Performance Evaluation Factors Research Articles

Analysis of thermohydraulic flow and enhancement heat performance in 3D dimple tube based on varying geometrical configurations

AbstractThis research work investigates how different dimple designs affect the flow field and thermal performance of three‐dimensional pipes. The study focuses on the effect of the number of improved dimples NOD (3, 4, and 5), different groups numbers DGNs (1, 2, and 3 groups), arranged around the pipe, and different distances between dimples (DBDs). Dimple geometry affects flow: Changing dimple parameters alters the velocity and pressure distribution within the pipe. Performance evaluation factor (PEF) varies with dimple configuration: The PEF, which balances heat transfer enhancement and pressure drop penalty, ranges from 1.187 to 1.23 for NOD and from 1.292 to 1.31 for DGN, and also from 1.26 to 1.302 for DBD. Reynolds number range, Re = 4000–15,000; turbulence model, standard k–ε model; numerical scheme, second‐order upwind scheme; test tube conditions, inlet temperature (Tin) = 25°C; pipe diameter D = 23 mm; thickness = 2 mm; heat flux q = 25,500 W/m²; and material (Cu). This research focuses on improving heat transfer efficiency in pipes using dimples. Dimple size and arrangement significantly impact flow dynamics and heat transfer. PEF is used to evaluate the overall performance considering both heat transfer improvement and pressure drop penalty. The study found a specific range for PEF under various conditions for different dimple configurations. The average enhancement in Nusselt number for model 2 was 15.16% compared with a smooth pipe and the heat transfer performance by 10.028%–28.963% at the effect of NOD, the DGN has slightly higher Nu values than smooth pipes, indicating improved heat transfer due to the dimples (around 7%–58% at Re 4000–15,000 and 9%–13% at Re 12,000), and at DBD (13.5%) at a Reynolds number of 12,000 and 4.6%–59% at Re 4000–15,000.

Hydrothermal analysis of parallel and symmetric microchannels with phase change slurry and porous fin designs

The dynamic information of microchannel systems with parallel and symmetric configurations is insufficient, which limits our ability to compare and optimize these systems in all directions. In this study, thermal and hydraulic characteristics in parallel and symmetric microchannel heat sinks (MCHSs) with porous fins cooled by phase change slurry are investigated. A 3-D steady state conjugate model is adopted to compare the effects of fin configuration, coolant type and structural parameters on hydrothermal properties of wavy MCHS. The variations of dimensionless parameters involving Nu, f, η (temperature control effectiveness) and PEF (performance evaluation factor) are considered to demonstrate the effectiveness of combined design on overall performance enhancement of wavy MCHS. Results indicate that lower temperature increment and higher pressure loss appear in wavy configuration with porous fins than in straight mode, and lowest thermal resistance arises in parallel porous fin design. At the narrow position of symmetric channel, the fluid changes from the low-speed drop-shaped micelle to high-speed bullet-shaped one with increasing A, which leads to higher Nu with larger pressure drop penalty. Due to the extended flow route and improved fluid mixing, η increases with decreasing wavelength in all cases, and η of porous microchannels with both phase change slurry and parallel fins is much larger than that of symmetric one and the one with only base fluid. Compared with wavy fin configurations with small and large ε, lower temperature and its more uniform distribution happen in the mode with medium porosity. In comparison with basic configuration, the parallel configuration with slurry as cooling medium has the maximum PEF value when the pore size is 0.14 mm, up to 1.64. Larger f increase occurs in wavy channel with increasing N, and the space shortening between adjacent channel cavities in symmetric mode makes the adjoining Dean vortices easier to contact and repel, thus making it appear larger rise of f than parallel mode. Compared with other channel parameters, it is not effective to improve the overall performance of wavy MCHS with porous fins by adjusting α. Overall, the throat effect of symmetric MCHS significantly occurs in channel configuration with larger A, bigger λ, lower ε, smaller dp, more N, and lesser α, leading to higher f rise than the parallel mode.

