Efficiency of two different types of cooling systems in broiler and layer poultry houses in arid regions

This paper presents the results of tests carried out to investigate the potential application of a direct evaporative cooling (DEC) system for improving the performance of a compact thermoelectric (TE) air conditioner. The compact TE air conditioner is composed of three TE modules. The cold and hot sides of the TE modules were fixed to rectangular fin heat sinks. The DEC system produced cooling air that was used to assist the release of heat from the heat sinks at the hot side of the TE modules. The results showed that the cooling air dry bulb temperature from the DEC system achieved drops of about 5.9°C in parallel with about a 33.4% rise in relative humidity. The cooling efficiency of the DEC system varies between 72.1% and 81.5%. It increases the cooling capacity of the compact TE air conditioner from 53.0 W to 74.5 W. The 21.5 W (40.6%) increase represents the difference between the compact air conditioner operating with ambient air flowing through the TE module’s heat sinks, and the compact air conditioner operating with the cooler air from the DEC system flowing through the TE module’s heat sinks. In both scenarios, electric current of 4.5 A was supplied to the TE modules. It also has been experimentally proven that the coefficient of performance (COP) of the compact TE air conditioner can be improved by up to 20.9% by incorporating the DEC system.

Simulation-based performance analysis of residential direct evaporative coolers in four climate regions of Iran

Building cooling is achieved by the extensive use of air conditioners. These mechanically driven devices provide thermal comfort by deteriorating the environment with increased energy consumption. To alleviate environmental degradation, the need for energy-efficient and eco-friendly systems for building cooling becomes essential. Evaporative cooling, a typical passive cooling technique, could meet the energy demand and global climatic issues. In conventional direct evaporative cooling, the sensible cooling of air is achieved by continuous water circulation over the cooling pad. Despite its simple operation, the problem of the pad material and water stagnation in the sump limits its usage. Moreover, the continuous pump operation increases the electrical energy consumption. In the present work, a porous material is used as the water storage medium eliminating the pump and sump. An experimental investigation is performed on the developed setup, and experiments are conducted for three different RH conditions (low, medium, and high) to assess the porous material’s ability as a cooling medium. Cooling capacity, effectiveness, and water evaporation rate are determined to evaluate the direct evaporative cooling system’s performance. The material that replaces the pump and sump is vermicompost due to its excellent water retention characteristics. There is no necessity to change material each time. However, the vermicompost is regenerated at the end of the experiment using a solar dryer. The passing of hot air over the vermicompost also avoids mould spores’ transmission, if any, present through the air. The results show that vermicompost produces an average temperature drop of 9.5°C during low RH conditions. Besides, vermicompost helps with the energy savings of 21.7% by eliminating the pump. Hence, vermicompost could be an alternate energy-efficient material to replace the pad-pump-sump of the conventional evaporative cooling system. Further, if this direct evaporative cooling system is integrated with solar-assisted drying of vermicompost, it is possible to provide a clean and sustainable indoor environment. This system could pave the way for year-round thermal management of building cooling applications with environmental safety.

Author(s): Zhao, R; Liu, J; Gu, J; Zhai, L; Ma, F | Abstract: A desirable operating temperature range and small temperature gradient is beneficial to the safety and longevity of lithium-ion (Li-ion) batteries, and battery thermal management systems (BTMSs) play a critical role in achieving the temperature control. Having the advantages of direct access and low viscosity, air is widely used as a cooling medium in BTMSs. In this paper, an air-based BTMS is modified by integrating a direct evaporative cooling (DEC) system, which helps reduce the inlet air temperature for enhanced heat dissipation. Experiments are carried out on 18650-type batteries and a 9-cell battery pack to study how relative humidity and air flow rate affect the DEC system. The maximum temperatures, temperature differences, and capacity fading of batteries are compared between three cooling conditions, which include the proposed DEC, air cooling, and natural convection cooling. In addition, a DEC tunnel that can produce reciprocating air flow is assembled to further reduce the maximum temperature and temperature difference inside the battery pack. It is demonstrated that the proposed DEC system can expand the usage of Li-ion batteries in more adverse and intensive operating conditions.

