Heat Exchanger Sizing Calculator

Heat Exchanger Sizing – Definition

A heat exchanger is a device used to transfer heat between two fluids without mixing them. Sizing a heat exchanger means determining the required heat transfer area needed to achieve a specified temperature change. Proper sizing is crucial for efficient thermal performance, cost optimization, and safe operation across industrial, HVAC, chemical, and process applications.

Background Theory

The sizing calculation is based on the Log Mean Temperature Difference (LMTD) method, which is widely used in thermal design:

Where:

• Q = heat duty (W)

• U = overall heat transfer coefficient (W/m²·K)

• A = required heat transfer area (m²)

• ΔTlm = log mean temperature difference (K)

The LMTD depends on the approach temperature differences between hot and cold fluids at each end of the exchanger. It varies with the flow arrangement:

• Counterflow: maximum temperature driving force

• Parallel flow: smaller temperature driving force

LMTD captures the non-linear temperature profile inside the exchanger, making it more accurate than a simple average temperature difference.

How This Calculator Works

This calculator sizes a heat exchanger by:

1. Taking user inputs:
   heat duty (Q), overall heat transfer coefficient (U), and inlet/outlet temperatures for both hot and cold streams.

2. Computing the two terminal temperature differences

3. Selecting the correct LMTD formula based on counterflow or parallel flow

4. Calculating the required heat transfer area using:

5. Displaying the required exchanger area in m²

This provides a fast and reliable estimation for preliminary heat exchanger design, energy analysis, and process engineering calculations.