An effective system for monitoring, reporting and verification (MRV) is the cornerstone of any carbon emissions trading market. This paper analyses existing MRV frameworks in China, including under the seven emission trading pilot schemes, to identify four key challenges for the establishment of an effective MRV system for China's forthcoming national carbon emissions trading market: (1) ambiguity in the legal status of relevant policies and regulations, (2) unclear requirements for the content of monitoring plans, (3) lack of consistency and harmonization in accounting and reporting guidelines, and (4) lack of information technology (IT). The paper then considers the experiences and lessons of the European Union Emissions Trading Scheme (EU-ETS) and the MRV systems in the seven carbon emissions trading pilots, and puts forward suggestions for tackling the four key challenges. Key policy insights. It is crucial to create general framework legislation that is legally binding and of a sufficiently high legal status to facilitate legal enforcement of the MRV requirements and increase the compliance levels of MRV activities.. Clear rules on the content of the monitoring plan and development of templates would harmonize approaches across regions and between reporting entities.. It is important for implementing regulations to include specific requirements on monitoring and reporting in order to ensure compliance with the main monitoring and reporting principles.. Use of IT should gradually evolve towards an integrated system that covers the whole compliance cycle, including monitoring plans, emission reports, verification and verification management, as well as multiple stakeholder access.

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Within the pressure range of 9-28 MPa, mass velocity range of 600-1 200 kg/(m 2 · s), and heat flux range of 200-500 kW/m 2 , experiments were performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with an inclined angle of 19.5 degrees, a maximum outer diameter of 38.1 mm, and a thickness of 7.5 mm. Based on the experiments, it was found that heat transfer enhancement of the internally ribbed tube could postpone departure from nucleate boiling at the sub-critical pressure. However, the heat transfer enhancement decreased near the critical pressure. At supercritical pressure, the temperature difference between the wall and the fluid increased near the pseudo-critical temperature, but the increase of wall temperature was less than that of departure from nucleate boiling at sub-critical pressure. When pressure is closer to the critical pressure, the temperature difference between the wall and the fluid increased greatly near the pseudo-critical temperature. Heat transfer to supercritical water in the inclined upward internally ribbed tube was enhanced or deteriorated near the pseudo-critical temperature with the variety of ratio between the mass velocity and the heat flux. Because the rotational flow of the internal groove reduced the effect of natural convection, the internal wall temperature of internally ribbed tube uniformly distributed along the circumference. The maximum internal wall temperature difference of the tube along the circumference was only 10 degrees when the fluid enthalpy exceeded 2 000 J/g. Considering the effect of acute variety of the fluid property on heat transfer, the correlation of heat transfer coefficient on the top of the internally ribbed tube was provided.