Research

25 pages, 3241 KiB

Open AccessArticle

Potential for Energy Utilization of Air Compression Section Using an Open Absorption Refrigeration System

by Bicui Ye, Shufei Sun and Zheng Wang

Appl. Sci. 2022, 12(13), 6373; https://doi.org/10.3390/app12136373 - 23 Jun 2022

Cited by 1 | Viewed by 1106

In this paper, an open absorption refrigeration system is proposed to recover part of the waste compression heat while producing cooling capacity to further cool the compressed air itself. The self-utilization of the compression waste heat can significantly reduce the energy consumption of [...] Read more.

In this paper, an open absorption refrigeration system is proposed to recover part of the waste compression heat while producing cooling capacity to further cool the compressed air itself. The self-utilization of the compression waste heat can significantly reduce the energy consumption of air compression, and hence increase the energy efficiency of the cryogenic air separation unit. To illuminate the energy distribution and energy conversion principle of the open absorption refrigerator-assisted air compression section, a thermodynamic model is built and the simulation work conducted based on a practical triple-stage air compression section of a middle-scale cryogenic air separation unit. Our results indicate that the energy saving ratio is mainly constrained by the distribution of the cooling load of compressed air, which corresponds to the heat load of the generator and cooling capacity of the evaporator in the open absorption refrigerator. The energy saving ratio ranges from 0.52–8.05%, corresponding to the temperature range of 5–30 °C and humidity range of 0.002–0.010 kg/kg. It is also estimated, based on the economic analysis, that the payback period of the open absorption refrigeration system is less than one year, and the net project revenue during its life cycle reaches USD 5.7 M, thus showing an attractive economic potential. Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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22 pages, 4621 KiB

Open AccessArticle

An Improved Gas Leakage Model and Research on the Leakage Field Strength Characteristics of R290 in Limited Space

by Yalun Li, Peixu Zhou, Yuan Zhuang, Xilei Wu, Ying Liu, Xiaohong Han and Guangming Chen

Appl. Sci. 2022, 12(11), 5657; https://doi.org/10.3390/app12115657 - 02 Jun 2022

Cited by 8 | Viewed by 1888

Abstract

Some alternative refrigerants with excellent environmental performance often have different flammable limits. When refrigerant leaks, the external space may have a certain explosion risk if the refrigerant is not diffused timely. To understand the leakage and diffusion characteristics of the refrigerant, an improved [...] Read more.

Some alternative refrigerants with excellent environmental performance often have different flammable limits. When refrigerant leaks, the external space may have a certain explosion risk if the refrigerant is not diffused timely. To understand the leakage and diffusion characteristics of the refrigerant, an improved gas leakage model was proposed in this paper, and the accuracy verification of the improved model was developed. Based on the above works, taking R290 as the research object, the variation law of the field strength between the leaked gas and external space and the influence of different initial leakage pressures on the field strength characteristics were analyzed. The simulation results showed that when the initial leakage pressure was 2 MPa, the R290 gas entered the external space as a supersonic jet, the gas underwent continuous expansion and compression processes in the near-field area and a Mach disk was formed within the flow area. During this process, parameters, such as the temperature, pressure, velocity and density of the leaked R290 gas, changed dramatically, and then the gas gradually returned to room temperature and normal pressure through interaction with the external space. The flammable area formed by the leaked R290 was mainly concentrated in the local flow area below the leak hole, and the existence of the Mach disk caused the R290 high concentration area to increase. With the increase in the initial leakage pressure, the distance from the Mach disk to the leak hole and the circumferential diameter of the Mach disk increased, and the flammable area increased slightly in the horizontal direction, whereas the flammable area increased significantly in the vertical direction. Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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16 pages, 4749 KiB

Open AccessArticle

Proposal and Experimental Study on a Diagnosis Method for Hermetic Refrigeration Compressor Using Dual Time-Frequency Image Fusion

by Kang Li, Zhe Sun, Huaqiang Jin, Yingjie Xu, Jiangping Gu, Yuejin Huang, Qinjian Zhang and Xi Shen

Appl. Sci. 2022, 12(6), 3033; https://doi.org/10.3390/app12063033 - 16 Mar 2022

Cited by 5 | Viewed by 1665

Abstract

The hermetic refrigeration compressor is the core component of the refrigeration system, failure of which will cause energy waste and reduce service life. Fault diagnosis based on vibration signal is a research hotspot. However, it is challenging to extract features of nonlinear and [...] Read more.

