Publications
51 results found
Hu Y, Luo K, Zhao D, et al., 2024, Thermoacoustic heat pump utilizing medium/low-grade heat sources for domestic building heating, Energy and Built Environment, Vol: 5, Pages: 628-639
Thermoacoustic heat pumps are a promising heating technology that utilizes medium/low-grade heat to reduce reliance on electricity. This study proposes a single direct-coupled configuration for a thermoacoustic heat pump, aimed at minimizing system complexity and making it suitable for domestic applications. Numerical investigations were conducted under typical household heating conditions, including performance analysis, exergy loss evaluation, and axial distribution of key parameters. Results show that the proposed thermoacoustic heat pump achieves a heating capacity of 5.7 kW and a coefficient of performance of 1.4, with a heating temperature of 300 °C and a heat-sink temperature of 55 °C. A comparison with existing absorption heat pumps reveals favorable adaptability for large temperature lift applications. A case study conducted in Finland over an annual cycle analyzes the economic and environmental performance of the system, identifying two distinct modes based on the driving heat source: medium temperature (≥250 °C) and low temperature (<250 °C), both of which exhibit favorable heating performance. When the thermoacoustic heat pump is driven by waste heat, energy savings of 20.1 MWh/year, emission reductions of 4143 kgCO2/year, and total environmental cost savings of 1629 €/year are obtained. These results demonstrate the potential of the proposed thermoacoustic heat pump as a cost-effective and environmentally friendly option for domestic building heating using medium/low-grade heat sources.
Guo L, Zhao D, Cheng L, et al., 2024, Enhancing energy conversion performances in standing-wave thermoacoustic engine with externally forcing periodic oscillations, Energy, Vol: 292, ISSN: 0360-5442
The present work focuses on enhancing thermo-acoustics energy conversion performance and nonlinear dynamics of heat-driven acoustics oscillations in standing-wave thermoacoustic engines (SWTAE) in the presence of externally forcing perturbations. Such perturbations could be applied in either pressure or velocity fluctuations. 2D numerical SWTAE models are developed and validated, and then applied to examine the effects of 1) the forcing perturbation frequencies, 2) its amplitudes, and 3) the inlet diameter of applying such perturbations on heat-driven acoustics behavior. Our results show that pressure perturbations attenuate heat-driven acoustic limit cycles, while forcing velocity perturbations at a specific frequency range can enhance the thermo-acoustics conversion in the SWTAEs. Our results also show that frequency lock-in is observed, when the ratio of the forcing velocity perturbations' energy to the self-excited acoustical energy is ranged from 0.11 to 0.66. Furthermore, Hopf supercritical bifurcations are observed, resulting in transitions from steady state to quasi-periodic and limit cycle oscillations. As the forcing perturbation frequency is approaching to that of the self-excited heat-driven acoustic oscillations (i.e. the ratio of the forcing frequency to that of self-excited oscillations is ranged from 0.89 to 1.11), apparent improvements are observed on the output heat-driven acoustic power and thermo-acoustic energy conversion efficiency, especially when the two frequencies are coincided (i.e. ∼180 Hz). Increasing the forcing perturbation's energy or enlarging the inlet diameter of applying such perturbations further enhances these improvements. Overall, the developed numerical model may serve as a valuable tool for predicting the heat-driven acoustic power output from a SWTAE in the presence of externally forcing perturbations.
