scholarly journals Effects of Cooling Systems on Greenhouse Microclimate and Cucumber Growth under Mediterranean Climatic Conditions

Agronomy ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 300 ◽  
Author(s):  
Georgios Nikolaou ◽  
Damianos Neocleous ◽  
Nikolaos Katsoulas ◽  
Constantinos Kittas
Keyword(s):  
Vapor Pressure Deficit ◽  
Cooling System ◽  
Ventilation System ◽  
Climatic Conditions ◽  
Irrigation Regime ◽  
Crop Water ◽  
Water Losses ◽  
Cooling Systems ◽  
Cropping Seasons ◽  
The Impact

Two experiments were conducted in different cropping seasons under Mediterranean climatic conditions to investigate the impact of two cooling systems (fan-pad evaporative as opposed to fan ventilation) on greenhouse microclimate and soilless cucumber growth. The second objective of the experiment was to determine the most appropriate irrigation regime (between 0.24 and 0.32 L m−2) in relation to crop water uptake and greenhouse fertigation effluents. The use of a fan ventilation system enhanced the vapor pressure deficit; thus, the crop transpiration improved by 60% in relation to the transpiration rates of plants grown under the fan-pad system. Higher transpiration rates alleviated the heat load as the external–inside greenhouse air differences declined from 6.2 °C to 3 °C. The leaf–air temperature differential indicated that plants were not facing any water stress conditions for both cooling systems tested; however, fan ventilation reduced drainage emissions outflows (95% decrease) compared with evaporative cooling. Results also demonstrated that an irrigation regime of 0.24 L m−2 can be applied successfully in soilless cucumber crops, keeping the drainage to a minimum (20% of the nutrient solution supply). These results suggest that fan ventilation cooling system in conjugation with an appropriate irrigation regime prevents overheating and minimizes the nutrient and water losses in spring-grown soilless cucumber crops in Mediterranean greenhouses without compromising yield.

Optimal Vacuum Calculation and Analysis of Composite-Cycle Air-Cooling System

2013 ◽  
Vol 718-720 ◽  
pp. 1687-1690 ◽  
Author(s):  
Sheng Long Wang ◽  
Wen Hao Li ◽  
Yin Hai Ge
Keyword(s):  
Cooling System ◽  
Calculation Model ◽  
Climatic Conditions ◽  
System Structure ◽  
Air Cooling ◽  
Air Cooling System ◽  
Working Principle ◽  
Annual Earnings ◽  
Correct Understanding ◽  
The Impact

In this paper, the research object is composite-cycle air-cooling system. First,gave a brief introduction of the system structure and the working principle in power plant. Then the optimal vacuum calculation model was established with the analysis of performance indicators and the amount of equipment production, consumption power of system. Analyze the impact of the ambient temperature to system optimal vacuum in variable conditions. Lastly, combining the climatic conditions of example, which can be drawn is that when the annual best vacuum is 4.8kPa, the running annual earnings is the highest. This article provides guiding significance for correct understanding and engineering applications of composite-cycle air-cooling systems, also further confirm the feasibility of composite-cycle air-cooling system.

NUMERICAL SIMULATION AND PARAMETRIC STUDIES FOR EVALUATION OF BALANCED VENTILATION AND EARTH AIR EXCHANGERS SYSTEM COUPLED TO A DOMESTIC BUILDING

2013 ◽  
Vol 21 (01) ◽  
pp. 1350002 ◽  
Author(s):  
YOUNES KARTACHI ◽  
ABDELLAH MECHAQRANE
Keyword(s):  
Heat Exchanger ◽  
Heat Recovery ◽  
High Efficiency ◽  
Residential Buildings ◽  
Ventilation System ◽  
Primary Energy ◽  
Climatic Conditions ◽  
Design Parameters ◽  
Climate Data ◽  
The Impact