The hermetic refrigeration compressor is the core component of the refrigeration system, failure of which will cause energy waste and reduce service life. Fault diagnosis based on vibration signal is a research hotspot. However, it is challenging to extract features of nonlinear and nonstationary vibration signals, which severely restricts the development of this method. This paper proposes a dual time-frequency images fusion method to obtain more effective features for diagnosing compressor manufacturing defects. Firstly, two time-frequency images are obtained by implementing continuous wavelet transform and Hilbert-Huang transform of the same vibration signal sample. Then, a convolutional neural network is used for image feature extraction and fusion, where the features extracted from two time-frequency images have complementarity. A data set containing six categories of typical manufacturing defects is used to verify the proposed method. The results show that the average diagnostic accuracy of the proposed method reaches 95.9%, and the proposed method has a better performance than other methods. Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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22 pages, 3141 KiB

Open AccessArticle

Experimental Investigations of a Passive Cooling System Based on the Gravity Loop Heat Pipe Principle for an Electrical Cabinet

by Mária Polačiková, Patrik Nemec, Milan Malcho and Jozef Jandačka

Appl. Sci. 2022, 12(3), 1634; https://doi.org/10.3390/app12031634 - 04 Feb 2022

Cited by 1 | Viewed by 2022

Abstract

This paper deals with the experimental research and verification of a passive cooling system operating on the principle of a loop gravity heat pipe designed for cooling electrical cabinets. This type of cooling works automatically by changing the state of the working substance [...] Read more.

This paper deals with the experimental research and verification of a passive cooling system operating on the principle of a loop gravity heat pipe designed for cooling electrical cabinets. This type of cooling works automatically by changing the state of the working substance and thus saves energy consumption. Since the designed cooling system ensures heat transfer from the interior cabinet to the outdoor space, where the heat can naturally dissipate to the surroundings, it is dustproof. The heat pipe consists of an innovative evaporator concept designed to minimize liquid and vapour phase interference in the refrigeration circuit. The aim of the research was to experimentally determine the limit performance parameters of the refrigeration system for different volumes of working medium in the evaporator and decrease heat loss in the cabinet interior. The designed device was verified experimentally and by mathematical calculations as well. The greatest benefit of the work is that the cooling device was able to ensure temperature conditions inside the electrical enclosure at a heat load of 2000 W under 60 °C, 1500 W under 55 °C, 1000 W under 50 °C, 750 W under 45 °C and 500 W under 40 °C. Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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13 pages, 7580 KiB

Open AccessArticle

Analysis of Carbon Emission Energy Inventory from Refrigerant Production and Recycling Carbon Compensation

by Haiying Wang, Yue Wang, Hong Mi, Jianbin Zang and Shuangshuang Wang

Appl. Sci. 2022, 12(1), 1; https://doi.org/10.3390/app12010001 - 21 Dec 2021

Cited by 24 | Viewed by 3888

Abstract

At present, the massive emissions of carbon dioxide and nitrogen oxides and other greenhouse gases caused by human activities have caused more and more serious negative effects on global climate change. In order to cope with global warming and achieve sustainable development, achieve [...] Read more.

