scholarly journals Modelling phase change in a novel turbo expander for application to heat pumps and refrigeration cycles

2019 ◽  
Vol 113 ◽  
pp. 03012 ◽  
Author(s):  
E. Geoffrey Engelbrecht ◽  
Zoitis Giakoumis ◽  
Stathis Sidiropoulos ◽  
Alexandros Chasoglou ◽  
Ndaona Chokani
Keyword(s):  
Phase Change ◽  
High Volume ◽  
Heat Pumps ◽  
Back Pressure ◽  
Successful Implementation ◽  
Refrigeration Cycle ◽  
Liquid Droplets ◽  
Relaxation Model ◽  
Turbo Expander ◽  
Cycle Efficiency

A novel turbo expander based on the Tesla turbine is proposed to be applied to a heat pump or refrigeration cycle to improve the overall cycle efficiency. Initial numerical modelling of this turbo expander at representative conditions was carried out using the homogeneous relaxation model (HRM) to assess the influence of phase change on performance. The presence of a dense cloud of liquid droplets within the rotor was predicted to produce a significant back pressure on the turbine nozzle postponing the phase change. This was expected to occur in the vicinity at the outlet of the nozzle, but high volume fractions of liquid was predicted to penetrate deeper inside the rotor, especially at higher RPM. The resulting lower velocities of the liquid flow at the inlet of the rotor was predicted to significantly degrades the performance of the turbine. It is thus important for a successful implementation of this concept to remove as much liquid droplets as possible before the flow enters the rotor in order to minimise the back pressure.

Computational Investigation of a Multiphase Turbo Expander for Heat Pumps and Refrigeration Cycles

2020 ◽  
Author(s):  
Zoitis Giakoumis ◽  
E. Geoffrey Engelbrecht ◽  
Alexandros Chasoglou ◽  
Ndaona Chokani
Keyword(s):  
Phase Change ◽  
Heat Pump ◽  
Liquid Flow ◽  
Volume Fraction ◽  
Heat Pumps ◽  
Flow Profile ◽  
Liquid Droplets ◽  
Dense Cloud ◽  
Turbo Expander ◽  
The Impact

Abstract The design and development of an innovative Tesla style turbo expander for two-phase fluids is proposed, as a substitute for the lamination valve of a traditional Heat Pump cycle. Thereby enhancing the overall performance of the Heat Pump, by recovering mechanical work to offset the compressor requirements. The major challenge in such configurations is the reliable operation of the expander, when phase change occurs across it, from a purely liquid flow to a mainly vapour flow by volume with a dense cloud of liquid droplets. To investigate the phase change, a modelling approach is adopted which is routinely applied to modelling fuel-flashing in direct injection diesel engines, where the phase change deviates strongly from equilibrium. The Homogeneous Relaxation Model (HRM) is employed, which utilizes an Eulerian approach. The proposed computational model is firstly validated against experimental results available in the literature. A sensitivity analysis of the phase change model relaxation parameter is performed. It was found that a value 10 times lower than the published value gave closer agreement to the measured results. It is believed that this result is due to the roughened walls of the experiment, which would produce more nucleation sites for vapour bubble formation. This suggests that this model maybe is sensitive to the geometry of the turbine. Following this validation, the detailed flow profile in the proposed Tesla turbo-expander is investigated. Two different expander designs are considered in this project, one working with water [4,20] and the other with butane (R600). This study focuses particularly on the butane expander design. The expander performance is evaluated for rotational speeds up to 32’000 RPM. Results on the turbo-expander under investigation, showed that the presence of a dense cloud of liquid droplets produces a significant pressure drop across the turbine rotor, which increases with RPM, postponing the phase change. High volume-fraction of liquid was predicted to penetrate deeper inside the rotor above 16’000 RPM for the butane expander. The resulting lower liquid flow velocity relative to the rotor disk speed at the inlet of the rotor is predicted to significantly degrade the performance of the turbine at high rotational speeds. Decreasing the nozzle throat area improves the situation, by initiating the phase change further upstream and increasing the RPM operational range by 50%. Angling the nozzle radially inward by 10° was found to not have a great impact on the performance of the turbine. It was determined from this study that it is critical to predict correctly where the phase change starts, in order to accurately predict the performance of the turbine. Important is to remove as much liquid as possible from the flow, before it enters the rotor, to minimize the impact of the phase change on the turbine performance.

