Hasil untuk "Heating and ventilation. Air conditioning"

Wang Wenhuan, Tan Niugao, Shen Jiubing et al.

Silicone rotor is the main dehumidification technology to realize humidity control of ambient air； optimizing the rotor size and reducing the operating energy consumption are inevitable trends in rotor dehumidification technology development. In this study， based on the theoretical research method of computational fluid dynamics （CFD）， we first established and verified a three-dimensional dynamic simulation model of the dehumidification and regeneration process of the rotor， and we conducted a dynamic simulation for the silica gel dehumidification rotor used for the protection of bridge cables， and we then analyzed and discussed the influence of rotor thickness， wind speed， and regeneration wind volume and temperature on the moisture removal capacity （MRC） and specific energy consumption （SEC） of the rotor to optimize the design of the rotor. The purpose was to optimize the rotor design. The results showed that the optimal thickness of the rotor existed under different wind speeds， and the optimal thickness increased with the increase in the wind speed. Compared with the original design， the optimized wheel improved the average MRC by approximately 10% while reducing the SEC by approximately 15%， demonstrating the effectiveness of dimensional optimization. Notably， the SEC decreased with increasing regeneration temperature. Therefore， in practical design， the regeneration temperature should be selected in accordance with the dehumidification requirements and maintained as low as feasible to enhance the overall economic performance.

Yabin Guo, Yaxin Liu, Zhanwei Wang et al.

At present, with the continuous global energy crisis, buildings, as a significant factor in energy consumption, have significant importance in achieving the energy-saving operation of buildings [...]

Zhengguang Liu, Ying Du, Chenchen Song et al.

Ground source heat pump (GSHP) technology has gained significant attention as a viable solution for the heating, ventilation, and air conditioning (HVAC) of buildings. One of the factors that can impact the performance of GSHP systems is the soil moisture content. In this study, an innovative approach, referred to as soil impedance topology, is introduced as an alternative to traditional methods for measuring soil moisture content in geothermal heat pump systems. This method is inspired by pipeline grid utilizes impedance measurement, which provides a direct measurement of soil moisture content without the need for sensors. The study also proposes a changing rule of impedance with varying moisture content, where capacitance increases and resistance decreases when the soil moisture content is less than 20% but stabilizes beyond a water content of 20%. The accuracy of the topological mechanism prediction method is high, as demonstrated through the verification of the Smith circle and measured data. However, it is noted that the performance may be insufficient in the high frequency band and high soil moisture content. The use of impedance topology provides a more accurate and reliable method for measuring soil moisture content as well as for modeling and predicting heat transfer rates and system performance. This technology has strong potential to improve efficiency, reduce energy costs, and enhance the environmental sustainability of geothermal heat pump systems.

Gu Guiyu, Sheng Wei, Zheng Haikun et al.

Superhydrophobic surfaces can reduce the attachment of droplets, reduce the increase of thermal resistance caused by the existence of droplets, and thereby improve the efficiency of air conditioning, power generation, and seawater desalination systems. This study experimentally investigates the growth characteristics of condensate droplets on a superhydrophobic surface under different cold surface temperatures (2–8 ℃), relative humidity values (40%–80%), and inclination angles (0°–90°) and analyzes the effects of different working conditions on superhydrophobic-surface condensation. The results show that with a decrease in the cold surface temperature, the average droplet growth radius and surface droplet coverage gradually increase. The lower the cold surface temperature, the faster the droplet growth rate. The droplets on the superhydrophobic surface grow faster under high humidity, while the droplet growth radius under low humidity will exceed that under medium and high humidity after sufficient time. The droplet coverage on the cold surface under low and medium humidity conditions is considerably less than that under high humidity conditions. The critical sweep radius of droplets decreases gradually with an increase in inclination angle, and the droplet coverage on the vertical surface decreases by 42% compared with that on the horizontal surface.

