Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Alfred Walters Reed. / Ph.D.

Counter Current Flow Limitation (CCFL) was observed in the pressurizer surge line of the Oregon State University APEX facility during test NRC-10. This test simulated a one-inch diameter cold leg break with a failure of three of four of the fourth-stage Automatic Depressurization System (ADS) valves. The result was a high vapor flow rate through ADS 1-3, that caused CCFL in the pressurizer surge line and liquid holdup in the pressurizer. Because this liquid was not available for core cooling, further study of the passive safety systems in the AP600 under Mode 5 Cold Shutdown conditions was deemed necessary. An analysis of the AP600 geometry and the existing CCFL database determined that Kutateladze scaling is appropriate for the APEX and AP600 surge lines. The Kutateladze CCFL correlation was used to assess CCFL in the APEX and AP600 pressurizer surge lines under Mode 5 Cold Shutdown conditions. The results indicate that CCFL would be expected in the pressurizer surge lines at low pressures and decay powers prior to ADS 4 actuation. Test NRC-35 examined CCFL and provided data to benchmark NRC's thermal hydraulic analysis codes. This thesis presents the results of test NRC-35 and the supporting CCFL calculations. / Graduation date: 1999

No description available.

Large cooling systems consume up to 25% of the total electricity used on deep level mines. These systems are integrated with the water reticulation system to provide chilled service water and cool ventilation air. Improving the energy efficiency of these large cooling systems is an important electrical demand-side management initiative. However, it is critical that the service delivery and system performance be maintained so as to not adversely affect productivity. A novel demand-side management strategy, based on variable water flow, was developed to improve the energy efficiency of large cooling systems like those found on deep mines. The strategy focuses on matching the cooling system supply to the demand through the use of modern energy efficient equipment, such as variable speed drives. The strategy involves the modulation of evaporator, condenser, bulk air cooler and pre-cooling water according to partial load conditions. A unique central energy management system was developed to integrate the proposed strategies on large cooling systems. The system features a generic platform and hierarchical network architecture. Real-time energy management is achieved through monitoring, optimally controlling and reporting on the developed strategy. The system is robust and versatile and can be applied to various large cooling systems. The feasibility of the strategy and energy management system was first investigated through the use of an adapted and verified simulation model and a techno-economic analysis. The strategy was then implemented on four large mine cooling systems and its in situ performance was assessed as experimental validation. The results of the Kusasalethu surface cooling system are discussed in detail as a primary case study while the results of the Kopanang, South Deep South Shaft and South Deep Twin Shaft cooling systems are summarised as secondary case studies. The potential to extend the variable water flow strategy to other industrial cooling systems is assessed through an investigation on the cooling system of the Saldanha Steel plant. Results indicate that, over a period of three months, average electrical load savings of 606-2 609 kW (29.3-35.4%) are realised on the four systems with payback periods of 5-17 months. The average electrical load saving between the sites is 33.3% at an average payback period of 10 months. The service delivery and performance of the cooling system and its critical subsystems are not adversely affected. The potential to extend the method to other large cooling systems is also shown. The developed variable water flow strategy is shown to improve the energy efficiency of large cooling systems, making a valuable contribution towards a more sustainable future. This thesis is presented as a detailed discussion of the entire research process. The key results have also been summarised in a series of five research articles attached as independent annexures. Three articles have been published in international scientific journals, one has been presented at and published in the proceedings of an international conference and one is still under review. / Thesis (PhD (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Large cooling systems consume up to 25% of the total electricity used on deep level mines. These systems are integrated with the water reticulation system to provide chilled service water and cool ventilation air. Improving the energy efficiency of these large cooling systems is an important electrical demand-side management initiative. However, it is critical that the service delivery and system performance be maintained so as to not adversely affect productivity. A novel demand-side management strategy, based on variable water flow, was developed to improve the energy efficiency of large cooling systems like those found on deep mines. The strategy focuses on matching the cooling system supply to the demand through the use of modern energy efficient equipment, such as variable speed drives. The strategy involves the modulation of evaporator, condenser, bulk air cooler and pre-cooling water according to partial load conditions. A unique