Recovery Device Research Articles

Analysis of OWC impulse turbine flow characteristics considering the blade tip clearance

Abstract Oscillating water column (OWC) ocean wave energy recovery device is a popular technology in current wave energy research, which possesses the advantages of a sturdy structure and low-maintenance requirements. The device recovers energy by unidirectional rotation in the reciprocating airflow generated by an impulse turbine. Its operational performance depends on the flow efficiency of the core component, the air turbine. In this paper, a prototype impulse turbine with blades tip clearance of 1 mm was considered, and the SST k-ω turbulence model is used to calculate the operating performance of the air turbine at different operating points. The calculation result shows that the efficiency of the turbine under the optimal operating conditions is about 51.41%. When the flow coefficient is less than 0.8, the primary focus of energy loss in the rotor occurs at the blade tip. The low flow rate leads to a high inlet angle causing fluid friction. In these small flow conditions, the pressure drop at the leaf top gap is cantered on the inlet, and the speed in the gap flow field is significantly reduced. When the flow coefficient is greater than 1.4, the concentration of energy loss in the rotor primarily occurs within the flow channel, where the high-velocity air causing a local high-speed zone.

Energy loss analysis of a double-suction centrifugal pump using in pump mode and turbine mode

As an economical energy recovery device, pump as turbine (PAT) is widely used in micro-hydropower stations and the chemical industry. The inlet and outlet pipelines connected to the double-suction pump are on the same horizontal line. As the pipeline layout is very convenient, in some chemical industries, the way of residual pressure energy utilization is increasing using the double-suction pump as a turbine. Based on numerical simulation, experimental verification, and entropy generation theory, the energy loss rule of each flow component in the pump mode and turbine mode under different flow rates is compared and analyzed. The results show that when the double-suction pump is used as a turbine, the flow rate at the best efficiency point (BEP) in the turbine mode shifts to a large flow rate by 30.89% and the BEP efficiency decreases by 1.30%. In the pump mode and turbine mode, the main energy loss component is the impeller, and the turbulent entropy generation power and the wall entropy generation power are the main sources of energy loss. The energy loss in the suction chamber and impeller increases sharply, and the energy loss is primarily enhanced in the blade trailing edge and the tongue near due to the unsteady flow in the turbine mode. Due to the complex structure, the spiral suction chamber is not suitable for the flow direction of the fluid flow out of the impeller, and the flow state inside the impeller is negatively affected by the suction chamber in the turbine mode. This paper provides a theoretical basis for the design and application of double-suction centrifugal PAT.

Scaling laws for optimized power-law fluid flow in self-similar tree-like branching networks

The power-law fluid flow in tree-like self-similar branching networks is prevalent throughout the natural world and also finds numerous applications in technology such as oil recovery and microfluidic devices. We investigate analysis of optimal power-law fluid flow conditions and the optimal structures within tree-like branching networks, focusing on maximizing flow conductance under the constraint of the network tube’s volume and the surface area. The study considered fully developed laminar power-law fluid flow regimes without considering any losses in the network system. A key observation was the sensitivity of the dimensionless effective flow conductance to the network’s geometrical parameters. We found that the maximum flow conductance occurs when a dimensionless radius ratio β∗ satisfies the equation β∗=N−1/3 and β∗=N−(n+1)/(3n+2) under constrained tube-volume and surface-area, respectively. Here, N represents the bifurcation number of branches splitting at each junction, and n is the fluid power-law index. We further find that this optimal condition occurs when pressure drops are equipartition across each branching level. We validated our results with various experimental results and theories under limiting conditions. Further, Hess–Murray’s law is justified and extended for the shear-thinning and shear-thickening fluid flows for an arbitrary number of branches N. Further, in this study, we also derive the relationships between the geometrical and flow characteristics of the parent and daughter tubes as well as the generalized scaling laws at the optimal conditions for the other essential parameters such as tube-wall stresses, length ratios, mean velocities, tube-volume, and surface-area of the tube distributing within the networks. We find that the fluid power-law index n does not influence the constrained tube-volume scaling at the optimal conditions; however, the scaling laws vary with n under the constrained tube’s surface area. These findings offer valuable design principles for developing efficient transport and flow systems.