Establishment, performance evaluation, and influence factors analysis of the α-amylase reference measurement procedure

Establishment, performance evaluation, and influence factors analysis of the α-amylase reference measurement procedure

Automatic generation method for long-focal-length unobscured freeform optical systems with small volume

The existing design methods for long-focal-length unobscured freeform systems rarely consider the imaging quality requirements and volume constraints simultaneously, causing most of the final designs to not fulfill the requirement of light weight. This study proposes a method to automatically design a long-focal-length unobscured reflective system that satisfies volume constraints while maintaining high imaging quality. First, a method to adaptively set the structural parameter range is proposed, and multiple parameters for different systemic specifications can be effectively calculated within it. Subsequently, the systemic volume and area functions are constructed using the ray tracing method, where the tilt angles, distances between mirrors, and radii of curvature of the mirrors are chosen as the optimization parameters. Third, a comprehensive objective function is jointly established combining ray obscuration and convergence as performance evaluation factors. Then, the structural parameters of a long-focal-length unobscured system with small volume are easily obtained via the simulated annealing method. Finally, the improved W-W method is used to further enhance the imaging quality of the system, and an unobscured freeform reflective optical system with three mirrors is automatically generated. Experimental results demonstrate that our method can automatically calculate the parameter ranges to facilitate the search for structural parameters, and effectively design the long-focal-length unobscured freeform systems with small volume and high imaging quality.

Driving factors and key paths of greenhouse gas and air pollutants synergistic control using hybrid multiple-criteria decision-making

Humanity has consumed a large amount of energy and resources to maintain the rapid development of the economy and society, causing greenhouse gas and air pollutants to rise continuously, generating enormous pressures for the sustainable development of many cities. It is economical to control greenhouse gas and air pollutants from the synergy perspective. To identify the key driving factors involved in synergistic control, this paper uses the pressure-state-response (PSR) model to design a performance evaluation model of greenhouse gas and air pollutants synergistic control (GASC) utilizing pressure, state, and response dimensions. The performance evaluation factor system of GASC comprises three primary aspects and 18 criteria. The analytic hierarchy process (AHP) was used to determine the weight of each factor in the evaluation system. The technique for order preference by similarity to an ideal solution (TOPSIS) method was used to calculate the ranking of the synergistic control effects of the four representative provinces in China. We use Importance-performance analysis (IPA) to analyze the performance of driving factors of synergistic control in the province with the lowest ranking from 2016 to 2020. The research shows that in Northeast China, represented by Liaoning province, the government’s response should include changing the support strategy for the new energy consumer, introducing synergistic control standards and policies, and making flexible adjustments to the supply chain. The research provides a scientific basis for the performance evaluation of GASC and decision-making support for lean response strategies.

Field synergy analysis on thermal-hydraulic behavior of phase change slurry in porous microchannel heat sink with graded porosity configuration

