scholarly journals An investigation of laboratory-grown ice spikes

2004 ◽  
Vol 50 (170) ◽  
pp. 371-374 ◽  
Author(s):  
Kenneth G. Libbrecht ◽  
Kevin Lui
Keyword(s):  
Free Surface ◽  
Air Temperature ◽  
Evaporative Cooling ◽  
Density Change ◽  
Optimal Conditions ◽  
Dissolved Solids ◽  
Ice Cube ◽  
Air Motion ◽  
Freezing Chamber ◽  
Dissolved Salts

AbstractWe have investigated the formation of 10-50 mm long ice spikes that sometimes appear on the free surface of water when it solidifies. By freezing water under different conditions, we measured the probability of ice-spike formation as a function of: (1) the air temperature in the freezing chamber, (2) air motion in the freezing chamber (which promotes evaporative cooling), (3) the quantity of dissolved salts in the water, and (4) the size, shape and composing material of the freezing vessel. We found that the probability of ice-spike formation is greatest when the air temperature is near -7°C, the water is pure and the air in the freezing chamber is moving. Even small quantities of dissolved solids greatly reduce the probability of ice-spike formation. Under optimal conditions, approximately half the ice cubes in an ordinary ice-cube tray will form ice spikes. Guided by these observations, we have examined the Bally-Dorsey model for the formation of ice spikes. In this model, the density change during solidification forces super cooled water up through a hollow ice tube, where it freezes around the rim to lengthen the tube. We propose that any dissolved solids in the water will tend to concentrate at the tip of a growing ice spike and inhibit its growth. This can qualitatively explain the observation that ice spikes do not readily form using water containing even small quantities of dissolved solids.

Use of a membrane module for semi-direct air evaporative cooling

2019 ◽  
Vol 29 (10) ◽  
pp. 1346-1358 ◽  
Author(s):  
Sebastian Englart
Keyword(s):  
Moisture Content ◽  
Relative Error ◽  
Air Temperature ◽  
Evaporative Cooling ◽  
Cross Flow ◽  
Membrane Module ◽  
Transfer Model ◽  
Air Cooling ◽  
Heating Efficiency ◽  
Circulating Water

This study discusses the use of a membrane module for semi-direct evaporative air cooling. A cross-flow membrane module was used to carry out this air treatment process. For such a flow, it was proposed to describe and solve the heat and mass transfer model as a one-dimensional problem. The mathematical model was used to determine the moisture content and air temperature at the outlet from the module and the temperature of the circulating water. Results obtained using the proposed model are in good agreement with the experimental data. The relative error for the air temperature at the module outlet did not exceed 0.5%. For the moisture content, the relative error did not exceed 4%. For the circulating water temperature, the relative error did not exceed 0.6%. This paper also discusses the heating efficiency of the evaporative cooling process. Methods for determining the unit cooling indicator and the energy efficiency ratio are also proposed.

scholarly journals Microencapsulation of Clostridium tyrobutyricum by Spray drying Method and Its Characteristics in-vitro

2020 ◽  
Vol 40 (04) ◽  
pp. 419-424
Author(s):  
Muhammad Umar Yaqoob
Keyword(s):  
High Temperature ◽  
Survival Rate ◽  
Air Temperature ◽  
Flow Rate ◽  
Modified Starch ◽  
Clostridium Tyrobutyricum ◽  
Optimal Conditions ◽  
Drying Method ◽  
Sample Flow Rate

Present study was conducted to improve microencapsulation process of Clostridium tyrobutyricum (Ct) by optimizing process parameters to improve its in-vitro characteristics over that of free cells. All process parameters including wall material (w/v concentration: modified starch 3-7%; gelatin 2-6%; maltodextrin 3-7%), sample flow rate (250-450 mLh-1) and inlet air temperature (105-145°C) were analysed through single factor analysis. Response surface design test was used to develop multiple quadratic regression equations to fit the functional relationship between factors and response values and to choose the optimal conditions. The optimal conditions for maximum survival rate (82.030%) of encapsulated Ct were: 4% gelatin, 5% modified starch and 5% maltodextrin concentration with sample flow rate of 350 mLh-1 at inlet air temperature of 105°C. Encapsulation reduced the survival loss of Ct from 1.990 to 1.080 lgCFUg-1 under strong acidic condition (pH1) than free Ct. Survival loss of free Ct was 31.914% more than encapsulated Ct under high temperature treatment (90°C). Similarly, protected Ct showed higher survival rate under simulated gastric condition with long storage life. Encapsulation of Ct through optimized spray drying method efficiently improved its survival rate under strong acidic or high temperature environment with safe transit through gastrointestinal tract and also eradicates the technological limitations which preventing the use of many probiotic strains

scholarly journals User Thermal Comfort in Historic Buildings: Evaluation of the Potential of Thermal Mass, Orientation, Evaporative Cooling and Ventilation

2020 ◽  
Vol 12 (22) ◽  
pp. 9672
Author(s):  
Mamdooh Alwetaishi ◽  
Ashraf Balabel ◽  
Ahmed Abdelhafiz ◽  
Usama Issa ◽  
Ibrahim Sharaky ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
High Altitude ◽  
Air Temperature ◽  
Thermal Performance ◽  
Indoor Air ◽  
Computer Modelling ◽  
Evaporative Cooling ◽  
Comfort Level ◽  
Thermal Mass ◽  
The Impact

The study investigated the level of thermal comfort in historical buildings located at a relatively high altitude in the Arabian Desert of Saudi Arabia. The study focused on the impact of the use of thermal mass and orientation on the level of thermal performance at Shubra and Boqri Palaces. Qualitative and quantitative analyses were used in this study, including a questionnaire interview with architecture experts living at the relatively high altitude of Taif city, to obtain data and information from local experts. The computer software TAS EDSL was used along with on-site equipment, such as thermal imaging cameras and data loggers, to observe the physical conditions of the building in terms of its thermal performance. The study revealed that the experts’ age and years of experience were important aspects while collecting data from them during the survey. The use of thermal mass had a slight impact on the indoor air temperature as well as the energy consumption, but it helped in providing thermal comfort. Use of ventilation can improve thermal comfort level. Evaporative cooling technique has a considerable impact on reducing indoor air temperature with 4 °C drop, improving the thermal comfort sensation level. The novelty of this work is that, it links the outcomes of qualitative results of experts with field monitoring as well as computer modelling. This can contribute as method to accurately collect data in similar case studies.

scholarly journals Performance Enhancement of Split Air Conditioner During Evaporative Cooling Application

2021 ◽  
Vol 86 (2) ◽  
pp. 147-156
Author(s):  
Rahmat Iman Mainil ◽  
Ahmad Wisnu Sulaiman ◽  
Afdhal Kurniawan Mainil ◽  
Azridjal Aziz
Keyword(s):  
Air Temperature ◽  
Flow Rate ◽  
Air Conditioning ◽  
Evaporative Cooling ◽  
Water Flow Rate ◽  
Coefficient Of Performance ◽  
Air Conditioner ◽  
Discharge Water ◽  
Cooling Module ◽  
The Impact

The increase of condenser temperature and pressure in air-conditioning leads to decreased cooling capacity and the increase of power consumption. Evaporative cooling could improve the thermal performance of the system. In this study, the evaporative cooling module was installed before the condenser to reduce the inlet air temperature to the condenser unit. The impact of condenser air temperature on the air conditioning system's overall performance was determined by varying the cooling pad discharge water flowrate of 880, 1040, and 1200 mL/min. The cooling load of 2000 W was employed in this experiment. The obtained results were compared with the air conditioning without an evaporative cooling module. It shows that the coefficient of performance (COP) increases with the increase of discharge water flow rate. The highest COP obtained is 7.09 at the flow rate of 1200 mL/min. The compressor work reduces about 6.57 % as compared with the air conditioner without evaporative cooling application. Besides, the COP increases by 12. 95 % at the highest flow rate.

scholarly journals Pedestrian-level ventilation in an urban environment adjacent to a river channel: A case study for Bucharest city – Romania

2019 ◽  
Vol 85 ◽  
pp. 07007
Author(s):  
Adrian Ciocănea ◽  
Andrei Dragomirescu ◽  
Bogdan Tofan ◽  
Mihai Toti
Keyword(s):  
Free Surface ◽  
Urban Heat Island ◽  
Air Temperature ◽  
Numerical Study ◽  
Cross Flow ◽  
Low Flow ◽  
Heat Island ◽  
Air Jet ◽  
Urban Heat ◽  
Bucharest City

Increasing evapotranspiration in cities, derived from vegetation and water bodies, can effectively mitigate the effect of urban heat island (UHI). This paper presents a study on an urban ventilation solution for Bucharest City in Romania. The solution is based on lifting air volumes from the free surface of Dambovita River, which crosses the city center where UHI has a significant impact, to the roadway and pedestrian level by using cross-flow fans mounted on floating panels planted with vegetation, which are placed at the river banks. The electric motors of the cross-flow fans are powered by PV solar cells. The real optimal value of evapotranspiration (ETRO) was computed for the case of lucerne in order to assess the air temperature at the surface of the floating panel and a numerical study was performed in order to obtain the velocities of the air flow and the temperature field in a domain containing the free surface of the river, the floating panel surface, and the roadway surface (at pedestrian level). It was observed that, at low flow rates, the cooler air reaches the roadway surface in a compact jet due to the Coanda effect - the coherent air jet is of about 30–40 cm above the ground level. For a day with clear sky and no wind conditions a decrease in the air temperature of 4–5 °C can be obtained at the pedestrian level, within a layer of 1 m height. The study opens the possibility to approach such issues at a greater scale in order to assess the viability of appropriate solutions for cooling down the urban heat island as well.

scholarly journals A method to partition the relative effects of evaporative cooling and shading on air temperature within vegetation canopy

2018 ◽  
Vol 4 (1) ◽  
Author(s):  
Puay Yok Tan ◽  
Nyuk Hien Wong ◽  
Chun Liang Tan ◽  
Steve Kardinal Jusuf ◽  
Mei Fen Chang ◽  
...  
Keyword(s):  
Air Temperature ◽  
Evaporative Cooling ◽  
Vegetation Canopy

Theoretical analysis of heat and mass transfer processes in an evaporative cooling system with zeolite desiccant powered by solar energy

2018 ◽  
Author(s):  
◽  
Amged Al Ezzi
Keyword(s):  
Water Vapor ◽  
Flat Plate ◽  
Air Temperature ◽  
Air Conditioning ◽  
Cooling System ◽  
Evaporative Cooling ◽  
Air Conditioning System ◽  
Coating Method ◽  
Evaporative Cooler ◽  
Desiccant Material

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Concerns about energy sources depletion and environmental pollution issues have been raised and is a top priority of the global community. Refrigeration machines have been received the major of attention because of their energy consumption and pollution. Different from traditional cooling strategies, desiccant cooling technology (DCT) has been emergent as a promising alternative giving the fact that the economic-ecological air conditioning system is not restricted to hot and dry climates only. In the current experimental study, an advancement solar assisted desiccant cooling system (SADCS) is presented. The advantage is to use only a fraction of the energy of typical compressor-based cooling systems. The advancements have taken place into the dehumidification, evaporator, and regeneration sections. The role of appropriate choosing of the desiccant material type on the adsorption process has been presented, and a Faujasite (FAU) 13X zeolite is utilized in the dehumidification stage. A novel monolayer coating method has conducted. The new coating method has insured no external water vapor condensation ruins the desiccant material during relative humidity working range (20-97) %. Moreover, the new coating method allows to increase the performance of the adsorption and desorption processes, respectively. By giving the coming air stream the ability to pass through and surround the zeolite beads, accessibility to adsorb and desorb water vapor molecules is easier as more rooms are available. That clearly has been stated as 6450 g of zeolite holds 684 g of water in full saturation status within 37 minutes and regenerates by less than 120 [degree]C air temperature within 66 minutes. In the evaporative cooling section, an effective small compact evaporative cooler (CEC) system dealing only with product flow is introduced. The new CEC is utilized direct and indirect evaporation of water mechanisms combined in cross channels to cool air. Dropping air temperature by (5-7) [degree]C has recorded without desiccant stage. Supplying the required regeneration energy from a green energy source was essential in this study. For this purpose, an innovative flat plate double-mesh air solar collector has designed and carried out. In the new collector, a double copper mesh frames were fixing within a double Plexiglas covers flat plate collector. Experimental results show a good consistent with the mathematical model. With an average 0.71 solar fraction and 80 [degree]C exit air temperature, the collector presents 0.73 as thermal efficiency. As the improvements of the desiccant air-conditioning system turns out globally recognized by the progress in different research outcomes, designs, setting up and evaluation methods, it is expected that the system will be one of the most important alternative systems for the maintenance of human's environment comfort and air quality when considering the reduced dependence on conventional energy usage. Present work and results provide a reference data sets related to real adsorption dehumidification process and show that the advancement SADCS has a great potential in the future of the evaporative cooler systems.

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 Evaporative Cooling Integrated with Solid Desiccant Systems: A Review

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5982
Author(s):  
Lanbo Lai ◽  
Xiaolin Wang ◽  
Gholamreza Kefayati ◽  
Eric Hu
Keyword(s):  
Air Temperature ◽  
Cooling System ◽  
Evaporative Cooling ◽  
Operating Cost ◽  
Weather Conditions ◽  
Dew Point ◽  
Air Conditioning System ◽  
Direct Evaporative Cooling ◽  
Dry Climates ◽  
Desiccant Material

Evaporative cooling technology (ECT) has been deemed as an alternative to the conventional vapor-compression air conditioning system for dry climates in recent years due to its simple structure and low operating cost. Generally speaking, the ECT includes two types of different technologies, direct evaporative cooling (DEC) and indirect evaporative cooling (IEC). Both technologies can theoretically reduce the air temperature to the wet-bulb temperature of outdoor air. The major difference between these two technologies is that DEC will introduce extra moisture to the supply air while IEC will not. The enhanced IEC, Maisotsenko-cycle (M-cyle) IEC, can even bring down the air temperature to the dew point temperature. The ECT integrated with solid desiccant systems, i.e., solid desiccant-assisted evaporative cooling technologies (SDECT), could make the technology applicable to a wider range of weather conditions, e.g., weather with high humidity. In this paper, the recent development of various evaporative cooling technologies (ECT), solid desiccant material and the integration of these two technologies, the SDECT, were thoroughly reviewed with respect to their configuration, optimization and desiccant unit improvement. Furthermore, modeling techniques for simulating SDECT with their pros and cons were also reviewed. Potential opportunities and research recommendations were indicated, which include improving the structure and material of M-cycle IEC, developing novel desiccant material and optimizing configuration, water consumption rate and operation strategy of SDECT system. This review paper indicated that the SDECT system could be a potential replacement for the conventional vapor-compressed cooling system and could be applied in hot and humid environments with proper arrangements.

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