The Simulation of Spray Type Evaporator Performance
Date Issued
2004
Date
2004
Author(s)
Cheng, Chuan-Hung
DOI
zh-TW
Abstract
The effect of nucleate boiling has been ignored in the predictive models and correlations for falling film evaporation in the previous studies. A new predictive model based on the superposition model in two-phase convection was developed to account for the nucleate boiling effect in falling film evaporation. The nucleate boiling suppression factor in the superposition model was found to different from that in the flooded evaporator or flow in pipes. A new suppression factor correlation with the plain tube is proposed and curve fitted from the experimental data of falling film evaporation using R-11, R-123, R-22, R-141b and R-134a from three different sources. The new model predicts the experimental data with the plain tube within ±25 %. Similarly, another suppression factor correlation was obtained from the experimental data of the Tu-B surfaces. This new model predicts the experimental data with the Tu-B surfaces within ±30 %. Besides, the present study developed a correlation to account for the lubricant effects on falling film evaporation. The lubricant effect correlation predicts the experimental data within ±30 %.
This study also developed a computer code, which used the elemental NTU-ε model to predict the heat transfer and pressure drop of flooded type and spray type evaporators.The results of prediction are in good agreement with the available experimental data. Parametric studies performed by the computer code reveals that the spray type evaporator has better heat transfer performance and smaller pressure drop than the flooded type.
Subjects
熱傳
模型
蒸發
噴淋
滴淋
Evaporation
Falling film
Spray
Model
Type
thesis
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