Understanding the dynamics of the soil–vegetation–atmosphere (SVA) system, particularly in arid and semiarid regions, remains challenging due to its intricate and interdependent nature. This system creates problems for rangeland administration, such as insurance and risk management. This paper focuses on the complex interactions within the SVA system, particularly on rangeland ecosystems in Spain's semiarid and arid regions. By employing multifractal detrended cross‐correlation analysis (MFCCA), we explore the joint behavior of key variables, including precipitation (PCP), evapotranspiration (ETP), aridity index (Arid. I.), soil water availability (SWA), biomass (Bio), and normalized difference vegetation index (NDVI). Analyzing a 20‐year data series from Madrid and Almeria provinces, we reveal distinct patterns in the studied variables’ persistence, multifractality, and asymmetry. Notably, the differences in the generalized Hurst exponents (( q )) between Madrid and Almeria for SWA with NDVI, SWA with Bio, and NDVI with Bio underscore distinct interactions in these regions. Moreover, multifractal analyses unveil differences in the complexity of joint variables’ behaviors in the two regions. Almeria exhibits higher multifractality across variables, indicating more complex and variable environmental interactions, likely due to its more arid conditions. These findings suggest that Almeria has more sensitivity to changes, requiring adaptive management strategies, while in Madrid, water availability and related variables play a more dominant role in driving vegetation dynamics. These findings shed light through MFCCA on the nuanced dynamics of rangeland ecosystems in semiarid and arid regions, emphasizing the importance of considering complexity‐based approaches to understand the intricate interplay among key variables in the SVA system.

Direct evaporative cooling (DEC) system, even in the simpler configuration, is concerned with the wet pad design for improving system cooling performance. The performance measure is assessed by the evaporation of the pad liquid content and changes of mainstream flow properties. This article examined a potential DEC design in laboratory scale that incorporates a water-based wet pad with metal plate attachment. The proposed system is modelled by a low speed uniform air flowing over a heated wet pad. The influence of metal thermal conductivity and the surface contact on air temperature and humidity was evaluated. The results shows that efficiency increases nearly 50 % despite poor influence of metal property and contact area on mainflow properties. Increasing contact area of metal plate plays a major role to preserve the cooling efficiency. Since, base pad without metal plate shows superior performance than that of with metal plate due to the loss sensible heat, DEC system must be designed with consideration of providing more homogenous air mixture and preventing the loss sensible heat.

Arid and humid ecosystems are undergoing significant changes over the past decades due to the warming temperature and frequent occurrence of climate extremes. Quantifying climatic vegetation sensitivity in regions with different climate classifications is crucial for understanding the interaction mechanisms between vegetation and ongoing climate change. However, such knowledge about the spatiotemporal variations of vegetation sensitivity and its climate driving factors in arid and humid regions is still unclear. Based on this consideration, a moving-window-based Vegetation Sensitivity Index (VSI) scheme was applied to Enhanced Vegetation Index (EVI), Leaf Area Index (LAI), and Solar-induced Chlorophyll Fluorescence (GOSIF) data to evaluate the spatiotemporal variations of terrestrial ecosystem in response to climate changes and explore its driving climatic factors from 2003 to 2020. Results indicated that high VSI (>60) was observed for tropical rainforests in humid regions and central Eurasia in semi-arid regions. By contrast, low VSI (<40) was typically observed in arid regions. Spatially, we found VSI exhibited a nonlinear parabolic variation along the gradient of aridity index in the arid and semi-arid regions but generally presented a linear variation with an upward trend in the humid regions. Temporally, VSI showed a significant declining trend over the past two decades but displayed a significantly increasing trend in arid areas. Temperature was the dominant climatic factor to explain the spatial variations of VSI globally, while precipitation mainly dominated the temporal variations of VSI. The dominant climatic factor of VSI varied across different aridity regions as temperature and precipitation were the main climate factor to drive spatiotemporal variations of VSI in humid and arid classifications, respectively. Our results provide unique insights into the vegetation sensitivity in response to ongoing and future climate change in regions with different climate classifications.

Rising temperature from climate change is the most threatening factor worldwide for crop production. Sustainable wheat production is a challenge due to climate change and variability, which is ultimately a serious threat to food security in Pakistan. A series of field experiments were conducted during seasons 2013–2014 and 2014–2015 in the semi-arid (Faisalabad) and arid (Layyah) regions of Punjab-Pakistan. Three spring wheat genotypes were evaluated under eleven sowing dates from 16 October to 16 March, with an interval of 14–16 days in the two regions. Data for the model calibration and evaluation were collected from field experiments following the standard procedures and protocols. The grain yield under future climate scenarios was simulated by using a well-calibrated CERES-wheat model included in DSSAT v4.7. Future (2051–2100) and baseline (1980–2015) climatic data were simulated using 29 global circulation models (GCMs) under representative concentration pathway (RCP) 8.5. These GCMs were distributed among five quadrants of climatic conditions (Hot/Wet, Hot/Dry, Cool/Dry, Cool/Wet, and Middle) by a stretched distribution approach based on temperature and rainfall change. A maximum of ten GCMs predicted the chances of Middle climatic conditions during the second half of the century (2051–2100). The average temperature during the wheat season in a semi-arid region and arid region would increase by 3.52 °C and 3.84 °C, respectively, under Middle climatic conditions using the RCP 8.5 scenario during the second half-century. The simulated grain yield was reduced by 23.5% in the semi-arid region and 35.45% in the arid region under Middle climatic conditions (scenario). Mean seasonal temperature (MST) of sowing dates ranged from 16 to 27.3 °C, while the mean temperature from the heading to maturity (MTHM) stage was varying between 12.9 to 30.4 °C. Coefficients of determination (R2) between wheat morphology parameters and temperature were highly significant, with a range of 0.84–0.96. Impacts of temperature on wheat sown on 15 March were found to be as severe as to exterminate the crop before heading. The spikes and spikelets were not formed under a mean seasonal temperature higher than 25.5 °C. In a nutshell, elevated temperature (3–4 °C) till the end-century can reduce grain yield by about 30% in semi-arid and arid regions of Pakistan. These findings are crucial for growers and especially for policymakers to decide on sustainable wheat production for food security in the region.

