Mist Research Articles

Structural Design and Optimization on Three‐Row J‐Type Air Cooling Channel of Pouch LiB Module

To enhance the cooling efficiency of pouch lithium‐ion battery modules, a three‐row J‐type air cooling channel structure is proposed, utilizing the previously developed multiple inlet/outlet air cooling frames. The influence of the location and number of inlets and outlets on heat dissipation performance is investigated through six air cooling channel schemes, providing a baseline for the multiobjective structural optimization of the proposed structure. Three important structural parameters, , , and l, of its air convergence and divergence plenums are selected as the design variables to improve the airflow uniformity in branch channels and minimize the pressure drop between inlets and outlets. The final design exhibits superior heat dissipation performance compared to baseline. It is noted that the airflow root mean square error in branch channels is reduced by 75.64%, while the pressure drop is increased by 19.74%. These are the critical factors for ensuring the heat dissipation performance of battery module. The maximum temperature and the maximum temperature difference of battery module are reduced by 5.29% and 23.91%, respectively, which help maintain its working temperature within a reasonable range.

Improving the air environment of vehicle cabins

BACKGROUND: The use of an innovative irrigated nozzle for air purification in the cabins of small class tractors is justified. The use of it makes it possible to comprehensively solve the problem of the state of air environment in the case of tractors operation in conditions of limited air exchange. AIM: Reduction of the content of harmful substances in the air of small tractors’ cabins. METHODS: Physical and chemical processes -chemical processes, during which the cabin air can be purified from harmful substances in the air cooler nozzle, are taken into account. RESULTS: The irrigated nozzle developed for the air coolers of the cabins of the mentioned tractors makes it possible to clean the exhaust gases from harmful impurities. CONCLUSION: Nozzles of a regular structure, irrigated with water with sodium bicarbonate and potassium permanganate dissolved in it, make it possible to comprehensively solve the problem of improving the state of air environment in the case of small class tractors operation in conditions of limited air exchange.

Design And Testing of a Compact, Reverse Brayton Cycle, Air (R729) Cooling Machine

Design And Testing of a Compact, Reverse Brayton Cycle, Air (R729) Cooling Machine

Experimental Study on the Performance of a Novel Data Center Air Conditioner Combining Air Cooling and Evaporative Cooling

Addressing challenges of high-temperature shutdowns, low energy efficiency, and limited natural cooling utilization in data center air conditioning, a novel hybrid air cooling and evaporative cooling air-conditioning(ACEC-AC) system has been developed. The system is well-suited for application in data centers located in regions with high outdoor temperatures and large dry-bulb to wet-bulb temperature differences during summer. Experimental evaluations in an enthalpy difference laboratory revealed that the hybrid system's performance in wet mode (combining air cooling and evaporative cooling) significantly outperforms its dry mode (solely air cooling) and traditional cooling units. At an outdoor temperature of 35.60°C dry-bulb and 29.95°C wet-bulb, the system achieved a COP of 3.85, a 21.45% improvement over dry mode and 16.16% higher than conventional Packaged computer room air conditioning (CRAC). Notably, the system maximizes its benefits in regions like Guangzhou, where the temperature difference between the dry bulb and wet bulb is significant, resulting in an annual operational cost savings of over 34.16%. In conclusion, the hybrid air cooling and evaporative cooling system represents an effective energy-saving technology with great potential to enhance data center performance and reduce energy consumption.

Experimental investigation on the post-fire mechanical properties of YSt-355FR (0.1 % Mo) low-alloyed fire-resistant steel

