Hasil untuk "Heating and ventilation. Air conditioning"

Siti Marwangi Mohamad Maharum, Muhammad Aliff Azim Hamzah, Muhammad Ridzwan Ahmad Yusri et al.

The Heating, Ventilation, and Air Conditioning (HVAC) system is commonly found in buildings such as industrial, commercial, residential, and institutional buildings. This HVAC system generates a significant speed of wind flow from its condenser unit. Surprisingly, this wind energy remains unexploited and thus dissipates into the surroundings. This project aims to leverage this unused wind energy from the condenser unit by developing an energy harvesting prototype that harnesses the HVAC system’s wind for a practical charging station. Specifically, a wind turbine is connected to a three-phase 12 VAC generator motor. This connection would efficiently convert wind energy into electrical power. An energy storage module is also incorporated to ensure uninterrupted functionality for the developed charging station prototype. The energy storage module has a substantial capacity of 25Ah, equivalent to a standard socket outlet. This ensures that the energy storage system can fully charge within three hours if there are no interruptions in the turbine's operation. An experimental validation was conducted by supplying different wind speeds to this project prototype, and it was observed that only when the wind speed is above 10 ms-1 does the energy storage system charge, and sockets provide a consistent output. The final output at the socket provided both 230VAC voltage and a USB charging option, making it versatile for users to charge commonly used electrical appliances such as smartphones and laptops. By repurposing this otherwise wasted wind energy, the developed system prototype contributes to cleaner and more sustainable energy utilization. It also converts unused energy into valuable, cleaner energy.

Hanna Bilovol, Mykola Naumenko

The paper presents an approach for assessing the sustainability of energy-saving measures in buildings based on the integral Sustainability Impact Index (SII), which incorporates the energy, environmental and circulatory characteristics of each solution. The methodology was tested on a case study of an office building, where energy-saving measures were structured into three groups and evaluated through a comparative analysis. The study also included the development of a circulatory solution based on the reuse of condenser heat from the building’s chiller units. The results demonstrate that the application of the SII clearly reflects the increasing importance of measures related to internal energy circulation. The SII value for the circulatory measure was found to be approximately twice as high as for the technical and operational groups, indicating its concentrated impact and potential to replace external energy resources. The proposed approach allows for a more accurate prioritization of sustainable solutions and can be applied in planning HVAC system modernization and developing building decarbonization strategies.

Alena Puchkova, Jorge Merino, Ajith Kumar Parlikad

Zhu Meng, Chen Hua, Hou Yujie

To solve the problems of poor thermal conductivity and low thermal energy storage efficiency of paraffin wax, carbon-containing materials with high thermal conductivity are used to improve its thermal energy storage performance. Three carbon nanotube powders with different diameters, 8–12 nm, 10–20 nm, and 20–40 nm, are added to paraffin wax at a mass fraction of 5% to evaluate the influence of the carbon nanotube diameter on the thermal energy storage properties and the anisotropic thermal conductivity of carbon nanotube/paraffin wax composite phase change material (CPCM). The experimental results show that the specific heat capacity and latent heat value of CPCM decreases as the diameter of the carbon nanotubes decreases. The phase change temperature decreases by approximately 1 ℃; the latent heat value decreases by 0.5%–3.8%, and the specific heat capacity decreases by 16.2%–16.5% compared with those of pure paraffin wax. The improved thermal conductivity and thermal diffusivity shorten the paraffin wax melting time, and the melting time of 8–12 nm composites is reduced by 18.2%–46.7%. Temperature uniformity in the vertical direction was also effectively improved. At the external measurement points, the temperature fluctuation of 8–12 nm composites was 47.7% compared with pure paraffin, whereas at the internal measurement points, the temperature fluctuation of 10–20 nm was 32.9% of pure paraffin. The diameter of the carbon nanotubes significantly improved the thermal energy storage properties of the CPCM.

Yu Qiancheng, Xie Yingming, Wang Ning et al.

