2024-02-03 13:10:00
A team of researchers led by Professor LUO Ercang from the Institute of Physics and Technical Chemistry (TIPC) of the Chinese Academy of Sciences, in collaboration with other experts, has developed an innovative thermally driven thermoacoustic refrigerator (HDTR). This new bypass configuration significantly improves the efficiency of this technology.
The HDTR is recognized as a promising new cooling technology with many advantages. For example, it has no moving parts, uses environmentally friendly substances (like helium and nitrogen), and is very reliable. However, its relatively low efficiency has hampered its commercial application.
The efficiency of HDTRs can be estimated by the coefficient of performance (COP), i.e. the ratio between the output cooling power and the input heating power. For existing advanced direct-coupled HDTRs, the researchers found an unexpected decrease in COP with an increase in heating temperature. Furthermore, they discovered the reason: there is a temperature matching constraint in these systems that prevents COP improvement at high heating temperatures.
An innovative configuration for greater efficiency
To overcome this obstacle, the researchers proposed a creative bypass configuration to eliminate the temperature matching constraint. This new configuration allows a portion of the acoustic power to be bypassed, thereby achieving efficient acoustic power matching between the motor unit and the cooling unit at high heating temperatures.
As a result, the system achieves energy flow field synergy, which significantly improves efficiency. The researchers then built a prototype HDTR on the kilowatt scale.
Using helium as the working gas, they achieved a record experimental COP of 1.12 with a cooling capacity of 2.53 kW, at heating, ambient, and cooling temperatures of 450 °C, 35 °C, and 7 °C. C, respectively. This COP is 2.7 times higher to the best result ever obtained for existing HDTRs.
The new thermoacoustic refrigerator controlled by heat and its performance. Credit: TIPC
A promising technology for commercial applications
According to the researchers, in the field of room temperature and thermal drive refrigeration, their new HDTR technology not only outperforms adsorption refrigerators and single-effect absorption refrigerators, but is comparable to double-effect absorption refrigerators. These results highlight the great potential of this new HDTR technology in commercial air conditioning applications.
Compared to helium, nitrogen is a more abundant, economical and environmentally friendly refrigerant. Therefore, the researchers also tested the performance of the system using nitrogen. The COP results are better than those previously reported by the TIPC.
Exceptional potential for the future
Researchers say the new HDTR system has an inherently higher COP than absorption refrigerators due to its efficient use of thermal energy at high temperatures. Their numerical analysis suggests a potentially exceptional COP value of 2 for the proposed HDTR system at a heating temperature of over 800 ℃.
The researchers said they will make some modifications to the current system and increase the heating temperature to further improve the system’s cooling performance. After making this change, they plan to achieve a COP that exceeds double-acting absorption refrigerators in the foreseeable future.
Article : “A highly efficient heat-driven thermoacoustic cooling system” – DOI: 10.1016/j.xcrp.2024.101815
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