Structural Design of Atypical Metal hydride Tank and Investigation of Generated Temperature Fields: Part I
Abstract
The article describes the structural design of an atypical metal hydride storage tank for hydrogen storage for mobile operations such as cars, buses, etc. The structural design of the tank consists of three main parts, namely an atypical bottom of an elliptical shape with a flange on which there is a 1/4NPT” thread, three seamless pipes and a second atypical bottom as a cap. Hydrogen storage works under low pressure of up to 30 bars and is based on TiFe alloys. In the next part, the article deals with the investigation of the temperature fields created in an atypical metal hydride tank, and then it is devoted to an effective method of cooling the metal hydride tank during the process of hydrogen absorption into the structure of the metal alloy.
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Introduction
Storage of hydrogen in high-pressure composite tanks with compressed gas (CGH2) at pressures from 350 to 700 bar is the most common method of supplying hydrogen to fuel cells. This solution has the advantages of relatively high hydrogen storage capacity, short refueling time (3-5 min) and virtually unlimited flow of hydrogen into the fuel cell. However, the volume capacity of hydrogen storage by the CGH2 system is too low. These systems also suffer from problems, namely: low safety and extremely expensive refueling infrastructure - both problems are associated with the high pressure of the stored hydrogen.
Metal hydrides (MHs) formed by the reversible reaction of gaseous H2 with a parent metal, alloy, or intermetallic compound to form a hydride are particularly promising for hydrogen storage. The use of MH can provide very high hydrogen storage capacity per unit volume (sometimes higher than liquid hydrogen), safety, reliability and high purity of supplied H2. Despite the conventional view of the low weight hydrogen storage capacity of "low temperature" intermetallic hydrides (≤ 2 wt.% H) as their main drawback in on-board hydrogen storage systems, in some special applications in vehicles the use of these materials appears to be very promising. Primarily this applies to material handling units, underground mining vehicles and water applications where the low gravimetric hydrogen storage capacity/high mass of metal hydrides can provide advantages in vehicle/vessel stabilization.
For this method of hydrogen storage to be used as effectively as possible, it is necessary to design the tank in such a way that it meets all operational parameters in terms of strength. It is also necessary to design an efficient cooling system of the tank during the process of hydrogen absorption into the structure of the metal alloy. This article discusses the solution to the structural design of an atypical metal hydride tank, as well as the design of effective cooling.
Conclusion
The task of this work was to design a metal hydride tank for storing hydrogen of an atypical shape for mobile applications. Another task of the work was the investigation of the occurrence of maximum temperatures in the tank during hydrogen refueling and subsequently the proposal of effective cooling for the designed tank.
In the first simulation, where no cooling was used, the maximum temperature in the tank was around 49.5 °C. Subsequently, after applying active cooling to the seamless pipes of the designed metal hydride reservoir, the temperature was reduced to approximately 42 °C, thanks to which the kinetics of hydrogen absorption into the metal hydride alloy increases.
Another task of this work will be to design a suitable shape of the internal heat transfer intensifier, for the most effective heat transfer to the inner wall of the steel tank, where this heat will be cooled by active cooling, which would further reduce the maximum temperature of the metal hydride alloy and which would significantly increase the kinetics of absorption hydrogen.