High Pumping Efficiency Research Articles

Electrochemically driven phase transformation for high-efficiency heat pumping

Electrochemically driven phase transformation for high-efficiency heat pumping

Wavelength-Tunable Narrow-Linewidth Laser Diode Based on Self-Injection Locking with a High-Q Lithium Niobate Microring Resonator.

We demonstrate a narrow linewidth 980 nm laser by self-injection locking of an electrically pumped distributed-feedback (DFB) laser diode to a high quality (Q) factor (>105) lithium niobate (LN) microring resonator. The lithium niobate microring resonator is fabricated by photolithography-assisted chemo-mechanical etching (PLACE) technique, and the Q factor of lithium niobate microring is measured as high as 6.91 × 105. The linewidth of the multimode 980 nm laser diode, which is ~2 nm measured from its output end, is narrowed down to 35 pm with a single-mode characteristic after coupling with the high-Q LN microring resonator. The output power of the narrow-linewidth microlaser is about 4.27 mW, and the wavelength tuning range reaches 2.57 nm. This work explores a hybrid integrated narrow linewidth 980 nm laser that has potential applications in high-efficient pump laser, optical tweezers, quantum information, as well as chip-based precision spectroscopy and metrology.

Classroom mock-up meeting Standard S12.60

The Acoustical Society of America (ASA) developed a standard entitled Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools (ASA/ANSI S12.60-2010) that provides a minimum set of requirements to help school planners and designers “provide good acoustical characteristics for classrooms and other learning spaces in which speech communication is an important part of the learning process.” In this revision, several details were revised for incorporation into building codes. Despite the obvious benefits of quieter classrooms, incorporating the standard into building codes met with resistance. A common perception was that in order to meet the standard’s requirements, specialized HVAC equipment and installation methods would be necessary, resulting in an installed cost beyond what most schools could afford. Acoustical prediction tools indicated that the requirements could be met using standard HVAC equipment and installation methods. To verify the predictions, a simulated classroom was built and several common types of equipment including a single-zone air handling unit, a high-efficiency water-source heat pump, and a packaged rooftop unit were tested. The selected products were standard catalog offerings, without any special attenuation features, that were operated at typical airflow and static pressures. This paper describes those tests, the conclusion, and the resulting recommendations.

Engineered zero-dispersion microcombs using CMOS-ready photonics

Normal group velocity dispersion (GVD) microcombs offer high comb line power and high pumping efficiency compared to bright pulse microcombs. The recent demonstration of normal GVD microcombs using CMOS foundry-produced microresonators is an important step toward scalable production. However, the chromatic dispersion of CMOS devices is large and impairs the generation of broadband microcombs. Here, we report the development of a microresonator in which GVD is reduced due to a coupled-ring resonator configuration. Operating in the turnkey self-injection locking mode, the resonator is integrated in a hybrid manner with a semiconductor laser pump to produce high-power efficiency combs spanning a bandwidth of 9.9 nm (1.22 THz) centered at 1560 nm, corresponding to 62 comb lines. Fast, linear optical sampling of the comb waveform is used to observe the rich set of near-zero GVD comb behaviors, including soliton molecules, switching waves (platicons), and their hybrids. Tuning of the 20 GHz repetition rate by electrical actuation enables servo locking to a microwave reference, which simultaneously stabilizes the comb repetition rate, offset frequency, and temporal waveform. This integrated hybrid system could be used in coherent communications or for ultrastable microwave signal generation by two-point optical frequency division.

