The Experts below are selected from a list of 8595 Experts worldwide ranked by ideXlab platform
Jie Lin - One of the best experts on this subject based on the ideXlab platform.
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a robust physics based model framework of the dew point Evaporative Cooler from fundamentals to applications
Energy Conversion and Management, 2021Co-Authors: Jianyu Long, Jie Lin, Muhammad Wakil Shahzad, K J ChuaAbstract:Abstract Owing to its great energy efficiency, dew point Evaporative cooling is an ideal solution for cooling of electronics, data centers and electric vehicles, where a large amount of sensible heat is generated. To promote the application of dew point Evaporative Coolers, a common research gap between theoretical and experimental studies is addressed, i.e., how fundamental understanding can be turned into practical applications? In this paper, a coupled scaling and regression analysis is proposed as the key approach to linking the physics-based model to fast data-driven optimization. Accordingly, a complete model framework is developed for the dew point Evaporative Cooler by establishing a core regression model with its governing dimensionless numbers. The model is integrated with a robust multi-objective optimization algorithm for real applications. Instant predictions of product air temperature and maximum pressure drop can be obtained from the regression model, while it still retains some physical insights into how the cooling performance is affected by the dominant factors. A few optimization studies are carried out to navigate the optimal design and control strategies of the dew point Evaporative Cooler under assorted ambient conditions. It is noted that the regression model can accurately predict the experimental data of two Coolers within ± 5.0% maximum discrepancy, and subsequent optimization suggests improved Cooler designs with 30%–60% enhancement in energy efficiency, compared to an existing Cooler prototype.
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a new method for prediction and analysis of heat and mass transfer in the counter flow dew point Evaporative Cooler under diverse climatic operating and geometric conditions
International Journal of Heat and Mass Transfer, 2018Co-Authors: Jie Lin, K J Chua, Yangda Wan, Chengqin RenAbstract:Abstract Dew point Evaporative Cooler, regarded as a zero polluting and energy efficient cooling device, has evolved to be a key technology in air-conditioning systems. The water evaporating process in the Cooler is a key performing factor as it leads to the heat sink phenomenon. The cooling effectiveness is dictated by its heat and mass transfer coefficients. The conventional methods (mean temperature difference and integration methods) of obtaining these coefficients have limitations. In this work, a new method to determine these coefficients is proposed. Firstly, a NTU - Le - R model is installed to detect these coefficients. It is based on the outlet data of the dew point Evaporative Cooler. Next, a two-dimensional computational fluid dynamic model is developed to simulate the Evaporative cooling process within the Cooler and compute the outlet data for the NTU - Le - R model. Upon validation, results from the computational fluid dynamic model demonstrate close agreement to within ± 6.0 % with results acquired from experiments. Finally, the effects of the various conditions on the heat and mass transfer coefficients, including climatic, operating and geometric conditions, are judiciously investigated. The new proposed method has the capability to capture the essential boundary conditions to precisely obtain the transfer coefficients. In contrast to existing practices that combine the assumption of the Nusselt number under constant surface heat flux or temperature conditions with the Chilton-Colburn analogy. This new method simplifies computation while providing accurate data to realize optimum design of the dew point Evaporative Cooler.
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the counter flow dew point Evaporative Cooler analyzing its transient and steady state behavior
Applied Thermal Engineering, 2018Co-Authors: Jie Lin, Duc Thuan Bui, R Z Wang, K J ChuaAbstract:Abstract The counter-flow dew point Evaporative Cooler offers a markedly improved approach to air cooling instead of the conventional vapor compression chiller. Earlier studies have focused on investigating the steady-state cooling effectiveness and energy efficiency of the Evaporative Cooler. However, there exists limited knowledge of the Cooler’s transient characteristics and flow resistance. In addition, existing Cooler prototypes mostly employ a water distribution system to spray the water into the wet channel, whereas the effect of water spray remains unclear. Therefore, in this paper, we present a transient and steady-state analysis of the counter-flow dew point Evaporative Cooler. The channel plate temperature development after water spray was measured and analyzed. A Cooler prototype was designed and engineered with a horizontal orientation according to the test results, and a 2-D mathematical model was developed to simulate its performance. The model was able to accurately predict the product air temperature, cooling effectiveness, cooling capacity and COP with a maximum discrepancy of ±5.0%. Key results that emerged from this study revealed that the transient responses of the channel plate and the Cooler agreed well with an exponential decay function. The pressure drops for the dry and wet channels spanned 16.0–29.1 Pa and 19.9–52.3 Pa, respectively. The achieved product air temperature ranged from 15.9 to 23.3 °C, with a COP spanning 8.6–27.0.
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On the exergy analysis of the counter-flow dew point Evaporative Cooler
Energy, 2018Co-Authors: Jie Lin, Duc Thuan Bui, Ruzhu Wang, K J ChuaAbstract:Abstract The dew point Evaporative Cooler has been proposed to replace the mechanical vapor compression chiller in air sensible cooling, for its significantly larger energy efficiency and simpler system layout. Many of the existing studies focused on applying a first-law thermodynamic analysis to the dew point Evaporative Cooler, however, its performance involving the second-law thermodynamic assessment remains unclear. Therefore, in this paper, an exergy analysis of the counter-flow dew point Evaporative Cooler is conducted. The exergy performance of the dew point Evaporative cooling process is examined by incorporating the first law of thermodynamics for energy and mass balances. A counter-flow dew point Evaporative Cooler prototype has been designed, fabricated and tested to investigate its cooling performance. A 2-D computational fluid dynamics (CFD) model is then formulated to simulate the flow, temperature and humidity fields of the Cooler. The model agrees well with the acquired experimental data with the maximum discrepancy of ±5.6%. The exergy flow, efficiency and efficiency ratio of the Cooler are discussed under various simulation conditions. Key findings that emerged from this study reveal that the saturated air state at ambient temperature is the rational dead state to properly describe the physical mechanisms involved in the dew point Evaporative cooling process. The exergy efficiency ratio of the dew point Evaporative Cooler is greater than 1.0, highlighting a remarkable second-law efficiency for air conditioning applications.
Jie Zhu - One of the best experts on this subject based on the ideXlab platform.
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Mathematical model of indirect Evaporative Cooler using porous ceramic and heat pipe
Applied Thermal Engineering, 2004Co-Authors: Saffa Riffat, Jie ZhuAbstract:The principle of an indirect Evaporative Cooler using porous ceramic as the cooling source and a heat pipe as the heat transfer device is presented in this paper. A heat and mass transfer mathematical model is developed to simulate the properties of the indirect Evaporative Cooler. The simulation results are verified by the experimental data. The theoretical model can be used to predict the performance of the indirect Evaporative Cooler.
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Modelling and testing of a novel Evaporative Cooler
International Journal of Computer Applications in Technology, 2004Co-Authors: Saffa Riffat, Jie ZhuAbstract:This paper describes the development of a novel indirect Evaporative Cooler for chilled ceiling applications. The Cooler is based on the integration of porous ceramic containers and heat pipes. Computer modelling and experimental work have been carried out under various operating conditions. Prototype systems have been developed and these have been tested in an environmental chamber under simulated weather conditions. The results demonstrate the potential of this novel Cooler to be applied to the building air conditioning systems.
Mahendra Singh Sodha - One of the best experts on this subject based on the ideXlab platform.
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Recent research on an indirect Evaporative Cooler. Part VI: Evolution of design pattern for indirect Evaporative Cooler
International Journal of Energy Research, 1999Co-Authors: Satendra Singh, T. R. Tulsidasani, R. L. Sawhney, Mahendra Singh SodhaAbstract:A rule of thumb for indirect Evaporative Cooler has been derived in terms of the size of floor area to be cooled and design parameters of tube type IEC, viz. process stream air flow rate and number of tubes; the three Indian climate zones, namely hot–dry, composite and warm–humid, represented by three cities of Jodhpur, Delhi and Madras, respectively, have been considered. Copyright © 1999 John Wiley & Sons, Ltd.
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Recent researches in indirect Evaporative Cooler V: relative thermal performance of buildings coupled to direct and indirect Evaporative Cooler
International Journal of Energy Research, 1997Co-Authors: Satendra Singh, T. R. Tulsidasani, R. L. Sawhney, Mahendra Singh SodhaAbstract:A mathematical model has been developed to evaluate the relative thermal performance of a building coupled with an indirect or direct Evaporative Cooler. Using periodic analysis for taking into account thermal storage of building envelope, explicit expressions have been obtained for room air temperature and room air humidity. For comparing their performance under different climatic conditions, numerical calculations have been made taking meteorological parameters for a typical day for Delhi (composite climate), Jodhpur (hot-dry climate) and Madras (hot-humid climate). It is found that the indirect Evaporative Cooler is a more effective and energy efficient system than the air-conditioner; it can hence be commercially used for computer and electronic exchange applications as well as for human comfort in a variety of climatic conditions, whereas direct Evaporative Cooler has limited use (only in hot-dry and composite climates). © 1997 by John Wiley & Sons, Ltd.
K J Chua - One of the best experts on this subject based on the ideXlab platform.
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towards a thermodynamically favorable dew point Evaporative Cooler via optimization
Energy Conversion and Management, 2020Co-Authors: Sibao Wang, Jianyu Long, K J ChuaAbstract:Abstract Dew point Evaporative cooling is an essential alternative to conventional vapor compression chillers in air conditioning systems to reduce electricity consumption and carbon emission. In this paper, we propose a robust optimization framework of the dew point Evaporative Cooler towards favorable dew point effectiveness, cooling capacity and Coefficient of Performance (COP). Two optimization algorithms, i.e., multi-to-single-objective and multi-objective optimizations, are developed using genetic algorithm. Concurrently, a 2-D thermodynamic model is established for a counter-flow dew point Evaporative Cooler and coupled with the optimization algorithms. The model agrees well with the experimental tests on a Cooler prototype, and the maximum discrepancy is within ±4.7%. The proposed optimization study is then carried out to investigate the ultimate objective functions and their corresponding decision variables. Key findings that have emerged from this study reveal that the multi-to-single-objective optimization is able to obtain appropriate objective functions according to predefined preference with less complexity and faster response, compared to a multi-objective optimization. The optimal channel length and working ratio are found to be constant in different scenarios, i.e., at 0.50 m and 0.40, respectively, hence they can be eliminated to reduce the number of decision variables.
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On the exergy analysis of the counter-flow dew point Evaporative Cooler
Energy, 2018Co-Authors: Jie Lin, Duc Thuan Bui, Ruzhu Wang, K J ChuaAbstract:Abstract The dew point Evaporative Cooler has been proposed to replace the mechanical vapor compression chiller in air sensible cooling, for its significantly larger energy efficiency and simpler system layout. Many of the existing studies focused on applying a first-law thermodynamic analysis to the dew point Evaporative Cooler, however, its performance involving the second-law thermodynamic assessment remains unclear. Therefore, in this paper, an exergy analysis of the counter-flow dew point Evaporative Cooler is conducted. The exergy performance of the dew point Evaporative cooling process is examined by incorporating the first law of thermodynamics for energy and mass balances. A counter-flow dew point Evaporative Cooler prototype has been designed, fabricated and tested to investigate its cooling performance. A 2-D computational fluid dynamics (CFD) model is then formulated to simulate the flow, temperature and humidity fields of the Cooler. The model agrees well with the acquired experimental data with the maximum discrepancy of ±5.6%. The exergy flow, efficiency and efficiency ratio of the Cooler are discussed under various simulation conditions. Key findings that emerged from this study reveal that the saturated air state at ambient temperature is the rational dead state to properly describe the physical mechanisms involved in the dew point Evaporative cooling process. The exergy efficiency ratio of the dew point Evaporative Cooler is greater than 1.0, highlighting a remarkable second-law efficiency for air conditioning applications.
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multivariate scaling and dimensional analysis of the counter flow dew point Evaporative Cooler
Energy Conversion and Management, 2017Co-Authors: M Kumja, K J ChuaAbstract:Abstract The theoretical study of the counter-flow dew point Evaporative Cooler is currently limited to the influence of different operating conditions and geometric parameters. Therefore, this paper presents an in-depth investigation on the governing factors of the dew point Evaporative cooling process. A 2-D mathematical model has been developed based on the momentum, continuity, energy and species balance equations. The model was able to achieve good agreement with a maximum discrepancy of ±8.0% in predicting the transient and steady-state performance of the counter-flow dew point Evaporative Cooler. A new dimensionless model was produced from the general model via scaling analysis. The relevant dimensionless groups controlling the operating conditions, geometric parameters and supply air conditions were derived. We further discussed the relative importance of the physical mechanisms involved in the heat and mass transfer process. In addition, a dimensional analysis was carried out to investigate the quantitative expressions of the dimensionless time constant and product air temperature. The key findings that emerged from this study are: (1) the dominant dimensionless groups for the Evaporative cooling process are Re , r , H L , δ H , T 0 ∗ and π ; and (2) the correlations for the dimensionless time constant and product air temperature have been developed and validated with data to demonstrate good accuracy.
Yuwen You - One of the best experts on this subject based on the ideXlab platform.
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Experimental study on total heat transfer efficiency evaluation of an indirect Evaporative Cooler
Applied Thermal Engineering, 2020Co-Authors: Qilong Liu, Chunmei Guo, Yuwen YouAbstract:Abstract Indirect Evaporative Cooler is applied as a device of the combined air conditioning system to precool the fresh air in hot and humid regions, which may cause condensation in the primary air channels. For this case, the trend of the existing evaluation indexes used to express the heat exchange efficiency is inconsistent with that of the total heat transfer. In this paper, a plate cross-flow indirect Evaporative cooling experimental system was set up, and the inadaptability of the existing evaluation indexes was analyzed by applying the experimental data. A new index called enthalpy efficiency was introduced in this paper. It was found that the change curve of enthalpy efficiency was highly consistent with that of the total heat transfer. By utilizing the data in other literatures, it was proved that the enthalpy efficiency can be used to evaluate the heat transfer capacity of plate cross-flow and counter-flow indirect Evaporative Coolers. The evaluation index can be used for thermal calculation, equipment selection design and performance optimization of an indirect Evaporative Cooler.
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An experimental study on condensate film of indirect Evaporative Cooler
Energy Procedia, 2019Co-Authors: Dandong Meng, Yi Chen, Yuwen YouAbstract:Abstract In hot and humid regions, the non-ignorable thermal resistance of condensate film can weaken the process of heat and mass transfer under total condensation in the dry channels of indirect Evaporative Cooler (IEC). In this study, the average thickness of condensate film was proposed and a comparison of thermal resistance of plate and condensate film was investigated under total condensation by a visualized cross-flow indirect Evaporative Cooler (IEC) experiment system. The experimental results showed that condensate film could be formed and the thermal resistance of condensate film was non-ignorable under total condensation due to thick water film. It could be a guidance in terms of reducing thermal resistance, saving energy and proposing a novel mathematical model under total condensation.