• Another Science Thesis before the School’s Centenary!


    International Research Team Develops a New Flexible Refrigeration Strategy

    Finding more efficient, energy-saving and green, portable refrigeration methods are the direction that human being is constantly struggling for. In today's (October 11th) online publication of the Science, a research project by an international joint research team between Nankai University and Texas State University at Dallas has been published, finding a new flexible refrigeration strategy: ‘Torsional Refrigeration’. Researchers found that changing the internal twist of the fiber can achieve refrigeration. Due to the higher refrigeration efficiency, smaller size and more suitability for a variety of common materials such as natural rubber, fishing line and nickel-titanium alloy, the ‘torsional refrigerator’ made by this method has also become promising.

    The discovery comes from the joint research by Professor Liu Zunfeng’s team from the College of Pharmacy of Nankai University and the Key Laboratory of Medicinal Chemistry Biology and the Key Laboratory of Functional Polymers, and Professor Ray H. Baughman’s team from Texas State University in Dallas. Professor Baughman has also been a lecturer of Nankai University’s Yang Shixian Lecture. Liu Zunfeng and Ray H. Baughman are the co-authors of the paper, and Nankai University is the first institute.

    Electric Energy Saving and Cost Reducing

    According to data from the International Refrigeration Research Institute, the world's energy consumption of air conditioning and refrigerator refrigeration accounts for about 20% of global energy consumption. Nowadays it is widely used in the principle of air compression, and its Carnot efficiency is generally less than 60%. The gas released by the traditional refrigerator during the refrigeration process is increasing the warming of the earth. As humans demand for refrigeration increases, it is imperative to explore new refrigeration theories and solutions to further improve refrigeration efficiency, reducing costs and minimizing the size of refrigeration equipment.

    The temperature of the stretched rubber will heat up and it will reduce after the rubber shrinking. This phenomenon is called ‘Elastic Thermal Refrigeration’. Other solid-state refrigeration technologies include new solutions, such as electrothermal refrigeration, magnetocaloric refrigeration, and nickel-titanium shape memory materials. However, the Carnot efficiency of these refrigeration technologies does not exceed the air compression refrigeration technology.

    Natural rubber-based ‘Elastic Thermal Refrigeration’ was discovered as early as the first decades of the 19th century. However, in order to obtain a better refrigeration effect, it is necessary to stretch the rubber to a very long size in advance. Through the ‘Torsional Refrigeration’ technology, people only need to solve the problem through untwisting. ‘Preliminary experiments have confirmed that the ‘Torsional Refrigeration’ technology can achieve a Carnot efficiency of 67%. This means that by using ordinary materials such as rubber and fishing lines, it is expected to achieve higher Carnot efficiency so that we can save more energy and reduce the cost of refrigeration’ said Professor Liu Zunfeng.

    ‘Reverse Torsional Refrigeration’ Effect and the ‘Torsional Refrigeration’ Color Change

    Under normal circumstances, the phenomenon of ‘Torsional Refrigeration’ using fishing lines is: the temperature rise when the line stretches, and the temperature drop when the line shrinks. ‘By using the opposite twist and spiral directions, we can achieve stretching refrigeration. This phenomenon is very peculiar’ said Professor Ray H. Baughman.

    The fiber is twisted and wound into a spiral, and if the twisting direction of the fiber is opposite to the prepared spiral direction, a ‘reverse spiral’ can be made. Unlike the conventional ‘Torsional Refrigeration’ effect, this ‘reverse spiral’ structure of rubber elastomers and fishing lines cools down under tension. This novel phenomenon is called the ‘Reverse Torsional Refrigeration’ effect.

    Another special phenomenon of Torsional Refrigeration’ is that different parts of the fiber exhibit different temperatures (In the infrared imager, the rise of temperature will be displayed in red and the cooling in blue). This is due to the periodic distribution of the spirals produced by the fiber twisting along the length of the fiber.

    Liu Zunfeng believes that the new refrigeration technology discovered by the research has expanded a new sector for the refrigeration field. It will provide a new way to reduce energy losses in the refrigeration sector.

    Also participated the research: University, Wuhan University, Georgia Southern University, Tsinghua University Shenzhen International Graduate School, Linde (United States) Research Center, Brazil Campinas State University, Tianjin University of Technology, Liaoning University of Science and Technology, China Pharmaceutical University and other institutes.