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A novel time-current-temperature difference (T-I-T) defrosting control method for air source heat pump based on outdoor fan operation characteristics in space heating

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APPLIED THERMAL ENGINEERING 2025年 259卷

作者： Tang, Rui Wei, Wenzhe Sun, Ping Zhao, Jihan Wang, Wei Sun, Yuying Deng, Shiming Beijing Univ Technol Beijing Key Lab Green Built Environm & Energy Effi Beijing 100124 Peoples R China Qingdao Prod Qual Testing Res Inst Qingdao 266101 Peoples R China Beijing Polytech Coll Mechatron Engn Beijing 100176 Peoples R China Qatar Univ Dept Mech & Ind Engn POB 2713 Doha Qatar

In space heating, air source heat pumps (ASHPs) always encounter mal-defrosting incidents, resulting in significant energy waste. To improve the defrosting accuracy of ASHP, this paper proposes a novel Time-CurrentTemperature difference (T-I-T) defrosting control method based on the characteristic parameter of outdoor fan operation (current). Through theoretical analysis and experimental tests, the influence of frosting on the characteristic parameters of outdoor fan operation was revealed. Then, based on the optimal defrosting control point theory, a method for selecting the defrosting current threshold close to the actual ASHP was proposed. Ultimately, a novel Time-Current-Temperature Difference (T-I-T) defrosting control method was developed, using the current increment to control the defrosting operation. The results showed that, the defrosting current thresholds decreased as the severity of frosting decreases, from 1.52 to 0.78 A. The T-I-T defrosting control method enables the ASHP unit to operate stably and efficiently in space heating. The defrosting frequency decreased from 0.93 to 0.56 times per hour, a reduction of 39.80 %;the average duration of the frosting/ defrosting cycle increases from 64.30 to 106.90 min (an increase of 66.25 %), and the average COP of the ASHP unit increases by 10.60 % compared to the T-T defrosting control method.

关键词： Air source heat pump Time-Current-Temperature Difference defrosting control method Outdoor fan operating parameters defrosting current threshold

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A visual defrosting control method for air source heat pump system based on machine vision

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ENERGY 2024年 302卷

作者： Zhao, Han Liu, Zihan Sang, Yufeng Chang, Junzhi Zheng, Xuejing Jurasz, Jakub Zheng, Wandong Tianjin Univ Sch Environm Sci & Engn Tianjin 300350 Peoples R China North China Municipal Engn Design & Res Inst Co Lt Tianjin 300074 Peoples R China Wroclaw Univ Sci & Technol Fac Environm Engn PL-50370 Wroclaw Poland Tianjin Univ Key Lab Efficient Utilizat Low & Medium Grade Ener Minist Educ China Tianjin 300350 Peoples R China

Frosting on the coil of the air source heat pump (ASHP) significantly affects its performance. An accurate defrosting control method is essential for the ASHP unit. Here, a novel visual defrosting control method based on machine vision is proposed. The frosting degree of the unit is accurately obtained by frosting image analysis with digital image processing to achieve on-demand defrosting. Fractal dimension, frosting degree coefficient, and single-circuit frosting evenness value are introduced to evaluate the frosting degree of coil images. The image acquisition point is determined with confusion matrix. Based on this, the logical framework of the proposed method is constructed, in which the defrosting starting and termination conditions are set as the moment when the frosting degree coefficient is equal to 0.9 and 0, respectively. A multi-variable model of fractal dimension is fitted, which improves the generalization of the proposed method. Finally, comparative experiments are conducted between the proposed method and the traditional temperature-time (T-T) method in typical cases. The results indicate that the COP and total heating capacity increase by 11.8 %, 10.6 % and 7.4 %, 6.6 %, respectively, and the defrosting frequency is reduced by 75 %, which demonstrates dominant advantages of the proposed method in accuracy, energy-saving, and indoor thermal comfort management.