Thermodynamic analysis of rotary pressure exchanger and ejectors for CO2 refrigeration system

Natural refrigerant CO2 has become a viable choice for refrigeration units for land-based and offshore applications due to its environment-friendly nature and compactness. The CO2 transcritical cycle allows operating in colder climates and in elevated ambient temperature conditions and with significant heat recovery. However, the energy efficiency of the system suffers at higher heat rejection conditions mainly due to expansion losses. This work theoretically investigates and proposes the implementation of a new expansion work recovery device, a pressure exchanger (CO2-PX), for the transcritical CO2 cycle. The numerical models are developed in the Engineering Equation solver (EES) to compare the performance of CO2-PX configuration with standard booster-, parallel-, and ejector- configurations for various conditions. The analysis is carried out for the evaporation temperature of 0 ℃ and the gas cooler outlet temperature of 33 ℃ to 37 ℃. The results indicate that the coefficient of performance (COP) is improved by 17.7–23.5%, 16.3–20.3%, and 2.4–5.5% to the standard booster, parallel and ejector configurations, respectively, at the investigated conditions.

Energy and Exergy Analysis of an Ejector Expansion Transcritical Carbon Dioxide Air Conditioning System

A carbon dioxide based transcritical air conditioning system integrated with an ejector is thermodynamically modeled and the system is simulated for different ambient conditions. Throughout the analysis, the isentropic efficiency of motive nozzle, suction nozzle and diffuser is assumed as 85% while the mixing takes place at constant pressure. A step-by-step iterative procedure is adopted to obtain the pressure lift and entrainment ratio. The present thermodynamic model is validated with the experimental results available in the open literature. Results were then compared to a conventional transcritical carbon dioxide system working between the same operating conditions. Results show a significant improvement of about 21% and more in system performance compared to a conventional system working under the same operating conditions. To justify the application of an ejector as an expansion work recovery device and to identify the component level exergy destruction rate, a comprehensive exergy analysis is implemented and the results show 20% reduction in total exergy destruction rate of the system, with an ejector.

(152) - Explantation of Durable Ventricular Assist Device for Myocardial Functional Recovery in Children: A Report from The Action Registry

(152) - Explantation of Durable Ventricular Assist Device for Myocardial Functional Recovery in Children: A Report from The Action Registry

Analysis of the Possibilities of Energy Recovery from Gravity Flows in Pipelines in a Copper Ore Enrichment Plant

Considering the need to reduce climate change and energy costs, the possibilities of energy recovery have been sought for many years, even if this should involve significant complexity of the technological process. Attempts to recover energy from a flowing medium containing a large amount of a solid phase are rather rare. This is mainly due to unfavorable erosion and sludge phenomena. The aim of this work is to analyze the possibility of recovering energy from gravity flows in the pipelines of a copper ore enrichment plant. The analysis will be carried out for a system operating in a plant in Poland. An energy recovery device will be designed taking into account the flow of a two-phase medium. For this purpose, flow calculations will be performed. The calculation results obtained for the two-phase flow will be verified based on the experimental results presented in the literature. The simulations will make it possible to determine the power of the designed device.

Investigation on the operating capacity expansion through parallel schemes of reciprocating-switcher energy recovery device for desalination: Simulation, verification and parameterization

Parallel operation is a significant and feasible method to compensate the insufficient capacity of single reciprocating-switcher energy recovery device (RS-ERD) in membrane desalination system. To grasp the operating characteristics in capacity expansion, three parallel schemes of RS-ERD, single-operation scheme, two-parallel scheme and three-parallel scheme, are investigated through the numerical simulation, experimental verification and theoretical parameterization. Results indicate that, the two-parallel scheme and three-parallel scheme achieve the flowrate continuity of low-pressure seawater and the flowrate fluctuation amplitudes in parallel RS-ERDs decrease by 50 % and 83 % respectively when compared with single-operation scheme. Parallel operation schemes also broaden the flowrate range with high efficiency for RS-ERD. To ensure the 95 % energy recovery efficiency, two-parallel and three-parallel schemes expand the maximum flowrates to 140 m3/h and 210 m3/h in contrast with the 70 m3/h of single-operation scheme. In addition, the two-parallel and three-parallel schemes of RS-ERD realize the much lower specific energy consumption (SEC) of 2.11 kWh/m3 and 2.09 kWh/m3 than the 2.23 kWh/m3 in single-operation scheme which contributes to the operating costs savings about 63,830 CNY and 75,778 CNY in one year. This research provides a new perspective in capacity expansion through the parallel operation of energy recovery devices.

