相領域変化を考慮した熱交換器の性能シミュレーション

抄録

A numerical simulation model of a plate-fin and tube type heat exchanger, which can switch a three phase state model with superheat, saturation, and subcool states and a two phase model with superheat and saturation states in accordance with operational conditions, is developed. Three and two phase models consist of mass, momentum, and energy balance equations for working fluid and air and result in a set of nonlinear algebraic equations, which is solved using a Newton-Raphson method. The switching from a three phase model to a two phase model is conducted when the heat transfer tube length in the subcool region becomes shorter than a threshold value. The switching from a two phase model to three phase model is conducted when the specific enthalpy of working fluid at the outlet of the heat exchanger is smaller than that of saturated liquid. A steady-state performance analysis on an air-cooled condenser, employed in a vapor compression heat pump system, reveals effectiveness of the developed switching approach for the consideration of the phase region change.