In this study, we analyze the impact of ventilation heat recovery with the heating and cooling potential of earth air heat exchanger in real climatic conditions in domestic buildings in the Middle Atlas region. In our case study, we calculate the primary energy used by a domestic building built as per the conventional house design parameters required by the Moroccan regulation. We use climate data for the city of Fes in Northern Moroccan. Three system configurations were considered. The first was the mechanical extract ventilation system both with and without heat recovery. The second was the mechanical extract ventilation system with earth to air heat exchanger system (EAHEX), and the third system was the mechanical balanced ventilation system coupled with EAHEX system. Primary energy use strongly influences natural resources efficiency and the environmental impacts of energy supply activities. In this study we explore the primary energy implications of the mechanical balanced ventilation system coupled with the EAHEX system in residential buildings. The results of this study shows that the use of a balanced ventilation system, with a high efficiency instead of a mechanical extract ventilation system, decreases the final and primary energy consumption. Moreover, it decreases or increases the CO2 emission depending on the primary energy sources.

scholarly journals Innovative Turbine Intake Air Cooling Systems and Their Rational Designing

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6201
Author(s):  
Andrii Radchenko ◽  
Eugeniy Trushliakov ◽  
Krzysztof Kosowski ◽  
Dariusz Mikielewicz ◽  
Mykola Radchenko
Keyword(s):  
Gas Turbines ◽  
Maximum Rate ◽  
Cooling System ◽  
Ambient Air ◽  
Cooling Capacity ◽  
Climatic Conditions ◽  
Air Cooling ◽  
Thermal Loads ◽  
Cooling Systems ◽  
Air Cooling System

The efficiency of cooling ambient air at the inlet of gas turbines in temperate climatic conditions was analyzed and reserves for its enhancing through deep cooling were revealed. A method of logical analysis of the actual operation efficiency of turbine intake air cooling systems in real varying environment, supplemented by the simplest numerical simulation was used to synthesize new solutions. As a result, a novel trend in engine intake air cooling to 7 or 10 °C in temperate climatic conditions by two-stage cooling in chillers of combined type, providing an annual fuel saving of practically 50%, surpasses its value gained due to traditional air cooling to about 15 °C in absorption lithium-bromide chiller of a simple cycle, and is proposed. On analyzing the actual efficiency of turbine intake air cooling system, the current changes in thermal loads on the system in response to varying ambient air parameters were taken into account and annual fuel reduction was considered to be a primary criterion, as an example. The improved methodology of the engine intake air cooling system designing based on the annual effect due to cooling was developed. It involves determining the optimal value of cooling capacity, providing the minimum system sizes at maximum rate of annual effect increment, and its rational value, providing a close to maximum annual effect without system oversizing at the second maximum rate of annual effect increment within the range beyond the first maximum rate. The rational value of design cooling capacity provides practically the maximum annual fuel saving but with the sizes of cooling systems reduced by 15 to 20% due to the correspondingly reduced design cooling capacity of the systems as compared with their values defined by traditional designing focused to cover current peaked short-term thermal loads. The optimal value of cooling capacity providing the minimum sizes of cooling system is very reasonable for applying the energy saving technologies, for instance, based on the thermal storage with accumulating excessive (not consumed) cooling capacities at lowered current thermal loads to cover the peak loads. The application of developed methodology enables revealing the thermal potential for enhancing the efficiency of any combustion engine (gas turbines and engines, internal combustion engines, etc.).

Development of an Improved Desiccant-Based Evaporative Cooling System for Gas Turbines

2008 ◽  
Author(s):  
Amir Abbas Zadpoor ◽  
Ali Asadi Nikooyan
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Evaporative Cooling ◽  
Climatic Conditions ◽  
Cooling Systems ◽  
Actual Performance ◽  
Evaporative Cooling System ◽  
Industrial Gas Turbine ◽  
Gas Turbine Cycle

