TO-98-03-1 -- Refrigerant Inventory of R-134a in a Small-Channel Cross-Flow Condenser

This study is the first to model refrigerant inventory or quantity of R-134a in small-channel¹ cross-flow condensers. The condenser in this study is used in automotive applications and uses smaller internal volumes than conventional heat exchangers to perform the same task.

The model is a one-dimensional, two-fluid (gas and liquid, single component) model that divides the condenser into several segments and modules. This model accurately predicts the rate of heat transfer and refrigerant pressure drop. The heat transfer was predicted within ±10% of the experiment and the pressure drop was predicted within ±30% for the majority of the data.

More importantly, the model calculates refrigerant inventory within ±10% of the experiments for 95% of the data. In the inlet header, the slip ratio was correlated to the Reynolds and Froude numbers and the homogeneous liquid volume fraction. In the small channels, the Reynolds and Weber numbers and the homogeneous liquid volume fraction were used to determine the slip ratio.

1. Small-channel heat exchanger technology is the subject of United States and foreign patents applied for and issued to Modine Manufacturing Company, Racine, Wis. U.S. Current United States patents include 4,615,385, 4,688,311, and 4,998,580.

Units: Dual