In this study, a novel design of porous microchannel heat sink (MCHS) with graded porosity configuration is proposed in the hope of attaining lower flow and thermal resistances than constant porosity (CP) configuration. The efficacy of new scheme is validated by utilizing a three-dimensional solid-fluid conjugate model based on the finite volume method, which considers the flow and heat transfer of microencapsulated phase change material slurry (MPCMS) inside the porous fins. It is reported that the thermal performance of porous MCHS with constant and graded porosity configurations is significantly better than that of non-porous MCHS. The feasibility of new design is verified by comparing the hydrothermal behavior of multiple graded porosity MCHSs and CP configuration for different fin designs (involving the number of graded equidistant fins N, graded length ratio R, and fin-to-pitch width ratio β) and operating conditions (including Reynolds number Re, mass fraction cm, and inlet velocity uin). The comprehensive performance improvement mechanism of MPCMS in graded porosity microchannels is discussed through the analysis of flow and thermal details, field synergy angle (θ) and field synergy number (Fc), and the overall performance of new design is evaluated by performance evaluation factor (PEF). Results indicate that the six types of porous MCHS with stepwise varying porosity exhibit lower thermal resistance than CP mode, and better thermal behavior and larger PEF can be obtained at N = 2 and β = 0.7. Smaller and larger R should be chosen for stepwise increasing porosity (SIP) and stepwise decreasing porosity (SDP) modes, respectively, to achieve higher heat transfer enhancement while avoiding greater friction losses. The Fc value of porous MCHS with various porosity configurations is about two orders of magnitude less than 1 and shows a monotonically reducing trend with Re, and the synergistic effect deteriorates at high Re. Compared to the CP mode, a low-θ “drift” toward the low porosity region of porous fin occurs within the graded porosity MCHS, which decreases and increases in the downstream and upstream directions of the “drift”, respectively. Among the novel MCHS designs, the z-directional SIP mode acquires the best overall performance due to the excellent synergy between the velocity and temperature fields, and its PEF consistently exceeds 1.13 and reaches up to 1.33. Generally speaking, the fin porosity of graded porosity MCHS near the channel cavity, channel top, and channel inlet should be greater for superior comprehensive performance.

Analysis of Machine Learning in Classifying Bank Profitability with Corruption Factor

Corruption, which is generally defined as the abuse of authority for personal benefit, is not a recent phenomenon and has become a major issue in almost all countries throughout the world. Indeed, a high level of corruption increases bank non-performing loans which in turn reduces profitability and intensifies the fragility of the banking industry. Given the adverse impacts, corruption has been used as one of the factors in bank performance evaluation. As research on corruption-bank performance with machine learning techniques is rarely reported in the literature, this paper presents the empirical comparison of different machine learning algorithms for classifying bank profitability. Besides machine learning performance comparisons, this paper presents the analysis of machine learning features importance to justify the effect of corruption factor in the different machine learning algorithms for classifying bank profitability. The results indicated that all the tested machine learning algorithms present a good ability of classifying bank profitability at accuracy percentages above 70% but corruption index has contributed very minimal effect to the machine learning performances. The framework of this research is highly reproducible to be extended with a more in-depth analysis, particularly on the bank profitability factors as well as on the machine learning algorithms.

Thermal evaluation of heat exchanger and a dry-cooled supercritical CO2 mixture Brayton cycle based on three-dimensional and one-dimensional models: Key factors and potential applications

High ambient temperatures in the desert environment and heat capacity mismatch of printed circuit heat exchanger (PCHE) are always main factors that limited cycle efficiency of supercritical CO2 Brayton cycle (SCBC). The SCBC was established to obtain the operating parameters of precooler, low temperature recuperator (LTR) and high temperature recuperator (HTR) in this paper. The performance evaluation factors were developed and applied. The findings demonstrated that the precooler total heat transfer coefficient (HTC) peaked near the pseudo-critical temperature. Smaller hot-side pressure, larger hot-side and cold-side mass flux could improve heat transfer performance (HTP) of the precooler. The CO2-H2S in the precooler had larger HTC and pressure drop (ΔP), the CO2-Propane in the LTR and HTR had larger total HTCs and ΔP for the same critical temperature. Heat transfer correlations about the precooler of pure CO2 and CO2 mixtures were proposed. A conclusion was drawn by analyzing the performance evaluation factors that the PCHE using CO2-H2S for the precooler and CO2-Propane for the LTR and HTR could achieve better HTP under the same ΔP, but had the smaller effectiveness under the same ΔP. The CO2-H2S had the potential for practical application because of the larger cycle thermal efficiency and relatively good tolerance to the change of critical temperature.

