R-744 and R-717 in refrigeration applications - Challenges and tips for best pump selection

Beschreibung

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Speaker

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Wann & Wo

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Di, 08.10.2024, 15:40 – 16:00

place

Halle 7A / 7A-638

Details

Format: Vortrag

Sprache: Englisch

Beschreibung

At the German pump manufacturer HERMETIC, the trend towards the use of R-717and R-744 in large-scale refrigeration systems, predicted against the background of the new F-gas regulation, has been confirmed. These refrigerants have no or very low global warming potential and are not harmful to the environment if small amounts escape. However, R-717and R-744 also pose risks to humans. HERMETIC explains the associated technical challenges for refrigerant pumps and gives tips for choosing a pump. R-717 as a refrigerant is characterized not only by its environmental compatibility but also by its high level of cost-effectiveness. The reason is its good thermodynamic properties. Main disadvantage: R-717 has a pungent smell and is toxic to humans. Inhaling R-717 as a highly concentrated gas can be fatal. For this reason, the use of R-717 places the highest demands on the safety and tightness of systems and components. R-744 is also dangerous if released in very large quantities. The main difficulty with R-744 as a coolant is the higher operating pressures. The need for thicker piping and more pressure-tolerant components increases material and construction costs. !CENTRIFUGAL PUMPS PREFERRED TYPE OF PUMP! Centrifugal pumps are preferred as refrigerant pumps. In a conventional centrifugal pump, the liquid in the impeller is thrown outwards by centrifugal force. In the subsequent housing or the guide apparatus, this fluid velocity is converted into pressure. This creates an almost pulsation-free flow. This creates a negative pressure at the impeller inlet. For this reason, it must be ensured that there is sufficient supply pressure, and that fluid is continuously provided. The weak point of this drive is the exit of the shaft from the housing, which must be sealed with a seal. The stuffing boxes or mechanical seals used for this can freeze at low temperatures and break when the pump starts up. Radial and axial bearings are also susceptible to wear due to their design. Failure analyses show: Over 50 % of pump failures are caused by leakage in the mechanical seal/stuffing box and 16 % by ball bearing failures. Hermetically sealed canned motor pumps are primarily suitable for avoiding these kinds of failures.
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