Performance improvement and comparison analysis of the hybrid concentrated dual-source heat pump system regarding proper throttling process

In this paper, a high-efficient and three-dimensional compact heat pump system integrated with the concentrated photovoltaic plus fins (CPV/fin-SAHP) is constructed and built. Smaller space occupation and higher energy utilization are realized. The mathematical model is completed and validated by experimental data. By changing the throttling device and adjusting the mass flow rate, the system performance is improved. From the results, the exergy efficiency, heating capacity, total output, COPPVT, and COPth of the CPV/fin-SAHP system are increased by 7.92%, 13.2%, 11.01%, 4.73%, and 7.12%. Moreover, compared with traditional single-source heat pumps, the CPV/fin-SAHP achieved the highest total output and COPPVT, showing great competitivity and potential. Then two-dimensional environmental variable coordinates are established to explore the compound impact of different ambient factors, and the capacities of the three systems with adjusted opening degrees are also comparatively analyzed. In general, wind speed and ambient temperature have greater impacts on the finned structure system, while the irradiance is dramatically affecting the PV-SAHP system. The compact CPV/fin-SAHP system is less dependent on a single ambient element, showing satisfied performance under various operating ambient and presenting the most potential in comprehensive ability.

Performance improvement potential of a PV/T integrated dual-source heat pump unit with a pressure booster ejector

• Ejector enhanced PV/T air dual-source heat pump is presented. • Optimum PV/T evaporation temperature is determined. • The COP of the heat pump can be improved by 22.6% when 15 m 2 PV/T collector is used. • Consumed electricity from the grid for heating can be reduced by 75% when 15 m 2 PV/T collector is used. Dual-source heat pump unit can utilize the evaporation of the refrigerant at two different pressures. By adopting an ejector, high-pressure refrigerant stream can be used to lift compressor inlet pressure which results in a higher coefficient of performance (COP). This study proposes a renewable energy sourced and high-efficiency heat pump system which can be easily building integrated to offer a renewable heating solution. The system is devised on the complementation of dual thermal sources; one is air and the other one is solar, to maximize the utilization of ambient energy for highly efficient operation of heat pump. Using the advantage of the relatively lower operating temperature in the solar collector line, the thermal efficiency of the collector would be sufficient in winter. Adaptation of photovoltaics in the collector as a PV/T unit, will benefit the system from the produced electricity for further reduction of the demand from the grid. Along with the use of PV/T collector, the system can be potentially carbon neutral for larger collector areas. In this study, the performance improvement potential of a dual-sourced heat pump unit with an ejector as a booster is investigated for different locations in Turkey which presents different solar and weather profiles. The optimum collector evaporation temperatures are determined, and COP improvement potentials are discussed for different conditions. For a heating supply of 5 kW, the COP of the system can be improved by 22.6% under 400 W/m 2 and 10°C ambient using 15 m 2 PV/T collector. Including the electricity generated from the PV, reduction of the electricity demand from the grid can reach to 75% for the same conditions.

Mathematical and experimental investigation about the dual-source heat pump integrating low concentrated photovoltaic and finned-tube exchanger

Traditional dual-source heat pumps are generally composed of separated flat PV evaporators and finned-tube evaporators connected in series or parallel, occupying too much extra space with low space/energy utilization. The heat pump system consisting of fins and low concentrated photovoltaic designed in this paper could obviously improve PV output and it brilliantly fixes the finned-tube structure under the concentrator. The compact structure could better exploit the three-dimensional space and energy, bring improvement of the comprehensive output and system performance. The experimental rig is built in Hefei, China with improved pipeline. The system shows a brilliant cooling effect on concentrated photovoltaics, lowering the temperature by about 50 °C, lifting the electrical efficiency by 4.6%. Interestingly, in the real outdoor environment, the efficiency of concentrated photovoltaics declines with the deteriorated irradiance (cloud cover), contrary to the traditional flat PV. On a sunny day, the average electrical efficiency, heating rate, power consumption, COPth, and COPPVT could be 14.4%, 2168 W, 592 W, 3.76, and 4.43 respectively. The impact of the mass injection and concentration ratio is also investigated mathematically. This article makes up the lacked experimental content, providing strong and reliable data support/reference for the actual design and performance prediction of the high-efficiency and low-carbon three-dimensional heat pump system.