关键词： Machine vision defrosting control method Fractal dimension Image processing technology Air source heat pump

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A novel Temperature-Humidity-Time defrosting control method based on a frosting map for air-source heat pumps

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INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 2015年 54卷 45-54页

作者： Zhu, Jiahe Sun, Yuying Wang, Wei Ge, Yijing Li, Lintao Liu, Jingdong Beijing Univ Technol Coll Architecture & Civil Engn Dept Bldg Environm & Facil Engn Beijing 100124 Peoples R China

To improve the defrosting accuracy and the energy efficiency of the air-source heat pump (ASHP) under frosting and defrosting conditions, a novel Temperature-Humidity-Time (T-H-T) defrosting control method, based on a frosting map for the ASHP unit, is proposed in this paper. A field test was conducted for two heating seasons, to verify the feasibility and applicability of the T-H-T method. The advantages of the T-H-T method, compared to the conventional Temperature-Time (T-T) defrosting control method, are presented. In total, eight cases are shown in this paper. Cases 1 to 4 were chosen to reveal the T-H-T performance under different frosting conditions. It was found that no matter what kind of frosting conditions, defrosting was always initiated in a similar situation: similar to 90% of the outdoor coil surface was covered by frost;the temperature difference between the compressor suction and discharge increased by similar to 20%;and the heating capacity decreased by similar to 30%. These results indicate that the T-H-T method can make an accurate decision under different frosting conditions. Cases 5a, 5b and Cases 6a, 6b were two groups of cases to compare the advantages of the T-H-T method against the conventional T-T method. Cases 5a and 5b were chosen for the non-frosting condition. It was found that the T-T method initiated the defrosting operation 31 times within 24 h. However, none of the defrosting operations was conducted for the T-H-T method. Cases 6a and 6b were chosen to compare these two methods under consecutive and variable frosting conditions. For the T-T method, 63% of the defrosting processes were found to be executed under conditions where defrosting was not necessary. However, for the T-H-T method, all the defrosting controls were found to be accurate and reasonable. These results indicated that the novel T-H-T method is suitable for the defrosting control of the ASHP, and has a more competitive performance than the conventional T-T method. (C

关键词： Air-source heat pump defrosting control method Frosting map Frosting rate defrosting interval Field test

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Optimizing Chiller defrosting control through Spiking Neural Networks-Based method 24

Optimizing Chiller Defrosting Control through Spiking Neural...

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16th International Conference on Machine Learning and Computing (ICMLC)

作者： Chen, Jingyu Zhou, Xiaojie Guangdong Univ Technol Sch Integrated Circuits Guangzhou Guangdong Peoples R China Guangdong Univ Technol Sch Comp Sci Guangzhou Guangdong Peoples R China

ISBN: (纸本)9798400709234

In this paper, a defrosting control method for chillers based on spiking neural networks is proposed to address the problem of ineffective existing defrosting control methods and the difficulty of implementing defrosting according to the actual situation of the refrigeration system. The method utilizes a camera to periodically capture images of the chiller and uses image difference to extract frost feature information as network input. The excitation layer of the spiking neural networks receives the impulse sequence encoded by the image, while the output layer integrates the output impulses from the excitation layer. Once the impulse intensity reaches a high level, the output layer neurons send a signal to initiate the defrost operation, thereby achieving on-demand defrosting. Experimental results demonstrate that the method exhibits high accuracy in frost identification, is efficient and reliable, and can timely control the defrost operation based on the chiller's condition. This approach improves the refrigeration working condition of the chiller and effectively reduces refrigeration costs.

关键词： defrosting control method Spiking neural networks Image difference On-demand defrosting

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Deep learning-based image recognition method for on-demand defrosting control to save energy in commercial energy systems

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APPLIED ENERGY 2022年 324卷

作者： Chen, Siliang Chen, Kang Zhu, Xu Jin, Xinqiao Du, Zhimin Shanghai Jiao Tong Univ Sch Mech Engn Shanghai 200240 Peoples R China

Periodical defrosting is essential to restore the initial capability of heat exchangers and improve the operating efficiency of commercial energy systems. The defrosting control method applying image recognition technology is considered a low-cost and easy-operating approach to implement demand-based defrosting cycles. However, with regard to different operation environments, the establishment of high-accuracy image recognition model will consume plenty of labor and cost, which leads to the low extensibility between homotypic or heterotypic devices and severely limits its practical application in commercial energy systems. To this end, a novel deep learning-based image recognition method was presented for the extensible implementation of on-demand defrosting control. In order to improve the recognition accuracy, a convolutional neural network (CNN) model was proposed to extract in-depth and complicated features for frosty state detection. By integrating deep clustering and image augmentation, the time-consuming experiments and labor-intensive labeling workload were greatly reduced. The recognition accuracy of proposed CNN model was on average 5.50% higher than that of conventional CNN model, and the recognition accuracy was further increased to 97.57% through the hyperparameters optimization. Based on the trained CNN model, a defrosting control method was proposed for the on-demand defrosting control according to the real-time frosty state recognition. Compared with original time-based control method (defrosting per device after a fixed interval), the field experiment testified that the defrosting frequency, accumulated time and energy consumption were decreased by 31.68%, 65.83% and 42.92% respectively by adopting the proposed control method. The economic and environmental analysis indicated that the payback time was approximately half a year and annual reduction in CO2 emission is 28.44 t, which signified the great application potential of the proposed method. Thi