At present, the massive emissions of carbon dioxide and nitrogen oxides and other greenhouse gases caused by human activities have caused more and more serious negative effects on global climate change. In order to cope with global warming and achieve sustainable development, achieve “carbon neutrality” as soon as possible. In the refrigeration industry, it is necessary to reduce greenhouse gas emissions related to refrigerants, including the production, use, and recycling of refrigerants. This paper has carried out the calculation of greenhouse gas emissions during the refrigerant preparation process, and compared and analyzed the emission reductions of refrigerant recycling and reuse; the research based on the energy consumption of the refrigerant production process uses the greenhouse gas emission inventory analysis method to Taking refrigerant R134a as an example, the carbon emission accounting boundary of the production process is set, the emission source is determined, the emission is calculated based on the emission factor method, and the emission inventory is established; the carbon offset effect of the recycling and reuse of the refrigerant is analyzed. The research results show that if the entire refrigerant industry fully recycles waste refrigerants, it can reduce carbon emissions by about 29.7% compared to just producing new refrigerants. Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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12 pages, 19529 KiB

Open AccessArticle

Experimental Study on the Heat Transfer Performance of Pump-Assisted Capillary Phase-Change Loop

by Xiaoping Yang, Gaoxiang Wang, Cancan Zhang, Jie Liu and Jinjia Wei

Appl. Sci. 2021, 11(22), 10954; https://doi.org/10.3390/app112210954 - 19 Nov 2021

Viewed by 1402

Abstract

To overcome the two-phase flow instability of traditional boiling heat dissipation technologies, a porous wick was used for liquid-vapor isolation, achieving efficient and stable boiling heat dissipation. A pump-assisted capillary phase-change loop with methanol as the working medium was established to study the [...] Read more.

To overcome the two-phase flow instability of traditional boiling heat dissipation technologies, a porous wick was used for liquid-vapor isolation, achieving efficient and stable boiling heat dissipation. A pump-assisted capillary phase-change loop with methanol as the working medium was established to study the effect of liquid-vapor pressure difference and heating power on its start-up and steady-state characteristics. The results indicated that the evaporator undergoes four heat transfer modes, including flooded, partially flooded, thin-film evaporation, and overheating. The thin-film evaporation mode was the most efficient with the shortest start-up period. In addition, heat transfer modes were determined by the liquid-vapor pressure difference and power. The heat transfer coefficient significantly improved and the thermal resistance was reduced by increasing liquid-vapor pressure as long as it did not exceed 8 kPa. However, when the liquid-vapor pressure exceeded 8 kPa, its influence on the heat transfer coefficient weakened. In addition, a two-dimensional heat transfer mode distribution diagram concerning both liquid-vapor pressure difference and power was drawn after a large number of experiments. During an engineering application, the liquid-vapor pressure difference can be controlled to maintain efficient thin-film evaporation in order to achieve the optimum heat dissipation effect. Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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20 pages, 7361 KiB

Open AccessArticle

Study of Novel Punched-Bionic Impellers for High Efficiency and Homogeneity in PCM Mixing and Other Solid-Liquid Stirs

by Weitao Zhang, Zengliang Gao, Qizhi Yang, Shuiqing Zhou and Ding Xia

Appl. Sci. 2021, 11(21), 9883; https://doi.org/10.3390/app11219883 - 22 Oct 2021

Cited by 7 | Viewed by 1757

Abstract

Improvement of stirring performance is one of the primary objectives in solid–liquid mixing processes, such as the preparation of phase change materials (PCMs) for energy saving in refrigeration and heat pump systems. In this paper, three novel impellers are proposed: pitched-blade punched turbine [...] Read more.

Improvement of stirring performance is one of the primary objectives in solid–liquid mixing processes, such as the preparation of phase change materials (PCMs) for energy saving in refrigeration and heat pump systems. In this paper, three novel impellers are proposed: pitched-blade punched turbine (PBPT), bionic cut blade turbine (BCBT) and bionic cut punched blade turbine (BCPBT). An experimental test was conducted to validate the stirring system model based on the Eulerian–Eulerian method with the kinetic theory of granular flow. Then the performance of the novel impellers was predicted, studied, and compared. The outcomes indicate that a novel impeller, specifically BCPBT, can effectively suspend particles and dramatically reduce power consumption. A better solid–liquid suspension quality was obtained with an aperture diameter of 8 mm and aperture ratio of 13%. Within the range of impeller speeds and liquid viscosity studied in this this paper, higher impeller speeds and more viscous liquids are more conducive to particle dispersion. One of the most important contributions of this work lies in the design of novel impellers, an extent of energy conservation to 17% and efficient mixing was achieved. These results have reference significance for improving the energy efficiency of temperature regulation systems. Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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22 pages, 5271 KiB

