High Pressure Generation Research Articles

Cuticle expansion during feeding in the tick Amblyomma hebraeum (Acari: Ixodidae): The role of hydrostatic pressure

Female Amblyomma hebraeum ticks (Acari: Ixodidae) increase their weight ∼10-fold during a ‘slow phase of engorgement’ (7–9days), and a further 10-fold during the ‘rapid phase’ (12–24h). During the rapid phase, the cuticle thins by half, with a plastic (permanent) deformation of greater than 40% in two orthogonal directions. A stress of 2.5MPa or higher is required to achieve this degree of deformation (Flynn and Kaufman, 2015). Using a dimensional analysis of the tick body and applying the Laplace equation, we calculated that the tick must achieve high internal hydrostatic pressures in order to engorge fully: greater than 55kPa at a fed:unfed mass ratio of ∼20:1, when cuticle thinning commences (Flynn and Kaufman, 2011). In this study we used a telemetric pressure transducer system to measure the internal hydrostatic pressure of ticks during feeding. Sustained periods of irregular high frequency (>20Hz) pulsatile bursts of high pressure (>55kPa) were observed in two ticks: they had been cannulated just prior to the rapid phase of engorgement, and given access to a host rabbit for completion of the feeding cycle. The pattern of periods of high pressure generation varied over the feeding cycle and between the two specimens. We believe that these pressures exceed those reported so far for any other animal.

Exergy analysis of a combined vapor power cycle and boiler flue gas driven double effect water–LiBr absorption refrigeration system

A combined vapor power cycle (PC) and double effect water–LiBr absorption refrigeration system (ARS) is proposed in this study. The boiler leaving flue gas of the PC is the heat source for the high pressure generator (HPG) of the double effect ARS. Exergy analysis of the proposed system is performed to show the performance variation of both the topping PC and the bottoming ARS with changing HPG temperature from 120°C to 150°C. Further the performance of double effect ARS integrated combined power and cooling system is compared with a similar system integrated with a single effect ARS. HPG temperature of the double effect ARS and generator temperature of the single effect ARS are considered as 120°C and 80°C respectively. Results show that the power and efficiency of the topping PC decreases with HPG temperature due to reduction in steam generation rate in the boiler. COP and exergy efficiency of the double effect ARS also reduces with increasing HPG temperature. The irreversible losses in the PC components decrease while the total irreversibility of the combined power and cooling system increases with HPG temperature due to increase in exergy loss with the HPG leaving flue gas and irreversibility of the ARS components. PC performance does not vary much due to replacement of the double effect ARS with the single effect ARS, however higher COP and exergy efficiency of the double effect system are achieved with much lower irreversible losses in the HPG and ARS condenser of the double effect system.

The health impacts of dietary sodium and a low-salt diet

High salt intake is now endemic worldwide. It contributes to the generation and maintenance of high blood pressure, which is now the biggest risk factor for global disease. There is now compelling evidence to support salt reduction in hypertensives and a substantial body of evidence to support salt reduction in the general population to reduce risk of death from cardiovascular disease. In specific diseases such as heart failure and chronic kidney disease, guidelines support the World Health Organization target for reduced salt intake at 5g daily. Achieving a diet that is lower in salt has challenges, but is more likely to be achieved through salt reduction strategies particularly focused on processed food and through educational programs. To be effective, these interventions require collaboration between industry, health agencies and governments.

