Yujiro Kitaide

Characteristics of Thermoacoustic Sound Generator and Its Application to Refrigerator

The simplified thermoacoustic sound wave generator was employed for preciously oscillatory flow in the resonance tube, and the propagated sound was converted to cold heat using a thermoacoustic sound refrigerator. This is a concept of refrigerator, without a refrigerant and moving part, which is different from conventional refrigerant cycle in present. For the thermoacoustic sound generator, ceramic honeycomb was introduced as a regenerator. When the temperature gradient of each side of the thin tube exceeded the critical temperature, the thermoacoustic sound was generated. The resonance frequency of this sound generator depends on the length of resonance tube and the diameter of a ceramic thin tube. On the other hand, the thermoacoustic sound created a low temperature field using a ceramic regenerator. In addition the resonance frequency must be match between thermoacoustic sound generator and refrigerator. The purpose of this study is to find an optimal system configuration and system condition to achieve a high performance thermoacoustic sound refrigerator with a thermoacoustic sound wave generator. The characteristics of thermoacoustic sound wave generator and refrigerator are evaluated experimentally in this paper. The performance of the thermoacoustic system is examined theoretically based on the experimental results.

Characteristics of a Loop-type Thermoacoustic Refrigerator with a Sound Generator

The loop-type thermoacoustic refrigerator with a thermoacoustic sound generator is introduced and the performance of this system is experimentally examined. This system can supply cold heat without using refrigerants or moving parts, which is different from the present refrigerant cycle. The loop-type thermoacoustic sound generator system is constructed and the performance of this system is examined first. For the thermoacoustic sound generator, a thin tube ceramic honeycomb was introduced as a regenerator, and air was introduced as a working gas. The experiment was conducted for several cell densities and temperature gradients of the regenerator inside a sound generator. Here, the pressure amplitude and phase difference of the sound inside a resonance tube was recorded and evaluated using a FFT analyzer. The work intensity, that is power intensity of the generated sound, is theoretically estimated from the experimental result. The optimum experimental condition for the loop-type thermoacoustic sound generator was applied to the loop-type thermoacoustic refrigerator. The cold heat was obtained by this system and the characteristics of the system are shown in this paper.

Environmental Evaluation and Effectiveness of Lightweight Electric-assist Tricycle with Next-generation Batteries

Life cycle environmental evaluation of a new lightweight electric-assist tricycle has been discussed in terms of materials supply, production, use and recycling/disposal stages. The effectiveness of such a novel tricycle is compared with existing transportation from the viewpoint of life cycle environmental impact. In life cycle environmental evaluation, photovoltaic and in-vehicle fuel cell power generations are applied as an energy source for the electric-assist bicycle as well as commercial purchased electricity. Its transportation by light truck, passenger car, scooter and the well-known two-wheel electric-assist bicycle is chosen here for comparison. The factors affecting the environmental impact of each type of transportation device were shown. The loadage of each means of transportation was determined so that the new electric-assist tricycle’s environmental impact would be less. As a result, our novel lightweight electric-assist tricycle was found to be effective for shortdistance transport of a small amount of lightweight materials, as in a factory or a local transportation.

Development and Evaluation of a Pulse Driven-type Electromagnetic Control Expansion Valve applied to a Small Scale Refrigerant Cycle (Part II: Experimental evaluation of pressure drop)

The application of a new pulse driven-type electromagnetic control expansion valve to an R744 cycle is proposed and the characteristics of the valve are theoretically evaluated and experimentally inspected in this paper. In this theoretical estimation, the structure of the valve is simulated using elements such as ducts, a pin hole, a groove and an orifice. The pressure drops caused by each element that make up the valve are estimated individually. The V-shaped groove and its entrance and exit interfaces create the majority of the overall resultant pressure drop. Especially, the influence of the machining tolerance is also estimated because the elements that make up the valve are very fine. Then, the validity of this estimation is verified by an experiment. The experiment is conducted by constructing a refrigerator cycle. The theoretically estimated pressure drop agrees with the experimental results even through the two-phase refrigerant fluid flow field. As a result, it was shown that the electromagnetic control expansion valve proposed in this paper can control the pressure drop in a way suitable for satisfying cooling demand. Also, the theoretical estimation proposed in this paper may be able to be applied for the estimation of the pressure drop of the expansion valve. Keywords: Electric expansion valve, Electromagnetic control, Refrigerator, Pulse drive, CO2(R744)