The cold thermal energy storage characteristics of CO2 hydrates were studied in different mass concentrations of SDS surfactant (0.4, 0.5, and 0.6 g/L), SDBS surfactant (0.2, 0.3, and 0.4 g/L), and compound surfactants (SDS+SDBS) using a vapor compression refrigeration system. Compared with a pure-water system, SDS, SDBS, and compound (SDS+SDBS) surfactants improve the CO2 hydrate cold thermal energy storage performance, and the best concentrations of the surfactants were 0.5 g/L, 0.3 g/L, and 0.5 g/L(SDS)+0.3 g/L(SDBS), respectively. Comparing the cold thermal energy storage performance of SDS, SDBS, and compound (SDS+SDBS) surfactants, the compound surfactant 0.5 g/L(SDS)+0.3 g/L(SDBS) had the best cold thermal energy storage performance: the precooling time (21.51 min) and cold thermal energy storage time (27.56 min) were the shortest. The latent heat storage capacity (1 308.27 kJ), total storage capacity (2 967.35 kJ), average charging rate (1.79 kW), and hydrate formation mass (2.55 kg) were the largest. The findings indicate that the compound surfactant had the most significant effect on the CO2 hydrate cold thermal energy storage characteristics of this system.

Liwei Fang

In modern age of technology, the concept of energy saving and environmental comfort raise the building services and controls as a significant issue during the design, installation, operation and management. Proper electrical services and sound control systems, especially for Heating, Ventilation and Air-conditioning (HVAC) sections, can not only make our lives more convenient and pleasant, but also increase the energy efficiency in the view of sustainable development.

Ákos Lakatos, István Csarnovics, Attila Csík

In the European Union, almost 40% of all energy consumption comes from buildings, while another 20–25% comes from transport. In the European Union, including Hungary, only buildings with almost-zero energy demand could be built after 2020, and the use of renewable energies must be strengthened. The Renewable Directive stipulated that by 2020, the share of renewable energy in buildings must be 25%, and in transport it must be 10%; the use of electric vehicles is vital. There are about four million dwellings in Hungary, of which approximately three million need to be renovated, and only some of these (a few hundred) meet the cost-optimized level of the 2020 directive. The use of insulation materials is very important in the transport sector, too. Insulation materials are also used by aircraft and electric vehicles. To reduce the energy loss from buildings, different insulation materials can be used; investigations of insulation materials are very important. This paper presents a comprehensive research report on insulation materials which could be used for building elements, HVAC (heating, ventilation, and air conditioning appliances) equipment, and vehicles. In this paper, laboratory investigations will be presented along with calculations to better understand the properties and behavior of these materials. For this, firstly structural analysis with scanning electron microscope will be presented. Moreover, the paper will present thermal conductivity and combustion heat measurement results. The sorption and hydrophobic behavior of the materials will be also revealed. Finally, the article will also display differential scanning calorimetry measurements and Raman spectroscopy results of the samples. The research was conducted on four different types of colorized microfiber lightweight wool insulation.

Fenglin Zhang, Nianping Li, Haijiao Cui et al.

Dongsheng Xu

Zhibo Kang, Zhenhua Shao, Lin Su et al.

Changfa Ji, Chenyang Ji, Huan Zhang et al.

Wang Meixia, Liang Wei, Ye Ping et al.

Establishing a high-quality biobank is very important, but the cryoprotective agent (CPA) type and concentration have a considerable influence on the cryopreservation effect. In this paper, HBL-100 human breast cells were treated with 10% Me2SO combined with trehalose (0-0.3 mol/L) and fetal bovine serum (FBS; 20%-60%) in Dulbecco’s modified Eagle’s medium (DMEM). Through gradual reduction of the temperature, the cells were cooled in a ﹣80 ℃ freezer for 4 h and then quickly transferred into liquid nitrogen. After storing for 7 days, the cells were shaken quickly at 37 ℃. The cell survival rate was assessed using the trypan blue test, cell counting kit (CCK) assay, and the attached rations after 24 hours. The results show that, compared with the control group, the effects of the trehalose and FBS are very obvious. In particular, when the trehalose concentration is constant, a higher FBS volume fraction yields a better effect. The FBS has no significant effect without trehalose. Further, when the FBS volume fraction is constant, the optimal effect is obtained for 0.2 mol/L trehalose. A high trehalose concentration may weaken the effect of the FBS. Considering the cost and other factors, the most suitable CPAs for the cryopreservation of HBL-100 human breast cells are 10% Me2SO + 40%-60% FBS + 0.2 mol/L trehalose.

Sonny Myrefelt

陈天及, 李玉红, 余克志 et al.

The air curtain characteristic plays a very important role on the performance of vertical refrigerated display case. The transient temperature of the display case shelves was measured for studying the temperature variation and distribution in the display case by changing the number and the velocity of air curtain. The result shows that it is necessary to keep three air curtains in a vertical open low temperature display case and the performance of the display case can be improved by selecting reasonable air curtain velocities.

王强, 张小艳, 吴裕远 et al.