In this study, a high-temperature steam generator (HTSG) of cyclone cylindrical type has been developed for energy harvesting applications. Solid refuse fuel (SRF) is considered the thermal energy source. The operating conditions are steam temperature of 773 K, steam pressure of 0.3 to 0.6 MPa, and mass flow rate of 10 to 35 kg/h. The pressure drop of steam in the HTSG is analyzed through numerical methods, which can control the outlet pressure of steam for hydrogen stack application based on the experimental results. The maximum heat transfer efficiency of the HTSG system is 66% at 0.3 MP and 35 kg/ h, which can generate 306 tons per year of high-temperature steam. Moreover, the produced steam can be converted to 15.3 tons of hydrogen. The HTSG system can harvest 767 MWh of energy per year, and it is expected to significantly reduce energy consumption while minimizing the environmental impact.

No abstract

The purpose of the present study is to analyze pressure difference changes inside a high-temperature steam generator (HTSG), which produces steam using the heat generated by waste incineration and decreases the pressure of the produced steam while increasing its temperature. The high-temperature, low-pressure steam produced by a HTSG is used for hydrogen production. Therefore, the steam temperature must be at least 700 • C, and the pressure must be lower than 300 kPa; hence, a device is needed to increase the steam temperature in the boiler and decrease the steam pressure. The physical behavior of the device was modeled and experimentally validated. The modeling and experimental results demonstrated good agreement when the steam was not preheated; however, an additional pressure drop required consideration of the opposite case.

Summary A high‐temperature steam generation system to supply steam to a water electrolysis system was designed and tested using solid‐recovered fuel (SRF). The energy loss must be reduced to supply hydrogen production stably, which are conducted by three strategies: (a) using a double pipe, (b) installing a baffle inside the pipe to obstruct steam flow, and (c) bypassing the overflowing steam. Double pipe reduced energy loss by 25% compared to single pipe. Consequently, a heat source with a temperature of 973 K or higher was obtained. In addition, CFD simulation was performed over a temperature range of 373 to 973 K to investigate the change in energy loss with the temperature of the external fluid. When the three baffles were installed inside the double pipe, it reduced heat dissipation approximately 6%. Therefore, installing three or four inner baffles inside the double tube proved to be the most effective method, and it was confirmed that the temperature of the external fluid should be maintained above 573 K. It was concluded that the system using the double pipe with inner baffles can produce approximately 43.8 ton/year of hydrogen when generating high‐temperature steam, and the CO2 emission is reduced to 1.1 ton‐CO2/ton‐hydrogen compared to liquefied natural gas.

The high-temperature steam is used in the fields of industrial, residential, and commercial. Especially, in case of high-temperature steam, it can be used to produce hydrogen and likewise it can be used to generate electricity in the field of power generation. However, the steam condition for producing hydrogen and the steam condition for producing electricity are different, it is considerably important to distribute the high-temperature steam in condition satisfying each demand. Moreover, the required pressure and the pressure loss of a steam distributor at the load side should be considered. Therefore, in this study, the numerical simulation using ANSYS fluent was performed by dividing into pipe A (4,000kPa at use of power generation system) and pipe B (300kPa at use of hydrogen production). In addition, it was simulated according to the variation of diameter of pipe B (20mm -30mm) for analysis of a steam distribution technology. The pressure outlet that can be used in hydrogen production was about 300kPa approximately when the diameter of pipe B was 20mm. As a result, the distribution technology that is used hydrogen production and in the power generation system was obtained through numerical simulation in proposed condition.

No abstract

The optimum operation conditions of a raw water source heat pump for a vertical water treatment building were derived by changing operation parameters, such as temperature of thermal storage tank, temperature and inlet air flow rate of the conditioned spaces, and circulating water flow rate between thermal storage tank and air handling unit (AHU) through dynamic simulator of a transient system simulation program (TRNSYS). Minimum electric power consumption was found at temperature of thermal storage tank, which was ranged 18–23°C for cooling season. In heating season, temperature 40–45°C brings the highest coefficient of performance (COP) and temperature range of 30–35°C brings the lowest power consumption. When the temperature of the conditioned spaces was controlled between 27–28°C for cooling season, and 18–20°C for heating season the minimum electric power consumption was obtained. Inlet air flow rate of 1.1 m3/h for the conditioned spaces shows the highest performance of the present system, and effects of circulating water flow rate between thermal storage tank and AHU on minimum electric power consumption of the system were negligible.

The dynamic characteristics of both raw-water source and air source heat pump utilized in water treatment facilities were investigated by using TRNSYS simulator. The modeling of the raw water source heat pump was verified by the measured data at the Cheongju water treatment facility, and the modeling at the air source heat pump was verified by the data from the Siheung water treatment facility. The average heating and cooling COPs from the raw-water source heat pump were higher than those of the air source heat pump by 19% and 18%, respectively. The power consumptions of the air source heat pump for the cooling and the heating were higher than those of the raw water source heat pump by 28% and 26%, respectively. Key words