Emanuele Cardillo, Changzhi Li, Alina Caddemi

Zhang Yuqi, Yu Zixuan, Zhou Xinli

The demand for oocyte vitrification has increased. However, the current step-by-step loading and removal of cryoprotectants by manual or automatic storage devices may cause osmotic injury and the loss of cells. In this study, low-cost polymethyl methacrylate (PMMA) microfluidic chips and quartz capillaries were used to build a microfluidic system that achieved not only the continuous loading and removal of cryoprotectants but also the subsequent immersion in liquid nitrogen to realize automatic vitrification. MII mouse oocytes were loaded or unloaded with cryoprotectants by manual multistep and microfluidic methods, and the cell volume changes, survival, and oocyte development rates were compared. The results demonstrate that the survival, cleavage, and blastocyst rates of oocytes were 93. 25%, 77. 12%, and 53. 00%, respectively, for the 8 min loading / unloading duration group. These are significantly higher than those of the manual multistep group but not significantly different from those of the control group (P <0. 05). In conclusion, the microfluidic system using the PMMA chip and quartz capillaries significantly reduced osmotic injury and cell loss, and simplified the operational steps. This system may provide key technical support for the development of automated devices for oocyte and embryo vitrification based on microfluidic technology.

Jose Rodriguez, Nelson Fumo

Ionel Laurentiu Alboteanu, Andrei Cosmin Militaru

Qingli Yu

Abstract People optimize the engineering technology of heating, ventilation and air conditioning scientifically and reasonably in order to improve the ability to cope with the change of temperature, which can create a better living atmosphere for the residents. With the continuous development of modern society, people have very high expectations on various convenient technologies. People have been constantly thinking of how to optimize the engineering technology of heating, ventilation and air conditioning scientifically and reasonably. Therefore, in the early stage of technical design, people’s needs should be taken as the base point to optimize various technical parameters to better improve the quality of subsequent heating, ventilation and air conditioning engineering construction and provide guarantee for improving people’s quality of life. This paper mainly discusses the optimization strategy of key technologies of heating, ventilation and air conditioning engineering to provide reference for the following optimization of heating, ventilation and air conditioning engineering technology.

Zhou Nianyong, Feng Hao, Xu Hongye et al.

In this study, an R134a closed-loop spray cooling system was built to investigate the effects of flow rate, subcooling degree, and refrigerant charge on the steady spray cooling heat transfer performance. The experimental flow rate ranged from 0.20 to 0.25 L/min, the subcooling degree ranged from 5 to 8 ℃, and the refrigerant charge ranged from 0.95 to 1.25 kg. Results show that at a flow rate of 0.184 L/min and refrigerant charge of 0.95 kg, the maximum heat flux and surface heat transfer coefficient were 105.25 W/cm2 and 2.54 W/（cm2?℃）, respectively. At low heat flux (45.93–72.55 W/cm2), with the increase in flow rate, subcooling degree, and refrigerant charge, the surface heat transfer coefficient, overall, increased. Under higher heat flux (84.02–105.25 W/cm2), the surface heat transfer coefficient increases gradually with the increase in flow rate. The surface heat transfer coefficient initially increased and then stabilized as the refrigerant charge increased. In addition, the Jacob number Ja decreases with an increase in charge, which is unfavorable for the improvement of the surface heat transfer coefficient at higher heat flux. There is an optimal refrigerant charge to maximize the heat transfer performance of the closed spray cooling system.

AbdulRahman S Almushaikah, Radwan A Almasri

Lately, with the growth in energy consumption worldwide to support global efforts to improve the climate, developing nations have to take significant measures. Kingdom of Saudi Arabia (KSA) implemented meaningful policy actions towards promoting energy efficiency (EE) in several sectors, especially in the building sector, to be more sustainable. In this paper, various EE measures and solar energy prospects are investigated for the residential sector, in two locations in the middle region of the KSA. An energy performance analysis of pre-existing residential buildings with an overall design is performed using simulation programs. However, installing EE measures in the building envelope is important to achieve an efficient sector regarding its energy consumption. The findings showed that applying EE measures for the building envelope, walls, roof, and windows should be considered first that makes the energy conservation possible. In Riyadh, EE measures are responsible for reducing energy consumption by 27% for walls, 14% for roof, and 6% for window, and by 29%, 13%, and 6% for walls, roof, and windows, respectively, for Qassim. However, the most impactful EE solution was selecting a heating, ventilation, and air conditioning (HVAC) system with a high energy efficiency rate (EER), which can minimize the energy consumption by 33% and 32% for Riyadh and Qassim, respectively. The study's feasibility showed that the number of years needed to offset the initial investment for a proposed roof PV system exceeds the project's life, if the energy produced is exported to the grid at the official export tariff of 0.019 $/kWh. However, the simple payback time was 13.42 years if the energy produced is exported to the grid at a rate of 0.048 $/kWh, reflecting the project's economic feasibility.