Thermoelectric, mechanical, and pressure sustained half-metallic properties of BaInO3 perovskite for spintronics applications: DFT computation

Oxide perovskites continue to promote research interest because of their concurrent use in spintronic and thermoelectric applications. The electronic, magnetic, and thermoelectric properties of new half-metallic BaInO3 perovskite are investigated using the density functional theory. The structural and thermodynamic stability of the proposed perovskite is provided by the tolerance factor, octahedral factor, formation energy, and phonon dispersion curves. The structural relaxation curves reveal that the ground state is ferromagnetic. The generalized gradient approximation and mBJ band structure plots show that the half-metallicity exclusively results from the strong exchange splitting of 2p-bands at the Fermi level. Compared with PBE, mBJ depicts highly localized magnetic moments around oxygen along with enhanced half-metallic gaps and band gaps in the spin-up channel. Under a compressive strain, the system undergoes a magnetic phase transition from half-metallic ferromagnet to non-magnetic metal at 30 GPa. The elastic stability at the studied pressure range has been verified from Blackman’s and Every’s diagrams. The material remains ductile and exhibits moderate elastic anisotropy in the studied pressure range. The quasi-harmonic Debye model is employed to study the temperature and pressure effects of thermodynamic parameters. The computed transport properties including the Seebeck coefficient and spin-Seebeck coefficient predict reasonable thermoelectric performance in generating thermally induced spin-polarized current and spin current, respectively. Such a detailed study of this material could open prospects in spintronic as well as waste energy recovery devices.

Research on the Influence of Lateral Force and Pressure Fluctuation on the Stability of a Rotary Energy Recovery Device in the Desalination System

The rotary energy recovery device (RERD) plays an important role in reverse osmosis (RO) desalination; however, few investigations on the formation and influence of lateral force on the RERD rotor have been published. The transient characteristics of lateral force and its relationship with pressure distribution and fluctuation in the clearance were analyzed via computational fluid dynamics (CFD) simulation. The clearance pressure distribution and lateral force were quantified under different working conditions. The eccentricity of the rotor, resistance torque and decrease in the rotary speed due to the lateral force were simulated and they were found to change with flow rate and pressure of high-pressure outlet (PHO). A new rotary speed prediction method including the effect of PHO was developed. With the increasing flow rate or PHO, the stability of RERD declined. A design optimization direction was proposed. The variation trends of rotary speed, pressure in the clearance and its fluctuation were verified through experiment. This research provides an explanation why in practice the rotary speed decreases with increasing pressure. The conclusions obtained herein can be of great significance for future research on improving the stability and lifespan and reducing the maintenance consumption of RERD.

Techno-economic analysis of various configurations of stand-alone PV-RO systems for Pakistan

The global water scarcity crisis has led to increased demand for reverse osmosis (RO) desalination technology. In response to the rising global temperatures, there is a growing focus on renewable energy sources such as solar photovoltaic (PV) and wind energy to power small-scale RO plants. This paper presents a comprehensive techno-economic analysis of stand-alone photovoltaic reverse osmosis (PV-RO) systems in Pakistan. It focuses on the design and optimization of PV-RO systems for Karachi and Lahore, evaluating the systems with and without energy recovery devices. A parametric study was conducted to optimize system performance, considering various configurations. The analysis includes a comparison of costs when operating with PV, diesel, and grid power. It was found that for Karachi, a four-stage PV-RO system without an energy recovery device provides water at $1.359 per cubic meter, while in Lahore, a three-stage system with an energy recovery device achieves $1.336 per cubic meter. These systems offer significant annual savings compared to diesel-powered systems, with Karachi and Lahore saving up to $10,138 and $17,664 respectively over ten years. The findings of this study show that PV-RO systems, especially those with multiple stages and energy recovery devices, offer a cost-effective and sustainable solution for water desalination in these regions.