Norouzi-Inallu M, Ghotbi Varzaneh A, Kameli P, et al., 2024, Transformation behavior and inverse magnetocaloric effect in Ni<inf>45</inf>Co<inf>5</inf>Mn<inf>36.7</inf>In<inf>13.3-x</inf>Ge<inf>x</inf> melt-spun ribbons, Intermetallics, Vol: 165, ISSN: 0966-9795
In the present work the influence of Ge doping on crystal structure, microstructure, martensitic transformation (MT) and magnetocaloric effect (MCE) of Heusler-type Ni45Co5Mn36.7In13.3-xGex (x = 0, 2, and 3 at. %) metamagnetic shape memory alloys (MetaMSMAs) have been studied. Melt-spinning was used to prepare ribbons of these alloys since the ribbon shape ensures a high surface-to-volume ratio favoring a high heat exchange rate in a solid-state refrigeration. Furthermore, melt-spinning can induce a specific microstructure and stabilize metastable phases at room temperature. The ribbons were examined by X-ray diffraction at different temperatures, scanning electron microscopy, calorimetry, thermomagnetization, and magnetic field induced adiabatic temperature change measurements carried out across MT. It was found that Ge doping gave rise to enhanced antiferromagnetic interactions, stabilized martensitic phase, increased the MT temperature, causing larger magnetization jumps at MT and making narrower MT hysteresis. The x = 3 ribbon exhibited an inverse MCE at 303 K characterized by the isothermal magnetic entropy change value of |26.9|J/kgK at μ0H = 5 T and an adiabatic temperature change of ǀ1.5ǀ K at μ0H = 1.96 T. These values are comparable with the previously reported data on the Ni–Mn-based metamagnetic shape memory alloys in a bulk form.
Chi J, Xiao L, Wu Z, et al., 2023, A high-efficiency gas–liquid coupled heat-driven thermoacoustic heat pump, International Journal of Refrigeration, Vol: 155, Pages: 296-304, ISSN: 0140-7007
The search for a diversified and sustainable technology for energy utilisation is crucial for reducing the consumption of fossil energy. This research proposed a novel heat-driven thermoacoustic heat pump with a gas–liquid coupled resonator that exhibits high efficiency, compact structure and easy fabrication. A series of theoretical and experimental studies has been performed in this work, including numerical and experimental domestic heating performance, onset characteristics as well as the effects of different liquid masses and high and ambient temperatures on the performance of a heat pump. Results show that the theoretical and experimental heat pump performance exhibit good agreement, with a standard error of about 5%. Moreover, the gas–liquid coupled heat-driven thermoacoustic heat pump has a low onset temperature (70 °C at 3 MPa), offering a wide range of applications for low-grade thermal energy utilisation. With high, ambient and domestic heating temperatures of 300 °C, 10 °C and 50 °C, respectively, a maximum domestic heating power of 18.4 kW is obtained, corresponding to the maximum coefficient of performance of domestic heating based on heating power (COPh) of 1.48. Furthermore, a maximum relative Carnot efficiency of 50.9% and a COPh of 1.31 with a hot-end temperature of 300 °C are achieved under ambient and domestic heating temperatures of −20 °C and 50 °C, respectively. These results present a new domestic heating approach for the utilisation of medium- and low-grade thermal energy.
Wang R, Jia Z, Hu J, et al., 2023, Investigation on gas-coupled vibration damping modules in free-piston Stirling generator, Applied Thermal Engineering, Vol: 233, ISSN: 1359-4311
The free-piston Stirling generator (FPSG) is efficient and environmentally friendly. However, the inherent vibration limits FPSG's application and shortens its life. This paper presents two novel vibration damping modules, which are placed inside the FPSG with the vibration damping piston (VDP) driven by the pressure fluctuation in the back space. One is a passive vibration damping module (PVDM), and the other is an active vibration damping module (AVDM). By adjusting the movement of VDP, the sum of the momentums of the moving parts can be zero, thus eliminating the shell's vibration. For PVDM, the movement of VDP is adjusted by changing the opening of a needle valve. For AVDM, it is adjusted by changing the electric power of the linear alternator. The performances of these two modules are investigated based on SAGE software. Both PVDM and AVDM enable FPSG's shell to work without vibration under the design condition with minimal reduction of thermal-acoustic-electric conversion efficiency. When the damping coefficient of vibration damping piston, external load, and heating block temperature deviate from the design value, PVDM can reduce the vibration to a certain extent. AVDM can eliminate the vibration completely under any operating conditions. For this module, the acoustic power in the back space and the input electric power are its two main energy sources, and the input electric power is relatively small. The efficiency of the whole system is reduced by no more than 1% to eliminate the vibration. Adopting these two vibration damping modules can facilitate the application of the free-piston Stirling generator.