Fire-resistant steel (YSt-355FR (0.1 % Mo)) has become the most utilized structural steel due to its superior performance at elevated temperatures compared to traditional structural steel at both the material and structural levels. However, its performance after exposure to fire remains questionable. This study investigates the post-fire performance of cold-formed fire-resistant steel at the material level. A total of 132 steel coupons and 84 Charpy test specimens were exposed to temperatures ranging from 100°C to 1000°C. These temperature-exposed steel coupons were subjected to four different cooling conditions: furnace cooling (FC), air cooling (AC), water-jet cooling (WJC), and water cooling (WC). Tensile tests were performed on the cooled steel coupons to obtain post-fire stress-strain curves, from which the residual mechanical properties were determined. Charpy impact tests were also conducted on the cooled steel specimens to obtain impact energies and identify the fracture patterns. Key observations regarding the post-fire behavior of fire-resistant steel in terms of strength, deformability, stiffness, and toughness parameters were made. Both the exposure temperature and the cooling condition significantly influence the post-fire performance of fire-resistant steel. Fire-resistant steel demonstrates superior post-fire behavior compared to traditional structural steel. Constitutive equations were proposed to predict the mechanical properties of fire-resistant steel under various post-fire conditions, and a sound reliability analysis was performed to examine the reliability of the predicted design parameters compared to the test results. The findings presented in this paper are significant as no prior investigation has assessed the post-fire performance of fire-resistant steel; thus, they may encourage the steel construction industry to prefer fire-resistant steel over traditional structural steels and promote the reuse of temperature-exposed fire-resistant steel for sustainable construction.

DEVELOPMENT OF A MECHATRONIC SYSTEM FOR A SILKWORM INCUBATOR

In this study, the effectiveness of using a mechatronic system in the incubation of silkworm eggs was studied. The incubator consists of an SCD41 sensor, an ESP32 microcontroller, a TES1-12706 air cooler, an electric heater and a ventilation systembo'lib, harorat, namlik va CO2, which provides automatic control of temperature, humidity and CO2 quantity2. The study showed that when using the new system, the level of egg viability increased by 4.1%, and the yield of cocoons-by 5.8%. However, the overall length of the silk fiber and the continuous length have also been improved. This innovative system can be of great importance for improving product quality and ensuring economic efficiency in the silk industry.

Cfd-based optimization of Direct evaporative cooling systems for canarian greenhouses in Semi-Arid regions

Direct Evaporative Cooling Systems (DECS) offer a promising solution for mitigating heat stress in greenhouses located in arid and semi-arid regins. To implement DECS efficiently in these regions, it is crucial to understand their impact on greenhouse microclimate parameters. This study investigates the influence of DECS on the microclimate within a canarian greenhouse and identifies key factors affecting their efficiency. Through Computational Fluid Dynamics (CFD) simulations using Ansys, we examined the effects of DECS on temperature, relative humidity, and air velocity within the greenhouse under semi-arid conditions.The results indicate that DECS efficiency is affected by several factors, including fan placement, evaporative pad height, fan spacing, and inlet air fan speed. Higher fan placement cools the upper canopy but increases humidity near the ceiling, whereas lower placement improves temperature uniformity but may require additional humidification. Closer fan spacing results in uneven air velocity, while wider spacing leads to stagnant zones within the greenhouse. Optimal placement of the the evaporative pad is crucial for maximizing the cooling coverage area and minimizes the temperature gradients. Inlet air fan speed also significantly impacts the microclimate, with higher speeds reducing both temperature and humidity. By optimizing these parameters, the DECS system was able to significantly decrease air temperature, increase humidity, and improve air velocity inside the greenhouse. With a pad height of 1.5 m, fans positioned at a height of 2 m, a distance of 6 m between each fan, and an air speed of 1.5 m/s at the entrance – the DECS enhances the local climate. Under these conditions, the mean air temperature drops from 40°C −in greenhouse with natural ventilation- to 21 °C using DECS, while relative humidity increases from 23 % −in greenhouse with natural ventilation- to 67 % using DECS, creating a more favorable environment for plant growth and potentially increasing crop yield and quality. Additionally, energy and environmental analyses show that implementing DECS in Canarian greenhouses, instead of traditional electrical cooling systems, results in substantial energy savings of 123,818.112 kWh/year annually and reduces carbon dioxide emissions by approximately 1.785 tons/year over a 20-year operational lifespan in a semi-arid climate.

