Over the past decade, Air Squared has been actively developing and improving the highly anticipated 15 m3/h tritium vacuum pump to replace the obsolete industry standard Normetex scroll pump. The all-metal pump features a metal bellows that hermetically seals all tritium gas from any material other than metal. Air Squared has listened to the tritium market's needs and is currently developing the latest addition to the Air Squared tritium vacuum pump line: the 150 m3/h liquid cooled all-metal (LCAM) scroll vacuum pump. Through numerous hours of testing, Air Squared has demonstrated the advantages of LCAM scroll vacuum pumps. The effect that thermal expansion has on highly toleranced all-metal pumps has been observed and characterized to predict pump performance as well as provide safe operational temperature limits. Performance characteristics of the 15 m3/h pump have been analyzed with different process gases to understand the effects of pumping light gases. Vacuum pumping speed curves have been generated at various interstage pressures to understand the advantages that roughing pump systems have when used in series with all-metal scroll vacuum pumps. This paper presents Air Squared's 15 m3/h designs and highlights the performance characteristics. The effects that pump temperature, process gas, and fore-vacuum have on all-metal scroll vacuum pumps are explained with empirical data collected over a decade of research. With the knowledge and data collected, Air Squared has a pathway for a new industry standard 15 m3/h and 150 m3/h positive displacement scroll pump for tritium service to support international nuclear fusion and tritium research.

Naval vessels typically require several ship service diesel generators (SSDGs) for electricity generation with an average thermal efficiency of approximately 40-45%. Waste heat SSDGs represents a significant opportunity to drive bottoming Organic Rankine Cycles (ORCs) to increase their fuel efficiency. Waste heat streams include both high-temperature exhaust gases and low-temperature cooling loops. In this work, a comprehensive numerical analysis is carried out to compare different cycle architectures to maximize the ORC power output at both full- and part-load SSDG conditions. Both subcritical and transcritical cycle architectures with evaporators in series and in parallel have been investigated. Novel, high-speed, spinning scroll expanders have been considered as expansion devices. Parametric studies were conducted to assess the trade-off between ORC output and effectiveness of operation to determine an optimum payback period.

An organic Rankine cycle (ORC) test setup for high-temperature waste-heat-recovery applications was constructed. The test setup was used to conduct an experimental study of a subcritical ORC architecture working with a high temperature gaseous heat source of approximately 10 kW and to evaluate the feasibility of employing an ORC to recover waste heat from small-scale internal combustion engines. The market affordability of all components including a prototype scroll expander, which contributes heavily to the cycle design, is considered. The cycle consists of a diaphragm pump, a plate heat exchanger as a regenerator, a novel micro-tube evaporator, an air-cooled condenser, and a scroll-type expander. Three expander prototypes of Oldham ring orbiting, idler shaft orbiting, and spinning scroll were evaluated for their performance within this ORC. Focus was given to constraining the high-side temperatures of R1233zd(E) due to its limited thermal stability while decreasing exergy destruction. In this work, a performance comparison between R245fa and R1233zd(E) for varying thermal inputs, expander types, and refrigerant superheating values is reported.

An organic Rankine cycle (ORC) test setup has been constructed to investigate high-temperature waste heat recovery from a stationary internal combustion engine. In particular, an experimental study of a subcritical ORC architecture working with a high temperature heat source is performed to evaluate the feasibility of employing an ORC to recover west heat from small-scale internal combustion engines (~10 kW). The affordability of such a system for the given application has a significant impact on the cycle design. The ORC test setup consists of a diaphragm pump, a plate heat exchanger as regenerator, a novel micro-tube evaporator, an air-cooled condenser, a scroll-type expander, and R245fa as working fluid. Focus is given to constraining the high-side temperatures of R245fa to minimize oil breakdown while decreasing exergy destruction in the evaporator. The cycle performance is evaluated for varying thermal inputs, expander pressure ratios and refrigerant superheating values.

