neural networks, criteria for evaluating the effectiveness of artificial neural networks, issues of choosing layers and the number of neurons in each layer are investigated. In the work, the mean square error, mean absolute error and mean absolute percentage error criteria are considered for evaluating the efficiency of neural networks. In general, one hidden layer of a neu-ral network is sufficient for most problems, two hidden layers can represent a function of any shape, and adding a third and more layers results in very little improvement in network performance. Expressions are given for the total number of parameters de-pending on the number, and the number of inputs from the binary sequence, as well as the minimum and maximum values of the training examples depending on the total number of parameters and the number of outputs. The studies have shown that the se-lection of the statistical model efficiency evaluation criteria depends on the problem to be solved. The results of the simulations performed using the MATLAB package are presented.

COMPARATIVE ANALYSIS OF EXERGETIC EFFICIENCY OF HEAT RECOVERY SYSTEMS OF BOILER PLANTS

The paper presents the results of a comparative analysis of the exergetic efficiency of heat recovery systems of boiler plants. The need to ensure the efficient operation of heat recovery systems for various purposes determines the importance and relevance of research conducted in this field. The purpose of the work is to increase the exergetic efficiency of heat recovery systems of various purposes. The results of solving the tasks necessary to achieve the set goal are given: - submit heat utilization systems of various purposes in the form of structural diagrams with the identification of exergetic flows of heat carriers; - choose exergetic efficiency evaluation criteria for heat recovery systems of various purposes, calculate their values and conduct a comparative analysis; - develop recommendations for the use of heat recovery systems for various purposes, taking into account the specifics of their application. For research, a complex methodology was used, which combines structural-variant methods of exergetic analysis with methods of presenting exergetic balances in matrix form. Three types of heat recovery systems with different numbers of consumers of recovered heat were considered. Structural diagrams of heat recovery systems of various purposes with identification of exergetic flows of heat carriers between individual discrete elements have been developed. Exergetic losses, thermal exergetic criterion and exergetic efficiency were selected as criteria for evaluating exergetic efficiency. Their values were obtained for heat recovery systems and their elements at different values of the relative power of the boiler. The largest exergy losses occur in the water-heating heat exchanger, smoke extractor and pumping system, the smallest - in the air-heating heat exchanger and gas heater. An increase in the relative power of the boiler leads to an increase in the relative contribution of the exergy losses of the water heating heat recovery system, as well as the pumping system and the pipeline system to the total exergy losses in the heat recovery system. It has been established that increasing the number of consumers of recovered heat in the heat recovery system and using rational ways of reducing total exergy losses increases the efficiency of heat recovery systems. Further developments in this field will allow to increase the exergetic efficiency of heat recovery systems for various purposes.