Xiao L, Luo K, Luo E, et al., 2023, A Summary: Dynamic and thermodynamic analysis of thermoacoustic and Stirling systems based on time-domain acoustic-electrical analogy, Applied Energy, Vol: 347, ISSN: 0306-2619
A unified fast transient simulation method for thermoacoustic and Stirling systems has been developed, named time-domain acoustic-electrical analogy (TDAEA) method. From a thermoacoustic theory point of view, the method captures the main acoustic impedance characteristics of the components and simplifies the calculations reasonably by using lumped models for components, thus remarkably reducing the computation. The TDAEA models of common components in thermoacoustic and Stirling systems are summarised with detail derivation. Two case studies are then carried out on free-piston Stirling generator (FPSG) and heat-driven thermoacoustic refrigerator (HDTR). Model verifications demonstrate the effectiveness and accuracy of the method: for the FPSG, the average deviation between the calculations and experiments in operating frequency, electric power, LA efficiency and thermal-to-electric efficiency are 5.0%, 16.3%, 2.4% and 26.9%, respectively; as for the HDTR, the deviation in cooling power lies in 29.9%. Using this method, transient evolutions can be obtained, which contains both start-up and steady stages. For start-up analysis, the transient operating frequency, pressure–volume diagram and limit cycle, etc, can be exhibited. Regarding the steady stage, the method is available to give the distribution of acoustic field and the losses in components. Moreover, the infulences of operating and geometric parameters on system performance can aslo be obtained. This study provides a new perspective and an effective method for fast transient simulation of thermoacoustic and Stirling systems, as well as gives a deeper understanding on the transient evolution of self-sustained oscillation and dynamic & thermodynamic cycles in these systems.
Huang J, Yang R, Wang J, et al., 2023, Performance evaluation of a liquid-sodium thermoacoustic engine with magnetohydrodynamic electricity generation based upon the Swift model, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, Vol: 154, Pages: 682-691, ISSN: 0001-4966
Chen Z, Hu J, Sun Y, et al., 2023, Piston offset inhibition method based on check valve backflow in a linear compressor, International Journal of Refrigeration, Vol: 151, Pages: 219-227, ISSN: 0140-7007
The linear compressor is one of the core components in cryogenic and refrigeration systems for space applications. Piston offset is a common phenomenon in linear reciprocating compressors, which can significantly deviate from the compressor's nominal design condition, thereby deteriorating performance. However, the reported work related to the methods of inhibiting piston offset is still limited. The check valve allows a unidirectional backflow, thus reducing piston offset. In this paper, a numerical study was performed on a linear compressor system with a check valve to explore the influence of operation parameters and valve parameters. Experiments were conducted on a prototype to validate the inhibition effect and compare it with the center port and DC superposition. This work may contribute to our understanding of eliminating piston offset in linear compressors in the future.
Xiao L, Luo K, Hu J, et al., 2023, Transient and steady performance analysis of a free-piston Stirling generator, Energy, Vol: 273, ISSN: 0360-5442
Free-piston Stirling generator (FPSG) is a promising distributed power generation system with compact configuration and high efficiency. In a new perspective on thermoacoustics, this paper develops a time-domain acoustic-electrical analogy method to explore the transient and steady-state performance of a highly efficient FPSG. The method captures the main characteristics of the FPSG, simplifying the calculation thus saving time, and its effectiveness has been verified by our experiments. Transient evolutions of key parameters such as volume flow rate, oscillating pressure and voltage, are first given, followed by an investigation of the acoustic field distribution. Subsequently, a performance analysis of the system is carried out. The results indicate that an increase in the damping coefficient leads to a deterioration in performance, particularly for the displacer. Operating parameters have strong influences on system performance: lower ambient temperature, higher heating temperature and larger external electric resistance contribute to higher pressure ratio and electric power, while excellent performance can be achieved at medium mean pressure. A maximum thermal-to-electric efficiency of 45.2% and a highest exergy efficiency of 68.0% are obtained at an electric resistance of 57.5 Ω and a heating temperature of 600 °C, accompanied by an electric power of 1517 W, which implies that the proposed FPSG has great promise in the field of kilowatt-scale distributed power generation. This paper provides a new viewpoint and an effective way for the rapid simulation of free-piston Stirling generator.
