Browsing by Author "Zhang, Qunli"

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Application of deep dehumidification technology in low-humidity industry : A review
(2024-04) Zhang, Qunli; Li, Yanxin; Zhang, Qiuyue; Ma, Fengge; Lü, Xiaoshu
A2 Katsausartikkeli tieteellisessä aikakauslehdessä
Humidity regulation plays a pivotal role in both residential and industrial environments, significantly impacting comfort, health, and process efficiency. The integration of dehumidification systems with air conditioning systems allows for the control of temperature and humidity, resulting in a decrease in carbon dioxide emissions. In order to address the demands of industries with low humidity levels, this study offers a comprehensive review of advanced deep dehumidification systems. The study initially delineates the specific ranges for deep dehumidification as outlined in academic research, as well as the humidity levels in low-humidity industries. Evaluation models are proposed for the analysis of the dehumidification performance, energy efficiency, economic feasibility, and environmental impact of the system. The review focuses on the deep dehumidification technology, which encompasses air compression dehumidification, liquid desiccant dehumidification, solid desiccant dehumidification, membrane dehumidification, and coupled dehumidification, with an emphasis on materials, components, and systems flow. The research provides a comprehensive overview of the various potential applications of dehumidification systems, including air humidification, water collection, air purification, intelligent control, and optimization. Moreover, a comprehensive comparative analysis of different dehumidification technologies is conducted with regard to industrial application humidity requirements, energy performance, economic factors, and environmental considerations. Drawing on advanced studies and findings, this research examines the primary areas for future development in advancing deep dehumidification systems. The objective of this study is to propose optimization techniques aimed at enhancing dehumidification efficiency and reducing energy consumption in low-humidity industrial settings.
Experimental investigation on flue gas condensation heat recovery system integrated with heat pump and spray heat exchanger
(2024-03) Zhang, Qunli; Liu, Tao; Cheng, Xuanrui; Guo, Shuaifei; Zhang, Lin; Lü, Xiaoshu
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
To deeply recover the flue gas condensation heat, a flue gas condensation heat recovery system that combines a compression heat pump (FGCHR-HP) is proposed. An experimental bench of the FGCHR-HP system was established to explore the thermal properties of the system under variable operating conditions. The experimental results show that when the inlet water temperature of the heat pump condensing heat exchanger is 50 °C and the flow rate is 40 L/min, the optimal experimental conditions are achieved. Under this working condition, the heat efficiency is 13.8 %, and the exhaust gas temperature is 26.9 °C. At the same time, the flue gas moisture recovery is up to 6.5–7.0 kg/hour, which is better than other boilers.The payback period of the FGCHR-HP system is 3.4 years. The system has achieved significant energy-saving and water-saving effects, and has certain promotion and application prospects.
Experimental research on direct expansion heat pump flue gas waste heat recovery and humidification nitrogen reduction system
(2023-06-20) Zhang, Qunli; Huang, Haotian; Zhai, Hongbao; Zhao, Wenqiang; Lü, Xiaoshu
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In order to solve the heat loss and the pollution of gas boilers, a synergistic system consisting of waste heat recovery tower and air humidification tower is proposed. Increasing in moisture content of the air can inhibit the generation of nitrogen oxides and increase the dew point of the flue gas, which is beneficial to the utilization of the waste heat from the flue gas. More heat is absorbed by the humidification water at the fin heat exchanger after the flue gas enters the waste heat recovery tower, which enhances the heat and mass exchange process in the air humidification tower. But the performance of the heat pump was found to show a downward trend, indicating a competitive relationship between nitrogen oxides reduction and waste heat recovery. Under the optimal condition, the experimental system can reduce nitrogen oxides emissions by 62.35%, and the exhaust gas temperature can be reduced to 24.46 °C. The heat pump can recover 6.94% heat while maintaining a minimum nitrogen oxides emission of 39.66 mg/m3. The heat pump makes more heat from the fuel to enter the heating network, which improves the heating efficiency of the boiler system. The system can meet the high-efficiency and clean production requirements of the energy system at the same time.
