College of Engineering Technical Reports

Permanent URI for this collectionhttps://hdl.handle.net/10125/19862

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Submerged breakwater protection at Kahului Harbor
(2013-11-06) Hansbrough, Jerre; Singh, Amarjit
Due to the complexity of the coastal zone, traditional coastal protection measures such as seawalls, breakwaters, and groins have not always been entirely successful. The challenge of mitigating wave energy has proven difficult for Kahului Harbor on the North Shore of Maui, Hawaii. The existing method for reducing wave energy at Kahului Harbor uses direct protection in the form of emerged rubble mound breakwaters. Despite these protective measures, the harbor entrance is not trafficable during winter swells and causes shipping delays. Improvements in coastal protection technologies allow for consideration of reducing the high wave energy by employing submerged breakwaters to address this problem. Case studies of existing submerged breakwaters provide examples of various techniques used in the construction of these structures, allowing a review of the benefits, difficulties, and overall effectiveness of each. An emphasis is given to geotextile breakwaters as it is among the newest technologies in this application. To accurately examine work tasks and their associated resource allocation, a process simulation model is prepared in the CYCLONE simulation language, and entered into EZstrobe. Critical subtasks are identified to identify where efficiencies in resources could be gained. All submerged breakwater solutions should cost less, and work more effectively than the originally planned breakwater extension. Modeled methods are optimized to maximize the utility factor and conduct a cost-benefit analysis, which is included in the overall analysis of the alternatives for Kahului harbor.
Factory Production of Large Panels for Mass Housing: Production, Simulation, and Cost Analysis
(1999) Singh, Amarjit
This report presents the operations of a precast panel factory, Perma Betonila at Kangasila surveyed in Finland. Quite a few activities at this factory are considerably automated, especially those related to material transportation. This is among the advanced precast factories in the world for the manufacture of precast panels, for which a simulation model is written in CYCLONE to presented and depict the operations of this factory. The aim of this research is to study innovative prefabrication methods for mass housing, using concrete components. The operations at this factory are used as a backdrop for innovative design of operations of a more responsive factory - one that can turn out panels with high agility, since mass housing to overcome world housing shortages requires rapid production systems. This report deals exclusively with the operations of this factory and a simulation model of it.
THE WORKINGS OF MAGLEV: A NEW WAY TO TRAVEL
(2017-04) Dona, Scott; Singh, Amarjit
Maglev is a relatively new form of transportation and the term is derived from magnetic levitation. This report describes what maglev is, how it works, and will prove that maglev can be successfully constructed and provide many fully operational advantages. The different types of maglev technology were analyzed. Several case studies were examined to understand the different maglev projects whether operational, still in construction, or proposed. This report presents a plan to construct a maglev network using Maglev 2000 vehicles in the United States. A maglev system provides energy, environmental, economic, and quality of life benefits. An energy and cost analysis was performed to determine whether maglev provides value worth pursuing. Maglev has both a lower energy equirement and lower energy costs than other modes of transportation. Maglev trains have about one-third of the energy requirement and about one third of energy cost of Amtrak trains. Compared to other maglev projects, the U.S. Maglev Network would be cheaper by a weighted average construction cost of $36 million per mile. Maglev could also be applied to convert the Honolulu Rail project in Hawaii from an elevated steel wheel on steel rail system into a maglev system. Due to the many benefits that Maglev offers and the proof that maglev can be implemented successfully, maglev could be the future of transportation not just in the United States but in the world. Maglev will improve the way that people travel.
CONSTRUCTION METHODOLOGIES, SCHEDULING, COSTING, AND PROCESS SIMULATION OF A SUBMERGED CONCRETE CAISSON BREAKWATER
(2017-04) Magallanes, Alvin; Singh, Amarjit; Sullivan, Ben; Singh, Amarjit; Sullivan, Ben
The overall aim of the Kahului Caisson Breakwater project is to increase the tranquility within the Harbor to allow more operational days. HOV Environment was contracted to develop the detailed construction and installation methodology, along with construction cost estimates and project schedule for the proposed caisson breakwater project. This investigation was further enhanced by verifying the project schedule and running a process simulation. In order to develop a better understanding of previous breakwater caisson projects, a detailed literature review was undertaken. It became apparent during this review that there were very few instances where caissons have been used to create a submerged breakwater; most examples refer to emerged caisson units. The closest project to a submerged structure is the Costa Azul breakwater developed for a liquid natural gas (LNG) facility in Baja, Mexico. It was decided that best practices would be adopted where possible; where no new methods would be developed. After conducting the literature review and developing a list of known installation methods a detailed site study was conducted. The aim of this study was to understand any restrictions related to the construction of the project and assess the available resources in Hawaii to implement the project. Three key factors were highlighted during the site visit: (1) no construction activities could take place in Kahului Port or the island of Maui. (2) The resources in Hawaii are limited for this type of project. (3) The construction window is very limited with a maximum of 5 months during the summer season where wave height and period are lower. The proposed approach will be to use Dry Dock 4 in Pearl Harbor, Oahu. The main reason being this is the only facility in Honolulu with the appropriate draft for the caisson units. The caisson units will be cast in Dry Dock 4 using state-of-the-art slipform in one single pour to avoid any cold joints. When ready, the dock will be flooded, and then the caisson will be tested for even floatation and transported onto a heavy lift vessel. The heavy lift vessel will then transport the unit from Oahu to the project site outside Kahului Harbor. Once at the site, the caissons will be unloaded and towed into place above the prepared foundation layer. Once all four caisson units have been installed and final surveys are complete the final stage of the project is to transplant coral fragments onto the structure. Two approaches have been suggested with the use of traditional coral transplanting or incorporating a Biorock structure on the outside of the caisson whilst in the dry dock. Further research into the supply of the coral fragments will be required. After verification of the project schedule, two process simulations were run using EZStrobe. The first simulation modeled the project schedule exactly, initializing all construction activities simultaneously. This involved initialization of construction activities at the dry dock, where the caissons will be constructed, and the initialization of construction activities at the construction site, outside Kahului Harbor. The approach for the second simulation was run with the initialization of the dry dock activities independent of the construction activities at the installation site. This approach was considered due to the constraint of the construction window; to have the construction of the caissons at the dry dock well before the commencement of works done at the construction site and to investigate the effects this shift in the schedule would have on the overall project duration. The initial project schedule and cost estimates determined that the duration of the project will take 139.9 days to complete and cost approximately US$20.7 million, with contingencies. Simulation I verifies these initial estimates having a completion time of 139.12 days and cost US$22.1 million, with contingencies. For Simulation II, project duration was determined to be 143.8 days and US$22.3 million, with contingencies. These simulations show that the project can be feasibly completed within the mandatory construction window of 150 days and at a budget of about US$20 million. However, due to this project’s sensitivity to time, any delays to the project will push the duration of the project outside the 150-day window and cause a considerable increase in costs.
CONSTRUCTION METHODOLOGY OF ASPHALT STRAIN GAUGES IN AIRPORT PAVEMENTS
(2018-11) Kioa, Greg; Singh, Amarjit; Singh, Amarjit
Pavement distresses at airports are expensive to repair. Moreover, the longer a distress goes unchecked, the worse its effect is, whereas design improvements have potential in pavement management. Normal distresses cannot be eliminated, perhaps only mitigated. With this in mind, a real-time study is underway to monitor distresses in a taxiway. Early detection of distress before it is visible on the surface can potentially inform on impending pavement repair. Specifically, it is seen that there is delamination between the three-inch surface layer of pavements and the underlying base layer. If left unchecked, this results in major visible slippage, shoving, and cracking. To install early detection sensors to measure delamination is an involved task: the pavement needs to be cordoned off, the surface must be milled, sensors installed, and a trench dug to take the wires from the sensors off the runway to a data acquisition center, resting on a concrete pad. The wires must be pulled, and then the trench and milled area must be covered back with concrete and asphalt respectively. On the face of it, these tasks are elementary, but compounding them is the narrow construction window available. The challenge here is to undertake the tasks at high speed within only three work days because airport taxiways, let alone runways, cannot be kept closed for long durations. The purpose of this report is to describe the construction methodology for strain gage installation in an airport runway/taxiway.
How Much Ethanol Fuel Can be Produced from Sugarcane in Hawaii?
(2014-03) Kwong, John; Singh, Amarjit; Francis, O.; Babcock, R.; Singh, Amarjit; Francis, O.; Babcock, R.
This study evaluates how much sugar ethanol Hawaii can produce. Fossil fuel reserves will diminish with time, and alternative energy may not be effective in totally replacing combustible engines for all application. Factors important to sugar ethanol production and distribution are examined and evaluated. Sugarcane was heavily produced in Hawaii’s past and can be converted into ethanol to use as automobile fuel. There are lots of arable lands available and the island of Hawaii and Maui have enough rain and ground water to supply the sugarcane crops. Sugarcane mills are self-sufficient and can produce their own electricity. However there are some significant barriers to ethanol production right now such as the disposal of odorous vinasse, low sale price of ethanol, and more profitable sugar sales. Each resource required for producing ethanol in Hawaii is investigated by review of available information and field trips to a sugar plantation on Maui, and calculations are performed on how much sugar ethanol can be made to supply Hawaii’s fuel needs. This report covers the process required to grow sugarcane in order to produce ethanol. It covers available land, rain and ground water, the process, and future projections for growing sugar and ethanol production. Other factors like desalination, vinasse, and the gasoline consumption in Hawaii are also evaluated. This report is not meant to give a solution to automobile fuel after the depletion of fossil fuels, but how sugar ethanol can address the fuel shortage problem of the future. If all the arable land was used to produce ethanol, 57% of the automobiles in Hawaii could be fueled by ethanol. The estimated probable cost of shipping sugar ethanol from the island of Hawaii and Maui to Oahu by fuel barge can be similar to the barge shipping cost for shipping gasoline from Oahu to the outer island, depending on the volume of fuel to be shipped. The disposal of vinasse is one of the main barriers to producing ethanol in Hawaii, for sugar ethanol to be produced in Hawaii, research and development must be performed to reduce the unpleasant odor of vinasse. If this can be achieved, then vinasse can be a beneficial by product, as it can be used as a fertilizer in Hawaii, where the plantations are close to developed areas. By addressing these issues, ethanol fuel could be produced in Hawaii, and Hawaii would be released from its dependency on fossil fuels.
Plasma Arc Gasification Application to the City and County of Honolulu, Hawaii
(2018-12) Tramontano, Rocoo; Singh, Amarjit; Singh, Amarjit
This report will examine the application of plasma arc gasification technology to the City and County of Honolulu for the disposal of municipal solid waste. The report will examine history of the technology, the technology itself, and how it can be used to address the existing concerns of the traditional disposal methods of municipal solid waste. The environmental aspects of the technology and its implications will be presented and compared to the traditional WTE process of incineration. Additionally, we will further examine the major financial and economic implications associated of the technology. In a basic explanation, plasma arc gasification is the process where feedstock material (municipal solid waste, construction & demolition debris, hazardous waste, ash, etc.) is burned at extremely high temperatures that creates a molten slag byproduct that can be used for construction applications when cooled, and a synthetic gas that can be used as fuel for electricity. The technology of Alter NRG, the parent company of Westinghouse Plasma Corporation is an industry leader in plasma technology and its application using municipal solid waste will be applied to this study. Their G65 reactor is capable of processing 1000 tons of feedstock (municipal solid waste) that would create 250 tons of slag, 41 net MW of electricity, and send 20 tons of waste to landfill (2% of the initial feedstock) that cannot be recycled through the plant. Our analysis breaks down the cost per ton to process municipal solid waste as a feedstock, and compares it to the existing facilities and technology used on the island. At the end of our analysis it was found that plasma arc gasification can generate a positive net revenue of up to $168 per ton of municipal solid waste depending on the feedstock. What makes this technology so profitable is the high cost of electricity in the State of Hawaii, which is three times the national average across all sectors. The electricity generated can be sold to the Hawaiian Electric Company for profit. Other sources of revenue generated are gate fees to process the waste, recycling of ferrous and nonferrous recyclable materials prior to processing, and the sale of the inert slag byproduct. Together these revenue streams from PAG in Hawaii offset the capital cost of $341.5 million to construct a 1000 ton per day facility. This study will attempt to show how this technology can be a solution to Oahu’s waste predicament as the existing landfill only has the capacity to last less than 25 more years, and how unique factors present in the State of Hawaii could make this technology both environmentally and economically profitable.
ANALYSIS OF MAINTENANCE OF CRITICAL UTILITY SYSTEMS ON U.S. NAVY INSTALLATIONS TO DETERMINE OPTIMUM TIMING FOR RECAPITALIZATION
(2023-12) Aderibigbe, Keji; Singh, Amarjit; Akiona, Randall; Robertson, Ian; Singh, Amarjit; Akiona, Randall; Robertson, Ian
The Naval Facilities Engineering Systems Command (NAVFAC) is responsible for providing Facility Management and Sustainment (FM&S) services for all U.S. Navy installations worldwide. A critical element of this service is maintaining critical utility infrastructure that is key to operating these installations. Currently, most of the critical utility infrastructure systems – electrical, potable water, and wastewater – on U.S. Navy installations are near or past their useful life. When infrastructure start to degrade, the U.S. Navy allocate funds for recapitalization, but budget constraints have made it difficult to predict the timing of this investment and so facility managers must determine how to best extend the life of their utility infrastructure. The purpose of this report is to conduct an analysis of NAVFAC’s preventive maintenance (PM) strategy, performance, and U.S. Navy’s utility infrastructure investment by: • Analyzing the PM strategies NAVFAC uses for facility maintenance on U.S. Navy installations. • Researching PM strategies used in the facility management industry. • Analyzing the PM completion rates for utility systems on U.S. Navy Installations. • Analyzing the level of investment that the U.S. Navy’s provides for maintenance of utility systems. • Determine the optimum time for investing in the recapitalization of critical utility systems at U.S. Navy installations. The methodology used for this report analyzed different processes and reviewed data for the items associated with the report’s objective. The methods include: • Interviewing facility management teams within NAVFAC to determine the PM strategies used at their installations. • Interviewing facility managers outside the Department of Defense to determine their organization’s maintenance strategy and use it as a point of comparison. • Reviewing data on the condition of critical utility systems on U.S. Navy installations. • Reviewing data of PM completion across the NAVFAC enterprise to determine if NAVFAC is meeting its 100% PM completion goal. • Reviewing data on the historical level of U.S. Navy’s investment for critical utility systems, to determine if it is adequate to maintain the systems. The analysis used data obtained from NAVFAC’s electronic facility management systems, and the notes from interviews conducted with facility managers at various U.S. Navy installations. Based on this analysis, the key findings of this report are: • NAVFAC-managed critical utility systems are old; with some past their useful life. • NAVFAC uses a combination of maintenance strategies to maintain its utility systems. • NAVFAC does not meet its PM completion goals. • Maintenance investment from the U.S. Navy is not adequate to maintain the systems. • The timing to receive funding for recapitalization is unpredictable, and utility systems do not compete well for funding during the project prioritization process. Based on these findings, some recommendations for prolonging the life of critical infrastructure and receiving funding for recapitalization include: • Incorporating elements of different maintenance strategies into NAVFAC’s PM strategy. • Addressing staffing issues to increase PM completion. • Advocating for increase in sustainment funding. • Advocating for increase in weighted priorities in the decision lens model, to increase the chances of utility infrastructure projects being selected for funding. • Advocating for targeted funding for recapitalization of utility infrastructure Navy wide. The optimum time to invest in recapitalization for critical utility infrastructure is when systems are at the most significant risk of failure – as determined by the facility condition assessment tools used by NAVFAC. However, the reality of funding unpredictability means that NAVFAC must implement a well-disciplined PM program to help extend the life of critical infrastructure and mitigate the risks associated with projects not being selected for funding during the project prioritization process.
POHAKULOA TRAINING AREA: FRAMING NEGOTIATIONS, ENVIRONMENTAL REMEDIATION, AND SUSTAINABLE PROCESSES FOR LONG-TERM USE
(2024-05) Walton, James; Singh, Amarjit; Singh, Amarjit
The Pohakuloa Training Area (PTA), located on the Island of Hawai’i, is a critical military training installation used by the U.S. Army and joint forces in the Indo-Pacific Area of Operations. This report reviews the environmental remediation requirements and sustainable processes necessary for extending the Army Land Lease Agreement with the State of Hawai’i, focuses on unexploded ordnance (UXO) remediation techniques and procedures. PTA, spanning over 133,000 acres, is strategically vital for U.S. Indo-Pacific Command forces. However, the presence of UXOs, hazardous materials, and cultural sensitivities presents challenges to renewing the existing lease set to expire in 2029. The U.S. Army currently leases approximately 22,000 acres from the State of Hawai’i. The lease agreement has been under much scrutiny due to environmental concerns and a lawsuit resulting in the development of a state mandated management plan. Key proposed actions for upcoming negotiations include ‘Full Retention’ (retain the entire 22,000 acres), ‘Modified Retention’ (retain ~ 19,700 acres), and ‘Minimum Retention and Access’ (retain ~ 10,100 acres and limited road access). This report addresses environmental challenges and data gaps in recent environmental impact statements by the executive agent overseeing the real estate transaction, the U.S. Army Corps of Engineers. The report offers an overview of UXO and environmental regulatory frameworks, and proposes techniques for Cost Engineering Requirements, UXO and environmental control and monitoring, and emerging technologies and procedures for remediation activities. Furthermore, the report closely examines the land lease agreement through evaluating historical context, cultural perspectives, legal and regulatory variables, and offers negotiation techniques and best alternatives to negotiated agreements. The report underscores the critical importance of UXO remediation at PTA and recommends leveraging advanced technologies and negotiation strategies to ensure environmental sustainability and maintain military readiness. Implementing comprehensive environmental monitoring systems and cost-effective remediation techniques will be essential for a favorable lease agreement with the State of Hawai’i.
A Feasibility Study on the Implementation of 100% Electric Buses in the State of Hawai'i
(2020-05) Phillip, Solomon; Singh, Amarjit; Akiona, Randall; Shen, Lin
This research will examine the feasibility of converting the present inventory of public transportation buses in the state of Hawaii to 100% battery-electric powered buses, along with all the necessary infrastructure modifications and additions. Moving forward, the term “e-bus” will be used to refer to a fully battery-electric powered, public transportation bus. It is imperative to understand that this study solely focuses on the public transportation bus system and does not include regular electric vehicles (EVs), publicly or privately owned.
Identifying Delamination in Airport Pavement at HNL with Embedded Asphalt Strain Gages
(2019-06) Riege, Matthew; Singh, Amarjit
The demand of air transportation requires high levels of performances from asphalt pavements. Failures of pavements can delay flights, damage airplanes, and require costly expedient repairs. Common failures airport pavements are slippage failures including surface shoving and slippage cracking. Slippage failure is typically caused by either the deterioration of bonding between asphalt layers (delamination) or a lack of shear resistivity within the surface layer asphalt mix. Bonding between asphalt layers can be measured using embedded asphalt strain gages. In 2018, an asphalt strain gage system was installed at Daniel K. Inouye International Airport (HNL), Honolulu, HI. This report details the background of pavement monitoring at HNL, collection and processing of strain data, and analyzes the strain responses collected. Indicators of delamination are identified either through large discrepancies in peak strain experienced in asphalt layers or a low correlation of strain responses from the force of an airplane on the pavement. Data collected for this report is the start of an aggregated comparison to determine performance of installed pavement versus design. Ideally this comparison will take data from installation of overlay layer until replacement. Statistical analysis methods are employed to determine if recordings and calculated amounts are comparable across the time frame of this report. Results of this report are that pavement installed in August of 2018 has indicators of delamination, but is performing as a homogenous well bonded pavement. There are several items noted that require further monitoring and visual inspection. There are recommendations for follow on work under this project.
Plasma Arc Gasification Plant Benefits to the County of Hawaii
(2022-12) Logan, Lydia; Singh, Amarjit
This report will examine the application and benefits of constructing a Plasma Arc Gasification plant on the Island of Hawaii. First, the waste composition and generation of the United States is discussed along with the current methods of disposal and their implications. Then, specifically the Island of Hawaii waste generation and management is analyzed. The State of Hawaii faces unique challenges of waste management due to its geographic isolation; this makes it a perfect candidate for a waste to energy technology. Incineration is a typical waste to energy technology but emits hazardous toxins and greenhouse gases through the combustion of waste. Plasma Arc Gasification however, uses extreme heat to vaporize the waste and converts it back into its elemental compounds. This process creates a syngas that can be used as fuel for electricity and a molten slag that is applicable as aggregate to the construction industry. Plasma Arc Gasification has multiple benefits including a flexible feedstock, electricity generation, a byproduct of non-hazardous slag. A cost analysis is performed comparing the current landfill operations with the potential profit of a Plasma Arc Gasification plant. A 1000 tpd PAG plant is used for this analysis because even though the Island of Hawaii disposed of approximately 185,000 tons of MSW in 2020, the waste disposal rate for the island on average increases 4.6 percent per year. The cost analysis determines that by constructing a PAG plant on the Island of Hawaii, there is a potential profit of $227.87 per ton of MSW, that equates to over $41 million a year. Compared to the current landfill operation there would be a net gain of $202.29 per ton of MSW or more than $37 million a year. The high initial capital cost of constructing a Plasma Arc Gasification plant is offset by its revenue generation.
Corrosion tests in Hawaiian geothermal fluids
(National Research Council of Canada, 1984) Larsen-Basse, Jorn; Lam, Kam-Fai
Exposure tests were conducted in binary geothermal brine on the island of Hawaii. The steam which flashes from the high pressure, high temperature water as it is brought to ambient pressure contains substantial amounts of H2S. In the absence of oxygen this steam is only moderately aggressive but in the aerated state it is highly aggressive to carbon steels and copper alloys. The liquid after flashing is intermediately aggressive. The Hawaiian fluid is unique in chemistry and corrosion behavior; its corrosiveness is relatively mild for a geothermal fluid falling close to the Iceland-type resources.
Hawaii Geothermal Project : the effect of steady withdrawal of fluid in geothermal reservoirs
(Hawaii Geothermal Project, University of Hawaii at Manoa, 1975) Cheng, Ping; Lau, Kah Hie
The problem of combined free and forced convection in geothermal reservoirs resulting from steady withdrawal of fluid is investigated numerically. The aquifer is confined by caprock on the top, heated by an impermeable surface at the bottom, and is recharged continuously from the ocean. The governing quasilinear partial differential equations in terms of pressure and temperature are approximated by finite difference equations which are solved numerically by iteration. Computations were carried out for both cylindrical and rectangular reservoirs for a selected set of parameters. It is found that the withdrawal rates and the location of the withdrawal site have a significant effect on heat transfer and fluid flow characteristics in a geothermal reservoir.
Hawaii Geothermal Project : the effect of dike intrusion on free convection in geothermal reservoirs
(Hawaii Geothermal Project, University of Hawaii at Manoa, 1974) Lau, Kah Hie; Cheng, Ping
A perturbation analysis is made for the simultaneous heat and mass transfer in unconfined geothermal reservoirs with dike intrusion. The perturbation equations are of elliptic type that can be solved numerically by the finite difference method. Up to the second-order approximations are retained in the numerical computation. The effects of dike intrusion on streamlines, temperature distribution, and the shape of water table in two-dimensional aquifers with low permeability are shown.
