The developments in urban rail transit (URT) construction are associated with the benefits of moving people efficiently and the negative impacts of noise and vibrations caused to surroundings. Despite a proliferation of studies conducted throughout the world, very few studies employed the field measurement approach due to various limitations. Using a metropolitan city, Tianjin (China), as an example, field measurement was set up to monitor the indoor vibration and noise spectrum in buildings near urban rapid transit lines to establish a baseline as well as the effectiveness of corresponding mitigation measures, namely wheel-rail polishing and train speed reduction. While our study suggests a maximum 6 dB reduction in indoor vibration, the effectiveness of noise and vibration reduction measures depends on the attenuation of the main frequency corresponding to the secondary radiation noise of the indoor vibration excitation in the building. In our field test, the peaks of the frequency spectrum were found to be 40, 50, 63 and 80 Hz. The secondary radiation noise attenuation and vibration were invariant to the change in frequency spectrum. Mitigation measures such as polishing may cause vibration frequency to peak in non-main frequency spectrums. URT speed reduction will lead to vibration and noise attenuation energy being concentrated at around 50 Hz. Given the presently inconsistent and widely varying industrial and international standards, this study can provide important field measurement data supporting future development in standards, regulation and legislation with respect to URT development, especially in mature townships.

Phase change materials (PCMs) are widely applied in recent decades due to their good thermal performance in energy systems. Their applications are mainly limited by the phase change temperature and latent heat. Many publications are reported around the characteristic improvement of binary organic PCMs. The thermal stability study on organic binary PCMs used in thermal energy storage applications becomes fundamental and meaningful. In this study, thermal stability of three types of organic binary PCMs was experimentally investigated, which are frequently used in building and industry applications. To qualitatively investigate the stability of composite PCMs, differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FT-IR) spectra testing of samples were also conducted. Experimental results showed that the selected composite PCMs, capric acid (CA), and myristic acid (MA), had the best thermal performances, with its phase change temperature unchanged and heat of fusion decreased only 8.88 J/g, or 4.55%, after 2000 thermal cycles. Furthermore, quality ratio of required PCMs as the variation of operation duration was analyzed to quantitatively prepare the materials. The PCMs can successfully operate about 3125 times when prepared as 1.20 times of its calculated value by starting fusion heat. Conclusions of this research work can also be used for guiding the selection and preparation of other energy storage materials.

An experimental study was conducted on the optimal charge of carbon dioxide in water–water heat pump systems (WWHPSs) with and without an internal heat exchanger (IHX). An appropriate carbon dioxide charge standard was obtained from the experimental results. All tests were conducted with the inlet and outlet water temperatures set to 12°C and 7°C in the evaporator, respectively and 20°C and 55°C in the gas cooler, respectively. During the tests, the evaporation temperature was 0°C. The coefficient of performance of cooling (COPc) and coefficient of performance of heating (COPh) increased by 8.3% and 0.7% in the WWHPS with an IHX compared with the WWHPS without an IHX. Under the test conditions, the optimal carbon dioxide charges with and without an IHX were found to be 2.0 kg and 2.25 kg, respectively. The test results show that the optimal carbon dioxide charge decreases by 11.1% when an IHX is included in the WWHPS.