The evaporative inlet cooling systems used for inlet cooling of gas turbines during hot summers do not work well in humid areas. However, desiccant wheels can be used to dehumidify the air before passing it trough the evaporative cooler. Since the desiccant wheels work adiabatically, the resulting air is hotter than the air introduced to the wheel and an evaporative cooling system is used to cool down the dehumidified air. Combined direct and indirect evaporative coolers have been already used to investigate the effects of dehumidification on the effectiveness of the evaporation cooling systems. It is shown that a single desiccant wheel does not offer much higher effectiveness compared to the multiple-stage evaporative systems. In this paper, an improved version of the desiccant inlet cooling system is presented. Additional dehumidification and indirect evaporative cooling stages are added to increase the effectiveness of the inlet cooling. A typical gas turbine cycle along with an industrial gas turbine with actual performance curves are used to simulate the thermal cycle in presence of the different inlet cooling systems. The simulations are carried out for three different climatic conditions. The improved and original desiccant-based systems are compared and it is shown that the added stages substantially improve the effectiveness of the desiccant-based inlet cooling.

Solar Assisted Desiccant Cooling Simulation for Different Climate Zones

2011 ◽  
Author(s):  
Wendell Concina ◽  
Suresh Sadineni ◽  
Robert Boehm
Keyword(s):  
Air Conditioning ◽  
Cooling System ◽  
Evaporative Cooling ◽  
The United States ◽  
Economic Benefits ◽  
Climatic Conditions ◽  
Hot Water ◽  
Low Grade ◽  
Cooling Systems ◽  
Climate Zones

Evaporative cooling is among the most cost effective methods of air conditioning, but is less efficient in humid climates. An evaporative system coupled with a desiccant wheel can operate effectively in broader climatic conditions. These cooling systems can substitute traditional vapor compression air conditioning systems as they involve environmentally friendly cooling processes with reduced electricity demand (which is commonly generated from fossil fuels) along with no harmful CFC based refrigerant usage. Furthermore, direct utilization of low grade energy sources such as solar thermal energy or flue gas heat can drive the desiccant regeneration process, thus providing economic benefits. This study presents the results of simulations of desiccant cooling system performance for different climate zones of the United States. Solar assisted desiccant air conditioning is particularly useful where there are abundant solar resources with high temperature and humidity levels. Building energy simulations determined cooling energy requirements for the building. Simulation of an evacuated solar hot water collector model provided the heat energy available for regeneration of the desiccant. Solid desiccant of common material such as silica gel used in a rotary wheel is simulated using established validated computer models; this is coupled with evaporative cooling. Transients of the overall system for different cooling loads and solar radiation levels are presented. Finally, feasibility studies of the desiccant cooling systems are presented in comparison with traditional cooling system. Further analysis of the data presents optimization opportunities. Energy savings were achieved in all climatic conditions with decreased effectiveness in more humid conditions.

An application of thermal exermal analysis to the development of mine cooling systems

2002 ◽  
Vol 216 (8) ◽  
pp. 845-857 ◽  
Author(s):  
C T Twort ◽  
I S Lowndes ◽  
S J Pickering
Keyword(s):  
Water Distribution ◽  
Cooling System ◽  
Ventilation System ◽  
Cost Effective ◽  
Mine Ventilation ◽  
Distribution Networks ◽  
Ventilation Network ◽  
Generic Model ◽  
Cooling Systems ◽  
Chilled Water

The extraction of minerals and coal at greater depth, employing higher-powered machinery to improve production levels, imposes an increased burden on the ability of a ventilation system to maintain an acceptable mine climate. Hence, mechanical mine cooling systems are often adopted, which can be expensive both in terms of their associated capital and operating costs. Consequently, in order to optimize the costs it is essential to provide the mine operator with a method with which to determine the most cost effective and efficient mine cooling system. The following paper overviews the development of a novel approach to the energy analysis of mine cooling systems using the concepts of thermal exergy analysis. Generic model mine ventilation networks are constructed and the subsurface environments of these mine networks predicted. Models of various cooling system methods are developed and applied to control the underground climate within these mine networks to within pre-set climatic limits. The exergy transfers that are produced by the application of the different cooling methods are compared using performance indices. Models to represent chilled water distribution networks, used to supply the air coolers within the various cooling systems, are designed and balanced. The results of the exergy analyses applied to the operation of the various chilled water pipe networks are discussed and used to assess the exergetic performance of the application of each cooling system to the mine ventilation network.