An investigation of heat recovery of submarine diesel engines for combined cooling, heating and power systems

High temperature and mass flow rate of the exhaust gases of submarine diesel engines provide an appropriate potential for their thermal recovery. The current study introduces a combined cooling, heating and power system for thermal recovery of submarine diesel engines. The cooling system is composed of a mixed effect absorption chiller with two high and low pressure generators. The exhaust of the diesel engine is used in the high pressure generator, and the low pressure generator was divided into two parts. The required heat for the first and second compartments is supplied by the cooling water of the engine and condensation of the vapor generated in the high pressure generator, respectively. The power generation system is a Rankine cycle with an organic working fluid, which is considered a normal thermal system to supply hot water. The whole system is encoded based on mass stability, condensation and energy equations. The obtained findings showed that the maximum heat recovery for the power cycle occurs in exhaust gas mass ratio of 0.23–0.29 and working fluid mass flow rate of 0.45–0.57kg/s. Further, for each specific mass ratio of exhaust gas, only a certain range of working fluid mass flow rate is used. In the refrigerant mass flow rate of 0.6kg/s and exhaust gas mass ratio of 0.27, the power output of the cycle is 53kW, which can also be achieved by simultaneous increase of refrigerant mass flow rate and exhaust gas mass ratio in a certain range of higher powers. In the next section, the overall distribution diagram of output water temperature of the thermal system is obtained according to the exhaust gas mass ratio in various mass flow rates, which can increase the potential of designing and controlling the thermal system. The effect of parameters of this system on output water temperature was also analyzed. Finally, the performance of mixed effect absorption chiller was examined and the findings indicated that in the exhaust gas mass ratio of 0.375, the system has a coefficient of performance equal to 0.94. The output water temperature of evaporator in this state is 3.64°C and the cooling system power is 176.87kW.

What causes large submarine landslides on low gradient (<2°) continental slopes with slow (∼0.15 m/kyr) sediment accumulation?

AbstractSubmarine landslides can cause damaging tsunamis, the height of which scales up with the volume of the displaced mass. The largest underwater landslides are far bigger than any landslides on land, and these submarine megaslides tend to occur on open continental slopes with remarkably low gradients of less than 2°. For geohazard assessments it is essential to understand what preconditions and triggers slope failure on such low gradients. Previous work has suggested that generation of high excess pore pressure due to rapid sediment deposition plays a key role in such failures. However, submarine slope failure also occurs where sedimentation rates are low (<0.15 m/kyr), such as off northwest Africa. We use a fully coupled stress and fluid flow finite element model to test whether such low sedimentation rates can generate sufficient excess pore pressures to cause failure of a 2° slope. The sensitivity of overpressure generation and slope stability is assessed with respect to different sedimentation rates and patterns, sediment consolidation properties, and stratigraphic layer configurations. The simulations show that, in general, it is difficult to generate significant excess pore pressure if sediment accumulation is slow and the only pressure source. However, we identify a sediment compression behavior that can lead to submarine landslides in locations worldwide. Our results imply that compressibility is an important factor for the stability of low gradient continental slopes.

Energy and exergy analysis of a double effect absorption refrigeration system based on different heat sources

Absorption refrigeration systems are environmental friendly since they can utilize industrial waste heat and/or solar energy. In terms of heat source of the systems, researchers prefer one type heat source usually such as hot water or steam. Some studies can be free from environment. In this study, energy and exergy analysis is performed on a double effect series flow absorption refrigeration system with water/lithium bromide as working fluid pair. The refrigeration system runs on various heat sources such as hot water, hot air and steam via High Pressure Generator (HPG) because of hot water/steam and hot air are the most common available heat source for absorption applications but the first law of thermodynamics may not be sufficient analyze the absorption refrigeration system and to show the difference of utilize for different type heat source. On the other hand operation temperatures of the overall system and its components have a major effect on their performance and functionality. In this regard, a parametric study conducted here to investigate this effect on heat capacity and exergy destruction of the HPG, coefficient of performance (COP) of the system, and mass flow rate of heat sources. Also, a comparative analysis is carried out on several heat sources (e.g. hot water, hot air and steam) in terms of exergy destruction and mass flow rate of heat source. From the analyses it is observed that exergy destruction of the HPG increases at higher temperature of the heat sources, condenser and absorber, and lower temperature of the HPG, LPG and evaporator. This destruction is maximized when hot air heat source is used and minimized with utilizing hot water heat source.