Development of a high-efficiency and cost-effective ground source heat pump system for hot-climate applications

This paper investigates the possibility of using a dry fluid cooler with advanced control strategies in a vertical closed-loop GSHP system to reduce the borehole size with the intention of increasing the cost-effectiveness of the system without compromising system efficiency. The developed system is expected to be a game changer in the residential sector of the USA involving the use of high-efficiency heat pump systems as a substitute for conventional systems for space cooling and heating in hot/warm climates. The simulation results show that (1) the use of a dry fluid cooler with advanced control strategies in a GSHP system contributes to increasing or maintaining the GSHP system’s efficiency in the long run by balancing the heating and cooling through charging thermal energy to the ground in hot climates; (2) the concept of integrating a dry fluid cooler into a GSHP system with advanced control strategies is proven to be effective for the studied house located in hot climates, such as Miami. In comparison to a conventional GSHP system, the initial system costs can be reduced by up to around 14% by shortening the borehole length without compromising system efficiency because of the use of a dry fluid cooler.

Research on the multifunction concentrated solar-air heat pump system

To improve space/energy utilization and meet various households’ needs, a high efficient and multifunction concentrated solar-air heat pump system(MC-SA-HP) is proposed in this paper. The concentrator is used to lift the energy density and unit generation of photovoltaic panel, and its three-dimensional feature could realize the layered utilization of space by placing the air source evaporator in the spare part below. By different operating strategies, the system could provide heating, electricity, and cooling. Through testing, MC-SA-HP obtained mean electrical generation and efficiency of 146W and 14.6%, condensing heat of 2114W, COPth and COPPVT of 3.7 and 4.4. Compared with the system using flat-panel photovoltaic, it could improve the electrical generation by 71.8%, heating capacity by 5.9%, total output by 12.6%, overall efficiency of 9.5%, COPPVT by 7.3%, and exergy efficiency of 36.1%. In the cooling mode during experiment, the water temperature drops from 14.6 to 2.6 °C, generating 1.51 × 107 J cooling capacity, and an average COPc of 2.3. The multifunction feature increases the attractiveness and feasibility of this novel system. After calculation, the high-efficient and compact MC-SA-HP system shows great effect on cost and emission reduction, which could help to better cope with climate change and achieve the goal of carbon peak and carbon neutrality.

Оптимизация проточной части осевого насоса с использованием поверхности отклика

To design high-efficiency vane pump flow part it is necessary to use various optimization algorithms, based on which the geometrical parameters of designed flow part are changed in order to provide the required value of some integral design parameter. The article considers the numerical method for finding an extremum based on one of the algorithms included in the DesignXplorer optimization tool, which is an integral module of the Ansys Workbench software package. Response Surface Optimization (RSO) is a kind of mathematical model (metamodel) describing analytical dependence of output parameters on input parameters. The function is based on the approximation of the numerical experiment data (Design of Experiments). The use of this method allows obtaining more efficient flow path of the catalog axial pump OP-5 without performing lengthy experimental research of the effect of the geometric parameters of the flow path on the pump characteristics.

Study on Er3+-Yb3+ co-doped La2O3–Al2O3 glasses for C-band optical waveguide amplifier with high luminous efficiency and low pump threshold

Efficient planar optical waveguide amplifiers at C-band are critical to the development of silicon photonics. In order to overcome the problem of low utilization efficiency of 980 nm pump for erbium-based planar optical waveguide amplifiers, an Er3+-Yb3+ co-doped La2O3–Al2O3 glass material for optical waveguide amplifiers was developed in this paper. While maintaining a high Er3+ doping concentration (∼1021 cm−3), the utilization efficiency of the material for 980 nm pumping is improved, so that the pump threshold of the waveguide amplifier fabricated with this material is lowered. Moreover, up-conversion and down-conversion luminescence are also suppressed in the material, resulting in a significant increase in the luminescence intensity of the C-band. A simple ridge waveguide simulation suggests that waveguide amplifiers fabricated by this material are expected to surpass the highest net gain reported so far for erbium-based planar waveguide amplifiers.

