MODELING OF BOILING TWO-PHASE FLOW IN THE BUBBLE PUMP OF DIFFUSION-ABSORPTION REFRIGERATION CYCLES

ABSTRACT

This work presents a numerical model developed to simulate steady-state refrigerant flow along a tube of a bubble pump at operating conditions of interest for diffusion-absorption refrigeration systems. The flow is considered one-dimensional, and non-metastable flow is neglected. The two-fluid model was employed to simulate the two-phase flow, considering the hydrodynamic nonequilibrium between the liquid and the vapor phases. Comparisons were made for void fraction versus vapor quality using the homogeneous model, the Rouhani and Axelsson drift model, and the Zivi annular model. The results show a great similarity among the values achieved in the present work and those calculated using the Rouhani and Axelsson and Zivi correlations. On the basis of the numerical simulations, a detailed description of the flow characteristics was obtained. The influence of the heat source on the flow characteristics was numerically examined.

Keywords:

• Bubble pump
• Diffusion-absorption refrigeration
• Mixture boiling
• Two-fluid model