Generation of high pressures during the shock wave–flame interaction

The interaction of a flame with shock waves generated by external sources is investigated using numerical simulation methods. It is shown that the effect of shock waves with various intensities on the combustion front in a closed volume (channel) leads to qualitatively different scenarios of the further development of combustion. Situations when the process development results in the generation of sufficiently high pressures, which exceed many times the pressures in the incident shock wave, are singled out individually. In this case, maximum high pressures occur as a result of thedeflagration-to-detonation transition (DDT). The detailed analysis of the dynamics of DDT, which is developed by various scenarios, showed that the most general mechanism of the transition is the localization of the pressure peak in the reaction zone. The well-known scenario of transition to detonation by the mechanism of the formation of “hot spots” ahead of the flame is observed in a relatively narrow range of initial conditions. The development of detonation in such a mode leads to generation of still higher pressures, which exceed the pressure in DDT, and the probability of the realization of this scenario rises with the decrease of mixtures reactivity.

High-Pressure Oxy-Firing (HiPrOx) of Fuels with Water for the Purpose of Direct Contact Steam Generation

High-pressure oxy-fired direct contact steam generation (HiPrOx/DCSG) can be achieved by the oxy-combustion of fuels in the presence of water. This process is capable of producing flue gas streams containing approximately 90% steam with a balance of primarily CO2. The product flue gas is suitable for processes where the purity of the steam is less important, such as the steam-assisted gravity drainage process used for in situ production of bitumen within the Canadian oil sands. This study had three primary objectives: (1) To show that high-moisture HiPrOx/DCSG can be achieved with hydrocarbon fuels. For this purpose, n-butanol was used because of its high volatility and ease of handling. (2) To see if this technology could be applied to fuels with lower volatilities. This was studied by attempting to combust a graphite–water slurry as well as mixtures of graphite–water slurry and butanol. (3) To determine the effects of different fuel mixtures, oxygen-to-fuel ratios, and water inputs on process stability ...

Appropriate heat load ratio of generator for different types of air cooled lithium bromide–water double effect absorption chiller

The lower coefficient of performance and higher risk of crystallization in the higher surrounding temperature is the primary disadvantage of air cooled lithium bromide–water double effect absorption chiller. Since the coefficient of performance and risk of crystallization strongly depend on the heat load ratio of generator, the appropriate heat load ratio of generator can improve the performance as the surrounding temperature is higher. The paper mainly deals with the appropriate heat load ratio of generator of air cooled lithium bromide–water double effect absorption chiller. Four type systems named series, pre-parallel, rear parallel and reverse parallel flow configuration were considered. The corresponding parametric model was developed to analyze the comprehensive effect of heat load ratio of generator on the coefficient of performance and risk of crystallization. It was found that the coefficient of performance goes up linearly with the decrease of heat load ratio of generator. Simultaneously, the risk of crystallization also rises slowly at first but increases fast finally. Consequently, the appropriate heat load ratio of generator for the series and pre-parallel flow type systems is suggested to be 0.02 greater than the minimum heat load ratio of generator and that for the rear parallel and reverse parallel flow chillers should be 0.01 higher than the minimum heat load ratio of generator. Besides, the changes of minimum heat load ratio of generator for different type systems with the working condition were analyzed and compared. It was found that the minimum heat load ratio of generator goes up with the increase of temperature of high pressure generator as well as surrounding temperature and it goes down with the rise of evaporator temperature and effectiveness of high temperature heat exchanger. The dependence of minimum heat load ratio of generator for the series and rear parallel flow system on the effectiveness of low temperature heat exchanger is weak. While the minimum heat load ratio of generator of pre-parallel and reverse parallel flow chiller rises with the increase of effectiveness of low temperature heat exchanger. The minimum heat load ratio of generator of reverse parallel flow configuration is independent upon the distribution ratio. The minimum heat load ratio of generator of pre-parallel flow system goes up fast with the rise of distribution ratio when the distribution ratio exceeds to 0.55. But the minimum heat load ratio of generator of rear parallel flow configuration just rises slightly with the increase of distribution ratio as the distribution is greater than 0.5. The paper is helpful to the development and performance improvement of air cooled lithium bromide–water double effect absorption chiller.