Chen G, Li Z, Li X, et al., 2023, Optimal cross-sectional area ratio between porous material and resonance tube for the onset of self-excited oscillations in standing-wave thermoacoustic engines, Thermal Science and Engineering Progress, Vol: 41
Thermoacoustic engines (TAEs) are heat-driven devices that rely on a temperature gradient in the porous material to initiate acoustic oscillations in the resonance tube. This study investigates the optimal cross-sectional area ratio between the porous material and resonance tube for the onset of self-excited acoustic oscillations in standing-wave TAEs. Experiments are conducted and numerical models are developed to explore the onset behavior of thermoacoustic systems. It is found that the system-level reduced-order network model can predict the onset temperature and frequency with high accuracy. There is an optimal area ratio between the porous material and resonance tube for achieving the lowest onset temperature. For the single-stage and double-stage TAEs with ambient air as the working fluid in this study, the lowest onset temperature of 79 K and 87 K are obtained with optimal area ratios being 3.5 and 5.1, and rh/δk (rh and δk are the hydraulic radius and thermal penetration depth) being 1.54 and 1.62, respectively. The research outcomes in this work will provide valuable guidance for the construction of low-onset-temperature thermoacoustic systems for low-grade heat recovery or energy harvesting purposes.
Xiao L, Luo K, Chi J, et al., 2023, Study on a direct-coupling thermoacoustic refrigerator using time-domain acoustic-electrical analogy method, Applied Energy, Vol: 339, ISSN: 0306-2619
Thermoacoustic refrigeration is a clean cooling technology with high reliability. In this study, a time-domain acoustic–electrical analogy (TDAEA) method is proposed and improved, then applied to explore the performance of a high-efficiency 2-stage looped direct-coupling heat-driven thermoacoustic refrigerator. The effectiveness of the method is verified by experiments. Transient evolutions of oscillating pressure and volume flow rate are first presented. System performance under different working gases is explored, and helium is chosen due to its much larger cooling power. The influences of cooling and ambient temperatures and cavity parameters on system performance are then investigated. The results show that a rise in ambient temperature leads to a dramatic decline in cooling power. Moreover, the influences of cavity parameters are complicated. When the diameter and length of the cavity are respectively 95 mm and 440 mm, the cooling power achieves a maximum of 3.65 kW with COP of 0.76; while with diameter and length reaching 90 mm and 360 mm, respectively, a peak COP of 0.82 with cooling power of 1.47 kW is obtained. Furthermore, a comparison between the presented direct-coupling system and a series-connection system is performed. The results show better performance of the direct-coupling system, which achieves a cooling power of 5.08 kW under air-conditioning case, 22.4 % higher than that of the series-connection system, implying its superiority in air-conditioning field for larger cooling capacity and more compact configuration. This study provides a new perspective for understanding ofthermoacoustic refrigerators.