Deneysel Tasarım Yöntemleri İle Bir Santrifüj Pompa Çarkında Dengeleme Deliği Tasarım Optimizasyonu

Bu çalışmanın amacı, rulmanlara gelen eksenel kuvvetleri azaltarak rulman ömrünü uzatmak için pompa çarkına açılacak en uygun dengeleme deliğinin belirlenmesidir. Çalışmada eksenel kuvvetlerin azaltılmasının yanı sıra pompa veriminde meydana gelen değişiklikler de dikkate alınmıştır. Bu çalışma için 1480 rpm hız, 350 m³/h debi ve 51 m basma yüksekliğine sahip tek kademeli santrifüj pompa seçilmiştir. Seçilen pompa çarkı üzerindeki dengeleme deliğinin tasarım optimizasyonu, deneysel tasarım metodu ve Hesaplamalı Akışkanlar Dinamiği (HAD) kullanılarak gerçekleştirilmiştir. HAD analizleri için Ansys Fluent programı kullanılmıştır. Optimum sonuca ulaşmak amacıyla dengeleme deliklerinin çark içerisindeki; delik merkezi açısı, delik çapı, delik merkezi çapı ve adedini belirleyen 4 parametre tespit edilmiş ve Çok Amaçlı Taguchi Yöntemi kullanılarak optimizasyon çalışması gerçekleştirilmiştir. Amaçlar; düşük eksenel yük ve yüksek pompa verimi olarak kabul edilmiştir. HAD sonuçları, varyans analizi (ANOVA) ve sinyal/gürültü (S/N) oranına göre değerlendirilmiştir. Yapılan çalışmalar sonucunda; delik çapının amaçlar üzerinde en etkili parametre olduğu tespit edilmiştir. Optimum tasarımın; belirlenen dört parametre için sırasıyla 0°, 12 mm, 100 mm ve 6 adet olduğu belirlenmiştir.

Energy, exergy, economic and environmental analyses and optimization of a novel vapor injection autocascade heat pump for high-temperature water heating

Aiming to develop a high-efficiency and low-cost high-temperature heat pump with large temperature lift ability, a novel vapor injection autocascade heat pump for high-temperature water heating is proposed in this paper. The proposed system utilizes the vapor injection technique to improve the limited performance of the conventional autocascade system and can achieve outstanding heating performance with over 100 °C heating temperature. The energy, exergy, economic and environmental performance of the proposed system are investigated by simulation method and compared with those of the conventional autocascade heat pump. The proposed system averagely improves the heating coefficient of performance and capacity by 51.8% and 104.3% over the conventional system when the evaporating temperature ranges from 0 °C to 20 °C, respectively. The exergy analysis indicates that the excellent exergy performance of the proposed system mainly benefits from the irreversible loss reductions in the throttling valves and cascade condensers. The proposed system possesses the lowest energy cost except for the coal-fired boiler, and produces the minimum pollutant emission except for the gas-fired boiler. The heating coefficient of performance of the proposed system is improved by 12.4% ∼ 14.0% through single-objective optimization. The optimal coefficient of performance and levelized cost of energy are 2.59 and 0.070 $ kWh−1, respectively.

A solar-assisted low-temperature district heating and cooling network coupled with a ground-source heat pump

