What is a Shell and Tube Heat Exchanger?

A shell and tube heat exchanger is the most common type of heat exchanger design used in oil refineries and other large chemical processes. It consists of a shell (a large pressure vessel) with a bundle of tubes inside it. One fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids.

How the Calculation Works

This calculator utilizes the standard heat transfer equation: Q = U × A × LMTD. To find the required surface area (A), we first determine the Logarithmic Mean Temperature Difference (LMTD), which provides a more accurate average temperature driving force than a simple arithmetic mean. The formula for LMTD is:

LMTD = (ΔT1 - ΔT2) / ln(ΔT1 / ΔT2)

Where ΔT1 is the temperature difference at one end of the exchanger and ΔT2 is the difference at the other end. Once the LMTD and the overall heat transfer coefficient (U) are known, the area is calculated as A = Q / (U × LMTD).

Steps to Use the Calculator

1. Enter the Hot Fluid Inlet and Outlet temperatures.
2. Enter the Cold Fluid Inlet and Outlet temperatures.
3. Input the Overall Heat Transfer Coefficient (U). This value depends on the fluids involved (e.g., water-to-water or oil-to-water).
4. Enter the desired Heat Duty (Q) in kilowatts (kW).
5. Click Calculate to see the LMTD and the minimum surface area required for your heat exchanger.

Frequently Asked Questions

What is a typical U-value? For water-to-water exchangers, U often ranges between 800-1500 W/m²·K, while steam-to-liquid can exceed 2000 W/m²·K.
Does this account for fouling? This basic calculator assumes the 'U' value provided already accounts for the fouling factor (resistance caused by scale or deposits).
What if ΔT1 equals ΔT2? In cases where the temperature differences are equal, the LMTD simplifies to the arithmetic difference, as the log formula would result in a division-by-zero error.