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱与半干旱区灌丛微生境中红砂枯落物分解特征及中小型节肢动物的作用 DOI: 10.5846/stxb202111193261 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 宁夏自然科学基金项目（2021AAC03047，2020AAC02014）；宁夏重点研发计划项目（2021BEG03007）；国家自然科学基金项目（41867005） The decomposition process of Reaumuria soongorica litter and the role of microarthropods in shrub microhabitats in arid and semi-arid regions Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在干旱区（内蒙古乌拉特后旗）和半干旱区（宁夏盐池）荒漠草原区，选择柠条灌丛内外微生境为研究样地，以红砂枯落物为研究对象，利用2种规格网孔分解袋（30目和250目网孔），探索中小型节肢动物在红砂枯落物分解过程中的作用规律，研究灌丛微生境中红砂枯落物质量损失变化特征及节肢动物群落的贡献。结果表明：（1）在干旱与半干旱区，红砂枯落物分解常数K均表现为灌丛内外微生境间无显著差异，且有无节肢动物参与对K的影响均较小。（2）分解至12个月时，无节肢动物参与的情况下，干旱与半干旱区红砂枯落物残留率均表现为裸地显著低于灌丛；但有节肢动物参与时，枯落物残留率则表现为灌丛内外微生境间无显著差异。分解至44个月时，无节肢动物参与的情况下，仅在干旱区枯落物残留率表现为裸地显著高于灌丛；而有节肢动物参与时，干旱与半干旱区枯落物残留率均表现为灌丛内外微生境间无显著差异。（3）节肢动物对红砂枯落物质量损失的贡献率呈现单峰值现象，且在分解至24个月时达到峰值。枯落物分解至12个月时，仅半干旱区节肢动物对红砂枯落物分解的贡献率表现为裸地显著低于灌丛；分解至44个月时，仅干旱区节肢动物对红砂枯落物分解的贡献率表现为裸地显著高于灌丛。（4）在半干旱区，节肢动物对红砂枯落物质量损失的贡献率与节肢动物类群数、土壤砂粒含量、土壤全碳和含水量密切相关；而在干旱区，节肢动物对红砂枯落物质量损失的贡献率与土壤pH值、土壤砂粒、土壤碳氮比d （C/N）和黏粉粒含量密切相关。综合表明，干旱和半干旱区灌丛微生境红砂枯落物分解特征受到节肢动物分解作用的影响较小；但在某些分解阶段，灌丛内外微生境中红砂枯落物质量损失的差异性受到节肢动物分解作用的显著影响，节肢动物的分解作用表现为弱（12个月）-强（24个月）-弱（44个月）的作用规律，而且受到气候区调节的灌丛微生境限制。 Abstract:In desertified grasslands of the arid Urad Rear Banner of the Inner Mongolia and the semi-arid Yanchi of Ningxia, the Caragana korshinskii shrub microhabitats beneath shrub canopies and in the open spaces were setup as study sites. The litter of Reaumuria soongorica was used as the research object. Two sizes of mesh (30-mesh, and 250-mesh) for litter bags were used to explore the role of soil microarthropods on litter decomposition of Reaumuria soongorica. The objective of present study was to probe into the mass loss of the litter and the contribution of soil microarthropod community in the shrub microhabitats. The results showed that:(1) there was no significant difference in decomposition constant K of litter between shrub canopy and open spaces; the presence or absence of microarthropods had little effect on K. (2) At decomposition stage of 12 months, there was significantly lower mass remaining rate of the litter in open spaces than beneath shrub canopy without the presence of microarthropods, but there was no significant difference between shrub canopy and open spaces in the case of microarthropods presence. At decomposition stage of 44 months, the mass remaining rate of litter was significantly higher in open spaces than beneath shrub canopy only in arid regions without the participation of microarthropods; however, there was no significant difference between both shrub microhabitats with microarthropod presence in both arid and semi-arid regions. (3) The contribution rate of microarthropods to the mass loss of litter showed a unimodal type during decomposition process, with a single peak at 24 months. At decomposition stage of 12 months, there was significantly lower contribution rate of microarthropods to the decomposition of litter in open spaces than beneath shrub canopy only in semi-arid region. At decomposition stage of 44 months, the contribution rate of microarthropods to the decomposition of litter was significantly higher in open spaces than beneath shrub canopy only in arid region. (4) In the semi-arid region, the contribution rate of microarthropods to litter mass loss was closely correlated to the group richness of microarthropod, soil sand content, soil total carbon, and water content. In the arid region, however, the contribution rate of microarthropods to the mass loss of litter was closely correlated to soil pH, soil sand, soil C/N, and clay and silt content. In conclusion, the overall litter decomposition in shrub microhabitats in arid and semi-arid regions was little affected by the role of microarthropods. However, at certain decomposition stages, the difference in mass loss of the litter between shrub microhabitats was affected remarkably by the role of microarthropods. There was a law of weak (12 months)-strong (24 months)-weak (44 months) role of microarthropods on litter decomposition that was regulated by the climatic factors. 参考文献 相似文献 引证文献