关键词： defrosting control method Image recognition Deep learning Commercial energy systems Experimental evaluation

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Applying neural network model to real-time frosting detection and intelligent defrosting control for air source heat pump

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APPLIED ENERGY 2025年 377卷

作者： Zhao, Han Li, Pengxiang Li, Jiaxing Liu, Zihan Sang, Yufeng Ye, Tianzhen Zheng, Wandong Tianjin Univ Sch Environm Sci & Engn Tianjin 300350 Peoples R China Tianjin Univ Key Lab Efficient Utilizat Low & Medium Grade Ener Minist Educ China Tianjin 300350 Peoples R China

Periodic defrosting is essential for efficient operation of air source heat pump to avoid the attenuation of performance caused by frosting. However, the mal-defrosting phenomena in practice, which are no defrosting progress when necessary and unnecessary defrosting operation under no frosting, happen occasionally. To improve the accuracy of defrosting, a convolutional neural network model based on deep learning with YOLOv5 is introduced for frosting detection in this paper. Firstly, the evaluation method of frosting degree combining fractal dimension and heating capacity attenuation is constructed. Then, an image dataset is built based on frosting degree evaluation. The optimized YOLOv5-frost network is constructed, which improves the accuracy of frosting detection by iterative training. Thirdly, a novel defrosting control method based on YOLOv5-frost network is proposed, in which the defrosting initiation and termination points are investigated. Finally, comparative experiments are conducted between the proposed defrosting control method and traditional methods. The results indicate that the mal-defrosting phenomena are effectively avoided under the proposed method. The COP and total heating capacity are increased by 11.83 % and 7.42 % respectively, as well as the defrosting frequency and energy consumption are decreased by 75.00 % and 88.24 %, respectively. Additionally, the time consumption, memory overhead, and central processing unit overhead of the proposed method are 2.72 %, 71.58 %, and 74.07 % of those for the traditional methods, respectively. The performance of air source heat pump unit in real-time frosting detection and on-demand defrosting in complex conditions can be effectively improved with the proposed method.

关键词： defrosting control method Frosting detection Air source heat pump Fractal dimension Energy efficiency

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A novel defrosting control method based on the degree of refrigerant superheat for air source heat pumps

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INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 2013年第8期36卷 2278-2288页

作者： Jiang, Yiqiang Dong, Jiankai Qu, Minglu Deng, Shiming Yao, Yang Harbin Inst Technol Sch Municipal & Environm Engn Harbin 150006 Peoples R China Hong Kong Polytech Univ Dept Bldg Serv Engn Kowloon Hong Kong Peoples R China

When an air source heat pump (ASHP) unit operates for space heating at a frosting environment, periodic defrosting is necessary to maintain a high system performance. To defrost efficiently, it is necessary to find an effective defrosting control method. In this paper, an experiment was carried out on an ASHP unit with a capillary tube as a throttle device, under simulated frosting and defrosting conditions using time control defrosting method, and the experimental results are firstly presented. Secondly, a novel defrosting control method based on the degree of refrigerant superheat (DS) is reported. To validate the novel defrosting control method, a further experiment was conducted on another ASHP unit with an electronic expansion valve (EEV) as a throttle device, under simulated frosting and defrosting conditions. The experimental results demonstrated that when applying the novel defrosting control method, defrosting was initiated before the operating performances of ASHP unit rapidly deteriorated, which was more reasonable. (C) 2013 Elsevier Ltd and IIR. All rights reserved.

关键词： defrosting control method Refrigerant Superheat Heat pump Air-source Experiment

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Experiment design of the defrosting control method of the variable refrigerant flow air source heat pump

Experiment design of the defrosting control method of the va...

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4th International Conference on Technology of Architecture and Structure (ICTAS 2011)

作者： Han, Xing Chen, Jianbo Univ Shanghai Sci & Technol Sch Environm & Architecture Shanghai Peoples R China

ISBN: (纸本)9783037852798

This paper first analyze the common air source heat pump defrosting control methods and their problems. Then, the impact of variable refrigerant flow technique on the air source heat pump frosting and defrosting is analyzed. Through experiment design, the influencing factors on inverter air source heat pump defrosting control methods will be studied.

关键词： Air source heat pump Variable refrigerant flow defrosting control method Experiment design

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