Shell-and-Tube Heat Exchanger Control Room: Effectiveness-NTU, Fouling and Bypass Valve (2D)

Presets

Events and faults

Speed1x

Alarms

Live readouts

Graphs

Numerical checks

running...

How to use

Read the P&ID: hot oil (red) enters the shell, water (blue) runs through the tubes in two passes. The valve XV-101 sends oil through the exchanger, XV-102 bypasses it.
The TIC-101 loop holds the water outlet temperature (TT-104) at the set-point by moving the bypass split. Watch the valve margin: when it reaches 100 % the exchanger can no longer deliver the duty.
Let the tubes foul (raise time compression): the deposit resistance Rf grows, U drops, the valve opens, and finally the alarm XV-101 fires. Use Clean the tubes for an outage.
Try the events: set-point step, hot-oil upset, cold-flow loss (trip logic), aggressive tuning (the loop rings), manual mode.
Space pauses, R resets. In 3D drag to orbit, wheel to zoom, use the camera buttons (Zoom shows the tube wall with the fouling layer).

The science

Exchanger: one shell pass, two tube passes (TEMA E). Hot oil on the shell side (Kern correlation), water in the tubes (Dittus-Boelter). Duty from the effectiveness-NTU method:

NTU = U·A / C_min, C* = C_min / C_max
ε = 2 / [ 1 + C* + √(1+C*²) · (1+e^(−NTU√(1+C*²))) / (1−e^(−NTU√(1+C*²))) ]
Q = ε · C_min · (T_h,in − T_c,in)

Overall coefficient referred to the outer tube area:

1/U = 1/h_o + R_f + d_o·ln(d_o/d_i)/(2k_w) + R_fi·d_o/d_i + d_o/(d_i·h_i)

Fouling uses the Kern-Seaton form: deposition falls with Reynolds number and rises with film temperature, removal grows with wall shear stress:

dR_f/dt = φ_d − R_f/τ_r , R_f(t) = R_f,∞ (1 − e^(−t/τ_r)) , R_f,∞ = φ_d·τ_r
φ_d ∝ Re^(−0.66) Pr^(−1/3) exp(−E/RT_f) , τ_r ∝ 1/τ_w

Control: a PI controller moves the fraction u of oil sent through the shell (the rest bypasses and re-mixes). The valve has a first-order actuator with a rate limit, the temperature sensor has a lag, and the controller output uses anti-windup (back-calculation). Trips isolate the hot oil on very high water outlet temperature or lost water flow.

Numerical checks run in the page

Duty from the LMTD × F method (Bowman correction for 1-2 passes) must equal the ε-NTU duty.
Hot-side and cold-side energy balances agree.
The fouling ODE integrated numerically (6000 steps) matches the closed form R_f,∞(1 − e^(−t/τ)).
The ε-NTU formula tends to 1 − e^(−NTU) when C* → 0.

Honest simplifications

Constant fluid properties except viscosity (water: Vogel-type fit, oil: Andrade fit); the exchanger is algebraic (ε-NTU) with first-order lags for the outlets, not a full dynamic model; fouling constants are calibrated for illustration, not measured for any real crude; the 3D tube bundle shows far fewer tubes than the 240 modelled, and the deposit thickness on the magnified tube is exaggerated (×160, k = 0.2 W/mK). Educational process-engineering model, not a design tool.