Computational Investigation of a Multiphase Turbo Expander for Heat Pumps and Refrigeration Cycles

2021 ◽  
Author(s):  
Zoitis Giakoumis ◽  
E. Geoffrey Engelbrecht ◽  
Alexandros Chasoglou ◽  
Ndaona Chokani
Keyword(s):  
Heat Pumps ◽  
Computational Investigation ◽  
Turbo Expander

Comparison and Analysis for the Differential Heating Modes in the Large-Scale CHP System

2013 ◽  
Author(s):  
Zhen Xian Lin ◽  
Lin Fu
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Thermal Power ◽  
Heat Pumps ◽  
Back Pressure ◽  
Energy Utilization ◽  
Utilization Efficiency ◽  
Heating Unit ◽  
Heating Efficiency ◽  
The Impact

With the process acceleration of China’s energy conservation and the full development of the market economy, the environmental protection is to coexist with the power plants’ benefits for thermal power plants. Relative to the traditional mode named “determining power by heat”, it is not adequate that the heating demand is only to be met, the maximizations of economy benefits and social benefits are also demanded. At present, several large-scale central heating modes are proposed by domestic and foreign scholars, such as the parallel arrangement and series arrangement of heating system for the traditional heating units and NCB heating units (NCB heating unit is a new condensing-extraction-backpressure steam turbine and used to generate the power and heat, it has the function of extraction heating turbine at constant power, back pressure turbine or extraction and back pressure heating turbine and extraction condensing heating turbine.), and running mode with heating units and absorbed heat pumps, and so on. Compare and analyze their heating efficiency, heating load, heating area, power generation, and the impact on the environment. The best heating mode can be found under the different boundary conditions, it can be used to instruct the further work. The energy utilization efficiency will be further improved.

Implementation of a high-quality biospecimen program to support molecular medicine.

2013 ◽  
Vol 31 (31_suppl) ◽  
pp. 200-200
Author(s):  
Susanne Morrill ◽  
Daniza Mandich ◽  
Richard Cartun ◽  
Andrew L. Salner
Keyword(s):  
Cancer Genomics ◽  
Care Program ◽  
High Volume ◽  
The Cancer Genome Atlas ◽  
Molecular Medicine ◽  
Successful Implementation ◽  
High Quality ◽  
Fresh Tissue ◽  
Tissue Samples ◽  
Tissue Handling

200 Background: The successful implementation of a tumor genomics program relies heavily upon the collection of high quality tumor tissue samples. Although there has been an evolution towards utilizing formalin-fixed paraffin embedded (FFPE) tissue, many research centers continue to rely upon frozen fresh tissue for these types of analyses. A comprehensive effort is required to supply high-volume and high-quality tissue for research. Most community hospitals, even with superb pathology departments, are not well suited to deliver consistent tissue samples without a concerted programmatic effort. As part of the NCI Community Cancer Centers Program (NCCCP), we undertook the development of such capability at our hospital. In addition, as a member of H. Lee Moffitt Cancer Center’s Total Cancer Care program, we received grant funding to help support this comprehensive effort. Our patients and clinicians expressed a strong desire to participate in this type of translational research. This project has been funded in part with federal funds from the National Cancer Institute, National Institutes of Health, under Contract No. HHSN261200800001E. Methods: We developed a comprehensive staffing model to implement this program, including a program coordinator, consenters, pathology assistant, lab aide, and data manager. We developed superb relationships with surgeons, interventional radiologists, pathologists and staffs to assure appropriate referrals and processes, and implemented quality checks as a standard. We developed relationships with Moffitt, The Cancer Genome Atlas, and other research efforts, which help provide funding. Results: We successfully implemented a program which resulted in high levels of patient and provider satisfaction, high numbers of fresh frozen and FFPE tissues (nearly 3,000 over 3 years), high quality pass rates, low ischemia time, and high satisfaction on the part of our research partners. We have incorporated best practices in our tissue handling protocols. Conclusions: We successfully implemented a comprehensive cancer genomics bio-specimen program utilizing dedicated staff, working with patients and clinicians closely, and assuring careful coordination of all efforts.

Implementation of Phase Change in Numerical Models of Heat Transfer

1983 ◽  
Vol 105 (4) ◽  
pp. 431-435 ◽  
Author(s):  
L. J. Hayes ◽  
K. R. Diller
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Latent Heat ◽  
Numerical Models ◽  
Grid Point ◽  
Nodal Point ◽  
Element Model ◽  
Biological Tissues ◽  
Temperature Fields ◽  
Successful Implementation

This paper investigates some of the numerical problems involved in simulating heat transfer in porous media in the presence of phase change. Applications of this type of simulation include modeling of certain metal forming processes, of biological tissues and organs during cryosurgery or cyropreservation, and of heat transfer in frozen soils subjected to transient environmental conditions. A two-dimensional finite element model was used in which the latent heat is treated directly as an energy source in the problem formulation. Several parameters addressed in this work are crucial to the successful implementation of numerical methods for nonlinear heat transport with phase change, including: the effect of nodal point spacing on the occurrence and magnitude of numerical oscillations in the temperature solution and the use of grid point spacing to control these oscillations; the limiting element size which should be used in order to insure stable temperature fields; and the effect which the range of temperatures over which latent heat is liberated has on the solution. The results indicate that numerical stability is achieved for combinations of the foregoing parameters which yield small values of the Stefan number.

