An Innovative Cooling System Based on Evaporation from a Porous Tank (original) (raw)
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Innovative low-energy evaporative cooling system for buildings: study of the porous evaporator wall
Journal of Building Performance Simulation, 2018
To face the current increase of building cooling demand and the concerns related to climate changes, an energy-efficient evaporative cooling system using porous material has been developed. This article presents the innovative cooling system and a detailed hygrothermal analysis of its main element: the porous evaporator. A mathematical model and an experimental setup are presented, which enable to determine the suitable material properties for the evaporator and its impact on the overall cooling system performance, focusing on the optimal use of both energy and water. A good agreement is observed between numerical and experimental results, and the evaporative cooling power is estimated from 12 to 72 W/m² of evaporator wall, depending on the evaporator characteristics. A parametric analysis is conducted to select the best material for the evaporative cooling system. An intrinsic permeability of the material of 4 × 10 −17 m 2 is recommended for this new cooling system.
Direct evaporative cooling performance of ambient air using a ceramic wet porous layer
Chemical Engineering Research and Design, 2018
Direct evaporative cooling is one of the efficient traditional strategies to provide summer comfort in a building or airconditioning in storage rooms. The present paper concerns a new mathematical approach to analyse the influence of the effective parameters on the performance of direct evaporation from a porous layer. The ambient air flows over a porous material, fed with water. The evaporation of an amount of water into the air reduces its temperature and, at the same time, raises the air's humidity. A mathematical model that accounts for simultaneous heat and mass transfer characteristics in the ambient air and water flow in corporating non-Darcian model in the porous region within vertical parallel walls is presented. The solution of the mathematical model is based on the finite volume method and the velocity-pressure coupling is treated with the SIMPLE algorithm. The results showed that the porous evaporative cooler could satisfy the cooling requirements in arid climates. An average drop of 15 °C of air temperature below the ambient temperature can be reached at the considered conditions. Therefore, the ambient air is satisfactorily cooled. Furthermore, the better cooling performance can be achieved for a high porosity with a thick porous medium and lower air velocity at the entrance.
Investigation of an Evaporative Cooler for Buildings in Hot and Dry Climates
Journal of Clean Energy Technologies, 2014
The paper presents a computer model and experimental results of a sub-wet bulb temperature evaporative cooling system for space cooling in buildings in hot and dry climates. The cooler uses porous ceramic materials as the wet media for water evaporation. Under selected test conditions of airflow dry bulb temperature of up to 45 o C and relative humidity of up to 50%, it was found that the supply air could be cooled to below the wet bulb temperature with a maximum cooling capacity of 280 W/m 2 of the wet ceramic surface area. It was also shown that the overall wet bulb effectiveness is greater than unity. This performance would make the system a potential alternative to conventional mechanical air conditioning systems in hot and dry regions.
Experimental and Numerical Study of a Heat Pipe Based Indirect Porous Ceramic Evaporative Cooler
International Journal of Environmental Science and Development, 2015
Indirect evaporative coolers are one of the most possible alternatives to conventional cooling methods for building airconditioning. It utilizes evaporation of water to cool the air, consumes much less power, and employs no harmful refrigerants comparing to other traditional cooling cycles such as vapor compression coolers. This paper presents a mathematical model and experimental investigation of thermal performance of an indirect porous ceramic evaporative cooler with integrated heat pipe for heat transfer. It is shown that good agreement was achieved between the computer model and measured parameters of the cooling system. In the regions with hot and dry climates the system can be an environmentally friendly and energy efficient cooling system. Index Terms-Indirect evaporative cooling, heat pipe, porous ceramic, dew-point effectiveness.
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.
Evaporation from Porous Building Materials and Its Cooling Potential
Journal of Materials in Civil Engineering, 2014
Evaporative cooling is a traditional strategy to improve summer comfort, which has gained renewed 9 relevance in the context of the transition to a greener economy. Here, we evaluate the potential for 10 evaporative cooling of two common porous building materials, natural stone and ceramic brick. The 11 work has relevance also to the protection of built heritage, since evaporation underlies the problems of 12 dampness and salt crystallization, which are so harmful and frequent in this heritage.
Heat Transfer Research, 2020
In this article the performance of one stage direct evaporative cooler (DEC) and two stage indirect-direct cooler (IEC-DEC) in the environment of Saudi Arabia is assessed experimentally. The wet pad used in direct evaporative coolers is one of the main part affecting the output of an evaporative cooler. In this study three combinations of pad materials: aspen fiber (Case-I), corrugated cellulose (Case-II) and a combination of fiber aspen and corrugated cellulose (Case-III) were focused as a wet media for water evaporation and the performance of these pad materials was analyzed in detail. The main design parameter considered is the water flow rate in the designing of both coolers. During the testing of the both coolers ambient temperature in the range from 28 oC to 42 oC and relative humidity lower than 65% was considered to cool the working air. Air temperatures and relative humidity were measured and the effectiveness of the coolers was determined. The results obtained show effectiveness of IEC-DEC cooler is in range of 95-110 %, while effectiveness of DEC cooler is 85-93%. As an overall the IEC-DEC cooler with pad material of combination of fiber aspen and corrugated cellulose showed comparatively better performance.
Performance of porous ceramic evaporators for building cooling application
Energy and Buildings, 2003
An experimental investigation of porous ceramic evaporators for building cooling has been carried out. Prototypes, classified as low, medium and high porosity prototypes in direct evaporative cooling mode were placed in an experimental duct within an environmental chamber. Performance was measured under different conditions of dry bulb temperature (DBT), relative humidity (RH), supply water pressure, and layout within the duct. The high porosity ceramic evaporator consistently performed best, while increased water supply head also improved performance. Dry bulb temperature drops of 6-8 K have been achieved parallel with a 30% rise in relative humidity. Maximum cooling of 224 W/m 2 has been measured during test of the high porosity ceramic evaporator placed in a single row stack with water supplied at 1.0 m head. Empirical formulae relating mean cooling performance to [e s − e], the ambient to saturated vapour pressure difference have been derived. The direct evaporation of water into supply air using porous ceramic surfaces has demonstrated significant potential for building cooling.
Mathematical Modelling of a Low Approach Evaporative Cooling Process for Space Cooling in Buildings
2012
This paper describes a mathematical model of a low approach open evaporative cooling tower for the production of high temperature indirect cooling water (14-16C) for use in building radiant cooling and displacement ventilation systems. There are several potential approaches to model evaporative cooling, including: the Poppe method, the Merkel method and the effectiveness-NTU (e-NTU) method. A common assumption, applied to the Merkel and e-NTU methods, is that the effect of change in tower water mass flow rate due to evaporation is ignored, which results in a simpler model with reduced computational requirements, but with somewhat decreased accuracy. In this paper, a new improved method, called the corrected e-NTU approach is proposed, where the water loss due to evaporation is taken into account. It is expected by this correction the results of improved e-NTU in the category of heat transfer will be more close to the results of more rigorous Poppe method. The current mathematical m...