Molecular dynamics simulation of interfacial heat transfer behavior during the boiling of low-boiling-point organic fluid

Abstract

Boiling heat transfer of low-boiling-point working fluid is one of the promising heat dissipation technologies commonly used in electronic equipment cooling. The study on interfacial heat transfer mechanism is of great significance to improve both heat removal capacity and heat dissipation efficiency. In this work, 1,1,1,2-tetrafluoroethane (R134a) was used as the working fluid, and the interfacial boiling behavior of R134a under different initial thicknesses of liquid film (δ0), solid-liquid interaction force and initial temperature (T0) was analyzed by molecular dynamics (MD) method. In the simulation, δ0 changes from 2.5 to 7.5 nm, the energy coefficient (α) characterizing solid-liquid interaction force changes from 0.25 to 4, T0 ranges from 180 to 200 K, and the temperature difference between the solid substrate and the liquid film is 220 K (i.e., the superheat for boiling). The results show that only δ0 could significantly alter the boiling mode of R134a.When δ0 = 2.5 nm, it shows thin film boiling, otherwise as δ0 gets thicker, it shifts into explosive boiling mode. Under the explosive boiling mode, the total thermal resistance (Rtot) consists of three parts, i.e., the solid interface thermal resistance (RW), thermal resistance of vapor layer (RV), and vapor-liquid interface thermal resistance above layer (RV-L). RV contributes the most to Rtot. However, during the thin film boiling, only RW contributes to Rtot. With the increase of δ0 and α, Rtot presents the similar trend, i.e., increasing first and decreasing afterwards. When δ0 = 7.5 nm and α is 1, Rtot reaches to the highest value of 3.49×10−8 K‧m2/W. For the influence of T0, it oppositely affects Rtot. Overall, the increase of α and T0 and the decrease of δ0 are all beneficial to accelerate the boiling of R134a.