**5. Concluding remarks**

( ) 0.55 0.12 0.5 0.67 55 0.4343ln - - = - *r r h p p Mq* (17)

*<sup>f</sup> S Bo* (18)

2 for

To account for the suppression of the nucleate boiling when vapor quality increases, Chen [43] defined the nucleate boiling suppression factor S, which is the ratio of mean superheat temperature, *ΔTe*, to the wall superheat temperature, *ΔTsat*. Jung et al. [38] introduced the suppression factor N as the function of Xtt and boiling number, Bo, to take into account the strong effect of nucleate boiling in flow boiling. On the other hand, to consider the effect of flow conditions, the Lockhart – Martinelli parameter Xtt is replaced by the two-phase frictional

> ( )0.002 <sup>2</sup> 0.816 <sup>=</sup>181.458 f

The new heat transfer coefficient correlation is developed using 461 data points. Fig. 13 shows the comparison of the experimental heat transfer coefficient and the predicted one. The new correlation archives a good prediction with a mean deviation of 9.93% and an average deviation of -2.42%. When the C factor of the Chisholm [18] method is used to obtain *ϕ<sup>f</sup>*

equations (11) and (16), the heat transfer coefficient also showed a good comparison mean

2

suppression factor was proposed by Choi et al. [6]. It is as follows:

**Figure 12.** Two-phase heat transfer multiplier as a function of *ϕ<sup>f</sup>*

. Using the regression program and the experimental data, a new nucleate boiling

multiplier, *ϕ<sup>f</sup>*

2

120 Heat Transfer Studies and Applications

deviation of 14.40%.

This chapter demonstrated the convective boiling pressure drop and heat transfer experiments of propane in horizontal minichannels. The content is summarized as follows:

