A novel evaporative cooling system with a polymer hollow fibre spindle

A polymer hollow fibre evaporative cooling system with a novel configuration of fibre bundle is proposed. With the aim to avoid the flow channelling or shielding of adjacent fibres the fibres inside each bundle were made into a spindle shape to maximize contact between the air stream and the fibres. For the porous wall of hollow fibre, the vapour of evaporated water can permeate through it effectively, while the liquid water droplets can be prevented from mixing with the processed air. For various dry bulb temperatures (27 °C, 30 °C, 33 °C, 36 °C and 39 °C) and relative humidity (23%, 32% and 40%) of the inlet air, the cooling performances of the proposed novel evaporative cooling system were experimentally investigated. The variations of outlet air dry bulb temperature, wet bulb effectiveness, dew point effectiveness and cooling capacity with respect to different incoming air dry bulb temperature were studied. The effects of various incoming air Reynolds number on the heat and mass transfer coefficients, heat flux and mass flux across the polymer hollow fibre module were analysed. Experimentally derived non-dimensional heat and mass transfer correlations were compared with other correlations from literature. Due to the proposed spindle shape of hollow fibre bundle, the shielding between adjacent fibres could be mitigated greatly, therefore the heat and mass transfer performance of the proposed system demonstrated significant improvement compared with other designs reported in literature

Prediction the Spatial Air Temperature Distribution of an Experimental Greenhouse Using Geostatistical Methods

Concerning the greenhouse environment, the ultimate goal of an investigation would be to determine the climatic parameters for all locations in the study area. Objective of the present study is to analyse the distribution of air temperature and air velocity of an experimental greenhouse with tomato crop, equipped with fan and pad evaporative cooling system, using geostatistical methods. The main aspects of geostatistics in terms of theoretical background for understanding spatial correlation models and kriging applications are presented. The most common variogram models were fitted to the experimental data sets obtained during summer period from an experimental greenhouse equipped with fan and pad evaporative cooling system. The Kriging approach was applied using the semivariograms corresponded to these data sets. Finally, the prediction maps of air temperature and air velocity were produced in different height levels inside the tomato crop canopy showing a great variability. Geostatistic analysis may be applied to determine not just optimal spatial predictions but also probabilities associated with risk-based analysis in order to improve the suitability and efficiency of climatic controls systems in greenhouses

Evaporative cooling system a way to energy efficiency

Статья подготовлена в связи с 65-летием внедрения первой в мире установки испарительного охлаждения. Изложены теоретические основы испарительного охлаждения и показаны преимущества данной системы с точки зрения энергоэффективности и экологии.The paper is dedicated to the 65th anniversary of the introduction of the world's first evaporative cooling plant. It lays down the theoretical basis of evaporative cooling and shows advantages of this system in terms of energy efficiency and environmental friendliness

Use of fluorocarbons in the cooling of LHC experiments

Perfluorochemicals sold by 3M under the trade name 3M Fluorinert Electronic Liquids have been used for many years as heat transfer media in a variety of industries. The suitability of these liquids for the cooling of LHC experiment originates from their high dielectric strength as well as from their chemical stability under ionizing radiation. The Fluorinerts are clear, colorless, non-flammable with low toxicity and low corrosiveness. Additionally, they offer low global waming potential – GWP – and zero ozone-depletion potential – ODP. Some examples of fluorinert application in the cooling of LHC experiments will be presented : (a) the ATLAS Inner detector C3F8 evaporative cooling system (b) the ATLAS TRF C6F14 monophase cooling system and (c) the ALICE SPD “active heat pipe” C4F10 evaporative cooling system. A brief comparison of evaporative and monophase cooling systems will be outlined

Mathematical Model for Direct Evaporative Space Cooling Systems

This paper deals with the development of a simple mathematical model for experimental validation of the performance of a small evaporative cooling system in a tropical climate. It also presents the coefficient of convective heat transfer of wide range of temperatures based on existing model. Extensive experiments have been performed during January to February 2013 for a small evaporative cooling system designed for storage of fruits and vegetables. The model considered the thermal properties of the material of the cooling pad and assumed that the cooling pad is a plain porous wall bounded by two convective air at different temperature at the two surfaces. The predicted and experimental value of various cooling efficiency at different range of inlet temperature has been determined. In addition the values of the coefficient of convective heat transfer for a wide range of temperatures is also presented

Evaluation of a low-cost energy-free evaporative cooling system for postharvest storage of perishable horticultural products produced by smallholder farmers of Umsinga in KwaZulu-Natal.

