Waste heat driven turbo-compression cooling

2018 Spring.Includes bibliographical references.Waste heat recovery systems utilize exhaust heat from power generation systems to produce mechanical work, provide cooling, or create high temperature thermal energy. One waste heat recovery application is to use the exhaust heat from a Natural Gas Combined Cycle Power Plant (NGCC) to drive a heat activated cooling system that can offset a portion of the plant condenser load. There are several heat activated cooling systems available including absorption, adsorption, ORVC, and ejector, but each has disadvantages. One system that can overcome the disadvantages of typical heat activated cooling systems is a turbo-compression cooling system (TCCS). In this system, the exhaust heat enters an organic Rankine cycle at the boiler and vaporizes the fluid that passes through a turbine. The turbine power is directly transferred to a compressor via a hermetically sealed shaft that is made possible by a magnetic coupling. The compressor operates a vapor-compression system which provides a cooling effect in the evaporator. The hermetic seal between the turbine and compressor allows for two separate fluids on the power and cooling cycles, which maximizes the efficiency of the turbine and compressor simultaneously. This study presents a thermodynamic modeling approach that makes system performance predictions for the baseline design case, and for off-design performance conditions. The off-design modeling approach uses turbo-compressor performance maps and a heat exchanger UA scaling methodology to accurately simulate system operation for a broad range of temperatures and cooling loads. A 250 kWth cooling capacity TCCS was constructed and tested to validate the modeling approach. The test facility simulates a 138:1 scaled NGCC power plant configuration in which the TCCS extracts 106°C waste heat from the flue gases and produces a cooling effect that offsets a portion of the NGCC condenser load. The design target for the test facility was to achieve a COP of 2.1 while chilling water from 17.2°C to 16°C at an ambient temperature of 15°C. Although the final design point was not tested for this study due to facility limitations, the off-design performance methodology was utilized to predict the performance for an ambient condition of 27.5°C and power and cooling cycle mass flow rate range between 0.35 kg s-1 - 0.5 kg s-1 and 0.65 kg s-1 – 0.85 kg s-1, respectively. The comparison between the experimental and modeling data suggested strong correlation over the data range presented with a maximum error in COP of only 2.0% among the selected data points. Future experimental data over a larger range of ambient temperatures and system conditions is suggested to further validate the system modeling. Regardless, the results in the present study show that the TCCS compares favorably with other heat activated cooling systems

Gas Bearings: Modelling, Design and Applications

This book focuses on the modelling and the design process of gas bearings, on the experimental validation of such models, and on their applications. In particular, recent developments about foil bearings, aerostatic bearings, porous bearings, and non-contact precision positioning systems are shown

Design of Auxiliary Passive Magnetic Bearing for Cryogenic Turboexpander

In the modern time of industrialisation high performance, high precision, smooth operations are a very vital requirement for a machine system. Such a very essential system is turboexpander which is used in the several applications to provide very low-temperature cooling and refrigeration. Nowadays, turboexpander systems are using gas bearings to operate friction free, noiseless and for smooth operation. The main problem for these turboexpander systems is a heavy contact of rotor parts with the static parts i.e. thrust bearing surface at the time of start-up and shut-down of the machinery. The rotary system of the modern turboexpanders, after using gas bearings to support against radial as well as axial thrust are facing the wearing problem with the static parts at the time of start and stop. To avoid the problem, an auxiliary passive magnetic bearing is modelled by using Finite Element Method Magnetics (FEMM) that can suspend the rotor system without heavy contact with the lower thrust bearing surface during start-up and shut-down. This magnetic bearing has to levitate a designed rotary system of weight approximately 2.64 N, which consists a rotor, a brake compressor and a turbine wheel. This pair of magnet bearings is axially magnetised and can levitate the rotor at an appropriate distance. After the simulation of different bearing dimensions with two types of Neodymium (NdFeB) alloy magnet of Grade N42 and N52, it is found that the grade N52 gives better values of repulsive forces at same gap and dimensions as compared to grade N42. It is also important to know that N52 has lower operating temperature (70oC) as compared to N42 (80oC). So according to the operating conditions any of the above grades can be used as an auxiliary passive magnetic bearing

A bibliography /with abstracts/ on gas-lubricated bearings Interim report

Gas lubricated bearings - annotated bibliograph

Design and Development of Different Applications of PATB (Porous Aerostatic Thrust Bearing): A Review

