Talk:NTU method

Notation

The maths notation, but especially the suffices, need doing properly - trouble is I forget how to use the maths editor over the intervening weeks... Anyone else want to tidy? (I will in due course, else) Linuxlad 12:28, 2 June 2007 (UTC)

I am interested in the article, but don't understand the notation, so would be grateful if it could be expanded. Featherard (talk) 20:55, 20 March 2009 (UTC)featherard

How about definition of terms? What is U ? I don't see it defined anywhere. —Preceding unsigned comment added by Xperrymint (talk • contribs) 06:15, 11 May 2010 (UTC)

U is defined as the overall heat transfer co-efficient. The total heat exchanged between the two fluids in a heat exchanger is equal to UxAxθm (Mean temperature difference) —Preceding unsigned comment added by 122.162.164.129 (talk) 05:16, 4 February 2011 (UTC)

The textbook uses epsilon rather than E for effectiveness. I believe the LaTeX code is \varepsilon. — Preceding unsigned comment added by 173.171.102.20 (talk) 21:10, 13 July 2014 (UTC)

Lower case epsilon and lower case chi, as well as E, have all been used.

The early extensive work (W.M. Kays and A.L. London) used epsilon:

1) Gas Turbine Plant Heat Exchangers-Basic Heat Transfer and Flow Friction Design Data, 1951 ASME.

2) Compact Heat Exchangers, 1955 (latest edition 1984?) Parmstr (talk) 16:16, 19 August 2024 (UTC)

Graph

It would be great to get a graph of NTU vs Effectiveness for different Cr's and an explanation of the graph behavior. Ahlfi006 (talk) 21:55, 27 April 2010 (UTC)

Mass Transfer

The E-NTU method has been very usefully applied to mass transfer processes, mainly humidification and dehumidification, e.g. cooling coils (dehumidifcation), sprayed coils and cooling towers. See, e.g. Banks and Cross-McLain, Jaber & Webb, Braun, et al, who introduced these applications throughout the 1980's. In these mass transfer formulations, mass flow rate replaces thermal capacitance rate, and the diffusion coefficient replaces U. Also a correction factor is sometimes needed to account for the shape of the saturation curve over the range liquid temperature spanned by the process. Enthalpy difference replaces temperature difference. For membrane processes, vapor pressure difference may be the appropriate driving potential if membrane resistance is greater than boundary-layer diffusion resistance. It might be best to split the article into "NTU Method for Heat Transfer" and "NTU Method for Mass Transfer" while retaining the similarities of the two methods.

 Parmstr (talk) 16:29, 19 August 2024 (UTC)