Master of Science in Horticultural Science. University of KwaZulu-Natal, Pietermaritzburg, 2017.In this study, a low-cost energy-free evaporative cooling system for postharvest storage of perishable horticultural was investigated. The evaporative cooler is a cost effective, energy free and easy to maintain way of cooling fruit and vegetables. It is basically what smallholder farmers can use as a postharvest storage condition to maintain their fruits and vegetables. However, before the evaporative cooling system was selected, the area of Umsinga where the cooler was installed was studied. The first chapter is a general introductory chapter, which clearly explains problem statement, has justification, hypothesis and outlines the aims and objectives. The second chapter is a review of literature which gives a broad idea of cooling technologies used to preserve quality and reduce postharvest losses on horticultural products. Consequently, it also gives an overview of the causes of postharvest losses. The third chapter of the study assesses vegetable postharvest loss challenges of smallholder farmers in the rural area of Umsinga in KwaZulu-Natal. The assessment was carried out as survey questionnaires. The fourth chapter of the study was evaluating the evaporative cooling system as an energy-free method for postharvest storage of tomatoes for smallholder farmers. The fifth chapter is evaluating the effect of different storage conditions on biochemical quality of tomatoes. The last chapter of the study is chapter six which has the general discussion, conclusion and recommendations

CFD Simulation and Analysis of the Combined Evaporative Cooling and Radiant Ceiling Air-conditioning System

Due to such disadvantages as large air duct and high energy consumption of the current all- outdoor air evaporative cooling systems used in the dry region of Northwest China, as well as the superiority of the ceiling cooling system in improving thermal comfort and saving energy, a combined system is presented in this paper. It combines an evaporative cooling system with ceiling cooling, in which the evaporative cooling system handles the entire latent load and one part of the sensible loads, and the ceiling cooling system deals with the other part of sensible loads in the air-conditioned zone, so that the condensation on radiant panels and the insufficiency of cooling capacity can be avoided. The cooling water at 18? used in the cooling coils of ceiling cooling system can be ground water, tap water or the cooled water from cooling towers in the summer. This new air-conditioning system and existing all- outdoor air evaporative cooling system are applied to a project in the city of Lanzhou. Energy consumption analysis of the building is carried out using the energy consumption code. Velocity and temperature distribution in the air-conditioned zone is computed using CFD. According to the results, the energy consumption and indoor human thermal comfort of both systems are then compared. It is concluded that the new system occupies less building space, reduces energy consumption, improves indoor human thermal comfort and saves initial investment

Experimental investigation on performance of fabrics for indirect evaporative cooling applications

© 2016 Indirect evaporative cooling, by using water evaporation to absorb heat to lower the air temperature without adding moisture, is an extremely low energy and environmentally friendly cooling principle. The properties of the wet channel surface in an indirect evaporating cooler, i.e. its moisture wicking ability, diffusivity and evaporation ability, can greatly affect cooling efficiency and performance. Irregular fibres help to divert moisture and enlarge the wetted area, thus promoting evaporation. A range of fabrics (textiles) weaved from various fibres were experimentally tested and compared to Kraft paper, which has been conventionally used as a wet surface medium in evaporative coolers. It was found that most of the textile fabrics have superior properties in moisture wicking ability, diffusivity and evaporation ability. Compared with Kraft paper, the wicking ability of some fabrics was found to be 171%–182% higher, the diffusion ability 298%–396% higher and evaporation ability 77%–93% higher. A general assessment concerning both the moisture transfer and mechanical properties found that two of the fabrics were most suitable for indirective evaporative cooling applications