A novel 1 kWe GENSET featuring an internal combustion engine (ICE) operating on Spark-Assisted Compression Ignition (SACI) combustion of natural gas is under development to achieve an overall power generation efficiency of 40%. The aim is to create an efficient electricity generation system that can provide the energy necessary for light residential use at high thermal efficiency and low user cost. In order to achieve such power generation efficiency for a small-scale energy/heat production unit, an organic Rankine cycle (ORC) has been proposed as a bottoming cycle to recover heat from the exhaust of the small internal combustion engine. The ORC has been optimized to operate with a heat source inlet temperature of 400 ºC, which is necessary for use with the integrated catalytic converter evaporator proposed for the system. By means of a thermodynamic cycle model, the final cycle architecture has been identified along with the design of a novel two-stage scroll expander integrated with working fluid pump. Results showed that by employing R1233zd(E) as the working fluid, the theoretical ORC thermal efficiency is as high as 14.79% with a net ORC power output of 148.6 W.

In a scroll-type compressor, compression is achieved through relative contact between two spiral curves. Since the scroll invention by Leon Creux (1905), multiple methods have been developed for calculating scroll geometry. What can generally be considered the most classical method, is defining each scroll curve as the involute of a circle. Gravesen and Henriksen (2001) introduced a new method to calculate scroll geometry by deriving each scroll curve from the radius of curvature parameterized with involute angle. This allows a wide range of involute geometries to be considered not included in the classical method. In this paper, Gravesen's method is extended to the tip region to include all tip geometries involved in a two arc configuration resulting in a more comprehensive scroll geometry definition. Lastly, with parametric representation of all scroll geometry, the pocket volume can be easily solved using a derived control volume approach.

Manufacturing cost of high precision scroll compressor parts remains a dominating factor in determining the overall production cost. Traditionally, scroll compressors are made of metallic parts which require high tolerances to avoid leakage. Precision is even more important when the compressor is designed for oil-free operation and metal to metal contact can potentially be detrimental to the overall performance. With implementation of non-metallic compressor parts such as plastics, various avenues such as injection molding can be taken to reduce production cost. In addition, various polymer blends can be chosen to alleviate the danger of contact through the use of self-lubricating materials. In the present study, a new compressor concept has been designed and built from both plastic and metallic materials. Performance tests have been conducted on the compressor concept and comparison between plastic and metallic compressor performance have been made.

In a scroll-type compressor, compression is achieved by relative contact between two spiral curves. Since the scroll invention by Leon Creux in (1905) multiple methods have been developed for calculating the scroll geometry and pocket volume. What can generally be considered the most classical method, is defining each scroll curve as the involute of a circle. The two sets of scroll curves are then closed by using the arc of a circle to form the tip of each spiral. In this paper, a new method to calculate the scroll geometry is introduced. By deriving each scroll curve from the radius of curvature parameterized with involute angle, a wide range of scroll involute geometries can be considered that are not included in the classical method. In addition, all possible tip conditions involved in a two arc configuration can be implemented to give a comprehensive scroll compressor geometry definition.

NASA’s future missions include sending astronauts back to the moon, and further. Challenges associated with these goals are not limited to the science involved with propelling these astronauts to their destination. In fact, life support systems must also advance to improve astronaut health during their long flights in space. Currently, food consumed in space is processed to be shelf stable, and recent experiments have shown that nutrients of these shelf stable foods decay over time (Cooper, Perchonok, & Douglas, 2017). Refrigeration storage for more nutritional food has remained undeveloped due to fluid flow and heat transfer management difficulties in microgravity. As part of a NASA SBIR Phase I project, the project team has designed a modular refrigerator that is able to preserve food in a frozen state. The proposed vapor compression cycle (VCC) reduces the instability of flow in microgravity through both reduction on liquid reliance via a coupled oil-free scroll compressor and expander, and through specific methods of design that manage two-phase refrigerant flow through the heat exchangers. R134a is the working fluid, as it is non-toxic, non-flammable, has favorable volumetric characteristics, and will be available in the future. Air is pulled across the evaporator of the vapor compression loop to be cooled, and then fed into four identical food storage compartments. Absorbed heat from the air is rejected out of the condenser into a central cooling water loop in the spacecraft. Developments of more effective vapor compression systems in space may also yield improved systems for use on earth.