Assessment of a Cowl-Incorporated Wind-Powered Forced-Air Evaporative Cooler for Preservation of Fruit and Vegetables

This paper reports the performance of a cowl-incorporated wind-powered forced-air evaporative cooler for preservation of fruit and vegetables. The evaluation took place in the Department of Mechanical Engineering, Obafemi Awolowo University, Ile-Ife in October. Freshly harvested tomatoes were used in the evaluation as tomatoes were common locally and are highly perishable. The produce (2.5 kg) was kept in the cooling chamber of the evaporative cooler, and the changes in weight were observed three times daily until the produce had lost more than 7 % of its weight. The no-load cool air temperatures ranged between 27.3and 34.5oC corresponding to ambient dry bulb temperatures 29.0and 43.9oC respectively. The no-load cool air relative humidity ranged between 63.0 and 87.2% corresponding to ambient relative humidity of 40.8 and 79.5% respectively. The evaporative cooler no-load cooling efficiency was 66.7% while the cooling efficiency when loaded was 50.0%. The evaporative cooler was able to preserve tomatoes for 9 days losing 4.8 % weight. The evaporative cooler had the potential of effectively preserving fruit and vegetables without dependence on electricity. If used in windier and less humid regions, the average cooling efficiency of the evaporativecooler would be higher than that observed in this research.

Enclosed Barn Conditioning System: A Comparison Between Traditional and Indirect Evaporative Cooling

Enclosed Barn Conditioning System: A Comparison Between Traditional and Indirect Evaporative Cooling

Performance assessment of a high-efficiency indirect dew-point evaporative cooler through three-dimensional modeling

The escalating demand for eco-friendly air cooling, driven by concerns over global warming, necessitates sustainable alternatives to air conditioners. Dew-point evaporative coolers offer a green alternative yet face challenges due to high flow resistances caused by the U-turn of the working air. Recently, we have developed a new compact counterflow dew-point cooler that eliminates the U-turn of the working air, mitigating flow resistance. In this paper, a precise three-dimensional simulation, based on fluid dynamics, heat transfer and mass transportation, is developed to assess the cooler's performance. The validation against experiments shows maximum 8 % deviation in input pressure and 3 % in product air temperature. The simulation provides insights into the cooler's operation, efficiency, and performance, which are not easily obtained experimentally. Optimal cooling coefficients of performance occurs at working ratios of 0.5–0.6. Notably, while metallic channel separator excels at higher flow rates, plastic ones like high-density polyethylene and polycarbonate match performance at lower rates. Furthermore, the cooler performs better in hotter, drier climates. In locales like Xian and New Delhi, the cooler is suitable for standalone use, while in regions like Dubai, Texas, Singapore, Beijing, and Monterrey, it can be coupled with air conditioners to enhance the ventilation and energy efficiency.

Optimization of a Typical Gas Injection Pressurization Process in Underground Gas Storage

In the early construction of an underground gas storage facility in an oil and gas field in southwest China, the increasing gas injection volume led to a continuous rise in energy consumption, which affects the economic sustainability of gas injection and extraction. In order to improve efficiency and reduce energy consumption, optimization of the pressurization process was carried out. An optimization model for the process of pressurization in underground gas storage has been established. Based on the model, a joint optimization approach is applied, where MATLAB is responsible for the iterative process of finding the optimal parameter combinations and HYSYS is responsible for the establishment of the process and calculation of the results of the process parameters. The key parameters include the outlet parameters of the compressor and the air cooler, which are critical in determining the overall energy consumption and operational performance of the system. Accordingly, the results related to the optimal parameter combinations for two-stage compression and three-stage compression were obtained in the case study. Compared with one-stage compression, two-stage and three-stage compression can diminish energy consumption by 1,464,789 kJ/h and 2,177,319 kJ/h, respectively. The reduced rate of energy consumption of three-stage compression was 16.10%, which was higher than that of two-stage compression by 10.83%. Although the construction costs of three-stage compression were higher than those of two-stage compression, from the perspective of long-term operation, three-stage compression had lower operating costs and superior economy and applicable value. The research results provided scientific references and new ideas for the optimization and adjustment of the pressurization process in underground gas storage.

Improving indoor air quality and cooling efficiency: Indirect dew-point evaporative cooling in South China summers