Guan Y, Becker S, Zhao D, et al., 2023, Entropy generation and CO2 emission in presence of pulsating oscillations in a bifurcating thermoacoustic combustor with a Helmholtz resonator at off-design conditions, Aerospace Science and Technology, Vol: 136, ISSN: 1270-9638
In this work, we develop a 2D numerical model of a Y-shaped bifurcating combustor with a Helmholtz resonator attached. Propane (C3H8) is fueled and burnt with air by applying single-step eddy dissipation combustion model and k−ϵ−RNG turbulence model for simplicity. To validate the numerical findings, experimental measurements are conducted on a bifurcating Y-shaped thermoacoustic combustor with an off-design Helmholtz resonator implemented. It is found that the frequency and amplitude of the dominant mode as experimentally measured agree well with the numerical results. Further agreement is obtained between numerically and theoretically predicted mode-shapes. With the model validated, it is applied to gain insights on the entropy generation and nonlinearity of the pulsating oscillations and the flow fluctuations across the resonator neck. It is found that the nonlinearities are originated in the unsteady heat release rate of the premixed propane flame, and the mass flow rate across the resonator neck. In addition, the rate of the entropy production depends strongly on the temperature fluctuations. Approximately 99% of the entropy production rate involves with the temperature oscillations. Furthermore, it is non-uniformly distributed along the combustor. In addition, the energy conversion rate between total heat release rate and the acoustical energy production rate is less than 0.0001%. Finally, the production of CO2 is increased exponentially, and then reduced gradually in the axial flow direction. In general, the present work provides a low-cost numerical tool of a bifurcating thermoaocustic system. It could be applied to predict the acoustic signature of the combustor and to examine and evaluate the performance of the Helmholtz resonator on attenuating self-sustained thermoacoustic oscillations.
Hu J, Hu J, Sun Y, et al., 2023, A displacer coupled thermoacoustic cooler driven by heat and electricity, Applied Thermal Engineering, Vol: 220, ISSN: 1359-4311
A small-scale, heat-driven cooling system is required for the on-site liquefaction of unconventional natural gas in a distributed station. The thermoacoustic cooler has been considered a promising candidate for meeting such demands due to its high reliability and environmental friendliness. However, conventional thermoacoustic systems use a resonance tube to couple the thermoacoustic engine and cooler, which degrades cooling performance due to poor phase-shifting capability and significant power dissipation of the resonance tube. To overcome the limitation, this paper introduces a novel driven by heat and electricity thermoacoustic cooler using displacers to replace the resonance tube, which enables better phase-shifting capability and less power dissipation, thus allowing better cooling performance. Numerical investigation and experimental study are performed on the displacer-coupled thermoacoustic cooler driven by heat and electricity. Firstly, the design method of the displacers is presented based on the acoustic impedance matching principle. Numerical investigations are then conducted to understand the operational characteristics better to explore the axial distribution of critical parameters. The effects of the displacer damping coefficient, operating frequency, and mean pressure are further studied. Experimental investigations are then carried out to understand the impact of operating temperatures on system performance. Experimental results show that the system achieves a record thermal-to-cooling exergy efficiency of 13.4 % and cooling power of 117 W at heating and cooling temperatures of 773 K and 110 K. This represents an over 34 % improvement in efficiency when compared to the previous record-holder thermoacoustic cooler.
Wang R, Hu J, Jia Z, et al., 2023, Performance study of a free-piston Stirling heat pump with a circumferential temperature gradient in the heating heat exchanger, International Journal of Refrigeration, Vol: 146, Pages: 274-289, ISSN: 0140-7007
The free-piston Stirling heat pump (FPSHP) is efficient, environmentally friendly and has a wide available temperature range, making it a promising device for building heating. The temperature of the external heat-carrying fluid is different at the inlet and outlet of the heating heat exchanger, so there is a temperature gradient in the heating heat exchanger. The larger the scale of the FPSHP, the more pronounced the temperature gradient. However, the influence of such a temperature gradient on system performance has not been investigated so far. This paper therefore presents a detailed study of the FPSHP with a circumferential temperature gradient in the heating heat exchanger. The calculation results show that a cascade output of energy can be achieved when there is a circumferential temperature gradient in the heating heat exchanger. With the same outlet temperature, the larger the temperature difference between the inlet and outlet of the heating heat exchanger, the higher the COP. However, due to the mixing of internal working gases with different temperatures in the compression space, part of the high temperature heat is directly transferred to the low temperature module and output at a lower level, adversely affecting system efficiency. Fortunately, this adverse effect is found to be insignificant when compared with multiple independent small FPSHPs without circumferential temperature gradients. Considering the higher investment cost of multiple small FPSHPs, a single large FPSHP is also a good choice for large heating capacity demand.