Exploration and optimization on thermoelectric conversion of waste heat of blast furnace slag

The iron and steel industry involves processes that generate abundant waste heat resources. The energy utilization rate can be improved by using thermoelectric conversion technology to directly convert waste heat into electric energy through the Seebeck effect. In this study, a special waste heat recovery device, designed according to the production environment characteristics of blast furnace (BF) slag, is proposed. The heat transfer process between the BF slag and thermoelectric generator (TEG) is analyzed, and the heat source temperature field model is constructed. Based on the temperature distribution, the size of the TEG is determined. The heat transfer behavior of the thermoelectric module (TEM) is optimized using a non-contact heat collection mode and a water-cooling device, which improves the temperature gradient. A thermal conductive silicone grease is introduced as the thermal conductive layer to achieve uniform distribution of the hot end temperature and improve the heat transfer capacity of the collector plate. After design optimization, the temperature gradient of the TEM increased by 15.3 °C and 38 % on average. The experimental results show that a single TEM can generate about 3.084 J of electric energy. Using 70 kg of BF slag with an initial temperature of 600 °C, the TEG per unit installed area can generate about 1.23 kJ of electric energy in 1 h. This study provides an important foundation for research in thermoelectric conversion, utilization of BF slag waste heat and sustainable development of the iron and steel industry.

Theoretical and experimental study on the secondary heat recovery cycle of the mixed working fluid in ocean thermal energy conversion

The small ocean temperature difference causes the power generation efficiency to not be high while the power generation cost is high; this method has not been commercially applied. Therefore, it is particularly important to find a new thermal cycle to improve the cycle efficiency. In this paper, a new cycle of the ocean temperature difference using a non-azeotropic mixed as working fluid is proposed, and a secondary heat recovery device is added to the solution branch separated by the separator. Theoretical analysis and numerical calculation were used to analyze the relationships between cycle efficiency and working fluid concentration, turbine inlet pressure and cold seawater temperature were obtained. The results show that the maximum cycle efficiency can reach 5.25% by adding a secondary heat recovery device. A 10 kW OTEC experimental system was constructed and analyzed; the system performance was obtained. The efficiency of the experimental system was found to be as high as 3.8%, while the experimental value of the test system was lower than the theoretical calculation value. Finally, the heat transfer coefficients of an evaporator and condenser under these conditions were obtained, which provides basic data and technical support for the engineering application of an OTEC plant.

A Tent-Inspired Portable Solar-Driven Water Purification Device for Wilderness Explorers.

Wilderness adventure favored by many enthusiasts often endanger lives due to lacking freshwater or drinking contaminated water. Therefore, compared to the inefficient methods of filtration, steaming, and direct solar heating, it is of great meaningfulness to develop a solar-driven water purification device with efficiency, lightweight, portability, and multi-water-quality purification by taking full advantage of solar-driven interfacial evaporation. Here, a tent-inspired portable solar-driven water purification device consisting of Janus-structured bacterial cellulose aerogel (JBCA) solar evaporator and tent-type condensation recovery device is reported. For the JBCA solar evaporator, it is prepared from biomass bacterial cellulose (BC) as raw material and hydroxylated carbon nanotubes (HCNT) as photothermal material, and the Janus property is achieved by the assistance of hydrophobic and hydrophilic chemical cross-linking. It exhibits lightweight, unibody, high photothermal conversion, efficient evaporation, and multi-water-quality purification capability for representative seawater, urine, and bacterial river water. For the tent-type condensation recovery device, it is based on the prototype of tent and uses flexible ultra-transparent polyvinyl chloride (PVC) film as raw material. Thanks to the rational prototype and material selection, it displays outstanding portability and lightweight through the folding/unfolding method. Therefore, the designed tent-inspired portable solar-driven water purification device demonstrates great potential application in wilderness exploration.

