Numerical study on condensation heat transfer of R290 inside a 4-mm-ID horizontal smooth tube

Abstract

This paper deals with the condensation heat transfer characteristic of propane (R290) inside a 4-mm-inner-diameter (ID) horizontal smooth tube. Three-dimensional Computational Fluid Dynamics (CFD) simulations were performed based on the volume of fluid (VOF) multiphase flow model and shear stress transport (SST) k-ω turbulence model together with a dedicated user-defined function (UDF) compiled for the phase change model. The flow pattern and velocity field distribution were derived, and the condensation heat transfer coefficient (HTC) versus mass flux, saturation temperature, and heat transfer temperature difference were analyzed in detail. The results demonstrate that the area-weighted average condensation HTC of the wall takes on an average increase rate of 33.69% as the mass flux increases from 180 to 360 kg/(m 2 s), and an average decrease rate of 19.83% with the increasing saturation temperature. Besides, the local condensation HTC swells more than twice as the temperature difference increases from 5 to 20 K. Compared with the saturation temperature, the mass flux and heat transfer temperature difference have a more remarkable effect on the condensation flow pattern and velocity field distribution. Under the specific conditions, the flow condensation of R290 inside the tube can be successively transformed from annular flow, annular wavy flow, half annular flow to plug flow, and the annular flow region can be enlarged with increasing mass flux. Comparing the simulated results with those of the experiment, it can be concluded that the numerical model adopted in this paper has good accuracy and the relative deviation is within ± 20%.

Numerical Study on R32 Flow Condensation in Horizontally Oriented Tubes with U-Bends

“…Previous studies pointed out that the appropriate value of β is influenced by various factors such as the fluid properties, geometry, boundary conditions and even mesh size [31,32]. Table 2 summarizes the recent literature [13,15,16,21,22,27,[33][34][35][36] on numerical simulation of flow condensation using VOF model coupled with Lee's phase change model. Inspired by the previous literature [13], the value of β is chosen to be 1 × 10 4 to 5 × 10 4 based on the simulation conditions by a trial and error method, taking into account the influence of calculation accuracy and calculation time.…”