Innovative approaches for deep decarbonization of data centers and building space heating networks : Modeling and comparison of novel waste heat recovery systems for liquid cooling systems
(2024-03-01) Lu, Tao; Lü, Xiaoshu; Välisuo, Petri; Zhang, Qunli; Clements-Croome, Derek
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The data usage surge drives greater data center demand, amplifying global CO2 emissions. Mitigating climate change necessitates reducing data center CO2 emissions. Reusing waste heat from data centers offers a potential energy efficiency boost and environmental impact reduction. This study utilizes liquid cooling technology to raise waste heat temperature for building space heating and introduces the concept of ‘data furnaces,’ where data centers directly supply waste heat to heat buildings on-site, reducing district heating consumption and lowering CO2 emissions. Efficiently designing a heat recovery heat exchanger system that accounts for both heat rejection and cooling sides of a liquid cooling system is crucial for achieving complete heat recovery without using heat pump, a commonly overlooked aspect in existing literature. To address this issue, we propose two heat exchanger schemes: connecting the building space heating network to the secondary side (Scheme 1) and the primary side (Scheme 2) of the cooling distribution unit. Implementing these innovations leads to the elimination of dependence on a heat pump, substantially cutting energy and CO2 emissions. Using TRNSYS software, we develop, model, and compare waste heat recovery schemes to curb district heating consumption and CO2 emissions. To demonstrate broad implications of the proposed approaches for energy efficiency and sustainability in the data centers and building space heating networks, a showcase study examines constant 25 kW waste heat from a direct-to-chip liquid-cooled rack in an office building with 285.7 MWh annual space heating demand. A novel waste heat recovery rate relationship graph is created to assist system design, uncovering an unexpected result in Scheme 2: waste heat recovery decreases as outdoor temperature falls. In contrast, Scheme 1 maintains a stable waste heat recovery rate around 25 kW, regardless of outdoor temperature fluctuations. As a result, Scheme 1 reuses 155.2 MWh of waste heat annually compared to 138 MWh for Scheme 2. Schemes 1 and 2 yield annual electricity savings of 2290.5 kWh and 905.2 kWh, respectively, for the cooling system. Both schemes achieve profitability within a year through a 25-year life cycle analysis (LCC) and substantially reduce CO2 emissions, with Scheme 1 saving 291,996 kgCO2 and Scheme 2 saving 258,192 kgCO2. The study addresses critical gaps in existing literature by emphasizes LCC. The proposed heat exchanger designs represent pioneering solutions for optimizing waste heat recovery, particularly in challenging climates. New findings offer substantial benefits to both liquid-cooled and air-cooled facilities, making significant contributions to achieve carbon neutrality in data center operations.
Investigation of the thermal performance of cascaded latent heat thermal energy storage system based on composite phase change materials
(2023) Zhang, Qunli; Liu, Yimo; Yang, ZS; Wang, Gang; Lu, XS
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper conducts thermodynamic analysis of the cascaded latent heat thermal energy storage system that is applicable to building heat storage, with focus on using the high performance composite phase change materials (CPCM). The 7.5wt. %EG/MgSO47H2O-KAl(SO4)212H2O were used as PCM, the performance of cascaded system and single-stage system were compared. The results show that exergy efficiency, heat charging rate and discharging rate of the cascaded system compared with the single-stage system can be increased at most by 11.6%, 49.7%, and 9.7%, respectively. This work has important guiding significance for the applied research of the heat storage system with the CPCM.
Novel hybrid modeling approach for utilizing simple linear regression models to solve multi-input nonlinear problems of indoor humidity modeling
(2022-04-01) Lu, Tao; Lü, Xiaoshu; Salonen, Heidi; Zhang, Qunli
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Investigating indoor humidity is important because abnormal moisture levels can damage building structures and result in poor indoor air quality. Outdoor humidity, ventilation rate, and internal moisture load are the three dominant factors affecting indoor humidity. State-of-the-art methods, particularly full-scale field studies for determining these three factors and indoor humidity can be both time consuming and labor intensive. This study proposes a radically new methodology to effectively model the influence of these three factors on indoor humidity for a mechanically ventilated building/space. The methodology starts with a simple linear regression (SLR) constructed by measuring indoor and outdoor humidity and then hybrids a novel analytical approach that accurately predicts the impact of ventilation rate and internal moisture load on indoor humidity. The proposed upgraded SLR model was successfully validated with high accuracy by both experiments and numerical simulations using TRNSYS commercial software. The results demonstrate the ability of the developed SLR to accurately model indoor humidity and account for the moisture exchange between indoor air and building structures/furnishings. Inferring these relationships and their influences on indoor humidity presents a challenging task. The developed model is generic and unique and supports fast and inexpensive field studies by ensuring that the measurements of indoor and outdoor humidity are sufficient to derive field tests of the impacts of outdoor humidity, ventilation rate, and internal moisture loads on indoor humidity. The proposed model can be further developed as a standardized moisture assessment tool for benchmarking building performance.
