Simulation Study on the Non-Uniform Characteristics of Boiling Flow and Heat Transfer in Parallel Small Channels

With the sharp increase in the heat flux of high-power electronic devices, efficient thermal management has become critically important. Boiling heat transfer in parallel small channels, which utilizes latent heat efficiently, has emerged as a key enabling technology for next-generation cooling solutions. However, parallel channel systems are extremely susceptible to flow instabilities, resulting in severely uneven distributions of flow rate and heat transfer among the channels. This unevenness often leads to local overheating, which in turn restricts the system’s reliability and limits its practical application. In this paper, a three-dimensional transient numerical simulation method was employed to investigate the non-uniform characteristics of flow boiling and heat transfer of R134a within parallel rectangular small channels. The differential characteristics of flow and heat transfer parameters among channels under varying mass flux and heat flux conditions were systematically investigated. The quantitative characterization methods for the degree of flow and heat transfer non-uniformity were proposed. Two quantitative characterization parameters, β₁ for flow non-uniformity and β₂ for heat transfer non-uniformity, are proposed. Besides, the predictive correlations for the non-uniformity degrees of flow and heat transfer were constructed. The β₁ increases with increasing heat flux and decreases with increasing mass flux, while β₂ decreases with increasing heat flux and mass flux. When the mass flux is constant, β₁ decreases with increasing β₂, and the decreasing rate of β₁ is much lower than the increasing rate of β₂. When the heat flux is constant, β₁ increases with increasing β₂, and the increasing rate of β₁ is much larger than the increasing rate of β₂. β₁ and β₂ obtained from simulations agree with the fitted predictions to within ±20%. This paper has important theoretical guiding significance for optimizing the safe and stable operation of high heat flux cooling systems.