Thermoelectric cooler with embedded teardrop-shaped milli-channel heat sink for electronics cooling

Thermoelectric coolers (TECs) offer a site-specific, on-demand, and solid-state thermal management solution for on-chip electronics cooling. To maximize their cooling performance, it is essential to integrate an effective heat exchanger, such as microchannels, on the TEC’s hot side. However, traditional microchannel heat sinks pose challenges, including the necessity for high-cost equipment and the manifestation of deleterious parasitic contact thermal resistance with the TEC. Recent studies have demonstrated the superior performance of teardrop-shaped microchannels compared to their conventional counterparts, yet their effectiveness at the milli-scale remains unexplored. In this work, through systematic numerical simulations across nine milli-channels with distinct variable cross-sections, we propose a teardrop-shaped milli-channel heat sink designed for fabrication through cost-effective mechanical machining. The optimized teardrop-shaped milli-channel exhibits a superior overall thermo-hydraulic performance evaluation factor (PEC) of approximately 1.8 with respect to its rectangular cross-sectional counterpart. Furthermore, we seamlessly embed the designed milli-channel heat sink into the substrate of the TEC to mitigate the parasitic contact thermal resistance. Measurements on the TEC embedded with the teardrop-shaped milli-channel heat sink show that the cold end temperature reaches a minimum value of −18.6 °C at an optimal input electrical current of 3.5 A and an inlet coolant flow velocity of 0.2 m/s. This temperature represents an improvement of approximately 3.5 °C and 4.4 °C compared to the TEC with an attached teardrop-shaped milli-channel and a conventional water block heat sink, respectively, under identical operating conditions. Additionally, a prototype TEC cooling system with the embedded teardrop-shaped milli-channel for high-power field-effect transistor (FET) cooling is demonstrated. Operating at an input electrical current of 3.5 A and an inlet flow velocity of 0.6 m/s, our proposed TEC cooling system achieves a steady-state working temperature of 51.3 °C for the FET at a high heat flux of 75 kW/m2, outperforming the TEC with an attached teardrop-shaped milli-channel and a conventional water block heat sink by approximately 1.4 °C and 2 °C, respectively.

Influence of different geometrical dimple configurations on flow behaviour and thermal performance within a 3D circular pipe

Numerical analysis has been performed to evaluate the heat transfer characteristics and per-formance of a circular pipe with geometrical dimple patterns. Using computational fluid dy-namics (CFD) codes, we examine the effects of geometrical configurations on the flow and thermal behavior of circular pipes with concavity (dimple) diameters. Fluid mixing and flow perturbation are facilitated by perforations across the pipe core and wall regions, thereby im-proving thermal efficiency. In addition, a concavity with a diameter of 4 mm enhances heat transfer. Based on the results of the study, the disrupted pipe wall and pipe core region pro-duce swirls and transverse vortices in the flow that provide superior heat transfer compared to conventional (smooth) pipes. In an increasing Reynolds number (Re), mixing, secondary, and separation flows become larger. Performance evaluation factor (PEF) values increased at low Reynolds numbers when dimple diameter was 1mm. As a result of these improved pipes, heat exchanger efficiency may improve in industrial applications, a key factor for energy con-servation.

The influence of corrugated pipes parameters on heat transfer characteristics

In order to investigate the influence mechanism of various corrugated structures on the heat transfer of continuous annular concave-convex corrugated pipes, this paper examines the influence of corrugation height (Ch = 1 mm, 1.5 mm, and 2 mm) and corrugation width (Cw = 1 mm, 1.5 mm, and 2 mm) on the flow pattern, turbulent kinetic energy, Nusselt number, friction coefficient, and performance evaluation factor. Then, the correlation equations for Nusselt number and friction coefficient are established with different corrugated structural parameters. The results show that with the increase of Ch, the vortex number, turbulent kinetic energy, and friction coefficient in the pipe increase while Nusselt number decreases. The maximum perfomance evaluation factor is 0.90 at Ch = 1 mm. However, with the increase of Cw, the vortex number and Nusselt number in the pipe increase, while turbulent kinetic energy and friction coefficient in the pipe do not change much. The maximum performance evaluation factor is 0.87 at Cw = 2 mm. Therefore, for this type of corrugated pipe, one should choose a small Ch and a large Cw.