Towards the development of highly integrated and energy efficient heating and cooling systems, with an energy community perspective, the present paper proposes a novel technical solution for the provision of air-conditioning, domestic hot water and electricity to a small residential district in heating-dominant regions. Three reference climates have been considered: Helsinki, Berlin and Strasbourg. Detailed dynamic models have been created using TRNSYS and NeMo, and long term operations of the energy system, including a new-generation ultra-low temperature district heating and cooling network have been performed. The core of the energy system is the network supplied by a high-efficiency ground source heat pump and used as the source and sink by booster heat pumps installed in the substations. Rooftop photovoltaic thermal panels partially meet the electrical demand of the district, as well as the thermal load for domestic hot water production. Moreover, the panels are cooled by the network, obtaining a reduction in the thermal unbalance to the ground and enhancing their electrical efficiency. This solution allows obtaining high coefficient of performance for the heat pumps in the substations and supply stations, reaching values of 5.4 and 4.0, respectively, for heating provision in the coldest locality. The proposed multi-energy district reaches an electrical self-consumption of 71% in the coldest locality and efficiently combines different renewable energy sources at district level in cold climates.

High-efficiency topological pumping with discrete supersymmetry transformations.

Making use of the isospectrality of Supersymmetry transformations, we propose a general and high-fidelity method to prepare gapped topological modes in discrete systems from a single-site excitation. The method consists of adiabatically connecting two superpartner structures, deforming the input state into the desired mode. We demonstrate the method by pumping topological states of the Su-Schrieffer-Heeger model in an optical waveguide array, where the adiabatic deformation is performed along the propagation direction. We obtain fidelities above F = 0.99 for a wide range of coupling strengths when pumping edge and interface states.

Analysis and Design of High-Efficiency Charge Pumps With Improved Current Driving Capability Using Gate Voltage Boosting Technique

This paper presents two high-efficiency charge pumps (CPs) by utilizing the gate voltage boosting technique (GVBT). Unlike traditional bulk-CMOS and all-NMOS CPs, an input bias voltage is independently applied to the gate terminal, and it improves the current driving capability without the need of large pumping capacitors or high-frequency clocks. Meanwhile, the GVBT decouples the state of transistors from the clocks connected to the pumping capacitor, and it can eliminate the reversion loss in both main and auxiliary circuits. Fabricated in a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> standard CMOS technology, the single-stage all-NMOS CP achieved a maximum output voltage of 6.589 V and a peak power efficiency of 80.08%. We also implemented the bulk-CMOS CP with GBVT for comparison, the single-stage all-NMOS CP achieved <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 1.24\times $ </tex-math></inline-formula> more output voltage than the bulk-CMOS CP under a load current of 1.5 mA. The voltage errors of the all-NMOS CP between the analytical and the measured results are less than 7%.

Barocaloric Properties of Thermoplastic Elastomers

Solid-state refrigeration represents a promising alternative to vapor compression refrigeration systems which are inefficient, unreliable, and have a high global warming potential. However, several solid-state cooling technologies—including those relying on a temperature change induced by an applied electric field (electrocaloric effect), magnetic field (magnetocaloric effect), and uniaxial stress (elastocaloric effect)—have been investigated, but their efficiency and scalability remain a concern. Materials with a large barocaloric response—temperature/entropy change induced by hydrostatic pressure—hold a significant promise for solid-state cooling but remain comparatively less explored. These materials need to be inexpensive, compressible, and show a large barocaloric response around the temperature of interest. Soft materials have the potential to meet these requirements and enable the development of low-cost high-efficiency solid-state heat pumps. Here, we investigate the barocaloric performance of commercially available block copolymer thermoplastic elastomers. We characterized the mechanical, thermal, and barocaloric properties of these materials and evaluated their potential for solid-state refrigeration. We utilized rheometric measurements to evaluate the isothermal compressibility and normalized refrigerant capacity of the thermoplastic elastomers. In addition, we directly measured the pressure-induced temperature change of the test materials and compared them with their normalized refrigeration capacity. The measured isothermal compressibility was in the 0.1–0.4 GPa−1 range, while the normalized refrigeration capacity varied between 13.2 and 41.9 kJ K−1 GPa−1 for a 100 MPa applied pressure and 65°C temperature span. The corresponding pressure-induced temperature change for an applied pressure of 434.1 MPa varied between 2.2 and 28°C. These results demonstrated the superior barocaloric properties of thermoplastic elastomers and their promise for next generation barocaloric solid-state refrigeration devices.

