Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer  

DOI： 10.1007/s00231-022-03310-2

Scopus

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

DOI： 10.3390/s22093175

Other Link： https://www.mdpi.com/1424-8220/22/9/3175

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：(MISC) Introduction and explanation (commerce magazine)  

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：(MISC) Introduction and explanation (commerce magazine)   Publisher：日本工業出版㈱　  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer  

DOI： 10.1007/s12650-020-00677-4

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Asian Conference on Refrigeration and Air Conditioning (ACRA)  

The GSHP that use a direct expansion method is expected to have higher performance of energy-saving than the conventional type of the GSHP. We evaluated the quantity of heat by measuring temperature, humidity and flow rate at the indoor unit of the GSHP system. The purpose of this study is to improve the accuracy of the flow rate measured by hot wire anemometers using PIV method. The average of difference between the flow rate obtained by the hot wire anemometers and the PIV method was 23.6% in the heating operation and that was 24.0% in the cooling operation. We obtained the compensation formula which corrects the result of the hot wire anemometers using the results of PIV method. The average of difference between the compensated flow rate by the hot wire anemometers and the flow rate by the PIV method was reduced to 5.2% in the heating operation and 1.9% in the cooling operation.

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Nuclear Society  

A depressurization accident is the one of the designbasis accidents of a Very-High-Temperature Reactor (VHTR). When a depressurization accident occurs, air is expected to enter into the reactor pressure vessel from the breach and oxidize in-core graphite structures. Therefore, it is important to understand the mixing processes of different kinds of gases in the stable and unstable stratified fluid layers. In particular, it is also important to examine the influence of localized natural convection and molecular diffusion on the mixing process from a safety viewpoint. Therefore, in order to predict or analyze the air ingress phenomena during a depressurization accident, it is important to develop a method for the prevention of air ingress during an accident. We carried out experiments and numerical analysis using three-dimensional (3D) CFD code to obtain the mixing process of two-component gases and the flow characteristics of localized natural convection. This study also investigated a control method for the natural circulation of air through the injection of helium gas. The numerical model consists of a storage tank and a reverse U-shaped vertical rectangular passage. They are separated by a horizontal partition plate. One sidewall of the high-temperature side vertical passage is heated and the other sidewall is cooled. The low-temperature vertical passage is cooled by ambient air. The experimental procedures and numerical analysis process are as follows. Firstly, the storage tank is filled with heavy gas and the reverse U-shaped vertical passage is filled with a light gas. In the vertical passage of the high-temperature side, localized natural convection is generated by the temperature difference between the vertical walls. These flow characteristics were obtained from the experiments and steady-state analysis. The experiment and analysis began after the partition plate was opened. The results obtained from the experiments were quantitatively simulated using 3D numerical analysis. The two component gases were mixed via molecular diffusion and natural convection. After some time elapsed, natural circulation occurred through the reverse U-shaped vertical passage. These flow characteristics are the same as those of phenomena generated in the passage between a permanent reflector and a pressure vessel wall of the VHTR.

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Asian Conference on Refrigeration and Air Conditioning (ACRA)  

This paper describes the experimental results and the performance of ground source heat pump using the direct expansion method. The underground temperatures are more stable than air temperature. The temperature beneath the about 10 m from the surface maintains a nearly constant temperature about 15-20°C. Ground Source Heat Pump (GSHP) absorbs energy from the earth by applying this constant temperature. Authors paid attention to shallower depth than 100 m under the ground surface. In order to obtain the basic data, authors tried to experiment on GSHP based on direct expansion. In this experiment, performance evaluation was carried out during 48 hours operation. The performance of the ground sources heat pump system was evaluated by coefficient of performance (COP), which is determined by the ratio of heat exchange rate to consumption power of the compressor. The COP approached to 12.3 in cooling mode and 4.2 in heating mode. Totally, COP of GSHP with direct expansion method is higher than that in air-source type heat exchanger or indirect heat exchange method. In addition, long term test operations have to be considered for practical application in the near future.

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Nuclear Society  

When the depressurization accident occurs in the Very-High-Temperature Reactor (VHTR), it is expected air enter into the reactor core from the breach. Therefore, it is important to know a mixing process of different kind of gases in the stable and unstable stratified fluid layer. Especially, it is also important to examine an influence of localized natural convection and molecular diffusion on mixing process from a viewpoint of safety. In order to research the mixing process of two component gases and flow characteristics of the localized natural convection, we have carried out an experiment and a numerical analysis using three dimensional CFD code. The numerical model consists of a storage tank and a reverse U-shaped vertical slot. They are separated by a partition plate. One side of the left wall of the left side vertical slot is heated and the other side was cooled. The right side vertical slot is cooled. The flow characteristics were obtained by the experiment and steady state analysis. The unsteady state experiment and analysis were started after the partition plate was opened. The result obtained in the experiment was simulated by the numerical analysis quantitatively. The gases were mixed by molecular diffusion and natural convection. After the time elapsed, natural circulation occurred.

