Experimental performance of a vapor delivery system

Includes bibliographical references (pages 125-128)Engineering can be described as the real world application of theoretical concepts; it is the will of an engineer to form a practical means to accomplish the application of such concepts. This study sought to put engineering application to the test by designing, constructing, and testing an apparatus that would implement a concept envisioned by individuals in industry and ultimately prove its feasibility. Pratt & Whitney, Rocketdyne originated the idea for the concept studied here and much of the problem statement and conditions comes from them. The concept analyzed was the notion of using a specific fluid close to its critical point and, through the use of excess thermal energy, vaporize the fluid to create a distinguishable and maintainable constant pressure vapor flow. This type of flow is commonly used to purge fuel tanks in propulsion systems, and is typically supplied by high pressure helium flowing through a mechanical pressure regulator. The new concept would control the supplied vapor pressure by controlling the temperature of a liquid-vapor mixture. Rocketdyne defines ???excess thermal??? energy as extra heat energy simply being wasted by being expelled to the surroundings, which is not unusual for propulsion systems. The goal of the experiments was to see if this high pressure vapor could purge a secondary fluid at a constant rate, i.e. the flow rates of both fluids and the pressure of the high pressure vapor could be constant over an appropriate time interval. Fundamental thermal-fluids equations were used to design the experimental apparatus. The Bernoulli equation was used to choose orifice sizes that would produce flow rates in a desired range. A first law of thermodynamics analysis of the vaporization process in the working fluid tank was used to estimate the necessary heat transfer rate to produce a steady vapor flow. Heat transfer correlations for boiling heat transfer were used to predict the temperature (and pressure) drop in the tank to produce the necessary heat rate. This study picked up where a previous CSUN student, Levon Gevorkyan, left off in determining appropriate fluids that could be used to prove this concept. For these experiments, carbon dioxide was chosen for its desirable density ratio at easily producible temperatures, its availability, and its low toxicity. The design of the experimental apparatus involved sizing the physical system, constructing the system, testing the system, and completing post data collection analysis. This study was deemed a success based on the fact that a working fluid was selected and used in a system that showed that steady conditions were created within a certain range of operable flow rates. Only the lowest flow rates tested were capable of producing steady conditions. It is recommended that further testing be completed at lower flow rates to more completely define the relationship between flow rate and accurate pressure control