Xiao L, Luo K, Zhao D, et al., 2023, Time-domain acoustic-electrical analogy investigation on a high-power traveling-wave thermoacoustic electric generator, ENERGY, Vol: 263, ISSN: 0360-5442
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- Citations: 4
Chi J, Yang Y, Wu Z, et al., 2023, Numerical and experimental investigation on a novel heat-driven thermoacoustic refrigerator for room-temperature cooling, Applied Thermal Engineering, Vol: 218, ISSN: 1359-4311
We report a two-unit thermoacoustic refrigerator driven by medium- and low-grade thermal energy for the room-temperature cooling. Carefully designed slim tubes and cavities were adopted as an efficient resonance component to further increase the power density of system. Systematic experiments, including onset characteristics, refrigeration performances, and impacts of DC (direct-current) and jet flow were tested for a comprehensive understanding of the working mechanism of the system. Experimental results show that a minimum onset temperature of 64 °C could be obtained, revealing a wide application foreground for low-grade thermal energy recovery. Additionally, a cooling power ranging from 0.66 kW to 5.62 kW, with the corresponding coefficient of performance from 0.12 to 0.41 and the cooling temperature from −30 °C to 10 °C, was achieved. Importantly, a power density as high as 14.95 kW/m3 was obtained. To the authors’ knowledge, this is the highest ever power density achieved in heat-driven thermoacoustic refrigerators for room-temperature cooling, with similar heating temperatures. This demonstrates attractive application for heat-driven room-temperature cooling.
Li Z, Yang C, Zhang Q, et al., 2023, Standardized Volume Power Density Boost in Frequency-Up Converted Contact-Separation Mode Triboelectric Nanogenerators, Research, Vol: 6, ISSN: 2096-5168
The influence of a mechanical structure's volume increment on the volume power density (VPD) of triboelectric nanogenerators (TENGs) is often neglected when considering surface charge density and surface power density. This paper aims to address this gap by introducing a standardized VPD metric for a more comprehensive evaluation of TENG performance. The study specifically focuses on 2 frequency-up mechanisms, namely, the integration of planetary gears (PG-TENG) and the implementation of a doublecantilever structure (DC-TENG), to investigate their impact on VPD. The study reveals that the PG-TENG achieves the highest volume average power density, measuring at 0.92 W/m3. This value surpasses the DC-TENG by 1.26 times and the counterpart TENG by a magnitude of 69.9 times. Additionally, the PG-TENG demonstrates superior average power output. These findings introduce a new approach for enhancing TENGs by incorporating frequency-up mechanisms, and highlight the importance of VPD as a key performance metric for evaluating TENGs.
Jiang Z, Xu J, Yu G, et al., 2023, A Stirling generator with multiple bypass expansion for variable-temperature waste heat recovery, Applied Energy, Vol: 329, ISSN: 0306-2619
Recovery heat from exhaust gas is a promising field in the context of global deepening of energy conservation and emission reduction. Small scale and cascade temperature variation make the exhaust gas waste heat recovery difficult. In order to make full use of the exhaust gas waste heat, a novel Stirling generator with a multiple-bypass configuration is proposed to fulfill the demand for recovery over a wide and continue temperature range. The exhaust gas is simplified into variable-temperature heat resource (VTHS, heat release accompanied by a decrease in temperature) and the cascade heat exchangers in the proposed system are assumed to converse heat with VTHS absorption continuously. In this paper, the ideal power efficiency of an infinite-stage generator is calculated. Then, a model of a 3-stage Stirling generator is established in software Sage. Theoretical analyses, exergy analyses and parameters analyses are carried out. The performance comparison between single-stage, 2-stage and 3-stage is presented at last. The result represents a significant increase by 29.3% in electric power when compared to the traditional single-stage system. These findings suggest a novel promising energy conversion technology for cascade utilization of exhaust gas waste heat.