The effect of pulsating air injection on the development of two-phase flow instabilities in an airlift pump

This paper aims at characterizing the instabilities created by the dynamic redistribution of air liquid two-phases through the pump to allow for utilizing a pulsating air injection as a new mode to control and optimize the pump performance. Baseline performance experiments for the pump operating under continuous air injection and for three submergence ratios of 0.5, 0.7 and 0.9 are used in the present analysis. The most efficient operating points of the pump were recorded at a range of air flow rates between 1.1 and 2.3 kg/hr. The characteristics of non-developing two-phase flow were evaluated using both flow pattern visualization using high speed imaging system and instantons void fraction using capacitance sensors at the points with the highest pump efficiency. In these experiments, the dynamics void fraction signals were collected at seven different locations along the pump riser. Both the fast Fourier transform, and power spectral density functions of the void fraction signals were used to identify the effective frequency range at which to perform the pulsation air injection experiments. At lower submergence ratios, the void fraction signals along the pump riser found to take a longer time to reach quasi-fully developed values. Also, pulsating mode of injected air was found to improve the pump performance for all submergence ratios. This is mainly due to the significant changes in the two-phase flow pattern in the pump riser when air pulsating used. In this case, pulsating the air injection at the optimum frequency allowed for maintaining a slug flow pattern during the pump operation and the best pump performance was achieve. Pulsating air injection at different offset frequencies were also evaluated for a dual injection airlift pump. It was found that an overlapping offset frequency or an alternating frequency between the two air injection ports can achieve a better pump performance for high submergence ratios while synchronous pulsation mode was found to be the most effective at improving the pump performance at low submergence ratios.

Dynamic Modeling and Flexibility Analysis of an Integrated Electrical and Thermal Energy System With the Heat Pump–Thermal Storage

The integration of high-efficiency heat pump and thermal storage devices is of great significance to realize the synergy between efficient and flexible operation of the integrated electric and thermal energy systems. This article proposed an integrated electric–thermal energy system with heat pump and thermal storage devices and introduced the heat current method for constructing its overall dynamic power flow model by considering energy transfer, conversion, and storage processes. On this basis, we derived the overall system constraint and component constraint equations. Under the objective of wind power curtailment minimization, the comprehensive effects of the dynamic characteristics of the heat pump, thermal storage capacity, new wind power installation, and new heat load on the electric and thermal output are analyzed. The results show that the dispatching accuracy of wind power output can be improved by up to 8% by taking into account the dynamic characteristics of the heat pump. The combination of heat pump and thermal storage device results in a leverage factor of 3.06 and 0.17 for the storage and release processes, respectively, effectively increasing the flexibility of system scheduling. The coordination between the newly added wind power installation and the added new heat load, with the higher operating temperature of the heat pump, is more conducive to promote wind power accommodation and improve the system’s overall flexibility. These results provide the necessary basis for the development of an integrated dispatch plan for the integrated electric and thermal energy systems containing the heat pump–thermal storage.

Numerical analysis of the flow parameters on the heat transfer performance of a two-stage spiral casing heat exchanger

The study of the performance of high-efficiency heat pump systems has been a hot issue of general interest in the field of heat pump air conditioning. For the designed and developed two-stage casing tandem heat exchanger of heat pump system, the 3D finite volume method and the realizable k-ε model are used to numerically analyze the influence law of inlet fluid temperature and flow velocity on the overall heat transfer coefficient as well as the Nussle number of inner and outer tubes. The results show that decreasing the inlet water temperature or increasing the inlet refrigerant temperature can improve the overall heat transfer performance; Nuin increases with the increase of water and refrigerant flow rates, while Nuout increases with the increase of water flow rate but decreases with the increase of refrigerant flow rate; Nuin and Nuout both increase with the decrease of water temperature or refrigerant temperature increases.