Rapid geometric characterization of ceramics fragments through split Hopkinson pressure bar tests

AbstractThe research on fracture mechanisms of brittle materials is extremely difficult such as the determination of the energy absorption modes and the geometric characteristics of debris. In this paper, a dynamic experimental fragment recovery device was developed to study the facture characteristics of A99 ceramics (the mass of Al2O3 accounts for 99%) based on the Split‐Hopkinson pressure bar (SHPB) experiments, in which the energy absorption mechanism was revealed. A three‐view characterization method was developed to obtain the geometric characterization formula under various strain rate; therefore, the geometric parameters of the fragments can be quickly characterized. The failure mode was investigated in correlation between strain rate and micro‐cracks. It was found that the shape of the strain rate controlled the proportion of dissipated energy. At a lower strain rate the fragment was prone to needle shape, while at a higher strain rate (above 2001 s−1) the proportion of dissipated energy increased to 72% and the fragment shape tended to be nearly spherical. A formula based on strain rate was proposed to characterize the geometric parameters of the fragments without the need of geometry dimensions; therefore, the fragment rate can be quickly obtained, which could provide guidance for the design of ceramics parts.

Experimental study of a booster pump-free isobaric energy recovery device (DAC) for reverse osmosis: Performance evaluation and comparison

Reverse osmosis (RO) is a widely used desalination technology known for its high energy requirements. However, the incorporation of energy recovery devices (ERDs) in RO plants has proven effective in reducing specific energy consumption. The booster pump (BP) is an essential component utilized in conjunction with isobaric ERDs. Approximately 5 to 10 % of the capital cost for small to medium-sized RO units is attributed to the BP. The objective of this paper is to investigate the feasibility of implementing a newly designed isobaric ERD called DAC. The study focuses on an RO plant with a capacity of 48 m3/day. The proposed ERD undergoes design, manufacturing, and experimental testing. The major benefit is its ability to utilize the system feed pump as a BP, eliminating the need for a separate BP. This equipment reduction not only lowers the initial cost but also simplifies the system complexity. Furthermore, the system is designed to allow a comparison between the DAC and a pressure exchanger (PX) under the same operating conditions. However, unlike the DAC, the PX becomes unresponsive and does not function when the BP is turned off to allow the system feed pump to take over.

A computational method to study heat transfer in a helicopter turboshaft engine compartment for waste energy recovery purposes

It is important to take action to make aviation more energy-efficient and less pollutant. One of the approaches currently under development is waste energy recovery. This would be specially advantageous in turboshaft engines, which present an exhaust flow that is not being used for propulsive purposes and with high thermal residual energy that increases infrared signature of helicopters.To evaluate where to locate waste energy recovery devices such as thermoelectric generators or organic Rankine cycles the following is needed: temperatures of exhaust gas flow temperature and exhaust ducts wall temperature, i.e. hot source temperature, and engine compartment temperature, i.e. heat sink temperature. This variables are usually not known beforehand. The present paper develops a method that, with minimal data input, translates flight conditions and engine operation into conditions inside the engine compartment that are later applied to obtain heat transfer in the exhaust ducts, where the waste energy recovery should take place to minimize the influence on the engine. The procedure is based on an algorithm that uses Computational Fluid Dynamics (CFD) simulations validated with experiments.The main findings of this work are: (i) cruise flight velocity has minimal impact on engine compartment temperatures, but hover operation increases it by 5–16 K, (ii) cruise altitude significantly affects engine compartment temperature, with a 12 K difference between 2500 ft and 10000 ft, (iii) considering only the axial component of velocity in exhaust ducts may underestimate wall temperature, (iv) heat transfer in exhaust ducts can be estimated using empirical correlations for natural convection, multiplied by a specific factor, (v) non-invasive methods can recover 23.6 to 31.2 kW of heat from exhaust duct walls, potentially converting up to half of it into useful work.