수처리용 섬유여과기 성능평가인자 도출 및 평가방법개발에 관한 연구

This study investigated the performance evaluation factors for the fiber filtration process in water treatment and researched the performance evaluation items and methods for assessing these factors. South Korea's water supply and sewage policies focus on modernizing civil structures and networks and introducing advanced treatment facilities. Reflecting these policies, the Waterworks Act describes the minimum requirements that water supply facilities must meet to ensure a consistent quality (water quality) of drinking water. Therefore, the Waterworks Act has introduced usage standards for water treatment processes and materials for water supply to manage the quality of drinking water. Firstly, the Ministry of Environment has issued water supply facility standards, which explain the minimum standards for water supply facilities. Secondly, there are hygiene and safety standards (suitability certification) and group standard certification. Standards and certifications are established to evaluate materials and products suitable for water supply facilities. Thus, two criteria are required to apply them to water supply facilities.
 In Republic of Korea, a new concept of water treatment process has been developed that can replace traditional water treatment processes. This involves a fiber filtration process that contracts and relaxes fiber strands, removing turbidity and suspended solids. There is a movement to adopt this process. Such fiber filters can provide better treatment efficiency, use smaller sites, and have faster processing speeds. However, the use of different evaluation methods by manufacturers has prevented consumers from accurately understanding the performance and raised doubts about the reliability of the technology.
 The result of this study is the development of a standardized performance evaluation method, and the derivation of performance evaluation factors for fiber filters. Through standardized performance evaluation factors and methods, an objective performance evaluation of the fiber filtration process can be conducted.

Numerical investigation on rheological and thermal performances of microencapsulated phase change material suspension (MPCMS) in microchannel

Rheological and thermal performances of microencapsulated phase change material suspension (MPCMS) in microchannel are investigated with different mass fractions, Reynolds numbers and particle size distributions. The deviations of the two-phase model and the single-phase model from experiments are also examined and compared. The solid-liquid phase change process of MPCMS is described by the effective heat capacity method. The results show that as the mass fraction Cm increases up to 30%, the MPCMS flow starts to transform from the Newtonian fluid to pseudoplastic behavior (shear rate 0–110 s−1), and the resultant performance evaluation factor (PEF) increases from 1 to 1.27. As the Reynolds number is raised from 96 to 960 (Cm = 15%), the viscosity remains nearly constant (shear rate 100–1000 s−1) flowing as a Newtonian fluid, and the PEF decreases from 1.24 to 1.14. With the particle size increasing (dp = 0.1–10 μm), non-Newtonian characteristics of the suspension become more obvious (shear rate 9300–15,000 s−1), and the PEFs are all 1.15. The average deviation of the single-phase model is 12.3% compared with the experimental data, while it is only 3.65% for the two-phase model. The results provide a reference for the optimization of MPCMS application in microchannel from a rheological perspective.

Two-phase flow condensation heat transfer characteristics of R-134a inside three-dimensional cylindrical micropillar enhanced tube

This paper presents an experimental investigation for evaluation of heat transfer coefficient, frictional pressure drops and flow regimes with their transitions during the condensation of R-134a inside a smooth, two microfins (MF1 and MF2) and a newly developed micropillar (MP) tubes. The experiments are carried out for a range of mass flux at an average saturation temperature of 35°C. Micropillar tube has produced the maximum heat transfer coefficient, while the microfin (MF1) tube resulted the highest frictional pressure gradient compared to other tubes. The experimental observations of microfin and micropillar tubes are plotted on the mass flux versus vapor quality flow map and Taitel and Duckler flow map to discuss the transitions within different flow patterns achieved. Visual inspection of the flow regimes with varying mass flux and vapor quality showed stratified-wavy, intermittent, and annular flow regimes. The occurrence of annular flow is found to be more in MF1 and MP tube. A performance evaluation factor (PEF) is defined to evaluate the thermal-hydraulic performance of the tubes. Using the same, it has been observed that the newly developed MP tube has a PEF value greater than unity which suggest augmentation of heat transfer coefficient at the expense of lesser pressure drop penalty.

