Heat exchangers

Rate or size a double-pipe, shell-and-tube or gasketed plate exchanger: duty, outlet temperatures, film coefficients, area and pressure drops — with the streams running through it, coloured by temperature.

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INPUT°C · kg/s · mm

1 · Hot stream Fluid

Inlet [°C] Flow [kg/s]

Fouling [m²K/W]

2 · Cold stream Fluid

Inlet [°C] Flow [kg/s]

Fouling [m²K/W]

3 · Hairpins

Inner pipe Outer pipe

Leg length [m] one straight leg Hairpins

In the inner pipe Flow

Parallel branches 1 = all in series Split into branches

Pipe material Annulus nozzles

Example values. Fluid properties from the VDI Heat Atlas tables, or enter your own fluid.

DUTY273.4 kW

OVERALL U846 W/m²K

AREA5.12 m²

OUTLETS92.6 · 85.4 °C

FLOW · LIVE

TEMPERATURE ALONG THE EXCHANGER

Water at 140 °C stays liquid only above 3.62 bar(a) — keep the system pressure above that.

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HOW IT'S CALCULATED · WITH YOUR NUMBERS

Step by step, with your numbers

01
Equilibrium████ ██ ███████ · ██████ = ██.██
02
Reactions████ ██ ███████ · ██████ = ██.██
03
Shear force████ ██ ███████ · ██████ = ██.██
04
Bending moment████ ██ ███████ · ██████ = ██.██
05
Deflection████ ██ ███████ · ██████ = ██.██
06
Stress████ ██ ███████ · ██████ = ██.██

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References: VDI Heat Atlas 2nd ed. (2010) — G1, G2 (Gnielinski), N6 (Martin) and the fluid tables of D2 and D4; Serth & Lestina, Process Heat Transfer 2nd ed. (2014), ch. 4–6 (hairpins, Delaware method); Shah & Sekulić, Fundamentals of Heat Exchanger Design, ch. 3 (ε-NTU, F); Kakaç et al., Heat Exchangers 3rd ed. (2012), ch. 7, 9, 11.

ASSUMPTIONS & LIMITS

Steady state, no heat loss to the surroundings, single-phase fluids (no boiling or condensing).
Properties at the mean temperature of each stream (VDI Heat Atlas tables, or your values); the wall temperature from the film resistances corrects for property variation.
One overall coefficient for the whole exchanger; fouling resistances as entered, on the side they belong to.
Effectiveness–NTU relations for the flow arrangement (Shah & Sekulić ch. 3); F = ΔT_m / ΔT_lm,counter.
Inner pipe: Gnielinski, VDI G1. Annulus: Gnielinski, VDI G2, heat through the inner pipe, outer pipe insulated. Each hairpin counts as a fresh entry length of 2 × the leg. G2 refers the annulus α to the hydraulic diameter D − d; older texts that use Kern's equivalent diameter give a lower annulus coefficient.
Pressure drop: straight pipe (Darcy, Konakov), 1.2 velocity heads per return bend (1.5 laminar), and on the annulus 1.5 nozzle velocity heads per hairpin when a nozzle size is given (Serth eqs. 4.A.5–4.A.8).

DISCLAIMER · For education and preliminary sizing only. Results must be reviewed by a qualified engineer before use in design.

BEYOND THE CORRELATIONS

Shell-side flow maldistribution, tube vibration, tubesheet and nozzle stresses, thermal fatigue — we model exchangers with CFD and FEA.

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