In several applications demanding precise and ultra-precision movements, porous aerostatic thrust bearings had been employed as a crucial precision engineering component and enabling technology. By acting as a lubricant between the moving part and the stationary part in aerostatic bearings, pressurized air almost completely eliminates friction. Since air acts as the lubricant, oil-based lubricants leave no debris behind. The air prolongs the life of the substances by preventing them from slipping and wearing. The aerostatic type uses graphite as a porous film to disrupt the air uniformly over the surface, or a tiny hole is drilled through the centre of the bearing to let the air circulate and produce a thin layer between the components. With an increased reliance on computational and mathematical methodologies for design and bearing performance optimization, this review paper aims to present the state-of-the-art in aerostatic bearings advancement and research. It also conducts a critical analysis of their future research directions and development trends in the next ten years and beyond. Air bearings are utilized in the production of tools like lathes, CMM, and grinders because they are highly precise in their operation and decrease mistakes and production time. Air bearings are available in a variety of forms and sizes. The assessment of future trends and obstacles in aerostatic bearings investigation, as well as their prospective applications in the precision engineering sectors, concludes the study

12th International Conference on Vibrations in Rotating Machinery

Since 1976, the Vibrations in Rotating Machinery conferences have successfully brought industry and academia together to advance state-of-the-art research in dynamics of rotating machinery. 12th International Conference on Vibrations in Rotating Machinery contains contributions presented at the 12th edition of the conference, from industrial and academic experts from different countries. The book discusses the challenges in rotor-dynamics, rub, whirl, instability and more. The topics addressed include: - Active, smart vibration control - Rotor balancing, dynamics, and smart rotors - Bearings and seals - Noise vibration and harshness - Active and passive damping - Applications: wind turbines, steam turbines, gas turbines, compressors - Joints and couplings - Challenging performance boundaries of rotating machines - High power density machines - Electrical machines for aerospace - Management of extreme events - Active machines - Electric supercharging - Blades and bladed assemblies (forced response, flutter, mistuning) - Fault detection and condition monitoring - Rub, whirl and instability - Torsional vibration Providing the latest research and useful guidance, 12th International Conference on Vibrations in Rotating Machinery aims at those from industry or academia that are involved in transport, power, process, medical engineering, manufacturing or construction

Closed Cycle Propulsion for Small Unmanned Aircraft

This study evaluates the merit of closed cycle propulsion systems for use in unmanned systems. The complexity and added weight of closed cycle engines is offset by benefits in high altitude performance, operation in polluted air environments, multi-fuel operation, and potential for flight in low oxygen environments using generic thermal heat sources. Although most closed thermal cycles cannot match the efficiency and power density potential of internal combustion engines (ICE) and turbomachines in aircraft propulsion applications, the addition of design requirements regarding noise output, and operation at high altitude results in IC and CC engine�s performance becoming much more comparable. Muffling devices increase backpressure on internal combustion engines thereby reducing power output and efficiency. Multi stage turbo supercharging for operation at high altitude can in some cases increase efficiency of ICE�s, but at the result of significant additional complexity and cost that also reduces practical reliability because of the often intricate mechanisms involved. It is in these scenarios that closed cycle engines offer a comparable performance alternative that may prove to be simpler, cheaper, and more reliable than high altitude or low noise internal combustion or turbomachine propulsion systems.Mechanical & Aerospace Engineerin

12th International Conference on Vibrations in Rotating Machinery

Since 1976, the Vibrations in Rotating Machinery conferences have successfully brought industry and academia together to advance state-of-the-art research in dynamics of rotating machinery. 12th International Conference on Vibrations in Rotating Machinery contains contributions presented at the 12th edition of the conference, from industrial and academic experts from different countries. The book discusses the challenges in rotor-dynamics, rub, whirl, instability and more. The topics addressed include: - Active, smart vibration control - Rotor balancing, dynamics, and smart rotors - Bearings and seals - Noise vibration and harshness - Active and passive damping - Applications: wind turbines, steam turbines, gas turbines, compressors - Joints and couplings - Challenging performance boundaries of rotating machines - High power density machines - Electrical machines for aerospace - Management of extreme events - Active machines - Electric supercharging - Blades and bladed assemblies (forced response, flutter, mistuning) - Fault detection and condition monitoring - Rub, whirl and instability - Torsional vibration Providing the latest research and useful guidance, 12th International Conference on Vibrations in Rotating Machinery aims at those from industry or academia that are involved in transport, power, process, medical engineering, manufacturing or construction