Discussion: “Heat Transfer Mechanisms During Flow Boiling in Microchannels” (Kandlikar, S. G., 2004, ASME J. Heat Transfer, 126(1), pp. 8–16)

In the paper Kandlikar, S. G., 2004, “Heat Transfer Mechanisms During Flow Boiling in Microchannels,” ASME J. Heat Transfer, 126(1), pp. 8–16, Kandlikar [(1)] derived two new nondimensional groups, K₁ and K₂, relevant to flow boiling phenomenon in microchannels as follows:Kandlikar [(1)] mentioned that these two groups were able to represent some of the key flow boiling characteristics, including the critical heat flux (CHF). In his closing remarks, he mentioned that the usage of the new nondimensional groups K₁ and K₂ in conjunction with the Weber number (We) and the capillary number (Ca) was expected to provide a better tool for analyzing the experimental data and developing more representative models.

Similar to the combination of the nondimensional groups, K₂K₁^0.75 [(1)] that used in representing the flow boiling CHF data by Vandervort et al. [(2)], these two new nondimensional groups, K₁ and K₂, can be combined using Eqs. 1,2 as:i.e., the ratio of K₂ and K₁ is equal to the all liquid Weber number (We_LO). As a result, it is enough to use the new nondimensional groups K₁ and K₂ in conjunction with the capillary number (Ca) only to provide a better tool for analyzing the experimental data and developing more representative models for heat transfer mechanisms during flow boiling in microchannels because K₂/K₁ = We_LO.

Moreover, it should be noted that the ratio of K₂ and K₁ (K₂/K₁) and the Capillary number (Ca) can be combined as:i.e., the ratio of (K₂/K₁) and Ca is equal to the all liquid Reynolds number (Re_LO).