Ioan Petri, Omer Rana, Yacine Rezgui et al.

Integrating data analytics, optimisation and dynamic control to support energy services has seen significant interest in recent years. Larger appliances used in an industry context are now provided with Internet of Things (IoT)-based interfaces that can be remotely monitored, with some also provided with actuation interfaces. The combined use of IoT and edge computing enables connectivity between energy systems and infrastructure, providing the means to implement both energy efficiency/optimisation and cost reduction strategies. We investigate the economic implications of harnessing IoT and edge/cloud technologies to support energy management for HVAC (Heating, Ventilation and Air Conditioning) systems in buildings. In particular, we evaluate the cost savings for building operations through energy optimisation. We use a real use case for energy optimisation as identified in the EU “Sporte2” project (focusing on the energy optimisation of sports facilities) and explore several scenarios in relation to costs and energy optimisation.

Xing Lin, Yan Jinzhou, Wang Kunhai et al.

A flexible design scheme for a direct expansion solar-assisted heat pump system is presented. Based on the flexible theory for the virtual operating point of the basis design, which was stored in the flexible space, all of the operating points within the flexible space could achieve almost the same heat transfer effect. The weights of the environmental factors for the system’s coefficient of performance (COP) were obtained in a simulation and verified in an experiment, including the irradiation intensity (52.2%), temperature (34.7%), and wind speed (13.1%). A total of 25 sets of systems were simulated under typical weather conditions. The purpose was to verify the operating points that fell in the flexible space based on the weights for the optimal combination of virtual operating points obtained. The values of the irradiation intensity (It), ambient temperature (T0), and wind velocity (uw) were 559.97 W/m2, 21.6 ℃, and 2.89 m/s respectively. The simulation results showed that the variance in the system’s COP was 0.156，which was superior to the traditional static design result.

Chen Zhenhua, Li Gaimin, Wu Jianhua

R290 has been considered for use in air-conditioning systems as a low global warming potential (GWP) refrigerant. This paper describes the tribological characteristic of the vane-piston tribopair in a R290 rotary compressor. For the purpose of simulating the tribopair working conditions, the vanes and rolling pistons of a compressor were directly adopted as test specimens. All of the tribological tests were performed under sealed high-pressure conditions, with test conditions such as the relative sliding speed, loads, and temperatures set based on actual operating conditions of a compressor, and the friction coefficients, scuffing resistances, and wear depths were measured. Furthermore, the morphological changes were investigated using a scanning electron microscope after the tests. As a comparison benchmark, tests were also conducted using R410A/polyolester oil. From these tests, it was evident that the friction coefficients and scuffing load of the vane-piston interface in the presence of R290/mineral oil were respectively 0.05–0.1 and 300 N higher than those of R410A/polyolester. On the other hand, the wear resistance ability with R290/mineral oil was better than that with R410A/polyolester.

Wang Fenghao, Yan Liang, Feng Chenchen et al.

A three dimensional numerical model of ground source heat pump system was established. The effects of testing time, starting time, borehole radius, initial ground temperature and heat injection rate on identified thermal conductivity of the deep ground soil were analyzed based on the numerical model. The simulation results showed that thermal response test time should be more than 70 h; For cylinder-source model, with the increase of the size of the borehole, the identified thermal conductivity gradually decreased; The initial temperature of ground soil has no effect on the result of thermal conductivity identification, but the testing precision of the initial temperature has larger effects to identification results when the parameter estimation method is adopted; For pure thermal conductivity model, heat injection rate has no effect on thermal conductivity identification results.

臧小亚, 梁德青, 樊栓狮

陈继辉, 童明伟