A hydrogen production method is proposed, which utilizes solar energy powered thermodynamic cycle using supercritical carbon dioxide (CO2) as working fluid for the combined production of hydrogen and thermal energy. The proposed system consists of evacuated solar collectors, power generating turbine, water electrolysis, heat recovery system, and feed pump. In the present study, an experimental prototype has been designed and constructed. The performance of the cycle is tested experimentally under different weather conditions. CO2 is efficiently converted into supercritical state in the collector, the CO2 temperature reaches about 190℃ in summer days, and even in winter days it can reach about 80℃. Such a high-temperature realizes the combined production of electricity and thermal energy. Different from the electrochemical hydrogen production via solar battery-based water splitting on hand, which requires the use of solar batteries with high energy requirements, the generated electricity in the supercritical cycle can be directly used to produce hydrogen gas from water. The amount of hydrogen gas produced by using the electricity generated in the supercritical cycle is about 1035 g per day using an evacuated solar collector of 100.0m2 for per family house in summer conditions, and it is about 568.0g even in winter days. Additionally, the estimated heat recovery efficiency is about 0.62. Such a high efficiency is sufficient to illustrate the cycle performance.

In this paper, a cryogenic refrigeration method is described, which utilizes CO2 solid-gas two phase flow and the dry ice. The CO2 solid-gas two phase flow is achieved by expanding liquid CO2 and thus refrigeration process less than CO2 triple point -56.6℃ can be available. The experimental work is divided into two parts and two experimental set-ups were designed, constructed and tested. The interest of the first experiment test is the feasibility of expanding liquid CO2 into CO2 solid–gas flow in a horizontal circular tube by expansion valve. The second experiment focuses on the feasibility of the refrigeration of liquid CO2 expanding into solid-gas two phase flows used in a prototype CO2 heat pump system. The results show that solid-gas two phase flows can be achieved by expanding liquid CO2 by expansion valve in a closed CO2 heat pump system loop and low temperature refrigeration below -56.6℃ is achieved in the experiments, which give greater possibility to create a cryogenic refrigeration process below -56.6℃ for food industries, bio-medical engineering, etc.

An experimental study is carried out to investigate the performance of a solar Rankine system using supercritical CO2 as a working fluid. The testing machine of the solar Rankine system consists of an evacuated solar collector, a pressure relief valve, heat exchangers and CO2 feed pump, etc. The solar energy powered system can provide electricity output as well as heat supply/refrigeration, etc. The system performance is evaluated based on daily, monthly and yearly experiment data. The results obtained show that heat collection efficiency for the CO2-based solar collector is measured at 65.0-70.0%. The power generation efficiency is found at 8.78-9.45%, which is higher than the value 8.20% of a solar cell. The result presents a potential future for the solar powered CO2 Rankine system to be used as distributed energy supply system for buildings or others.

Purpose-The purpose of this paper is to investigate flow behavior of electrorheological (ER) fluid in a closed piston-cylinder system. Design/methodology/approach -A basic study of flow characteristics of ER fluid in a damper model is conducted experimentally and numerically. The electric field is applied between inner wall of the cylinder and outer wall of the piston, and the pressure difference between upper and lower chamber of the cylinder is measured. A numerical prediction of ER fluid flow in the damper model system is performed in order to study the ER fluid flow characteristics. Visualization experiment isalso made and used to qualitatively verify the numerical formulation. Findings -The agreement between the numerical predictions and experimental results is encouraging, and the ER fluid flow patterns under different piston aspect ratios, movement speeds and applied electric field strengths are presented. The results show that the piston aspect ratio has much smaller influence on the ER flow pattern than other influencing factors. Increasing piston movement speed or reducing the electric field applied is helpful to reduce the pressure response time period, which is an important indicator showing sensitiveness of the damper. It is also seen that the pressure difference between the upper and lower chamber of the cylinder increases with the electric field strength and the piston movement speed. Originality/value -First time the detailed investigation into the hydrodynamics behavior in such working models of neering applications for ER fluid.

Experiment and numerical study were conducted to investigate the heat transfer characteristics of a thermo-sensitive magnetic fluid (TSMF) filled in a cubic container with a heat generating square cylinder stick inside and under a uniform magnetic field. The experimental results show that, regardless of the heat generating object sizes, the heat transfer characteristic of the TSMF is enhanced when the magnetic field is applied to the TSMF. However, the heat transfer of the TSMF becomes poor as the size of the inside heat generating object increases because the space where the fluids go through becomes narrower and the flow is obstructed when the heat generating object size becomes bigger. Numerical simulation based on the Lattice Boltzmann method confirmed the experimental findings, and disclosed more flow details of the natural convection of the TSMF inside cavity.