New prediction methods for CO2 evaporation inside tubes: Part II—An updated general flow boiling heat transfer model based on flow patterns

Fundamental issues, mechanisms and models of flow boiling heat transfer in microscale channels

“…This has been validated by the flow pattern based CO 2 flow boiling model of Cheng et al [24][25][26], which covers both macroscale and microscale channels for CO 2 flow boiling heat transfer and two phase flow. 13 Their generalized flow pattern based CO 2 flow boiling heat transfer model predicts both macroscale and microscale channel flow patterns and heat transfer reasonably well.…”

“…However, one may distinguish between flow boiling behaviours such as heat transfer, fluid flow and flow patterns behaviours in macroscale and microscale channels [11, 28-30, 33, 34, 37, 38]. It is definitely effective from a practical application viewpoint if the flow patterns can be incorporated into flow boiling heat transfer and two phase frictional pressure drop prediction methods simultaneously with the corresponding heat transfer mechanisms such as those by Katten et al [46], Wojtan et al [31,32], Cheng et al [24][25][26] and Moreno Quibén [35,36]. Such a prediction method actually works reasonably well if related flow regimes and bubble dynamics to the corresponding heat transfer behaviours.…”

“…The different heat transfer trends may be explained by their respective heat transfer mechanisms and they may also due to many other affecting factors such as the measurement accuracy, channel size and shape, fluid types and physical properties, the test parameter ranges, the data analysis and presentations al. [24][25][26] and Moreno Quibén et al [35,36] which are based on the asymptotic model and the relevant flow patterns, the mechanistic heat transfer models for flow boiling heat transfer in microscale channels such as the three zone heat transfer model for flow boiling in microchannels by Thome et al [87,88] and annular flow heat transfer model developed by Cioncolini and…”

“…Figure 1(a) shows a cross-section of a board of chips (about 30 chips per board) with the microchannel evaporator. Schmidt and Notohardjono [15] have demonstrated the successful use of a refrigeration unit with a microscale channel evaporator to cool IBM S/390 G4 server as shown in [25,26]. They have found that superior heat transfer performance may be achieved with flow boiling in microscale channels.…”

On the Phenomenal Mechanisms and Prediction Methods of Flow Boiling Heat Transfer in Microchannels

“…At low vapour qualities, nucleate boiling effects prevail while at high vapour qualities and prior to the liquid dryout, the heat transfer coefficient is mainly controlled by convective effects. These heat transfer mechanisms are commonly considered when developing flow boiling heat transfer correlations in conventional channels such as the Chen correlation [10] and others [11][12][13][14][15][16][17]. However, nearly all conventional flow boiling correlations have been found to be inadequate to predict the flow boiling heat transfer data in the microchannels [2,18].…”