Nomenclature check for value reported on HX spec sheet
Nomenclature check for value reported on HX spec sheet
(OP)
Hi everyone,
I received a spec sheet for a HX on site from back in the early 90s. On the spec sheet was the following item: MTD (CORRECTED) °F 18.57
Is the wording MTD (CORRECTED) the same thing as log mean temperature delta (LMTD)? I have never seen anything but LMTD quoted or discussed before. The value given is reasonable compared to the LMTDs I calculated for the HX but I want to make sure.
Thanks!
~J
I received a spec sheet for a HX on site from back in the early 90s. On the spec sheet was the following item: MTD (CORRECTED) °F 18.57
Is the wording MTD (CORRECTED) the same thing as log mean temperature delta (LMTD)? I have never seen anything but LMTD quoted or discussed before. The value given is reasonable compared to the LMTDs I calculated for the HX but I want to make sure.
Thanks!
~J





RE: Nomenclature check for value reported on HX spec sheet
RE: Nomenclature check for value reported on HX spec sheet
a) The temperature approach correction factor, commonly written as F. See TEMA design books, or Perry or DQ Kern for computation of this factor - this depends on the no of shellside and tubeside passes per HX.
b) A factor which takes into account the non linearity of the the heat release with temp over the entire length of the HX. This gets more complicated in multicomponent reboilers and condensors. In single phase units where Cp varies little with temp, this factor tends to 1.0
RE: Nomenclature check for value reported on HX spec sheet
RE: Nomenclature check for value reported on HX spec sheet
Thanks!
~J
RE: Nomenclature check for value reported on HX spec sheet
-Christine
RE: Nomenclature check for value reported on HX spec sheet
Perry's has the correction factor table, so now I have to collect some more data to calculate the plotted ratios.
@Christine74
That's interesting, haven't run across such a scenario yet. The particular HX I am working with was built in 1990, would that fall within the time period you are considering under the label "modern"? The HXs I've had to dig up info for range in built years of late 80s to late 90s and the spec sheets always had some version of a mean temperature difference value. Maybe if I ever have a chance to specify or work on equipment that isn't older than me I will see this[rofl]
Maybe LMTD was used because it's familiar to all engineers that studied heat transfer without having to be experts but now its so easy to have software give you graphs and 3D models that the simplification isn't needed to convey the information. But I digress
RE: Nomenclature check for value reported on HX spec sheet