One documented arrangement and thermal basis
Terminal-Temperature LMTD & Area Calculator
Calculate a numerically stable log-mean temperature difference for one documented counterflow or parallel-flow arrangement, then apply a documented correction factor, duty and overall U-value.
Documented LMTD result
Implemented terminal pairings
Parallel flow: ΔT₁=Tₕ,ᵢ−T𝒄,ᵢ ; ΔT₂=Tₕ,ₒ−T𝒄,ₒ
ΔTlm=(ΔT₁−ΔT₂)/ln(ΔT₁/ΔT₂)
A=Q/(UFΔTlm)
Temperature differences in kelvins and degrees Celsius have the same numerical magnitude. The implementation uses log1p for close terminal differences and the exact continuous limit ΔTlm=ΔT when ΔT₁=ΔT₂.
Source and scope
A NASA heat-exchanger design report uses the general relation q=UAΔTlm and defines the terminal log-mean temperature difference. This page adds a user-documented correction factor F for arrangements where the chosen idealized pairing does not alone represent the actual geometry. F=1 is not assumed; it must be entered with its source.
Why the former comparison was removed
The former page computed counterflow and parallel-flow results from the same four outlet temperatures and announced that counterflow was more efficient and always preferred. Changing arrangement generally changes outlet temperatures, duty, U and feasible construction, so those two arithmetic pairings were not a controlled design comparison. The page also estimated both areas with no correction factor or Q/U provenance.
Not exchanger design approval: verify stream energy balance, phase/property changes, pressure drop, fouling, U/area definition, correction-factor method, minimum approach, flow distribution, transient/off-design cases and mechanical/process-code requirements.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
