Computational fluid dynamics modeling of surface condensation

Abstract

This study experimentally and numerically investigates the condensation problem, which is one of the most important problems in chilled ceiling application. In a wide range of applications, including air-conditioning, drying, food storage, airflow contact with surface and heat transfer occurs with a fluid through this surface. Since heat transfer is influenced by the movement of both airflow and this fluid, it is important to solve a temperature field as well as a velocity field in all heating, cooling and ventilation applications. Commercial package programs, which have been widely used in recent years, have become "user-friendly" design tools that make it possible to find "location- and time-dependent" distributions of temperature. Since these programs solve the "mass transport" equation in addition to the "momentum" and "energy" equations, it makes it easy to examine the "moist air" which constitutes the scope of psychrometry. However, the "condensation on the cold surface" encountered in most HVAC-R applications cannot be simulated directly with these programs. In order to introduce the phase changes to this program, the user must write additional codes. In this study, the "user-defined function" module of Ansys-Fluent (R) program was used to introduce the condensation to the program in terms of psychrometrics. In the study, which was compared with experimental results, psychrometric equations were added as source term to mass transport and energy equation. As a result, in the context of mass transport-energy balance relationship, it is possible to predict the psychrometric critical values before the design by computational methods.