Scopus

Language：English  

Language：Japanese  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Mechanical Engineers (ASME)  

The Very High Temperature Reactor (VHTR) is a next generation nuclear reactor system. It has the characteristic that the thermal capacity of the core is so large. Therefore, even if the depressurization accident occurs and the reactor power goes up instantly, the temperature of the core will change slowly. The VHTR system can passively remove the decay heat of the core by natural convection and radiation from the surface of the reactor pressure vessel (RPV). The objectives of this study is to investigate the heat transfer characteristics of natural convection of an one-side heated vertical rectangular channel inserting porous materials with high porosity and to develop the passive cooling system for the VHTR. We carried out the experiment and numerical analysis using the one-side heated vertical rectangular channel. The heat transfer and fluid flow characteristics of the natural convection cooling were analyzed using the commercial CFD code. The result shows that the amount of removed heat inserting the copper wire (porosity = 0.9964) was about 8% higher than that without the copper wire.

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Mechanical Engineers (ASME)  

When the depressurization accident occurs in the Very-High-Temperature Reactor (VHTR), it is expected that air enter into the reactor core. Therefore, it is important to know a mixing process of different kind of gases in the stable or unstable stratified fluid layer. Especially, it is also important to examine an influence of localized natural convection and molecular diffusion on mixing process from a viewpoint of safety. In order to research the mixing process of two component gases and flow characteristics of the localized natural convection, we have carried out numerical analysis using three dimensional CFD code. The numerical model was consisted of a storage tank and a reverse U-shaped vertical slot. They were separated by a partition plate. One side of the left vertical fluid layer was heated and the other side was cooled. The right vertical fluid layer was also cooled. The procedure of numerical analysis is as follows. Firstly, the storage tank was filled with heavy gas and the reverse U-shaped vertical slot was filled with light gas. In the left vertical fluid layer, the localized natural convection was generated by the temperature difference between the vertical walls. The flow characteristics were obtained by a steady state analysis. The unsteady state analysis was started when the partition plate was opened. The gases were mixed by molecular diffusion and natural convection. After the time elapsed, natural circulation occurred. The result obtained in this numerical analysis is as follows. The temperature difference of the left vertical fluid layer was set to 100K. The combination of the mixed gas was nitrogen and argon. After 76 minutes elapsed, natural circulation occurred.

Scopus

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Begell House Inc.  

Ground source heat pumps (GSHPs) use buried pipes to extract heat from the ground. This heat can be used in radiators, in under-floor and warm-air heating systems, and in hot water heaters in houses. In a conventional GSHP, a closed loop and vertical borehole system are used. Since underground temperatures remain constant, these heat pumps can be used throughout the year. In a conventional GSHP system, which uses an indirect heat exchange method, vertical systems use two long pipes connected by a U-shaped fitting at the bottom of a hole bored in the ground. These pipes form part of a closed loop, called the ground loop, through which a mixture of water and antifreeze circulate. In contrast, a GSHP that uses a direct expansion method circulates a mixed refrigerant through the ground loop. In our tests of this method, the depth of the borehole was 30 m, and the refrigerant was R410A. To compare the performance of these two types of GSHPs, the heat exchanger of a ready-made air-conditioner was replaced by an underground heat exchanger. In the direct expansion GSHP, the underground heat exchanger consisted of narrow copper tubes inserted into the bottom end of a long pipe filled with water. The coefficients of performance (COP) were obtained for both types of GSHPs running in cooling mode. The obtained values for COP are compared here, along with the amounts of heat transferred by the underground heat exchangers.

Scopus

Language：English  

Language：English  

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：English  

Language：English  

Language：English  

Language：English  

Language：Japanese  

Applicant：舩谷俊平

Application no：特願2013-135760  Date applied：2013.6

Country of applicant：Domestic  

Application no：特願2013-135760  Date applied：2013.6

Application no：特願2011-206808  Date applied：2011.9

Country of applicant：Domestic  

Application no：特願2011-206808  Date applied：2011.9

Applicant：株式会社コロナ

Application no：特開2011-214746  Date applied：2010.3

Country of applicant：Domestic  

Application no：特開2011-214746  Date applied：2010.3