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In this paper, a numerical study of heat and mass transfer in counter-flow indirect evaporative air coolers is presented using an approach proposed by previous work. The mathematical model equations of continuity, momentum, energy and concentration are solved by the finite volume method to obtain the value of primary outlet dimensionless temperature. This mathematical model developed is validated against published data acquired from literature. The key target of presented analysis is to develop a performance correlation based on five dimensionless factors: ratio of channel length to half width of secondary air channel, ratio of water to secondary air mass flow rate, primary air inlet Reynolds number, secondary air inlet dimensionless temperature and water film inlet dimensionless temperature. Numerical simulations are performed by changing the value of each dimensionless factor under a constant value for other parameters. The simulation results are regressed to obtain the empirical constants of the correlation. The value of outlet dimensionless temperature is varied from 0.47 to 0.92. The developed correlation can predict the performance of the counter-flow indirect evaporative air coolers within a discrepancy of 12.6%. The correlation would be helpful to provide a simpler equation to improve the calculation speed within the engineering allowable accuracy range. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: With the aim to develop a generalized model for predicting the frost growth on cold flat plate, experiments were conducted in a suction-type open-loop wind tunnel under variant frosting conditions. Based on the Hayashi correlation, a modified correlation of initial frost density was developed by the experimental results. After validating this proposed correlation, dynamic frosting characteristics, such as the frost thickness, density, frost surface temperature and heat flux were predicted under a wide range of frosting conditions. Compared with 25 groups of experimental results taken from this paper or previous open literatures, the average simulating errors were found to be limited within ±10%. The validation results indicate the proposed model is suitable to predict the dynamic heat and mass transfer process of the frost growth under a wide range of frosting conditions. [Copyright &y& Elsevier]

Abstract: A state-of-the-art review of horizontal-tube, falling film evaporation is presented; the review is critical, in an attempt to uncover strengths and weaknesses in prior research, with the overall purpose of clearly identifying gaps in our understanding. The review covers flow-pattern studies, and the experimental parameters that affect the heat transfer performance on plain single tubes, enhanced surfaces and tube bundles. In addition, this paper presents a comprehensive review of the significant efforts to develop mathematical models, and empirical correlations for the heat transfer coefficient. Emphasis is placed on studies that are related to refrigeration applications. [Copyright &y& Elsevier]