Sustainable Transformation Evaluation and Obstacle Factor Analysis of Mature Coal Resource Cities: A Study Using Jinzhong City as an Example

Transformation and development performance evaluation and obstacle factor research are standard and important bases for measuring the transformation of mature resource cities. Based on the connotation of transformational development, this paper presents the selection of indices for the construction of a measurement index system that covers four aspects: economics, people’s well-being, resources, and the ecological environment. Taking Jinzhong City as an example, this study measures the implementation effect of sustainable development planning in resource cities and applies the entropy-weight TOPSIS method and obstacle degree model to evaluate its transformation and development performance and diagnose obstacle factors from 2007 to 2020. The results are as follows: (1) Jinzhong City has made remarkable achievements in transitional development. In the past 14 years, transformation performance has increased from 0.260 to 0.711, and there has been a change from the fair transformation stage to the good transformation stage. (2) The transformational development of Jinzhong City presents two phases: the initial exploratory phase (2007~2013) and the steadily improving phase (2014~2020). The four systems differ significantly in their drive for transformational development in the two stages. (3) The main obstacle factors for the transformation and development of Jinzhong City show stage differences. However, as a whole, economic development and the ecological environment were the main obstacle factors constraining the transformation and development of the city. Hence, it is essential for mature coal resource cities to improve transformation in the future and construct a long-term mechanism for sustainable development, cultivating continuous alternative industries and improving the ecological environment and the security of people’s livelihoods.

Thermal performance promotion of a novel double-tube heat exchanger by helical fin with perforations

Double-tube heat exchangers are widely used in many fields. A novel double-tube heat exchanger with a perforated helical fin on the annulus side is proposed in this paper for thermal performance promotion. The effect of different perforation diameters ranging from 0 to 12 mm on the fluid flow and heat transfer are numerically studied under a turbulent state with Re ranges between 4000 and 16,000. The results showed that perforation diameter has a significant influence on the thermal performance. There exists an optimum perforation diameter for the best thermal performance. The largest value of Nu in the helical finned annulus increases by 20.2% by perforation, while the corresponding f only increases by 11.0% compared with the normal helical finned configuration without perforation. The thermal performance evaluation factor JF is also improved by up to 16.1% compared with the helical finned configuration without perforation, and is increased by 48.6% compared with the smooth annulus. Correlation formulas of f, Nu, and JF are fitted and the deviations are within ±4%, ±9%, and ± 5% for f, Nu, and JF, respectively. Perforated helical fin is an efficient annular-side heat transfer enhancement technology that can be applied to the optimized design of double-tube heat exchangers.

Research on Buyer-Supplier Relationship Strategy, Contribution to The Company’s Business Development

Supplier-buyer courting method is one of the key elements contributing to the performance of the pharmaceutical enterprise because it affects the capacity of providers to deliver and steady uncooked substances for the producing process.The enterprise faces availability issues of uncooked substances in phrases of time and amount required because of delays in deliver from providers (inconsistent uncooked cloth deliver and delivery), this trouble is getting worst because of low and fluctuating forecast accuracy conditions. The phenomenon of the COVID-19 pandemic also worsened the condition of the availability of raw materials because the pandemic caused a shortage and disruption of raw material supply. This have a look at is a qualitative have a look at with descriptive evaluation from interviews consultant informants of consumers and providers. The cause of have a look at is to research the important thing elements that impact dating techniques between providers and consumers, in the long run contributing to enterprise continuity and performance. The effects of this situation have a look at highlight motivation factors, dedication and obligation factors, consider and reputation factors, courting factors, communique and statistics sharing factors, agreement factors, fine and reliability factors, overall performance evaluation factors, help control factors, and procurement strategies. Factors are key factors in a buyer-dealer courting approach to make sure and make sure the provision of uncooked substances in enough quantity, timeliness and fine, contributing to commercial enterprise continuity and overall performance.