Systematic Assessment of Combustion Turbine Inlet Air-Cooling Techniques

2005 ◽  
Vol 127 (1) ◽  
pp. 159-169 ◽  
Author(s):  
Abdalla M. Al-Amiri ◽  
Montaser M. Zamzam
Keyword(s):  
Air Temperature ◽  
Evaporative Cooling ◽  
Heat Rate ◽  
Climatic Conditions ◽  
Coefficient Of Performance ◽  
Air Cooling ◽  
Cooling Systems ◽  
Turbine Inlet ◽  
Wide Range ◽  
The Impact

The current study is centered on assessing the benefits of incorporating combustion turbine inlet air-cooling systems into a reference combustion turbine plant, which is based on a simple cycle under base load mode. Actual climatic conditions of a selected site were examined thoroughly to identify the different governing weather patterns. The main performance characteristics of both refrigerative and evaporative cooling systems were explored by examining the effect of several parameters including inlet air temperature, airflow-to-turbine output ratio, coefficient of performance (for refrigerative cooling systems), and evaporative degree hours (for evaporative cooling systems). The impact of these parameters was presented against the annual gross energy increase, average heat rate reduction, cooling load requirements and net power increase. Finally, a feasibility design chart was constructed to outline the economic returns of employing a refrigerative cooling unit against different prescribed inlet air temperature values using a wide range of combustion turbine mass flow rates.

scholarly journals DESEMPENHO DE UM SISTEMA DE RESFRIAMENTO EVAPORATIVO DO AR EM CASA-DE-VEGETAÇÃO

Irriga ◽  
2010 ◽  
Vol 15 (2) ◽  
pp. 140-150
Author(s):  
Antonio José Steidle Neto ◽  
SÉRGIO ZOLNIER
Keyword(s):  
Vapor Pressure ◽  
Air Temperature ◽  
Vapor Pressure Deficit ◽  
Cooling System ◽  
Evaporative Cooling ◽  
Climatic Conditions ◽  
Air Cooling ◽  
Cooling Efficiency ◽  
Growing Period ◽  
Air Cooling System

Este trabalho foi conduzido com o objetivo de analisar o desempenho de um sistema de resfriamento evaporativo do ar (tipo painel-exaustor) em casa-de-vegetação, ao longo do período diurno em dias com condições climáticas distintas. Foram realizadas medições de temperatura e umidade relativa do ar no interior e exterior de uma casa-de-vegetação durante o período de crescimento e desenvolvimento de tomateiros cultivados em substrato de areia. Verificou-se que as eficiências médias diárias de resfriamento evaporativo do ar variaram entre 74% e 81%. Os decréscimos máximos na temperatura do ar, imediatamente após a sua passagem pelo painel de celulose, foram de 8,2ºC e 11,4ºC. Observou-se ainda que, a eficiência de resfriamento do ar foi sensivelmente melhorada quando o déficit de pressão de vapor d'água do ar externo foi superior a 1,8 kPa.   UNITERMOS: déficit de pressão de vapor d'água do ar, temperatura do ar, eficiência de resfriamento evaporativo.     STEIDLE NETO, A. J.; ZOLNIER, S. EVAPORATIVE AIR COOLING SYSTEM PERFORMANCE IN A GREENHOUSE     2 ABSTRACT   This work aimed to analyze the performance of an evaporative air cooling system (pad-fan type) in greenhouse along daytime period in days with different climatic conditions. Air temperature and relative humidity measurements inside and outside of an greenhouse were made during the growing period of tomato plants cultivated in sand substrate. It was verified that the average daily evaporative cooling efficiency ranged from 74% to 81%. The maximum air temperature decrements, immediately after its passage through the cellulose pad, were 8.2°C and 11.4°C. It was also observed that the air cooling efficiency was sensitively improved when the vapor pressure deficit of the external air was higher than 1.8 kPa.   KEYWORDS: vapor pressure deficit, air temperature, evaporative cooling efficiency.  