Open AccessArticle

Transient Numerical Model on the Design Optimization of the Adiabatic Section Length for the Pulsating Heat Pipe

by Kangli Bao, Yuan Zhuang, Xu Gao, Yuanyuan Xu, Xilei Wu and Xiaohong Han

Appl. Sci. 2021, 11(20), 9432; https://doi.org/10.3390/app11209432 - 11 Oct 2021

Cited by 5 | Viewed by 1301

Abstract

In the application of pulsating heat pipes (PHPs), the lengths of the adiabatic sections are usually determined by the distance between the heat source and the heat sink, and have important effects on the performance of PHPs. However, there was little research on [...] Read more.

In the application of pulsating heat pipes (PHPs), the lengths of the adiabatic sections are usually determined by the distance between the heat source and the heat sink, and have important effects on the performance of PHPs. However, there was little research on the effect of the adiabatic section lengths on the performance of PHPs. In this work, a new transient numerical model was proposed to investigate the transient flow and the heat transfer for PHPs with various adiabatic section lengths of 60, 120, 180, and 240 mm. Based on the numerical results, the flow and the heat transfer characteristics of the PHPs were analyzed. It was found that the flow velocities in the PHP with different adiabatic lengths increased with the increase in the heat input, and the mean velocity was calculated to be in the range of 0.139–0.428 m/s, which was consistent with the previous experimental results. The start-up performance of the PHP was better with shorter adiabatic section length. Furthermore, the thermal resistances of the PHPs with different adiabatic section lengths were calculated to analyze the effects of the adiabatic section length on the performance of the PHP. The results showed that when the heat input was 20 W, the PHP with the adiabatic section of 60 mm showed the lowest thermal resistance, whereas the PHP with longer adiabatic section length presented lower thermal resistance at high heat input (≥25 W). Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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20 pages, 7501 KiB

Open AccessArticle

Optimization of Multi-Blade Centrifugal Fan Blade Design for Ventilation and Air-Conditioning System Based on Disturbance CST Function

by Shuiqing Zhou, Ke Yang, Weitao Zhang, Kai Zhang, Chihu Wang and Weiya Jin

Appl. Sci. 2021, 11(17), 7784; https://doi.org/10.3390/app11177784 - 24 Aug 2021

Cited by 11 | Viewed by 6576

Abstract

The multi-blade centrifugal fan is commonly used in modern building ventilation and air-conditioning system. However, it does not readily satisfy the increasing demand for energy saving, high efficiency or noise reduction. Its performance is inherently limited by the geometrical structure of single circular [...] Read more.

The multi-blade centrifugal fan is commonly used in modern building ventilation and air-conditioning system. However, it does not readily satisfy the increasing demand for energy saving, high efficiency or noise reduction. Its performance is inherently limited by the geometrical structure of single circular arc blades. Q35-type multi-blade centrifugal fan studied as an example by combining the disturbance CST function to parameterize the blades. The optimization parameter change range is confirmed, and test samples are extracted before establishing an RBF proxy model. The NSGA-II algorithm is incorporated, and multi-objective optimization is performed with flow rate and total pressure efficiency as optimization goals. The results show that the fan performance is effectively improved. At the design working point, the air volume of the multi-blade centrifugal fan increases by 1.4 m³/min; at the same time, the total pressure efficiency increases by 3.1%, and the noise is reduced by 1.12 dB, applying the proposed design. The obtained higher fan efficiency can effectively improve performance of the whole ventilation and air-conditioning system. This novel optimization method also has relatively few parameters, which makes it potentially valuable for designing multi-wing centrifugal and other types of fans, providing a new idea for energy saving and emission reduction design of fan. Full article

(This article belongs to the Special Issue Refrigeration and Heat Dissipation: Refrigeration System, Low-GWP Refrigerants, and Cooling Technology for High Heat Flux Space)

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