Water consumption of an evaporative cooling system in the midwest

Dairy Research, 2009 is known as Dairy Day, 2009Water meters were installed on the evaporative cooling system of a long, low-profile, cross-ventilated dairy in the upper Midwest. The evaporative pad along the west side measured 10 by 350 ft. The water usage per unit surface area of the evaporative pad was 0.29 gallons/hour per square foot of evaporative pad surface area. The total daily water usage per stall averaged 13 gallons with a maximum of 22.7 gallons. Results from this study indicate that peak hourly water usage may be as much as 3 times the average values. The evaporative pad efficiency was 65% between noon and 0800 hours and 79% between midnight and 0400 hours

Modeling Of Evaporative Cooling System For Naturally-Ventilated Tropical Greenhouses

Natural ventilation in tropical greenhouse is a common method for ventilation which gives higher inside temperatures compared to the outside temperatures. This type of ventilation is not enough to reduce high temperature inside the structure in low land areas. Thus the requirement of cooling is increased. Use of fossil fuel to run the cooling fans are not economically viable due to increasing fuel cost and greenhouses are not always located near the electrical grid. The objectives of this research was to study the inside microclimate of the greenhouse, the natural ventilation of the greenhouse, the evaporative cooling system by means of misting fans and to study the use of photovoltaic (PV) as an alternative energy source to cool down the greenhouse. This study presents the theoretical and experimental results of the inhouse microclimate, ventilation rate induced by stack effect, wind effect and combination of both stack and wind effects for naturally ventilated single and multispan tropical greenhouses, effect of height and plants on inside temperature and ventilation rate. Ventilation rate induced by the stack effect was found to increase with increasing temperature difference between inside and outside of greenhouse structures according to power law, with an index of 0.5. The wind effect ventilation rate was found to increase linearly with increasing outside wind speed. Ventilation rate inside single span structure (smaller floor area) was higher than in multi-span structure. This was due to that the fast movement and air exchanges in single span structure. However, the bigger floor area gives higher in-house temperatures. Inside temperature and outside wind speed were calculated to verify the mathematical models which were developed. This method was used because of the difficulty to use tracer gas method in porous large scale greenhouse structures. The comparison between calculated and measured inside temperature showed there was no significant difference between them. The effect of height on ventilation rate is also crucial in greenhouse design. The ventilation rate increases with the increasing height (distance between the middle of the side opening and the middle of the roof opening) of the structure. Ventilation rate inside the house with plant was found lower than inside the house without plant. This was due to the temperature difference between inside and outside structure. Evaporative cooling by means of misting fans in single span was also presented in this study. Four misting fans were used to cool the greenhouse. They were installed two meters above ground with two fans near the southern sidewall and two fans in the middle of the greenhouse operating from 10:00 am to 16:00 pm daily. Data was collected from three rows with total 57 points inside the greenhouse. The distance between points was 2.5 m along the length of the greenhouse. The data was processed using GIS (Geographic Information System) to model the inside temperature and wind speed. The temperature inside the greenhouse with fans was found to be lower than that without fans, while the inside relative humidity of the air was found to be higher in the greenhouse with fans than that without and the outside. However these values of relative humidity lie at the optimum value that is less than 90% which do not give negative effect on the plants inside the structure. Based on the results, the contours and 3D maps of the in-house temperature and wind speed distribution in the single span greenhouse were developed. The efficiency of misting fans was lower than the previous studies. This was due to the usage of misting fans in porous naturally ventilated greenhouse, while the previous studies were carried out in closed greenhouses and glasshouses. Photovoltaic (PV) hybrid system design and simulation was discussed in this study. The results show that PV system would be suitable to supply electricity to cover the load requirement without purchasing energy from grid, and the battery state of charge was found to be in the range of 75-100%