K. Tang

Low temperature difference thermoacoustic prime mover with asymmetric multi-stage loop configuration

Environmentally friendly and low-cost technologies to recover low-grade heat source into usable energy can contribute to ease the energy shortage. Thermoacoustic technology is expected as one promising approach in this ascendant field. In this work, the multi-stage looped thermoacoustic prime movers with asymmetric configuration, which can provide travelling-wave resonator and appropriate acoustic field for efficient regenerator, have been proposed and experimentally studied. The presented looped thermoacoustic prime movers can start to oscillate with quite low temperature difference along the regenerator. The lowest onset temperature difference obtained in the experiments is only 17 °C (the corresponding heating temperature is 29 °C), which can be achieved in both three-stage and four-stage looped thermoacoustic prime movers, with CO2 of 1 MPa or 1.5 MPa as the working fluid. An electric generator driven by a three-stage looped thermoacoustic prime mover with low heating temperature was tested to achieve the acoustic to electric conversion.

Experimental Investigation of Thermoacoustically Driven Pulse Tube Refrigerator Using Noble Gas Mixtures

Based on the estimation of thermophysical properties of binary noble gas fluids, He-Ar mixtures are used as working fluids to improve the performance of a pulse tube refrigerator driven by a thermoacoustic engine. Computed and experimental results are reported in detail, and some discussion is given. With 20% molar fraction of Ar the refrigeration temperature was lowered by 3 K as compared to pure He.

Theoretical prediction on the coupling of thermoacoustic prime mover and RC load

Publisher Summary This chapter investigates a thermoacoustic prime mover to use it to drive a load, such as a pulse tube refrigerator or a thermoacoustic refrigerator etc. When the load is connected to the prime mover, the coupling between them is of great importance for the performance of the thermoacoustic system. To investigate the coupling relation, a standing wave thermoacoustic prime mover connected with an RC (resistance and capacitance) load is simulated with linear thermoacoustics. The coupling of thermoacoustic prime mover and its load is of great importance for the performance of thermoacoustic system. A standing wave thermoacoustic prime mover with RC load is simulated, and the influence of RC load and dimensions of the resonance tube on the behavior of the thermoacoustic system is discussed according to the computed results. The computed results indicate that the behavior of the thermoacoustic system is greatly influenced by the impedance of the load and the dimensions of the resonance tube. C of RC load is a key influencing factor when 1/ωC is larger than R, while R is of great importance, when 1/ωC is less than R. The maximum acoustic power output can be achieved when 1/ωC equals to R, while pressure amplitude is the minimum and hot end temperature of the stack is the highest.

Thermoacoustically driven pulse tube refrigeration below 90K

Publisher Summary This chapter focuses on the matching between thermoacoustic prime mover and pulse tube refrigerator, especially the frequency matching. Recent modification has been made to improve the refrigeration performance of thermoacoustically driven pulse tube refrigerator, and a refrigeration temperature as low as 88.6K, with helium filling of 2.1MPa as the working fluids, is achieved. The onset temperature is reduced about 200oC (from 550oC to 340oC) by the simple operation of the double inlet valve which would broaden the utilization of low-grade heat energy. With helium as working fluid (filling pressure of 2.1MPa), an 8 m resonant tube results in a resonance frequency of 44 Hz (the input power is 2200 Watts), and a refrigeration temperature of 88.6K is obtained in self-made thermoacoustically driven pulse tube refrigerator system while the mean pressure and the pressure ratio are 2.64MPa and 1.128, respectively. The simple operation on the double inlet valve, which was closed before the onset of acoustic oscillation and turned to the optimal value as soon as the oscillation started, could decrease the onset temperature of the system greatly. It would broaden the access of utilizing the low-grade heat energy.

Chapter 65 – Influence of He-H2 Mixture Proportion on the Performance of Pulse Tube Refrigerator*

Publisher Summary This chapter explores the influence of mixture working fluids on the pulse tube refrigeration performance. The performance of pulse tube refrigerator (PTR) can be improved by using mixtures as its working fluid. Based on an experimental work on a two-stage PTR with He-He 2 mixture whose hydrogen percentage rising from 0% to 100%, an optimal proportion of H 2 in the He-He 2 mixture for the cooling temperature around 30K is found. The pulse tube refrigeration performance with He-H 2 mixtures is better than that with pure helium in 30K cooling temperature region when the hydrogen fraction is less than about 80%. A 30–45% increment of both the cooling power and COP has been obtained with 60–70% H 2 in He-H 2 mixtures. The great performance improvement of the PTR may be attributed to not only the excellent cycle thermodynamic performance and the reasonable heat transfer and flow properties of He-H 2 mixtures, but also the high volume specific heat of Er 3 NiH x regenerative materials.

Influence of He-H 2 Mixture Proportion on the Performance of Pulse Tube Refrigerator

Publisher Summary This chapter explores the influence of mixture working fluids on the pulse tube refrigeration performance. The performance of pulse tube refrigerator (PTR) can be improved by using mixtures as its working fluid. Based on an experimental work on a two-stage PTR with He-He 2 mixture whose hydrogen percentage rising from 0% to 100%, an optimal proportion of H 2 in the He-He 2 mixture for the cooling temperature around 30K is found. The pulse tube refrigeration performance with He-H 2 mixtures is better than that with pure helium in 30K cooling temperature region when the hydrogen fraction is less than about 80%. A 30–45% increment of both the cooling power and COP has been obtained with 60–70% H 2 in He-H 2 mixtures. The great performance improvement of the PTR may be attributed to not only the excellent cycle thermodynamic performance and the reasonable heat transfer and flow properties of He-H 2 mixtures, but also the high volume specific heat of Er 3 NiH x regenerative materials.