Thermal Energy Conservation Technology

NIRE is studying various forms of heat-exchange technologies that use phase change of working fluids. We are developing various types of heat pipes, a typical high-efficiency heat exchanger, with applied heat-transfer modules containing liquid sodium as the working fluid. Our goal is to apply these modules to a waste heat recovery system in a solid oxide fuel-cell power generation plant and to a thermoionic-thermoelectric direct power generation system.

The most important phenomenon determining the performance of a heat pipe is the behavior of bubbles from the working fluid vapor, which are generated at the evaporator section inside the pipe. We are conducting basic research to understand and control the behavior of such bubbles. Related research to develop a novel heat exchanger that enhances heat-transfer rates by active control of bubbles has begun. A closed-cycle, heat-driven pump system is being developed as well. This system enables heat transport from higher to lower positions without an external power supply by transforming the alternative pressure change due to boiling and condensing of the working fluid into fluid motion.

Fig. Heat Pipe with Wick

[Thermal Energy and Combustion Engineering Department]

New Combustion Technology

NIRE is investigating a new combustion system to solve global environmental problems resulting from current technologies. Single-stage combustion is divided into oxidation and reduction processes. Both are connected by the recalculation of mediator particles which transport oxygen. In this way, it is possible to minimize energy loss during combustion. The system can also reduce pollutant emissions and increase combustion efficiency. In addition, pure C0₂ is easily recovered by cooling the exhaust gas. To develop this system, NIRE conducted basic research on the reactivity of particles and gases, system hydrodynamics, and process system synthesis.

Fig. Mediator Recirculating Combustion System

[Thermal Energy and Combustion Engineering Department]

Pressurized fluidized bed combustion is an advanced coal combustion system with higher thermal efficiency and lower pollution than typical modern-day systems. In this process, a mixture of coal and limestone (bed material) is fluidized and burned efficiently under high air pressure from a compressor. The generated heat, recovered as steam by in-bed tubes, drives a steam turbine generator. The still-pressurized, hot exhaust gas from the combustor is recovered and used to drive a gas-turbine generator. Further basic research on nitrogen oxide (NOx) formation mechanisms, desulfurization reactions, and heat transfer are necessary. NIRE is conducting such research in laboratory-scale pressurized vessels.

Fig. Out line of PFBC

[Thermal Energy and Combustion Engineering Department]

Sulfur oxides and nitrogen oxides are emitted on fossil fuel combustion and they cause health injuries and acid rain. Though many control processes of SOx and NOx for large scale combustors are in cmmercial use, NOx control technologies for small scale combustors, especially for Diesel engines are under developing. We have been investigating deNOx catalyst which can be applied to Diesel exhaust. In our laboratory, a new catalyst was developed which can reduce lean NOx effectively by using alcohols instead of harmful ammonia as reductants. It is expected to contribute the spread of highly efficient heat and power cogeneration systems.

Fig: Flue gas deNOx system for a cogeneration system

[Thermal Energy and Combustion Engineering Department]