Do non-metallic material and radiation shields affect the operation of direct evaporative cooling systems?

Performance analysis of a solid desiccant cooling system for a residential air conditioning system

Evaporative cooling (EC) is an ancient technique that is usually suitable for hot and dry climatic conditions due to the potential of water vapor evaporation. In this study, three kinds of evaporative cooling systems such as direct EC (DEC), indirect EC (IEC), and Maisotsenko cycle EC (MEC) were locally developed at lab-scale. The performance of the systems was evaluated and compared for agricultural storage and livestock air-conditioning application in Pakistan. The experiments were performed for climatic conditions of Multan city (Pakistan) and the data were collected for hourly and daily basis. According to the results, it was observed that the DEC system has the ability to reduce the temperature of ambient air to an average of 8.5 °C. Whilst IEC and MEC systems were able to drop the temperature of ambient air to an average of 6.8 °C and 8.9 °C, respectively. As per the results, the DEC system remained behind to provide desired conditions for livestock and agricultural product storage applications due to excessive humidity. On the other hand, the IEC and MEC systems can achieve the desired conditions for livestock application, but could not provide feasible conditions for various fruits and vegetable storage. The study concludes that hybrid EC systems can be developed to provide desired conditions for a wide range of applications under varying climatic conditions.

In the 21st century, the poultry sector is a vital concern for the developing economies including Pakistan. The summer conditions of the city of Multan (Pakistan) are not comfortable for poultry birds. Conventionally, swamp coolers are used in the poultry sheds/houses of the city, which are not efficient enough, whereas compressor-based systems are not economical. Therefore, this study is aimed to explore a low-cost air-conditioning (AC) option from the viewpoint of heat stress in poultry birds. In this regard, the study investigates the applicability of three evaporative cooling (EC) options, i.e., direct EC (DEC), indirect EC (IEC), and Maisotsenko-cycle EC (MEC). Performance of the EC systems is investigated using wet-bulb effectiveness (WBE) for the climatic conditions of Multan. Heat stress is investigated as a function of poultry weight. Thermal comfort of the poultry birds is calculated in terms of temperature-humidity index (THI) corresponding to the ambient and output conditions. The heat production from the poultry birds is calculated using the Pederson model (available in the literature) at various temperatures. The results indicate a maximum temperature gradient of 10.2 °C (MEC system), 9 °C (DEC system), and 6.5 °C (IEC systems) is achieved. However, in the monsoon/rainfall season, the performance of the EC systems is significantly reduced due to higher relative humidity in ambient air.

Existing information relating to the application of phytoremediation in arid regions, for mitigating the toxicity of organic and inorganic contaminants is summarized, emphasizing the comparative merits of different phyto-strategies. Adverse climatic conditions in arid and semi-arid environments along with the intrinsic abiotic stresses need specific considerations, which are discussed here. The current “state of art” for petrochemical and metal phytoremediation, as well as phytodesalination is presented, making it possible to choose the very best decision, when the technology is applied for various contaminant scenarios. Information is also provided on contaminants in arid regions, remediation approaches and different phytoremediation strategies to be adopted, depending on the nature of contaminants and the site situations. Furthermore, phytodesalination may well occur in parallel with phytoremediation of heavy metal polluted soils in arid regions, enhancing the potential of this process. This has drawn a great deal of interest during recent years and is reviewed here. Finally, the lacunae in the current knowledge are identified, which has to be addressed to improve the effectiveness of phytoremediation under arid conditions.

Elevation dependency of temperature trend over the Qinghai-Tibetan Plateau during 1901–2015