HEAT PIPE TRANSIENT SIMULATION MODEL

There are some complicated models for simulating heat pipe transient behavior or operation. These models, in general, are designed to provide an understanding of the details of the complex physics involved in heat pipe transients. While this is an accepted approach, there still exists a strong demand for a general and flexible design model that yields accurate results without the use of excessive computer time.
A finite difference heat pipe simulation for a general heat pipe was developed based upon Chang (1981), Chang and Colwell (1985) and Chang and Leland (1989) transient heat pipe operation. The initial model was designed for a specific heat pipe configuration and was extensively modified to allow for more general treatment of the heat pipe's physical geometry and characteristics. Modifications included eliminating the central slab and its initial screened wick structure, incorporating a continuous circumferential wick structure with pertinent equations to determine relevant parameters for common wick structures and incorporating general boundary conditions as a function of axial direction. The model's capability was also expanded to analyze cryogenic and low-temperature heat pipes. All pertinent equations were derived for revalidation of the basis model and incorporation of the new geometric and parametric changes. Refrigerant-11 and oxygen heat pipes were simulated yielding effective, efficient, and accurate data (Pratt, 1991).