central energy management system was developed to integrate the proposed strategies on large cooling systems. The system features a generic platform and hierarchical network architecture. Real-time energy management is achieved through monitoring, optimally controlling and reporting on the developed strategy. The system is robust and versatile and can be applied to various large cooling systems. The feasibility of the strategy and energy management system was first investigated through the use of an adapted and verified simulation model and a techno-economic analysis. The strategy was then implemented on four large mine cooling systems and its in situ performance was assessed as experimental validation. The results of the Kusasalethu surface cooling system are discussed in detail as a primary case study while the results of the Kopanang, South Deep South Shaft and South Deep Twin Shaft cooling systems are summarised as secondary case studies. The potential to extend the variable water flow strategy to other industrial cooling systems is assessed through an investigation on the cooling system of the Saldanha Steel plant. Results indicate that, over a period of three months, average electrical load savings of 606-2 609 kW (29.3-35.4%) are realised on the four systems with payback periods of 5-17 months. The average electrical load saving between the sites is 33.3% at an average payback period of 10 months. The service delivery and performance of the cooling system and its critical subsystems are not adversely affected. The potential to extend the method to other large cooling systems is also shown. The developed variable water flow strategy is shown to improve the energy efficiency of large cooling systems, making a valuable contribution towards a more sustainable future. This thesis is presented as a detailed discussion of the entire research process. The key results have also been summarised in a series of five research articles attached as independent annexures. Three articles have been published in international scientific journals, one has been presented at and published in the proceedings of an international conference and one is still under review. / Thesis (PhD (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Using seawater in cooling systems is a common practice in many parts of the world where there is a shortage of freshwater. However, biofouling is one of the major operational problems associated with the usage of seawater in cooling systems. Microfouling is caused by the activities of microorganisms, such as bacteria and algae, producing a very thin layer that sticks to the inside surface of the tubes in heat exchangers. This thin layer has a tremendously negative impact on heat transferred across the heat exchanger tubes in the system. In some instances, even a 250 micrometer thickness of fouling film can reduce the heat exchanger's heat transfer coefficient by 50 percent. On the other hand, macrofouling is the blockage caused by relatively large marine organisms, such as oysters, mussels, clams, and barnacles. A biocide is typically added to eliminate, or at least reduce, biofouling. Typically, microfouling can be controlled by intermittent dosages, and macrofouling can be controlled by continuous dosages of biocide. The aim of this research work is to develop a systematic approach to the optimal operating and design alternatives for integrated seawater cooling systems in industrial facilities. A process integration framework is used to provide a holistic approach to optimizing the design and operation of the seawater cooling system, along with the dosage and discharge systems. Optimization formulations are employed to systematize the decision-making and to reconcile the various economic, technical, and environmental aspects of the problem. Building blocks of the approach include the biocide water chemistry and kinetics, process cooling requirements, dosage scenarios and dynamic profiles, biofilm growth, seawater discharge, and environmental regulations. Seawater chemistry is studied with emphasis on the usage of biocide for seawater cooling. A multi-period optimization formulation is developed and solved to determine: * The optimal levels of dosing and dechlorination chemicals * The timing of maintenance to clean the heat-exchange * The dynamic dependence of the biofilm growth on the applied doses, the seawater-biocide chemistry, the process conditions, and seawater characteristics for each time period. The technical, economic, and environmental considerations of the system are accounted for and discussed through case studies.

Made available in DSpace on 2014-10-09T12:49:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:16Z (GMT). No. of bitstreams: 1 09834.pdf: 11774838 bytes, checksum: 940cf578592bd4491d6495c63535f0a7 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:43:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:23Z (GMT). No. of bitstreams: 1 06171.pdf: 4113918 bytes, checksum: f80c43f20a8b10129dced614d40007ba (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:49:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:16Z (GMT). No. of bitstreams: 1 09834.pdf: 11774838 bytes, checksum: 940cf578592bd4491d6495c63535f0a7 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:43:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:23Z (GMT). No. of bitstreams: 1 06171.pdf: 4113918 bytes, checksum: f80c43f20a8b10129dced614d40007ba (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP