Seawater Heat Research Articles

Energy Integration of LNG Light Hydrocarbon Recovery and Air Separation

Liquefied natural gas (LNG) needs to be heated and vaporized before entering the natural gas pipeline network. The traditional seawater heating method not only wastes the cold energy from LNG regasification, but also causes adverse environmental impact, hence the design of cold energy utilization system is necessary. Air separation process is the most common type used in Chinese LNG receiving terminals, and the utilization ratio of LNG cold energy is only about 40 %. The light hydrocarbon separation process is another way to utilize cold energy, which can recover high-value hydrocarbons like ethane from LNG. This paper first presents an integrated process of light hydrocarbon separation and air separation to realize the cascade utilization of LNG cold energy and obtain higher economic benefits. Then, different temperature ranges of LNG regasification for the air separation and light hydrocarbon separation are determined by sensitivity analyses. Results show the utilization ratio of LNG cold energy is increased by 35.77 %. Air separation and light hydrocarbon separation can be easily miniaturized, and they are suitably applied for the LNG receiving terminals.

Mathematical Modeling and Performance Analysis of Seawater Heat Exchanger in Closed-Loop Seawater-Source Heat Pump System

AbstractThe seawater source heat pump (SWHP) utilizes low-grade energy from seawater to satisfy heating/cooling requirements of coastal buildings. Compared with the open-loop SWHP system, the close...

Failure analysis on leaked titanium tubes of seawater heat exchangers in recirculating cooling water system of coastal nuclear power plant

Thanks to the superior resistance to corrosions, especially the chloride-induced pitting corrosion, titanium and its alloys are generally regarded ideal for application in the seawater environment. However in this paper, one failure case regarding leakage on the titanium tubes of the seawater heat exchangers in the recirculating cooling water system of one coastal nuclear power plant was reported. Actually, similar problem with severer extent on even a larger number of tubes in this equipment had already occurred before and been effectively solved, nevertheless it emerged again this time but merely affected several individual tubes. To avoid contamination of the moderator system, plugging was temporarily adopted for the leaked tubes, but undoubtedly root causes analysis of this failure was immediately necessitated to reduce both the safety risks and the economic losses. Hence, comprehensive investigation of the base materials, environmental media, defects morphologies and micro-area compositions etc. was carried out for identification of the failure causes, based on which the relevant mechanisms were discussed and the pertinent countermeasures were proposed. Achievement of this paper will not only help to solve the practical engineering problem for this sole nuclear equipment, but also lead to a better understanding of the degradation behaviors of titanium alloys under complex service conditions.

Влияние скорости тепловой акклимации на жирнокислотный состав и фазовые переходы гликолипидов Saccharina japonica (J.E. Areschoug)

Saccharina japonica is a valuable commercial species and the most common object of mariculture. Temperature is a powerful factor determining the growth and development of macroalgae. Rational mariculture and an understanding of the dynamics of marine ecosystems require the study of the physicochemical basis of temperature adaptation. The key mechanism of this process is the redistribution of the fatty acid (FA) composition of polar lipids, maintaining the optimal liquid-crystalline state of the biomembrane lipid matrix. In the conditions of increasing ambient temperature variability, the rate of changes aimed at the thermal adaptation of ectothermic organisms, which include plants, becomes particularly important. However, to date, the effect of the temperature acclimation rate on ectothermic organisms has been little studied. The present paper aims to study the ability of S. japonica to adapt the physicochemical properties of the main polar lipids to elevated ambient temperature at different rates of seawater heating. Algae were collected in the Sea of Japan in winter at a water temperature of 4 °C and warmed to a summer temperature of 20 °C at rates of 16 °C/d (rapid acclimation) and 2 °C/d (slow acclimation). We isolated glycolipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and sulfoquinovosyldiacylglycerol (SQDG) from acclimated algae as well as their thalli, collected in winter and summer, and studied their FA composition, the composition of molecular species and thermal transitions from crystalline state to liquid crystalline state, which is optimal for functioning of biomembranes, by GLC, HPLC-MS and differential scanning calorimetry (DSC), respectively. Statistical significance was analyzed using Student’s t-test (p ≤ 0.05). The results of this study showed that rapid thermal acclimation caused an increase in the unsaturation index (UI) and the ratio of unsaturated/saturated FA of the main lipid of thylakoid membranes MGDG (See Table 1), in contrast to both acclimatization and acclimation changes in the FA composition of the remaining glycolipids DGDG and SQDG when a season changes from winter to summer (See Tables 2-3). The opposite character of changes in the unsaturation of the FA composition of MGDG compared with DGDG and SQDG was also preserved during slow thermal acclimation. Slow warming only strengthened this feature in MGDG, contributed to increasing the unsaturation of FA composition of DGDG as opposed to the effect of rapid acclimation or weakened its effect in SQDG. The ratio of n-3/n-6 polyunsaturated fatty acids (PUFAs), the decrease of which, that is, increase in the share of n-6 PUFAs in polar lipids of marine macrophytes during thermal acclimatization is important both for regulating the viscosity of membrane lipids, and for strengthening mediators derived from PUFAs in the physiologically active season. However, during thermal acclimation, the n-3/n-6 ratio of PUFAs changed a little in MGDG and SQDG of S. japonica regardless of the acclimation rate. Only in DGDG, the n-3/n-6 ratio of PUFAs decreased in accordance with the seasonal trend, especially at rapid acclimation. These changes in the FA composition of glycolipids were accompanied by equally ambiguous changes in their thermotropic behavior. Thermal acclimation caused the phase separation of MGDG, which was characterized by splitting of the peak of crystal – liquid crystal thermal transition of the glycolipid into the low and high temperature peaks, while the seasonal effect contributed to a decrease in the peak maximum temperature (Tmax) to the low temperature region by 20°C (See Fig. 1a). Phase separation of MGDG was accompanied by an increase in the percentage of molecular PUFA/PUFA forms, as well as monounsaturated FA (MUFA)/PUFA, and a decrease in saturated FA (SFA)/ PUFA (See Table 4). However, the warming up of sea water at a rate of 16°C/d and 2°C/d was not enough to bring the profile of the thermogram acclimatization and acclimation closer to that of the summer sample. Similar acclimation changes, which had a character of the emerging trend of fitting the profile of thermograms, were observed in the DGDG and SQDG calorimetric transitions (See Fig. 1b, c), which were based not so much on the FA composition as a whole but on the composition of their molecular species/forms (See Tables 5-6). Consequently, an increase in seawater temperature from 4 °C to 20 °C at rates of 16 °C/d or 2 °C/d showed an ambiguous, stressful nature of the FA composition and calorimetric transitions of glycolipids from S. japonica during thermal acclimation. The low efficiency of molecular mechanisms underlying maintenance of the liquid crystalline state of the main polar lipids of S. japonica that is optimal for functioning of the membranes is probably due to cold-loving nature and absence of sharp temperature fluctuations in the natural habitats of this species of marine macroalgae.

Feasibility of seawater heat extraction from sub-Arctic coastal water; a case study of Onundarfjordur, northwest Iceland

We studied the feasibility of seawater heat extraction in Onundarfjordur (Icelandic: Önundarfjörður), a fjord located in the north-western part of Iceland, with sub-Arctic Ocean temperatures. The in-situ seawater temperature in the fjord was measured at different depths and locations from April 2015 to April 2016. Also, a 2-dimensional numerical simulation of key oceanographic parameters throughout the fjord was carried out. Measurements as well as simulations show that the seawater temperature in the fjord is generally higher than 1 °C with an upper limit of 10 °C. The simulations indicate that the area of interest is tidally dominated with higher current velocity which prominently flanks alongshore during ebb. Our findings indicate, based on oceanographic conditions of the area of study, that heat extraction from Onundarfjordur is theoretically feasible. The average seawater speed of 0.03 m/s in the fjord can gives heat power amounting to 120 kW/(m2K) when assuming natural convection through an in-situ heat exchanger. The results imply the possibility of large-scale harnessing of seawater in coastal Arctic and sub-Arctic regions, including e.g. Greenland, using heat pumps that can provide up to 80 °C hot water for space heating.

Modelling of single-stage refrigerating machine of provision chamber

The single-stage refrigerating machine model’s review has been made. The analysis of these models and the possibility of its application are given. The model of a single-stage refrigerating plant of the provision chamber is developed. The results of simulation of the seawater heat sink of the refrigeration unit in various operating conditions are presented.

Selection of cooling fluid for an organic Rankine cycle unit recovering heat on a container ship sailing in the Arctic region

As Arctic sea ice coverage declines it is expected that marine traffic could increase in this northern region due to shorter routes. Navigating in the Arctic offers opportunities and challenges for waste heat recovery systems (WHRS). Lower temperatures require larger heating power on board, hence a larger demand for waste heat usage, to cover services and maintaining on board spaces temperatures. However, a lower heat rejection temperature increases the WHRS thermal efficiency. The air temperature for the Arctic route selected is colder than that of the seawater, opening the opportunity of having air as coolant. This paper explores the use of two different coolants, air and seawater, for an organic Rankine cycle (ORC) unit using the available waste heat in the scavenge air system of a container ship navigating in Arctic Circle. Using a two-step single objective optimisation process, detailed models of air and seawater heat exchangers are evaluated as the WHRS condensers. The results suggest that an ORC unit using R1233zd(E) as its working fluid coupled with seawater as its coolant is the preferable option to reduce CO2 emissions. Using the ambient air as the coolant while a less effective option could be cheaper to install.

Study of a sea water heat exchanger using Computing Fluid Dynamics

In order to have a better visualization of the heat transfer that might occur in a tubular seawater heat exchanger, I have created a simulation using Ansysy Fluent program. The first stage of the simulation is the representation of the subject in the Geometry. The next step is the mesh in a finite number of cells. All settings and information defined in the first two phases are taken in the third (Setup), where are imposed boundary conditions (the input and output). The next step is the calculation (Solutions) where the problem is solved iteratively using one of the methods of calculation selected. The software can solve numerical equations of Navier-Stokes flow, continuity equation, energy conservation etc. that are available in the database of the program. The last part is especially designed for the analysis and interpretation of results (distribution of speeds, temperatures, pressures etc.). Due to the fact that many types of heat pump used as working fluid water, a mixture of water and glycol or Freon, I have required two ways of calculation: the first in which the working fluid is water and the second in where water is replaced by a solution consisting of 50% glycol and 50% water.

Seawater Desalination Pilot Plant: Optimal Design and Sizing of Solar Driven-Four Effect Evaporators Combined with Heat Integration Analysis

This paper puts forward the results and methodology used for thermal analysis, sizing and design of four effects pilot scale desalination unit combined with solar thermal energy and using falling film evaporators for a production capacity of 7m3/day. The modelling equations are given at steady-state conditions and are based on mass and heat balances equations, heat transfer equations, and thermodynamic and physical properties of each stream. MATLAB programming is used for the resolution of the developed algorithm. The impact of the important parameters, such as evaporator type, tube dimensions, heating medium and top brine temperatures on the performance ratio and heat transfer rate, has been studied. Besides, this work is completed by Pinch analysis to provide the optimal Heat Exchanger Network (HEN) taking into account three different configurations and the impact of the minimum temperature difference ∆Tmin. Results show that it is beneficial to use the horizontal falling film evaporators allowing high heat transfer coefficient values ranging between 3.18 and 3.32kW/m2/K. In addition, the optimal HEN enables a 62% reduction of thermal power needed to feed seawater heating. Also, in this study, several suggestions and criteria for evaporators and HEN design and optimization have also been dealt with.

Low GWP 냉매를 적용한 해수열 히트펌프의 성능해석

In this study, the seawater Heat Pump System using seawater with temperature of annual domestic conditions (0℃ to 25℃) is designed in order to compare its performance against the Heat Pump using unused heat of seawater. As a potential replacement for current refrigerants that exacerbate global warming and ozone delpetion, a Low GWP refrigerant’s performance is analyzed. The basic water to water Heat Pump system is chosen and three commercial refrigerants - R134a, R410a, R32 – are used to compare against new Low GWP refrigerant R1234ze. When seawater with temperature of 25℃ is used, the performance change showed maximal increase in COP, 38.3%. low GWP refrigerant R1234ze, showed great performance characteristics reach to 5.242 and Existing commercial refrigerant, R134a showed only less than 0.03 performance difference against R1234ze. The study confirms notable performance of R1234ze refrigerant through simulation as environmentally friendly refrigerant for domestic seawater Heat Pump.

Cleaner energy scenarios for building clusters in campus areas based on the Rational Exergy Management Model

Principles based on the quality of energy, namely exergy, can assist in attaining a more efficient and cleaner energy supply structure. This paper analyzes two building clusters in campus areas based on a stepwise approach with four steps according to the Rational Exergy Management Model. The clusters involve 8 buildings at the KTH Royal Institute of Technology and those in the Albano district that is a former industrial site and will become a joint campus area in Stockholm. The energy supply for the campus and urban vicinity includes a combined heat and power plant with district heating and cooling. In this context, the energy and exergy profiles of the building clusters are compared. The level of exergy match in the energy system is analyzed. Four scenarios are then devised, which involve energy savings and different shares of various supply options. These include a new biofuel unit, seawater heat pumps, large scale aquifer thermal energy storage, heat supply from solar collectors, and electricity and heat from photovoltaic thermal arrays. The present case and four scenarios are found to have exergy matches that range between 0.49 and 0.81. The scenarios indicate that savings of 16 GWh energy, 9.6 GWh exergy, and 2663 tonnes of carbon dioxide emissions are possible. The paper contributes to exergy based analyzes for campus areas and concludes with the prospect of using campus areas as pioneering case studies for advancing the transition to cleaner energy scenarios.

Design and Analysis of Heat Exchanger Using Sea Water Heat Source for Cooling

Purpose: The temperature in Seoul has risen 3 times more than the average global temperature increase for the past 100 years. Today, summer starts 15 days earlier than the early 20th century and is 32 days longer. This tendency causes rapid increase of cooling energy demand. Following this effect, seawater heat resources are to be used as an countermeasure for global warming. Incheon Port near the Western Sea has the lowest water temperature in the winter in South Korea in which it is suitable to use seawater cold heat resources. Method: The cold heat resource is gained from seawater when the water temperature is the lowest in the winter time and saved in a seasonal thermal storage. This can be used as cold heat resource in the summer time. A heat exchanger is essential to gain seawater cold energy. Due to this necessity, sea water heat resource heat exchangers are modeled by heat transfer equations and the fluid characteristics are analyzed. Also, a CFD (computational fluid dynamics) program is used to conduct simulation on the fluid characteristics of heat exchangers. The analyzed data of deducted from this process are comprehensively analyzed and discussed. Result: Regarding the performance of the heat exchanger, the heat exchanger was operated following the prediction within the range of heat transfer rate of minimum 3.3KW to maximum 33.6KW per device. In the temperature change analysis of the heat exchanger, fluid analysis by heat transfer equations almost corresponded to the temperature change by CFD simulation. Therefore, it is considered that the results of this study can be used as design data of heat exchangers.

Mathematical formulation and demonstration of a dynamic system-level ship thermal management tool

This paper presents the mathematical formulation and unique capability of a system-level ship thermal management tool, vemESRDC, developed to provide quick ship thermal responses in early design stages. The physical model combines principles of classical thermodynamics and heat transfer, along with appropriate empirical correlations to simplify the model and expedite the computations. As a result, the tool is capable of simulating dynamic thermal response of an entire ship, characterized by intricate thermal interactions within a complex ship structure, within an acceptable time frame. In this work, vemESRDC is demonstrated through three case studies in which transient thermal responses of an all-electric ship to different ship operation modes, weather conditions, and partial loss of cooling are investigated. The analysis examines particularly the following: (1) the required cooling capacities to maintain each ship component within its design limit; (2) equipment temperature variations with respect to partial cooling loss in battle mode; and (3) the assets of installing seawater heat exchangers to pre-cool deionized freshwater before chillers. For the notional all-electric ship conceived and assessed in this work, the results verify the capability of vemESRDC to capture dynamic thermal interactions between shipboard equipment and their respective surroundings and cooling systems, e.g., the tool provides practical insights into pulse load cooling strategy, and different solutions are obtained for distinct weather conditions. In addition to the case studies performed in this work, vemESRDC can be employed to conduct diverse studies based on which concrete ship thermal management strategies can be formulated in early design stages.

Error of Assembly Microcontroller Arduino Mega and ATmega in the Control of Temperature for Heating and Cooling System

Microcontroller Arduino Mega and ATmega is a computer chip that needed and developed to control system or process. Microcontroller Arduino Mega and ATmega can be used to temperature control systems [1][2][3], the room lighting control, security control, the hazard warning [4], scheduling, monitoring water flow and dams actuator door and etc. Most studies on the microcontroller is focused on the functional capability of a microcontroller to read or measure the object. In addition to aspects of good function, microcontroller must have a high sensitivity in order to avoid delay or in-accuracies in the sensor reading measured object such as temperature. Microcontrollers has some advantages and disadvantages of the process accuracy depends on the processor and the ability microcontroller. In this paper focuses on the measurement errors that occur on microcontroller Arduino Mega and ATmega 8535 with a temperature sensor LM 35 and hygrometer digitizes dt05 for the application process cooling and heating sea water controls. The volume of sea water is measured is 3 to 35 litters with a temperature set point 28°C of lower temperatures above 25°C and 31°C. The results show that the maximum error obtained by using microcontroller Arduino Mega is 1,32°C or 13,2 mV and ATmega 8535 is 0,2°C or 2 mV. Also the microcontroller Arduino Mega is more suitable for control temperature measurement in the process of heating and cooling sea water.

산질화 표면에서 액적의 증발열전달 특성

Abstract The present study aims to experimentally investigate the evaporative heat transfer characteristics of Oxi-nitriding SPCC sur-face. Moreover, the heat transfer coefficient was examined with respect to surface temperature during droplet evaporation. Infact, the nitriding surface showed significant enhancement for anticorrosion performance compared to bare SPCC surface butthe thermal resistance also increased due to the formation of compound layer. From the experimental results, the evaporativebehavior of sessile droplet on nitriding surface showed similar tendency with the bare surface. Total evaporation time ofsessile droplet on the nitriding surface was delayed less than 5%. The difference in heat transfer coefficient increased withthe surface temperature, and the maximum difference was estimated to be around 11% at 80 o C surface. Thus, this nitridingsurface treatment method could be useful for seawater heat exchanger industries. 기호설명 ρ 액체의 밀도, kg/m 3 θ 동적 접촉각, degθ ECA 평형 접촉각, degA 액적의 접촉면적, m

Model for seawater fouling and effects of temperature, flow velocity and surface free energy on seawater fouling

A kinetic model was proposed to predict the seawater fouling process in the seawater heat exchangers. The new model adopted an expression combining depositional and removal behaviors for seawater fouling based on the Kern–Seaton model. The present model parameters include the integrated kinetic rate of deposition (kd) and the integrated kinetic rate of removal (kr), which have clear physical significance. A seawater-fouling monitoring device was established to validate the model. The experimental data were well fitted to the model, and the parameters were obtained in different conditions. SEM and EDX analyses were performed after the experiments, and the results show that the main components of seawater fouling are magnesium hydroxide and aluminum hydroxide. The effects of surface temperature, flow velocity and surface free energy were assessed by the model and the experimental data. The results indicate that the seawater fouling becomes aggravated as the surface temperature increased in a certain range, and the seawater fouling resistance reduced as the flow velocity of seawater increased. Furthermore, the effect of the surface free energy of metals was analyzed, showing that the lower surface free energy mitigates the seawater fouling accumulation.

東北地方太平洋沖地震における福島第一原子力発電所の地震応答に関する分析について

The Fukushima Daiichi (1F) accident in unit 1 to 4 was likely to be caused by the tsunami induced loss of emergency power and seawater heat sink that is consistently elucidated based on the performance of the plants until the tsunami hit after the seismic SCRAM by Great East Japan Earthquake. However it is fact that the actual damages of components have difficulty to be completely inspected under high radioactivity, and to make clear distinction between tsunami induced damage and seismic induced damage. This paper will support above conclusion based on the result of seismic response analysis for safety related components of each plant, the result of the plant walk down in the similar unit in the same station, and also the result of analysis for the observed seismic records from the perspective of generalization of the damage possibility of nuclear components designed by Japanese seismic standards. The result of seismic response analysis using observed seismic motion shows all safety related components fulfill the seismic criteria and seem to maintain structural integrity. Also we could find few seismic induced damage in the walk down for unit 5 of 1F that shows similar result would be expected in unit 1 to 4. It is concluded that the design method using seismic static load contributes additional robustness of nuclear components, even the lower seismic class components, and that the damage by the earthquake should be quite limited based on the analysis of observed seismic motions.

Performance evaluation of sea water heat exchanger installed in the submerged bottom-structure of floating architecture

Floating architecture is a type of building that is geographically located on a sea or a river. It floats under the influence of buoyancy, and does not have an engine for moving it. Korea is a peninsula surrounded by sea except on the north side, so floating architectures have been mainly focused on two points: solving the issue of small territory and providing various leisure & cultural spaces. Floating architectures are expected to save energy effectively, if they use sea water heat, which is known to be clean energy with infinite reserves. To use sea water heat as the heat source and/or heat sink, this study proposes a model in which a sea water heat exchanger is embedded in the concrete structure in the lower part of the floating architecture that is submerged under the sea. Based on the results of performance evaluations of the sea water heat exchanger using CFD (computational fluid dynamics) analysis and mock-up experiments under various conditions, it is found out that the temperature difference between the inlet and outlet of the heat exchanger is in the range of 3.06~9.57 °C, and that the quantity of heat transfer measured is in the range of 3,812~7,180 W. The CFD evaluation results shows a difference of 5% with respect to the results of mock-up experiment.

Performance evaluation of sea water heat exchanger installed in concrete structure of pontoon

At the viewpoint of energy saving and the increasing needs of seaside leisure activities in Korea, floating architecture is recently to be focused on, but it is in the early stage of technological development. Considering the features of floating structures that can float and move on sea and/or river, this study proposes Single-U type Sea Water Heat Exchanger (SWHEx) and Spring type SWHEx that installed into or outside the submerged concrete structure of pontoon, respectively. As the results from CFD and mock-up tests, it is found out that the mean temperature difference is 3°C between the inlet and outlet temperatures of working fluid which flows inside the Single-U type SWHEx and 1.5°C for Spring type SWHEx. Also it is clear that the heat exchange performance of Single-U type SWHEx is better than Spring type.

Sea water heat exchanger washing with CO_2 microbubble

Sea water heat exchanger washing with CO_2 microbubble