Publication

Flow Boiling in Horizontal and Vertical Tubes: the Effect of Tube orientation on Heat Transfer.

Daniel Favrat
1996
Conference Papers

Abstract

As part of a comprehensive study on factors affecting flow boiling in horizontal tubes, local boiling heat transfer coefficients were measured for R- 134a evaporating inside the same 12.00 mm bore, plain tube for horizontal flow, vertical upflow and vertical downflow over a wide range of mass velocities, vapor qualities and heat flux for a direct comparison of the effects on tube orientation on heat transfer. The experiments show a significant effect of flow direction on local heat transfer coefficients with upflow giving significantly lower values and downflow yielding even lower values. A flashing/subcooling effect on the heat transfer process caused by the negative/positive pressure gradient for upflow/downflow, respectively, is proposed as an important new factor affecting flow boiling.

Official source

https://infoscience.epfl.ch/entities/publication/def69f10-7c44-4ca1-bbaa-0f48685d6a61

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Daniel Favrat
1996
Conference Papers

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/def69f10-7c44-4ca1-bbaa-0f48685d6a61

About this result

Related concepts (32)

Heat transfer

Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species (mass transfer in the form of advection), either cold or hot, to achieve heat transfer.

Heat

In thermodynamics, heat is the thermal energy transferred between systems due to a temperature difference. In colloquial use, heat sometimes refers to thermal energy itself. An example of formal vs. informal usage may be obtained from the right-hand photo, in which the metal bar is "conducting heat" from its hot end to its cold end, but if the metal bar is considered a thermodynamic system, then the energy flowing within the metal bar is called internal energy, not heat.

Critical heat flux

In the study of heat transfer, critical heat flux (CHF) is the heat flux at which boiling ceases to be an effective form of transferring heat from a solid surface to a liquid. Boiling systems are those in which liquid coolant absorbs energy from a heated solid surface and undergoes a change in phase. In flow boiling systems, the saturated fluid progresses through a series of flow regimes as vapor quality is increased. In systems that utilize boiling, the heat transfer rate is significantly higher than if the fluid were a single phase (i.

Related publications (32)

Flow Boiling in Horizontal and Vertical Tubes: the Effect of Tube orientation on Heat Transfer.

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