Hu Y, Wang X, Wu Z, et al., 2022, A thermoacoustic cooler with a bypass expansion for distributed-temperature heat loads, APPLIED PHYSICS LETTERS, Vol: 121, ISSN: 0003-6951
Chi J, Chen L, Chen G, et al., 2022, Numerical study on a heat-driven thermoacoustic cryocooler operating near liquid-helium temperature ranges, Applied Thermal Engineering, Vol: 216, ISSN: 1359-4311
In recent decades, the demands for cooling requirements near liquid-helium temperature ranges, i.e., 4 K, are becoming urgent for the increasing developments in frontier science of aerospace exploration, medical science and superconductivity power. Existing cryocoolers capable of achieving near liquid-helium temperatures contain moving components that reduce the reliability and lifetime. To solve the problem, a novel heat-driven thermoacoustic cryocooler without any moving components is proposed in this paper. Theoretical analyses are first performed on the thermoacoustic cryocooler to explore the no-load temperature and system performance. With a heating temperature of 923 K, the calculated results show that the no-load temperature of 5.9 K is achieved at the cold end. For a better understanding of the process of internal energy conversion, distributions of key parameters are presented. Investigations are further performed on exergy losses of components. The effects of key parameters, including liquid mass, cooling temperature and heating temperature, are then studied under different mean pressures. With a heating temperature of 923 K, the cryocooler achieves a maximum cooling power of 21.5 mW at a cooling temperature of 6 K. When the cooling temperature is increased to 12 K, the maximum cooling power is 509 mW. These findings extend the lowest possible temperature achievable for the thermoacoustic cryocoolers, and open new avenues for their applications in the ultra-low cryogenic cooling.
Xiao L, Xu J, Luo K, et al., 2022, Numerical study of a heat-driven thermoacoustic refrigerator based on a time-domain lumped acoustic–electrical analogy model, Energy Conversion and Management, Vol: 268, ISSN: 0196-8904
Thermoacoustic technology is a promising clean energy solution for the recovery of low-grade heat from renewable energy sources and waste heat. Existing methods for simulating thermoacoustic systems are inconsistent or time-consuming. In this study, a time-saving and reliable time-domain lumped acoustic–electrical analogy model is proposed to investigate the performance of thermoacoustic systems. In the proposed model, each component of a thermoacoustic system is simplified as a lumped acoustic–electrical analogy model. The nonlinear effects of both regenerator and liquid acoustic resistances in gas–liquid resonators are considered to obtain nonlinear dynamic evolution equations. Case studies were performed on a looped heat-driven thermoacoustic refrigerator for low-grade heat recovery to investigate its onset and steady characteristics. The evolutions of the oscillating pressure and volume flow rate were explored, which initially increase rapidly until reaching the saturation state. The minimum onset temperature was 32.5 K at a pressure of 2.5 MPa with hydrogen as the working gas. In addition, the influences of the mean pressure, heating temperature, and cooling temperature on the steady-state system performance with various working fluids were investigated. The results indicated that the cooling power increased significantly with increasing mean pressure, heating temperature, and cooling temperature. A higher working liquid density resulted in a lower onset temperature, lower working frequency, and larger pressure ratio. With the use of helium or hydrogen, the refrigerator performed better in terms of a lower onset temperature and a larger pressure ratio, cooling power, and coefficient of performance. The proposed model provides a new perspective and an effective approach to characterise the onset and steady characteristics of thermoacoustic systems.