Hawaii Geothermal Project : buoyancy induced flows in a saturated porous medium adjacent to impermeable horizontal surfaces
(Hawaii Geothermal Project, University of Hawaii at Manoa, 1975) Cheng, Ping; Chang, I-Dee
Boundary-layer analysis is performed for the buoyancy-induced flows in a saturated porous medium adjacent to horizontal impermeable surfaces. Similarity solutions are obtained for the convective flow above a heated surface or below a cooled surface, where wall temperature is a power function of distance from the origin. Analytical expressions for boundary layer thickness, local and overall surface heat flux are obtained. Applications to convective flow in a liquid-dominated geothermal reservoir are discussed.
Hawaii Geothermal Project : free convection about a vertical cylinder embedded in a porous medium
(Hawaii Geothermal Project, University of Hawaii at Manoa, 1975) Minkowycz, W.J.; Cheng, Ping
An analysis is made for free convective flow about a vertical cylinder embedded in a saturated porous medium, where surface temperature of the cylinder varies as xλ, a power function of distance from the leading edge. Within the framework of boundary layer approximations, exact solution is obtained for the special case where surface temperature varies linearly with x, i.e., λ = 1. For other values of λ, approximate solutions based on local similarity and local non-similarity models are obtained. It is found that the local similarity solutions are sufficiently accurate for all practical purposes. Analytical expressions for local surface heat flux and overall surface heat flux are obtained.
Hawaii Geothermal Project : similarity solutions for free convection about a dike
(Hawaii Geothermal Project, University of Hawaii at Manoa, 1975) Cheng, Ping; Minkowycz, W.J.
An analysis is made for steady free convection of groundwater about a hot dike trapped in an aquifer of infinite extent. Within the framework of boundary layer approximations, similarity solutions are obtained for a class of problems where wall temperature varies as xλ, i.e., a power function of distance from the origin where wall temperature begins to deviate from that of the surrounding groundwater. The uniform heat flux solution emerged as a special case with λ = 1/3. It is found that vertical velocity and the temperature profiles are of the same shape, and that the boundary layer thickness is proportional to the square root of the distance from the leading edge. Analytical expressions are obtained for boundary layer thickness, local and overall surface heat flux, as well as the local and average heat transfer coefficients. Some representative velocity and temperature profiles around a dike are also presented.
Hawaii Geothermal Project : numerical solutions for steady free convection in island geothermal reservoirs
(Hawaii Geothermal Project, University of Hawaii at Manoa, 1975) Cheng, Ping; Yeung, K.C.; Lau, Kah Hie
The problem of steady free convection in an island aquifer, confined by caprock at the top and heated by an impermeable surface from below is considered. The governing non-linear partial differential equations are approximated by a set of finite difference equations, which are solved numerically by the iteration method. To guarantee convergence of the iteration process, the non-linear convective terms in the energy equation are approximated by the upwind difference scheme. The effects of thermal conditions at the caprock, the geometry of the reservoir, the variation of Rayleigh number, the length of the heating surface, and the magmatic intrusion, on fluid flow and heat transfer characteristics in island geothermal reservoirs are discussed.
Hawaii Geothermal Project : characteristics of vapor flashing geothermal plants
(Hawaii Geothermal Project, University of Hawaii at Manoa, 1974) Ahluwalia, Rajesh K.; Chou, James C.S.
A study of the important parameters of a vapor flashing plant and characteristics of its major components is presented. The investigations by others showed that a steam and water mixture can be transported in a single pipe without the problems of water hammer, cavitation, and vibration, and that the pressure drop of a two-phase fluid can be determined using Lockhart and Martinelli correlation. The optimum flashing temperature has been calculated by numerical method, and the effects of wellhead pressure and number of stages on power output were analyzed. The design and operating features of a bottom outlet cyclone separator are given. The steam rates of a mixed pressure turbine for geothermal application were estimated in terms of the size, loading, throttle pressure and temperature, and condensing pressure. A procedure is described to determine the performance and size of an induced-draft, cross-flow cooling tower. By performing a simple heat balance calculation, effects of non-condensable gas content and condensing pressure on the net power output were determined. Finally, the possible arrangements of the heat rejection equipment and the factors involved in the selection of a plant site are discussed.

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