Evaporative Cooling Integrated with Solid Desiccant Systems: A Review

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

10.32469/10355/70681 ◽

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.

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Modelling pavement temperature for winter maintenance operations

Canadian Journal of Civil Engineering ◽

10.1139/l03-107 ◽

2004 ◽

Vol 31 (2) ◽

pp. 369-378 ◽

Cited By ~ 8

Author(s):

Aly Sherif ◽

Yasser Hassan

Keyword(s):

Surface Temperature ◽

Air Temperature ◽

Negative Impact ◽

Weather Conditions ◽

Statistical Modelling ◽

Dew Point ◽

Road Maintenance ◽

Winter Maintenance ◽

Pavement Surface ◽

Pavement Temperature

Road and highway maintenance is vital for the safety of citizens and for enabling emergency and security services to perform their essential functions. Accumulation of snow and (or) ice on the pavement surface during the wintertime substantially increases the risk of road crashes and can have negative impact on the economy of the region. Recently, road maintenance engineers have used pavement surface temperature as a guide to the application of deicers. Stations for road weather information systems (RWIS) have been installed across Europe and North America to collect data that can be used to predict weather conditions such as air temperature. Modelling pavement surface temperature as a function of such weather conditions (air temperature, dew point, relative humidity, and wind speed) can provide an additional component that is essential for winter maintenance operations. This paper uses data collected by RWIS stations at the City of Ottawa to device a procedure that maximizes the use of a data batch containing complete, partially complete, and unusable data and to study the relationship between the pavement surface temperature and weather variables. Statistical models were developed, where stepwise regression was first applied to eliminate those variables whose estimated coefficients are not statistically significant. The remaining variables were further examined according to their contribution to the criterion of best fit and their physical relationships to each other to eliminate multicollinearities. The models were further corrected for the autocorrelation in their error structures. The final version of the developed models may then be used as a part of the decision-making process for winter maintenance operations.Key words: winter maintenance, pavement temperature, statistical modelling, RWIS.

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The Effect of Dry and Wet Bulb Temperature Variation on the Performance of the Indirect Evaporative Cooler

Tikrit Journal of Engineering Sciences ◽

10.25130/tjes.26.4.02 ◽

2019 ◽

Vol 26 (4) ◽

pp. 8-15

Author(s):

Maki Zaidan ◽

Fayadh Abed ◽

Ali Farhad

Keyword(s):

Heat Exchanger ◽

Environmental Changes ◽

Cooling System ◽

Evaporative Cooling ◽

Computer Software ◽

Volumetric Flow Rate ◽

Weather Conditions ◽

Centrifugal Fan ◽

Pipe Length ◽

Evaporative Cooling System

The research is about designing and building up an evaporative cooling system, working by two- stages evaporative cooling system using outer air (pure air). The system is founded by designing and making a heat exchanger of orthogonal flow from Aluminum sheets of (30*60*40) cm, which represents the first stage of the system (indirect stage). The second stage (direct stage) of the system is represented by making an equipment of air washing (cylindrical) with (45 height, 60 width, 3 thickness) cm. The cooling system pulls outer air by a Centrifugal fan. The air passes through the heat exchanger pipes to be cooled tangibly (without moistening). Then it goes over the equipment of air washing to be cooled and cools the specified space. Computer software was designed by FORTRAN Language (FORTRAN 90) to predict the evaporative air cooler performance to know the proper environmental and design conditions of the system. Some variables were made to study their effect on the thermal performance of the system. The studied variable is to change the volumetric flow rate of air from (750 cfm) to (2000 cfm) of the dry side, and from (750 cfm) to (2500 cfm) of the wet side. The pipe length was changed from (20 cm) to (45 cm), and its diameter from (0.5 cm) to (3 cm). Those were the design changes. On the environmental changes, we studied the effect of changing the temperature on the dry or wet bulb of the system. The study is taken place in Tikrit University (34. 35N; 43.37 E), to determine the suitability of the weather conditions of the region for the work of the system. It was taken place in the late August for two consecutive days, with readings of 24 hours. The results show that the best quantity of the air supplied, which represent the best performance of the system (750 cfm) and (1000 cfm) for the wet side when the diameter (1-1.5 cm) and length is (45 cm). The results show also the possibility of the work of this system for the region mentioned because it is characterized by its hot and dry climate in the summer, as the efficiency of evaporative evaporator increases the hot and dry environment by 80%.

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An Overview of Different Indirect and Semi-Indirect Evaporative Cooling System for Study Potency of Nanopore Skinless Bamboo as An Evaporative Cooling New Porous Material

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences ◽

10.37934/arfmts.79.2.123130 ◽

2021 ◽

Vol 79 (2) ◽

pp. 123-130

Author(s):

I Nyoman Suprapta Winaya ◽

Hendra Wijaksana ◽

Made Sucipta ◽

Ainul Ghurri

Keyword(s):

Energy Consumption ◽

Porous Material ◽

Cooling System ◽

Evaporative Cooling ◽

Temperature Drop ◽

High Energy ◽

Dew Point ◽

Air Cooling ◽

Evaporative Cooling System ◽

Indirect Evaporative Cooling

The high energy consumption of compressor based cooling system has prompted the researchers to study and develop non-compressor based cooling system that less energy consumption, less environment damaging but still has high enough cooling performances. Indirect and semi indirect evaporative cooling system is the feasible non-compressor based cooling systems that can reach the cooling performance required. This two evaporative cooling system has some different in construction, porous material used, airflow scheme and secondary air cooling method used for various applications. This paper would report the cooling performances achieved by those two cooling system in terms of cooling efficiency, cooling capacity, wet bulb effectiveness, dew point effectiveness, and temperature drop. Porous material used in indirect and semi-indirect evaporative cooling would be highlighted in terms of their type, size, thickness and any other feature. The introduction of nanopore skinless bamboo potency as a new porous material for either indirect or semi-indirect evaporative cooling would be described. In the future study of nanopore skinless bamboo, a surface morphology and several hygrothermal test including sorption, water vapor transmission, thermal conductivity test would be applied, before it utilize as a new porous material for direct or semi indirect evaporative cooling.

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