The escalating impact of global warming and the increase in respiratory illnesses have heightened the demand for fresh air systems. However, the substantial power consumption and environmental harm associated with traditional air conditioning systems conflict with current international aspirations for carbon neutrality. To address these issues, a high-performance and compact counterflow indirect dew-point evaporative cooler have developed. This innovative design eliminates the U-turn of the working air seen in conventional M-cycle coolers, resulting in reduced pressure drop and enhanced energy efficiency. This study evaluates the performance of the newly developed dew-point cooler and explores its potential use in providing cool and fresh air for indoor spaces during the sub-tropical summer season in Zhenjiang city, Jiangsu province, China. The results indicate that despite the relatively low fan efficiency (ranging from 5% to 36%), a high cooling coefficient of performance (COP) between 5.2 and 9.3 was achieved. The cooler has demonstrated its effectiveness in improving both thermal comfort and air quality indoors. In Zhenjiang, the cooler can function as a standalone cooling device in June. However, during the hotter months of July and August, it is more suitable as an efficient pre-cooling device when used in conjunction with a conventional air conditioner. The developed cooler exhibited highly stable performance over a three-month test period, consistently maintaining effective cooling and fresh air supply. This study confirms the potential of the counterflow indirect dew-point evaporative cooler as a sustainable and efficient solution for improving indoor air ventilation and thermal comfort.

Impact of Air Conditioning Type on Outdoor Ozone Intrusion into Homes in a Semi-Arid Climate

Outdoor ozone (O3) is elevated on hot, sunny days when residential air conditioning is used most. We evaluated the impact of direct evaporative coolers (ECs) and vapor-compression air conditioners (ACs) on indoor O3 concentrations in homes (N = 31) in Utah County, Utah, United States of America. Indoor and outdoor O3 concentrations were measured for 24 h at each home using nitrite-impregnated glass-fiber filters. AC homes (n = 16) provided a protective envelope from outdoor O3 pollution. Only one AC home had O3 levels above the limit of detection (LOD). Conversely, EC homes (n = 15) provided minimal protection from outdoor O3. Only one EC home had O3 levels below the LOD. The average indoor O3 concentration in EC homes was 23 ppb (95% CI 20, 25). The indoor-to-outdoor (I/O) ratio for O3 in EC homes was 0.65 (95% CI 0.58, 0.72), while the upper bound for the I/O ratio for AC homes was 0.13 (p < 0.001). Indoor exposure to O3 for residents in EC homes is approximately five times greater than for residents of AC homes. Although ECs offer energy and cost-saving advantages, public health awareness campaigns in O3-prone areas are needed, as well as research into O3 pollution controls for direct ECs such as activated carbon filtration.

Mechanical Properties of Q345 Weathering Steel Exposed to High-Temperature After Air and Water Cooling

Mechanical Properties of Q345 Weathering Steel Exposed to High-Temperature After Air and Water Cooling

Energy efficient design of buildings in hot climates through cooling of the envelope

The building envelope can afford many enhancements for lowering the cooling load in hot regions. In this paper, an active upgraded model utilizing an evaporative system to cool the envelope will be tested in the relatively humid climate of the coastal area of the Arabian Gulf. A couple of buildings were erected for this purpose. One was fully enclosed by a secondary structure around it, and the gap between the two was cooled using an evaporative cooler. This was compared to the second, which was insulated according to Dubai Municipality standards. A third comparison was also performed, which concerned the standalone secondary envelope with no evaporative cooling. The interior of all three cases was cooled using DX window-type air conditioners, and the power consumption measured. Thermal simulations were performed on similarly designed models using Ecotect 5.5 to see how each system would perform in full-scale functioning buildings. The measured tests on the building models showed a reduction of electrical consumption in both upgrades compared to the regulation insulated reference. The secondary envelope provided savings of 40 % and 47.3 % in the hot months of June and July, while the evaporative solution saved 52.1 % and 53.7 %, respectively. The simulation of a full-size building over the entire year showed the secondary envelope saving 48.9 % and the evaporative assisted 57.15 %.

Influence of irregular fiber filling on the performance of hollow fiber membrane modules for cold water production

The countercurrent hollow fiber membrane-based evaporative water cooler (MEWC) offers an eco-friendly and compact solution for cold water generation. This study introduces a random sequential addition algorithm to model the real-world irregular fiber filling within the MEWC. Inspired by the honeycomb structure, the developed 3-D numerical model adopts a calculation unit featuring a hexagonal prism comprising multiple fibers. Validation against experimental data reveals an average relative error of 2.81 % concerning outlet water temperature. The effects of fiber filling patterns (regular layout and random layout) on the velocity and temperature fields of the MEWC are investigated. Comparisons of outlet water temperature, cooling efficiency, consumptive electric power ratio, and heat and mass transfer resistance composition between these layouts under various operating conditions are conducted. The results indicate that the random layout fosters severe channeling effect and large flow dead zones, impairing air side heat and moisture transfer. The random layout exhibits over 15.9 % reduction in cooling efficiency and 36.3 % decrease in consumptive electric power ratio compared to the regular layout. Irregular fiber filling leads to a notable 158.6 % increase in air side heat transfer resistance and a 35.9 % rise in mass transfer resistance. Although irregular filling compromises the cooling performance, it demonstrates potential for energy savings under certain conditions. Design schemes should be carefully tailored to meet specific application requirements by considering these trade-offs.

