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Optimisation of the operating heat flux of a bubble pump in an absorption-diffusion refrigeration system.

Optimisation du flux de chaleur de fonctionnement d'une pompe à bulles d'une machine frigorifique à absorption-diffusion.

Number: pap. n. 2.6

Author(s) : GABSI S., BENHMIDENE A., CHAOUACHI B., et al.

Summary

The bubble pump is an essential component of an absorption refrigeration unit distribution. Indeed, it performs two functions: the pumping of fluid and desorption of refrigerant dissolved in the solution. This is a fluid pump which operates by thermal energy. Upon addition of heat to the pump tube bubble, the vapor from the boiling process forms small bubbles which unify in larger bubbles: which is the bubble regime. For this system the steam generated is not capable of lifting the liquid, there is an oscillation phenomenon. The addition of heat to the pump tube causes merging of the bubbles which form vapor pistons whose diameters are approximately equal to the diameter of the tube. These pistons are separated by liquid slugs. At this point the bubble pump operates in piston regime. However, the pumping action occurs only from a critical heat flux for which the first drop of liquid reaches the top of the tube of the pump. From this critical heat flux, the steam pistons will be able to lift the liquid in a continuous manner so that it begins to circulate. The operation of the pump depends on the bubble geometrical parameters such as diameter and length of the tube and the operating parameters such as heating power, the height of submersion and the configuration of the bubble pump. This bubble pump is a vertical pipe of circular cross-section along the length uniformly heated. To model the operation of a bubble pump, the authors used the two-fluid model that has applied some simplifications and modifications that exist primarily to neglect the effects of stress at the interface and surface tension. The two-fluid model thus obtained is composed of a system of nine equations: six equations mass balance, momentum and energy and three equations coupling. The resolution of the model equations was performed under conditions of no equilibrium hydrodynamic and regime permanent. The equations of limits used are detailed and the numerical method used to solve the equations of this model is explained. The simulation results show the importance of the density of heat flow as a critical parameter for the operation of the bubble pump. This heat flux density depends on the diameter of the tube and the mass flow.

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Details

  • Original title: Optimisation du flux de chaleur de fonctionnement d'une pompe à bulles d'une machine frigorifique à absorption-diffusion.
  • Record ID : 30006043
  • Languages: French
  • Source: 4th Jordanian IIR International Conference on Refrigeration and Air Conditioning. Proceedings: Amman, Jordan, September 10-12, 2012.
  • Publication date: 2012/09/10

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