scholarly journals Impact of Orientation on the Thermal Performances in Vernacular Buildings in Hot Arid Climate

2019 ◽  
Vol 9 (2) ◽  
pp. 4840-4847
Keyword(s):  
Thermal Comfort ◽  
Large Scale ◽  
Cooling System ◽  
Vernacular Architecture ◽  
Climatic Conditions ◽  
Point Of View ◽  
Occupant Comfort ◽  
Vernacular Buildings ◽  
Scale Integration ◽  
The Impact

Morocco faces enormous climatic constraints. A large part of the national territory has a hot and dry climate, hence the importance of the climate aspect in the choice of an energy saving strategy. The use of reinterpreted, decontextualized, totally or partially vernacular architectural techniques and/or forms is visible at different levels in the Maghreb countries. The large-scale integration of this aspect seems to be ignored by the designers. The objective of this research is to evaluate the impact of the building orientation and vernacular architecture towards the occupant comfort, in order to meet its energy and comfort needs at a lower cost on one hand, and on the other hand, to design more efficient collective buildings from a thermal and energy point of view. The proposed methodology allows examining the thermal performances of a traditional building under the climatic conditions of the city of Rissani in order to naturally control comfort summer and winter, in addition to ensure a good thermal comfort without using any heating or cooling system. Finally, the simulations carried out lead to the identification of the optimal orientation that demonstrates an effective reduction in indoor temperatures and a decrease in the large daily fluctuations in these temperatures. The research focuses on the influence of the orientation of a building's facades in relation to the solar radiation and on providing the necessary thermal comfort.

scholarly journals Herbaria as Functional Trait Databases

2018 ◽  
Vol 2 ◽  
pp. e25766 ◽  
Author(s):  
Sofie Meeus
Keyword(s):  
Tree Species ◽  
Functional Trait ◽  
Climatic Conditions ◽  
Congo Basin ◽  
Forest Community ◽  
Herbarium Specimens ◽  
Water Losses ◽  
Climatological Data ◽  
The Impact

Although tropical rainforests play an important role in regulating the world’s climate, they are at the same time particularly vulnerable to changes in the climate. Intense and prolonged droughts, for instance, can lead to biomass loss which will further accelerate these changes. Especially for tree species it becomes problematic, due to their long lifespan, to quickly adapt to or evade unfavorable climatic conditions affecting the composition of the forest community as a whole and consequently the ecosystem services that the rainforests provide. A long-term drying trend currently threatens tropical regions worldwide but is especially strong in the central African rainforest, the second-largest rainforest on Earth. The impact of this decrease in precipitation on the vegetation is, however, still largely unknown due to the limited amount of historical eco-climatological data. Fortunately, these kind of data do exist albeit in a poorly accessible (analog) format in herbarium collections. To investigate if trees show changes in morphology and/or physiology invoked by climatic changes in the last century, the COBECORE team (Congo Basin Eco-Climatological Data Recovery and Valorization”) is exploring the usability of herbaria as potential sources of plant leaf functional trait data using established protocols adjusted to dried leaf material. Photosynthesis as well as gas exchange and transpiration are processes regulated by a plant’s leaves, and depend on the specific leaf area (SLA) and the number and size of the stomata. The less area the latter structures occupy on the leaf the less the plant will suffer from water losses which increases the resistance to drought of plants. We explored the recently digitized African Herbarium of the Botanic Garden Meise which contains over 1.2 million African specimens with a very good coverage of the Congo Basin, dating back to 1880. Currently, we obtained average SLA measurements for 833 herbarium specimens from 59 of the most common tree species of central African rainforests. Pictures for stomata counts and size measurements were taken from over one hundred specimens mainly focused on three Prioria species, giant tree species (up to 60 metres) currently suffering from overexploitation. The data generated in this project will be valuable to understand some lower-level vegetation responses such as plant water use needed to model and predict long-term climate change impacts on vegetation.

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