Thermodynamics of the Sodium–Iron–Phosphate–Water System Under Hydrothermal Conditions: The Gibbs Energy of Formation of Sodium Iron(III) Hydroxy Phosphate, Na3Fe(PO4)2·(Na4/3H2/3O), from Solubility Measurements in Equilibrium with Hematite at 498–598 K

Sodium iron hydroxy phosphate, Na3FeIII(PO4)2·(Na4/3H2/3O), “SIHP”, is an important iron(III) corrosion product in high-pressure steam generators operating under phosphate pH control. Experimental solubilities of sodium iron hydroxy phosphate, in equilibrium with a large excess of hematite, have been determined in stirred Hastelloy and Zircalloy pressure vessels at temperatures from 498 to 598 K. Equilibrium constants have been determined for the solubility reaction: 3Fe2O3(s) + 26Na+(aq) + 12\( {\text{HPO}}_{4}^{{2 - }} ({\text{aq}})\) + 2OH−(aq) ⇌ 6Na3Fe(PO4)2·(Na4/3H2/3O)(s) + 5H2O. The experimental apparent Gibbs energy of formation of Na3Fe(PO4)2·(Na4/3H2/3O)(s) at 523 K, ∆a G 523 ° (SIHP, s) = –3641.21 ± 5.86 kJ·mol−1, has been combined with previously reported molar heat capacities and the enthalpy of formation at 298.15 K to calculate the Gibbs energy of formation under standard conditions ∆f G 298 ° (SIHP, s) = −3544.77 ± 5.77 kJ·mol−1. A thermodynamic model for the solubility of SIHP over the experimental temperature range is reported.

First law analysis of a novel double effect air-cooled non-adiabatic ammonia/salt absorption refrigeration cycle

This paper thermodynamically analyzes an air-cooled type double effect absorption refrigeration system using ammonia/lithium nitrate and ammonia/sodium thiocyanate solutions as working pairs and driven by high temperature heat source such as waste heat energy, innovatively, an air-cooled type non-adiabatic absorber is implemented in the system to improve the cycle performance. Comparing to the single effect absorption refrigeration system, the double effect system is designed not only to directly and efficiently utilize high temperature waste heat energy for cycle performance improvement, but also to greatly extend the application occasion to high ambient temperature condition. Parametric analysis of the present system show that COP of the double effect system is 30–60% higher than the single effect system under air cooling working condition and the high pressure generating temperature of the double effect system can be extended to as high as 220°C. Influences of high pressure generator temperature, low pressure generator temperature, absorber outlet solution temperature as well as other system working parameters on cycle performance are numerically simulated and parametric optimization is provided in the present model. Cycle performance comparison of NH3/LiNO3 system with NH3/NaSCN system has been carried out. According to the simulation results, COP of NH3/NaSCN system is found to be 10–15% higher than that of NH3/LiNO3 system in evaporating temperature range of -10°C<Te<5°C. However in low evaporating temperature conditions, Te⩽-10°C, NH3/LiNO3 systems are found to be more competitive than that of NH3/NaSCN system. The main concern of the present study is that implementation of non-adiabatic absorbers in air-cooled type double effect ammonia/salt absorption refrigeration systems is essential, and only under non-adiabatic absorption conditions can the double effect ammonia/salt system realize miniaturization.

High-pressure solid hydrogen target for muon catalyzed fusion

We have developed a high-pressure solid hydrogen target for muon-catalyzed fusion to study temperature dependence of fusion cycling rates and muon loss probabilities in solid hydrogen at higher temperature than the melting point. The constructed target is a simple standalone-system consisting of a solid hydrogen target, a high-pressure generator, an isolation valve and a buffer tank. The solid hydrogen target and high-pressure generator are independently cooled down and temperature-controlled by closed-cycle helium-refrigerators. In the performance test, the solid D2 target was formed successfully at 33.6 K with applying D2 gas pressure at 79 MPa.

