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Phase change material (PCM) can be used in building envelope for heat insulation and energy-saving. However, the energy-saving effect of the PCM wall system is limited in summer since the PCM storing heat in the daytime will become a secondary heat source and release heat into the room again at night. This paper proposed a novel pipe-encapsulated PCM wall system. It integrates phase change technology and nocturnal radiation cooling technology together to realize building insulation and active heat removal. A simulation platform is established for the thermal performance simulation of this wall system. It mainly includes the simplified pipe-encapsulated PCM wall model and nocturnal radiation model. The simplified wall model includes the 5R2C wall model, 4R2C PCM model and 2R1C pipe model. The model parameters are identified and the model is also validated with good accuracy. Based on this platform, the thermal performance of a light weight room with pipe-encapsulated PCM wall system in Wuhan is simulated. About 50%-60% of heat from the outdoor environment can be conserved by the pipe-encapsulated PCM wall, and 50% of that can be removed by the radiant cooler at night. Results show the pipe-encapsulated PCM wall system has good thermal performance for light weight building.

Heavy-duty vehicles powered by compressed natural gas (CNG) store the fuel in large onboard cylinders. Fast fill of depleted CNG cylinders is a common refueling method because it achieves refueling time comparable to liquid fuels. However, under-filling of CNG cylinders occurs during fast fill due to the recompression work of CNG in the cylinder that heats the fuel during the fill. The heated fuel has a lower density at the rated pressure, and thus less mass of CNG can be stored than if it was at ambient temperature. To increase the mass of dispensed CNG during fast fill, an active heat removal method is proposed. In this study, analytical and numerical models of the filling process of CNG into a Type-III cylinder with and without active heat removal are developed. In the analytical study, mass and energy conservation equations are coupled with an ideal-gas equation of state and orifice flow equations to predict the heat generation rates during fast fill. The influence of heat removal via a cooling coil inserted into the cylinder during fill on the dispensed mass and fill time is quantified. The analytical study is compared to numerical simulations employing a two-dimensional axisymmetric computational fluid dynamics (CFD) model for unsteady, compressible turbulent flow in a Type-III cylinder with and without active heat removal. Dynamic average temperature, pressure and mass curves as well as the local temperature distribution in the cylinder are obtained at different time instances during the fill. The effect of the location of the heat removal coils is also investigated. The results of the analytical/numerical study illustrate the benefit of heat removal from the cylinder as a means of improving fast-fill efficiency in natural gas fueled heavy-duty vehicles. [ABSTRACT FROM AUTHOR]