Incident investigation of hydrogen explosion and fire in a residue desulfurization process

A large hydrogen explosion and fire occurred on October 27, 2022 in a residue desulfurization (RDS) process in a refinery in Kaohsiung, Taiwan. RDS is an important process that use hydrogen to convert the sulfur in the fuel into hydrogen sulfide for producing low sulfur fuel. The incident occurred during pressurization of the RDS reactors and downstream coolers by hydrogen. The incident led to significant damages to the downstream coolers and some part of the RDS reactors. Detailed incident investigation was carried out. A reactor effluent air cooler (REAC) in the downstream of RDS reactors was found to be ruptured in the rectangular header box. With security videos, process DCS data, leak and dispersion modelling, and actual damage on the process, it is possible to reproduce the leak rate, size of the initial fireball and damages done to the process. It is also found that the hydrogen leak was accompanied by prompt ignition which is commonly encountered in high-pressure hydrogen services. Recommendations are made to prevent and mitigate any future incident from the RDS process.

Performance analysis of a conventional two-stage indirect evaporative cooler

With the aim of saving a portion of the high-quality energy consumed in mechanical vapor compression systems for air conditioning applications, the present work focuses on utilization of low-quality energy conversion processes due to fluid evaporation. The conventional indirect evaporative cooler is selected based on its preference for further modification compared to a regenerative indirect evaporative cooler. It is configured to be operated with two identical stages in series. This task is achieved by developing a thermodynamic model to analyze the performance of the cooling unit and to indicate the extent of its development compared to the cooler in one stage. Preliminary results show that the best operating condition is when the ratio of primary air to secondary air is 1. The cooling unit produces fairly comfortable air within limited climatic conditions. It delivers air at 26 °C and lower even at climatic temperatures as high as 48 °C, but within a very low relative humidity range. The relative humidity range extends to less than 58% as the outdoor air temperature decreases. At high humidity levels (64 to 80% depending on climate temperature), cool air cannot be obtained at 26 °C, and the cooling unit performance is limited only by what the first stage produces. The average performance of the cooling unit exceeds that of the first stage by 42.6%. Increasing air flow rate leads to an increase in cooling capacity, but it also has a negative impact on supply temperature and effectiveness.

Evaporation Cooling - Future Potentials of Electric Drives under New Cooling Conditions

Evaporation Cooling - Future Potentials of Electric Drives under New Cooling Conditions

Exploring the Impact of Temperature and Solvent Ratio on Phenol and Flavonoid Levels in Alpinia galangal L. Extract Using Evaporative Vacuum Cooling

The objective of this research is to determine the impact of temperature gradients and solvent ratios in the evaporative vacuum cooling method on the yield of phenol and flavonoid content in galangal extract; ascertain the impact of these factors on the yield generated by galangal extract; and ascertain the mass balance analysis of materials are the objectives of this study. Throughout the extraction of galangal. The study's findings demonstrated that the evaporative vacuum cooling technique, conducted at 49 ºC and with a 1:1 solvent ratio of 1.4432±0.7317 mg GAE/g, produced the highest total phenol concentration. The three differences in the temperature of the evaporative vacuum produced the total phenol content cooling. The overall phenol content obtained decreases with increasing solvent ratio addition. Although the evaporative vacuum cooling treatment at 45 °C yielded the highest total flavonoid content (1.2418±0.2365 mg QE/g) at a 1:2 solvent ratio, the total flavonoid content varied between the three evaporative vacuum cooling temperature variations. The yield of total phenolic and flavonoid compounds was not significantly affected by temperature gradient adjustments or the ratio of galangal extract to solvent (Sig. > 0.05) in any of the data samples pertaining to phenolic and flavonoid compounds. Keywords: Evaporative vacuum cooling, Flavonoids, Galangal, Phenol.