High-pressure generation using double stage micro-paired diamond anvils shaped by focused ion beam.

Micron-sized diamond anvils with a 3 μm culet were successfully processed using a focused ion beam (FIB) system and the generation of high pressures was confirmed using the double stage diamond anvil cell technique. The difficulty of aligning two second-stage micro-anvils was solved via the paired micro-anvil method. Micro-manufacturing using a FIB system enables us to control anvil shape, process any materials, including nano-polycrystalline diamond and single crystal diamond, and assemble the sample exactly in a very small space between the second-stage anvils. This method is highly reproducible. High pressures over 300 GPa were achieved, and the pressure distribution around the micro-anvil culet was evaluated by using a well-focused synchrotron micro-X-ray beam.

Reduced graphene oxide coated polydimethylsiloxane film as an optoacoustic transmitter for high pressure and high frequency ultrasound generation

We demonstrate that reduced graphene oxide coated thin polydimethylsiloxane (rGO-PDMS) film is an effective optoacoustic transmitter for generating high pressure and high frequency ultrasound, previously unattainable using other techniques. Various coatings such as rGO-Aluminum, rGO-PDMS, PDMS-alone, and aluminum-alone are deposited on the glass substrate. Under a pulsed laser excitation, rGO-PDMS transmitter generated remarkable optoacoustic pressure which is 76 times stronger than Al-alone, 5 times stronger than PDMS-alone, and 2.2 times stronger than rGO-Al transmitter. The observed signal enhancement persisted over a broadband frequency range, and thus by optimizing the thermoelasticity of PDMS film and the thermal conductivity of rGO, a promising optoacoustic wave generation was confirmed for laser-induced ultrasound applications.

The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output.

Giraffes--the tallest extant animals on Earth--are renowned for their high central arterial blood pressure, which is necessary to secure brain perfusion. Arterial pressure may exceed 300 mmHg and has historically been attributed to an exceptionally large heart. Recently, this has been refuted by several studies demonstrating that the mass of giraffe heart is similar to that of other mammals when expressed relative to body mass. It thus remains unexplained how the normal-sized giraffe heart generates such massive arterial pressures. We hypothesized that giraffe hearts have a small intraventricular cavity and a relatively thick ventricular wall, allowing for generation of high arterial pressures at normal left ventricular wall tension. In nine anaesthetized giraffes (495±38 kg), we determined in vivo ventricular dimensions using echocardiography along with intraventricular and aortic pressures to calculate left ventricular wall stress. Cardiac output was also determined by inert gas rebreathing to provide an additional and independent estimate of stroke volume. Echocardiography and inert gas-rebreathing yielded similar cardiac outputs of 16.1±2.5 and 16.4±1.4 l min(-1), respectively. End-diastolic and end-systolic volumes were 521±61 ml and 228±42 ml, respectively, yielding an ejection fraction of 56±4% and a stroke volume of 0.59 ml kg(-1). Left ventricular circumferential wall stress was 7.83±1.76 kPa. We conclude that, relative to body mass, a small left ventricular cavity and a low stroke volume characterizes the giraffe heart. The adaptations result in typical mammalian left ventricular wall tensions, but produce a lowered cardiac output.

Dynamic study of steam generation from low-grade waste heat in a zeolite–water adsorption heat pump

A novel zeolite–water adsorption heat pump system based on a direct-contact heat exchange method to generate steam from low-grade waste gas and water has been proposed and examined experimentally. Superheated steam (200 °C, 0.1 MPa) is generated from hot water (70–80 °C) and dry air (100–130 °C). A dynamic model for steam generation process is developed to describe local mass and heat transfer. This model features a three-phase calculation and a moving water–gas interface. The calculations are carried out in the zeolite–water and zeolite–gas regions. Model outputs are compared with experimental results for validation. The thermal response inside the reactor and mass of steam generated is well predicted. Numerical results show that preheat process with low-temperature steam is an effective method to achieve local equilibrium quickly, thus generation process is enhanced by prolonging the time and increasing mass of the generated steam. Besides, high-pressure steam generation up to 0.5 MPa is possible from the validated dynamic model. Future work could be emphasized on enhancing high-pressure steam generation with preheat process or mass recovery operation.

Investigation of a mixed effect absorption chiller powered by jacket water and exhaust gas waste heat of internal combustion engine

CCHP (combined cooling heating and power) system based on ICE (internal combustion engine) has been widely used. A key issue is to efficiently recover the jacket water and exhaust gas waste heat for refrigeration. In this work, a mixed effect absorption chiller (AC), which couples single effect and double effect processes together, is investigated to recover these two kinds of waste heat simultaneously. The high pressure generator is powered by exhaust gas while one low pressure generator is powered by jacket water waste heat. Thermodynamic characteristics and off-design performance are simulated. Considering thermodynamic constraints, the start point temperature in low pressure generator should be 77°Cor lower. For a 16 kW ICE, the cooling output can reach 34.4 kW with COP of 0.96 and exergy efficiency of 0.186. Comparing with double effect or single effect AC, it can make a better use of different waste heat in CCHP system.

Simulation of a Double-Effect Solar Absorption System for Traditional House in Yemen

During the last few years, the awareness of the pollution and the global warming has dramatically increased which encourage the researchers around the world to find an alternative source of energy. One of the most efficient sources of energy is the solar energy especially for cooling and heating applications. This paper, described the simulation of a double-effect solar absorption system in Yemen using water lithium bromide solution as a working fluid. The system will be applied to a typical traditional house in Yemen. The performance of the system will be analyzed based on different high pressure generator temperature for the yearly solar radiation data. At higher pressure generator temperature, the results show a higher coefficient of performance of the system. This simulation also estimate high pressure generator heat transfer required to operate the system. As a result, the size of solar collector area and the cost of such system will be calculated.

High-pressure layer generation in a compression corner at a supersonic flow velocity

The results of an experimental and numerical investigation of a three-dimensional laminar separated flow in a compression corner are presented. The freestream Mach number M∞ =6. The model under study is a plate with a sharp leading edge on which a step with a 30° inclination angle is mounted. The model width is equal to the plate length from the leading edge to the step. A thin high-pressure layer located above the boundary layer, downstream of the reattachment line is shown to exist.

The compressibility and shear characteristics of soils associated with landslides in geologically different localities—case examples from Nigeria

Field and Shuttle Radar Topographic Mission data were used to create Digital Elevation Model and geologic maps to study the roles of geology, discontinuities, elevation, steep slopes, deep valleys, and drainage patterns on the frequent occurrence of long-travel landslides along the Nigeria–Cameroon border. The undrained shear behaviors of sandy specimens from two localities with different mode and magnitude of landslides were analyzed at different stress levels and related directly to their compressibility and permeability characteristics. The weathered granitic-sandy specimens from Kwande debris avalanche showed significant change in bulk permeability and sample height, and exhibited the greatest evidence of grain crushing. This behavior correlates well with their shear response which manifested in considerable increase in excess pore pressure and drastic reduction of shear resistance. Due to grain crushing, finer grains that lowered permeability were formed at the shear zone. It is likely that the decrease in permeability facilitated the generation of high excess pore pressures leading to significant reduction of shear resistance to low values at steady state. Contrastingly, the reduction in sample height and permeability of Iva valley sands was not as significant, which also correlates with the generation of low excess pore pressure and higher steady state strengths; conditions that may be responsible for the predominance of short-travel slides in the area. The behavior of silica sands, however, which suffered higher grain crushing and reduction in sample height and permeability, appeared closer to that of the samples from the avalanche site.