A novel methodology and new concept of structural dynamic moisture buffering for modeling building moisture dynamics
(2020-08) Lü, Xiaoshu; Lu, Tao; Kibert, Charles; Zhang, Qunli; Hughes, Mark
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper presents a new methodology that takes a physical-statistical approach to dynamically model indoor air humidity and moisture transport in building structures. A new concept, structural dynamics moisture buffer capacity (SDMBC), is introduced that improves on the most commonly used moisture buffer measure. The paper proposes and experimentally proves several novel hypotheses regarding the linear relationship between model variables, great simplifying the derivation of the model equations. The resulting dynamic model is simple, efficient, and easy-to-implement. Furthermore, full-scale experiments using three identical wooden test houses were built to support the development of the dynamic model. Airflow rates were calibrated and verified by experiment. The results of this study establish the practicality of this new modeling methodology which can aid researchers in constructing improved simulation models and designers in selecting building materials to optimize indoor humidity, minimize energy consumption, and provide good indoor environmental quality.
A novel methodology for the path alignment of visual SLAM in indoor construction inspection
(2021-07) Lu, Tao; Tervola, Sonja; Lü, Xiaoshu; Kibert, Charles J.; Zhang, Qunli; Li, Tong; Yao, Zhitong
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Path alignment is the process of mapping an indoor construction inspection path reconstructed by a visual SLAM system onto a 2D map with user interaction required to pinpoint at least two common tie points. In practice, more points are often needed due to path distortions and linear transformations, potentially resulting in reduced productivity. This paper proposes a methodology that combines two novel algorithms for the path alignment: (1) PCA_STAN_ALGO applies principal component analysis to remove path distortions caused by the xz plane of a camera coordinate system not being parallel to the floor plane; and (2) GRPX_TRANS utilizes a graphical user interface to facilitate the path alignment. The proposed methodology enables the users to utilize just two tie points for successful path alignment. An experimental study showed that applying both PCA_STAN_ALGO and GRPX_TRANS saved about 50% in time compared to using only GRPX_TRANS, a result of needing minimal moving points.
Optimizing Data Center Waste Heat Reuse : Case Studies and Environmental Implications
(2024) Lu, Xiaoshu; Lu, Tao; Zhang, Qunli
A4 Artikkeli konferenssijulkaisussa
As data centers (DCs) are the backbones of information and communications technology (ICT), internet and big data, the utilization of energy by DCs has increased exponentially, which presents a significant impact on the environment. To simultaneously solve the dilemma of DC huge amount of electricity used for cooling on the one hand and a large amount of waste heat that is converted from nearly all the consumed electricity on the other hand, better use of low-grade waste heat from DCs represents a significant source of energy savings for both future fourth generation of district heating (DH) networks and reducing environmental impact. This study presents an innovative waste heat reuse approach and develops a generalizable methodology that employs a simple dynamic estimate of the potential for reutilising DC waste heat in the heat demand in DH for buildings. Brief economic calculations for building operators are also provided. The proposed modeling method is a two-stage approach for calibration and validation based on two real DCs in Finland. After validation, the model is then applied for investigating the potential environmental impacts of a real DC in its design phase. The analysis demonstrates that reusing waste heat from an 18 MW data center to heat 400,000 m2 greenhouse and buildings results in a substantial reduction of 603,366 tons of carbon dioxide (CO2) emissions over a 25-year period. From the building owners’ perspective, the payback time is remarkably short, spanning only five years. The results highlight the feasibility and effectiveness of the DC waste heat recovery to tackle the energy and environmental problems.
Research on the indoor temperature regulation characteristics of a nearly zero energy building with the nonlinear heat capacity building components : A simple model
(2023-10-01) Zhang, Qunli; Liu, Yimo; Zhang, Qiuyue; Wang, Gang; Lü, Xiaoshu
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
With establishment of global carbon reduction targets, energy conservation and emission reduction of building is imperative. By passive building design method, nearly zero energy buildings (nZEB) can decrease building energy consumption requirements. To reduce indoor temperature fluctuation of the nZEB in heating season, the conventional energy storage materials (CESM) or phase change materials (PCM) are utilized in the building components for thermal storage. The heat capacity of the PCM was simplified as ideal nonlinear heat capacity. To reveal the indoor temperature distribution characteristic in the nZEB affected by the building components with or without the nonlinear heat capacity, a simplified mathematical model was established. Several evaluation indicators were put forward to describe indoor temperature regulation difference between the CESM and the PCM. The results show that indoor temperature distribution characteristics of the nZEB with PCM was significantly different with that of the CESM building. The maximum indoor temperature distribution frequency of the PCM building is much larger than that of the CESM building. The maximum indoor temperature distribution frequency of PCM building was more concentrated and occurred close to the phase transition temperature. The maximum indoor temperature distribution frequency of the CESM is not exceed 10%, however, that of the PCM building can reach 42% in the same work condition. The maximum indoor temperature distribution frequency, the indoor comfort guarantee ratio and the latent heat utilization time ratio of the PCM building can be obviously increased by selecting the phase transition temperature close to the average indoor temperature in the heating season. The study work represent that the PCM building components with the nonlinear heat capacity can regulate the indoor temperature distribution frequency by change phase transition temperature.