Performance Evaluation Factors Reflecting Player and Casting Judgments of Football Coaches

PURPOSE This study aimed to extract football coaches’ categories of performance evaluation factors (PEF) and examine the reflective characteristics of the football coaches’ player and casting judgments.METHODS PEF were extracted through an open-ended questionnaire and categorization from 80 AFC C or higher football coaches. Reflection was calculated in player and casting judgments through an analytic hierarchy process. The difference between the football coaches’ player and casting judgments was examined using SPSS 21.0.RESULTS First, the PEF of football coaches were categorized into four general categories: physical intelligence, psychological intelligence, growth potential, and competition intelligence. Second, the importance of football coaches’ player judgments were reflected by the PEF as football intelligence, situation judgment, football talent, tactical understanding, tactical operation, etc. The importance of the casting judgment were reflected by the PEF as tactical understanding, mediative skills, fitness, tactical operation, situation judgment, etc. Third, a statistically significant difference was noted between player and casting judgments. Football coaches tended to value growth potential and talent as sub-factors in the player evaluations. Football coaches’ PEF were aligned with the importance of player and casting judgments in psychological and competition intelligence as sub-factors such as skills, physical, attitude, passion, etc., but differed from physical intelligence and growth potential as sub-factors including mediative skills, physical, football talent, and tactical understanding.CONCLUSIONS In the football coaches’ player evaluations, the idealistic principle centered on growth potential. However, in the casting evaluation, the realistic principle centered on victory takes effect .

Thermal-hydraulic characteristics analysis of steam–air condensation in vertical porous-wall corrugated tubes

In the passive containment cooling systems (PCCS) of Generation III nuclear power plants, the condensation performance of steam containing non-condensable gas (NCG) in condensate tubes is critical for removing heat from the nuclear power plant containment. By applying a novel porous-wall corrugated structure in the condenser tubes of this system, it was found that under certain conditions, a double vortex is formed inside and outside the porous layer, which is conductive to the transportation and condensation of steam to the condensing wall. The VOF multiphase relation and Brinkman–Forchheimerextended Darcy model in combination of local heat balance, condensation and species transport equations are employed to describe the heat and mass transfer in the porous-wall corrugated tube during condensation. The numerical analysis are conducted to investigate the effects of waveform channel, porous layer and its thicknesses, subcooling of cooling wall and inlet air mass fractions on flow and condensation under different inlet velocities, in which simulations agree with the experimental data. The results show that the condensation heat transfer is greatly influenced by the vortex distribution and air accumulation. At inflowing velocity of 1 m/s, the waveform with amplitude of 1 mm and wavelength of 18 mm can achieve the highest performance evaluation factor, φ (about 67.5 % enhancement than the smooth tubes). The ratio of waveform amplitude to wavelength needs to be chosen properly in consideration of convection between solid matrix and steam–air mixture in porous layer, and non-condensation gas distribution near cooling wall of condensation tube.

The role and influencing factors of government performance evaluation: A test of Chinese public officials’ perceptions in Gaoming district

Government performance evaluation has a long history. However, major differences of opinion regarding its role still exist both in Western and Chinese academia, from theoretical, and practical perspectives. In this article, we conduct an empirical measurement of the role played by government performance evaluation and construct a regression model to explore the major factors influencing public officials’ perception, relying on survey data from a district government of county level in Guangdong Province. The study reveals that the average value of 14 items measuring government performance evaluation was 3.36 points (out of a possible 5 points). The role of the government in setting annual objectives, tasks, and priorities, as well as strategic planning, and target setting, and strengthening departmental accountability, had the most significant effect on the perception of efficacy of performance evaluation, whereas departmental budget setting, resource allocation, and reduction of operating costs had the least effect. Furthermore, performance communication and feedback, as well as the validity of the performance indicator system, also significantly influence the perception of the role played by government performance evaluation. The article concludes with a discussion of the differences between government performance evaluation in the West and in China.