Zhanghua Wu

Bio: Zhanghua Wu is an academic researcher. The author has contributed to research in topics: Carnot cycle & Refrigerator car. The author has an hindex of 1, co-authored 1 publications receiving 4 citations.

A Traveling Wave Thermoacoustic Refrigerator within Room Temperature Range

Abstract: Thermoacoustic refrigerators use sound waves to generate cooling. Furthermore, they use inert gases that are friendly to the environment. Their unique working mechanism and promising future have attracted many researchers. This article focuses on the design of a traveling wave thermoacoustic refrigerator that works in the civil refrigeration range, since traveling wave refrigerators have higher efficiencies than standing wave refrigerators. According to linear thermoacoustic theory, two analytical methods, the lumped-element network and transfer matrixes, are discussed for analysis of the thermoacoustic systems. Several possible modes for achieving efficient thermoacoustic refrigeration are analyzed with the simplified lumped-element network method. Then, a feasible thermoacoustic refrigeration mode is chosen and optimized with the transfer matrix method. The goal is to achieve a relatively high cooling capacity at a temperature of 250 K. The calculation results show that, with helium, the refrigerator can have a cooling power of 80 W and achieve a COP of 2.86; this corresponds to a relative Carnot efficiency of 57%. According to this, we have constructed a refrigerator. It has achieved a no-load cooling temperature of 263 K when driven by a mechanical compressor with helium, and achieved a cooling power of 80 W at 274 K when driven by a standing wave thermoacoustic engine with nitrogen at the pressure ratio of 1.09.

The Prospects of Alternatives to Vapor Compression Technology for Space Cooling and Food Refrigeration Applications

Abstract: This article identifies and describes five alternative cooling technologies (magnetic, thermionic, thermoacoustic, thermoelectric, and thermotunnel) and qualitatively assesses the prospects of each technology relative to vapor compression for space cooling and food refrigeration applications. Assessment of the alternatives was based on the theoretical maximum percent of Carnot efficiency, the current state of development, the best percent of Carnot efficiency currently achieved, developmental barriers, and the extent of development activity. The prospect for each alternative was assigned an overall qualitative rating based on the subjective, composite view of the five characteristics.

A Study of a Loudspeaker-driven and a Thermo-Acoustically-driven Travelling-wave Thermo-Acoustic Refrigerator

Abstract: This paper describes the experimental investigation conducted on a Loudspeaker-Driven Thermo-Acoustic Refrigerator (LDTWTAR), a Standing Wave Thermo-Acoustic Engine (SWTAE) and a Thermo-Acoustically Driven Travelling Wave Thermo-Acoustic Refrigerator (TADTWTAR). This work aims at getting an insight into the coupling of a standing wave thermo-acoustic engine and a travelling wave thermo-acoustic refrigerator and to investigate its potential for cooling. Experiments were conducted in three stages. First, an analysis of LDTWTAR to analyze the effect of the geometric configuration on the temperature difference across the regenerator and to get an insight into the effect of the parameters of the system on its performance. Secondly, analysis of a SWTAE to investigate the relationship between the frequency of the engine and the length of the resonator. Lastly, both the SWTAE and the TWTAR were coupled together to form a TADTWTAR system. An experiment on the coupled system was conducted to get an insight into the coupling of a SWTAE and a TWTAR and analyse how the parameters of the SWTAE affect the cooling performance. The investigation of the SWTAE has shown that longer resonator lengths and lower power inputs yield lower frequencies, longer onset time and higher onset temperature of the engine. The investigation of the LDTWTAR has shown that different configurations of the refrigerator loop give different results indicating that the geometric configuration of the thermo-acoustic system affects its performance. Lastly, the investigation of the TDTWTAR showed a potential of the coupling even though the results reported were significantly hindered by the limitations inherent of the SWTAE considered, particularly the heat source.