scholarly journals CHALLENGES OF SNOW DISPOSAL AND INNOVATIVE SOLUTIONS IN THE CONDITIONS OF NUR-SULTAN

2021 ◽  
Vol 26 (1) ◽  
pp. 20-29
Author(s):  
M. T. Yermekov ◽  
◽  
O. V. Rozhkova ◽  
S. G. Sandibekova ◽  
Ye. T. Tolysbayev ◽  
...  
Keyword(s):  
Urban Areas ◽  
Sewage Treatment ◽  
Heat Pumps ◽  
Successful Implementation ◽  
Snow Melting ◽  
Sewer System ◽  
Snow Removal ◽  
Advantages And Disadvantages ◽  
The Impact ◽  
The City

Introduction. In this paper, we analyze various methods of snow removal in urban areas and consider the most cost-effective and efficient solutions for snow removal and disposal using heat from sewage drains by means of stationary snow-melting points (SMP) in Nur-Sultan. In cooperation with Astana su Arnasy specialists, responsible for the operation of the city sewer system, as well as cleaning and disinfection of urban sewage drains, we reviewed the main advantages and disadvantages. Methods. The paper looks into the possibility of utilizing heat from sewage drains with the help of heat pumps. This method has been successfully tested at a sewage treatment plant and is currently used to heat auxiliary premises. The same principle can be applied in SMPs with a separate discharge of meltwater to the storm sewer. Results. Having studied the experience of using various methods for snow removal in urban areas, we find that snow removal with the use of sewage drains through the creation of special snow-melting complexes integrated with the city sewer system is the most promising method for Nur-Sultan since it allows for reducing costs, intensifying the process of snow melting, and eliminating the hazardous impact of meltwater on the environment. Conclusion. To ensure successful implementation and use of this snow removal method in Nur-Sultan, it is required to conduct a number of additional studies on the impact of sewage treatment plants on the technological processes, as well as to test options for separating sewage drains with the help of heat pumps, and, based on the studies conducted, to determine the final configuration of snow-melting complexes.

Mechanical Design and Analysis of Land Grid Array (LGA) Sockets

2005 ◽  
Author(s):  
Vinayak Pandey ◽  
Sankara Subramanian ◽  
Sudarshan Rangaraj ◽  
Tod Byquist
Keyword(s):  
Mechanical Load ◽  
Mechanical Design ◽  
Cost Effective ◽  
High Volume ◽  
Electrical Performance ◽  
Successful Implementation ◽  
Mechanical Shock ◽  
Stack Analysis ◽  
Case Study Methods

Sockets offer a cost effective and high-volume manufacturing friendly interface between CPU packages and motherboards. Land-grid-array (LGA) technology offers avenues to enhance the electrical performance of sockets over its predecessors e.g. pin grid array (PGA) technology. The present paper will describe various technical challenges encountered in the design of Intel’s LGA sockets. The recently launched LGA775 socket will be used as a case study. Methods adopted to overcome these design challenges and successfully implement LGA sockets will be discussed. Design features like direct socket loading (DSL), various issues related to the design of socket housings, LGA contact design optimization and socket reliability enhancement under stresses such as thermal cycling, mechanical shock, vibration and bake will be discussed. DSL is an integrated mechanism that enables application of a compressive mechanical load between the LGA contact pins on the socket and the package LGA pads, so that their interfaces achieve and maintain electrical continuity through the socket design life. Similarly, optimizing the design of the socket contacts significantly impacts the stressing, reliability of the second level interconnect (SLI) ball grid array (BGA) that connects the LGA775 to the motherboard. The successful implementation of these designs is achieved through a combination of geometric tolerance stack analysis, numerical modeling studies, detailed experiments, reliability testing and correlation between these. The details of the same are be discussed in this article.

Analysis of a Combined Power and Ejector Refrigeration Cycle for Low Temperature Heat Sources

2009 ◽  
Author(s):  
Bin Zheng ◽  
Yiwu Weng
Keyword(s):  
Low Temperature ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Combined Cycle ◽  
Refrigeration Cycle ◽  
Heat Sources ◽  
Working Fluids ◽  
Temperature Heat ◽  
Cycle Efficiency

This paper presents a combined power and ejector refrigeration cycle for low temperature heat sources. The proposed cycle combines the organic Rankine cycle and the ejector refrigeration cycle. It can be used as an independent cycle powered by the low temperature sources, such as solar energy, geothermal energy, or as a bottom cycle of the conventional power plant for the recovery of low temperature waste heat. A program was developed to calculate the performance of the combined cycle. Several substances were selected as the working fluids including R113, R123, R245fa, R141b and R600. Simulation results show that R141b has the highest cycle efficiency, followed by R123, R113, R600 and then R245fa. While the working fluids are calculated by per unit, R600 can produce more power and refrigeration outputs due to the large latent heat. Simulations at different generating temperatures, evaporating temperatures and condensing temperatures were also discussed.

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