- #1
DanKot
- 2
- 0
Strange unit of mass flow rate G?
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Discussion Overview
The discussion revolves around the unit of mass flow rate denoted as G - kg/(m2*s), as encountered in an article related to heat and mass transfer. Participants are exploring the validity and implications of this unit in comparison to the conventional unit of mass flow rate, kg/s, particularly in the context of steam flow in tubes and condensation processes.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant questions the correctness of the unit G, suggesting that mass flow rate is typically expressed as kg/s.
- Another participant proposes that G represents mass flow rate per unit area, indicating its relevance in contexts such as flow through an orifice or over a surface.
- There is a suggestion that calculating the mass flow rate in kg/s could be done by considering the surface area in scenarios like steam flow in a tube.
- A later post reflects uncertainty, indicating a need to further investigate the relationship between G and concepts like resistance to flow or momentum.
- One participant requests equations that involve G and m to clarify their application.
- Another participant mentions a specific article that uses G without providing an equivalent unit, suggesting that G is used in the context of steam condensation in horizontal tubes.
- It is noted that G is typically understood to represent mass flux, which is mass flow rate per unit area.
- A participant discusses the relationship between flow rate, contact surface area, and condensate production, suggesting that both factors are important in calculations related to condensation.
Areas of Agreement / Disagreement
Participants express differing views on the interpretation and validity of the unit G. While some propose that it is a valid representation of mass flow rate per unit area, others remain uncertain about its application and seek further clarification. The discussion does not reach a consensus on the matter.
Contextual Notes
Participants reference specific articles and equations, but there is no consensus on the equivalence of G to other units of mass flow rate. The discussion includes assumptions about the context in which G is used, particularly in relation to surface area and flow dynamics.
- #2
RogueOne
- 130
- 57
Looks to be the unit of mass flow rate over a given surface area " m^2". Either through an orifice or over a surface. Would that make sense?
- #3
DanKot
- 2
- 0
RogueOne said:
That was option I was thinking about. So If I have steam flow in tube, I can just calculate the surface and then I got well-known mass flow rate m - kg/s ?
Thanks
- #4
RogueOne
- 130
- 57
DanKot said:
Looking at the equation again, I take back what I said in the last post. I'll look into it more tomorrow, but I think it may actually have to do with resistance to flow or momentum
- #5
JBA
Science Advisor
Gold Member
- 1,532
- 462
From the above post it would appear RogueOne has access to the equation(s) in which G and m are used. Could you post those applicable equations; and, maybe where and how they are applied?
- #6
DanKot
- 2
- 0
I think there is no eqv. . I got this table form an article http://www.sciencedirect.com/science/article/pii/S0017931016331337 where autors study condensation of steam in horizontal tube. But just G is used in the article. I can attach random graph from this article where G appears. Is that clear?
Attachments
- #7
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The symbol G is usually used to represent mass flux (mass flow rate per unit area).
- #8
JBA
Science Advisor
Gold Member
- 1,532
- 462
I have reviewed the abstract, which is of little value in resolving the issue. The only thing that strikes me is the same possibility presented above regarding the inclusion of surface area. From a condensation production standpoint, all other factors being equal, the amount of condensate produced at a given flow rate will be proportional to the available total steam contact area of the flow section; so, in a calculation or equation for condensate production based upon differential temperatures then both the rate of flow and contact surface area would be contributing factors.
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