Chen G, Xu J, 2022, Development of a small-scale piezoelectric-driven thermoacoustic cooler, Applied Thermal Engineering, Vol: 213, ISSN: 1359-4311
With the continuous increase of system power and shrinkage of size, heat removal from central processing units in electronic devices becomes more challenging. In this study, a small-scale piezoelectric-driven thermoacoustic cooler (TAC) is proposed as a novel method for electronic cooling. A prototype of the TAC that is merely 7.5 cm long, 2.3 cm in diameter, and uses ambient air as working fluid, has been built and tested. Theoretical models based on linear acoustics and thermoacoustics are established to predict the acoustical and thermal characteristics of the TAC. Results show that the piezoelectric-driven TAC achieves high pressure amplitudes at 1743 Hz (i.e., the acoustic resonance frequency of the acoustic cavity) and 2717 Hz (i.e., the mechanical resonance frequency of the piezoelectric actuator). A maximum temperature difference of 4.4 ℃ is obtained when the TAC operates at 2717 Hz with an electric power input of around 0.4 W. Approaches to further improve the cooling performance of the TAC are suggested. This work demonstrates the great potential of TACs, extending the application of thermoacoustic technology in thermal management of miniature electronics.
Chen G, Xu J, 2022, Active control of heat transport inside the porous material of a looped-tube dual-acoustic-driver thermoacoustic refrigerator, CRYOGENICS, Vol: 125, ISSN: 0011-2275
Yang Y, Chi J, Wu Z, et al., 2022, A heat-driven combined cooling and heating system based on thermoacoustic technology, Applied Physics Letters, Vol: 120, ISSN: 0003-6951
Energy crisis and environmental pollution have become global issues. This study reported a heat-driven combined cooling and heating system based on thermoacoustic technology, which adopted two units of thermoacoustic engine and cooler cores to improve the efficiency. This system can be used as a refrigerator and a heat pump at the same time. Experimental results showed that with a charging pressure of 10 MPa, a high temperature of 300 °C, and a medium temperature of 45 °C, cooling power ranging from 0.61 to 3.89 kW and coefficient of performance varying from 0.08 to 0.30 with low temperature changing from -30 to -5 °C were achieved when the system was working as a refrigerator. Meanwhile, under a low temperature of -30 and -10 °C, a heating power of 7.85 and 14.3 kW with a medium temperature of 45 °C could be achieved corresponding to a coefficient of performance of 1.08 and 1.24 when the system was working as a heat pump. These experimental performances show remarkable advantages and a promising prospect for thermal energy utilization in the future.
Wang X, Xu J, Wu Z, et al., 2022, A thermoacoustic refrigerator with multiple-bypass expansion cooling configuration for natural gas liquefaction*, APPLIED ENERGY, Vol: 313, ISSN: 0306-2619
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- Citations: 8
Xu J, Hu J, Luo E, et al., 2022, Numerical study on a heat-driven piston-coupled multi-stage thermoacoustic-Stirling cooler, APPLIED ENERGY, Vol: 305, ISSN: 0306-2619
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- Citations: 16
Chi J, Xu J, Zhang L, et al., 2021, Study of a gas-liquid-coupled heat-driven room-temperature thermoacoustic refrigerator with different working gases, ENERGY CONVERSION AND MANAGEMENT, Vol: 246, ISSN: 0196-8904
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- Citations: 15
Xu J, Luo E, Hochgreb S, 2021, A thermoacoustic combined cooling, heating, and power (CCHP) system for waste heat and LNG cold energy recovery, ENERGY, Vol: 227, ISSN: 0360-5442
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- Citations: 34
Xu J, Jian S, Kai W, et al., 2020, A hybrid photovoltaic-thermal (PV-T) based combined cooling, heating and power system for tourism sectors in hot climate zones, International Conference on Applied Energy 2020
Xu J, Hu J, Sun Y, et al., 2020, A cascade-looped thermoacoustic driven cryocooler with different-diameter resonance tubes. Part II: Experimental study and comparison, ENERGY, Vol: 207, ISSN: 0360-5442
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- Citations: 17
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