An Experimental Study of Heating Heavy Fuel Oil by Hot Air using Helical Fins in a Double-Pipe Heat Exchanger

In present work, the effect of helical fins with height 20 mm and pitch 100 mm on the performance of the double pipe heat exchange investigated experimentally. The heat exchanger had been chosen as a heat recovery device in bricks factory to recover heat from exhaust gases to preheat the heavy fuel oil. Air had been chosen as a hot gas instead of furnace exhaust gases because of the similar thermal properties and it flows in the inner pipe with different velocity (20, 27, and 34) m/s and inlet temperature (200, 225) °C while, heavy fuel oil enters shell side with counter flow at mass flow rates (0.06, 0.08, and 0.1) kg/s and constant inlet temperature of 40 °C. Both of pipes and helical fins are made from stainless steel. The experimental results show that increasing Reynolds number from 139139 to 333934 led to increase heat transfer rate, oil outlet temperature, overall heat transfer coefficient and effectiveness of heat exchanger with (8%, 4%, 5% and 5%) respectively while, increasing oil mass flow rate from (0.06 to 0.1) kg/s cause decreasing oil outlet temperature and effectiveness of with (10% ,14%) respectively. The results shown the double pipe heat exchanger with helical fins produce heat transfer rate and oil outlet temperature higher than smooth double pipe heat with average 15% and 8.6%, as well as increasing Nusselt number, Overall heat transfer coefficient and effectiveness of heat exchanger with average 26%,15% and 13% respectively. The results clear that, for 225°C exhaust air and velocity 27 m/s, the application of double pipe with helical fins by preheat heavy fuel oil could reduce the viscosity and reduce electric power required and save 1.69 MW annually for one factory.

Photo-addressable microwell devices for rapid functional screening and isolation of pathogen inhibitors from bacterial strain libraries.

Discovery of new strains of bacteria that inhibit pathogen growth can facilitate improvements in biocontrol and probiotic strategies. Traditional, plate-based co-culture approaches that probe microbial interactions can impede this discovery as these methods are inherently low-throughput, labor-intensive, and qualitative. We report a second-generation, photo-addressable microwell device, developed to iteratively screen interactions between candidate biocontrol agents existing in bacterial strain libraries and pathogens under increasing pathogen pressure. Microwells (0.6 pl volume) provide unique co-culture sites between library strains and pathogens at controlled cellular ratios. During sequential screening iterations, library strains are challenged against increasing numbers of pathogens to quantitatively identify microwells containing strains inhibiting the highest numbers of pathogens. Ring-patterned 365 nm light is then used to ablate a photodegradable hydrogel membrane and sequentially release inhibitory strains from the device for recovery. Pathogen inhibition with each recovered strain is validated, followed by whole genome sequencing. To demonstrate the rapid nature of this approach, the device was used to screen a 293-membered biovar 1 agrobacterial strain library for strains inhibitory to the plant pathogen Agrobacterium tumefaciens sp. 15955. One iterative screen revealed nine new inhibitory strains. For comparison, plate-based methods did not uncover any inhibitory strains from the library (n = 30 plates). The novel pathogen-challenge screening mode developed here enables rapid selection and recovery of strains that effectively suppress pathogen growth from bacterial strain libraries, expanding this microwell technology platform toward rapid, cost-effective, and scalable screening for probiotics, biocontrol agents, and inhibitory molecules that can protect against known or emerging pathogens.

Investigation of the Real Efficiency of a Decentralized Heat Recovery Ventilation System

The paper presents the measurement method and values of the temperatures of the incoming and outgoing air obtained as a result of the connection and automation of 4 decentralized heat recovery ventilation units into one system, and the measured results of the thermal efficiency of the entire system. The built system consists of four single-room heat recovery devices, which are integrated into an automated system. The built-in sensors can be used to measure the average temperature of the ventilated rooms or the current temperature and relative humidity of the air flowing through the ventilation units, as well as the carbon dioxide level of the rooms. The units received automation that complements the original individual control elements, which is capable of complex control tasks from any computing device, graphic interface and Wi-Fi connection. The units' sensors, which can be moved into the air stream, are suitable for the momentary measurement of the parameters of the flowing air, thereby estimating the thermal efficiency of the entire system.