Heat Exchange Calculator
Heat Exchanger Performance
What Is a Heat Exchanger?
A heat exchanger is a device used to transfer heat between two or more fluids without mixing them. You’ll find them everywhere — from power plants and refineries to air conditioners and refrigerators.
Common types include:
- Shell and Tube Heat Exchangers – widely used in industrial systems.
- Plate Heat Exchangers – compact and efficient, ideal for HVAC.
- Air-to-Air or Oil-to-Water Exchangers – used for process and thermal management applications.
What Does the Heat Exchange Calculator Do?
The Heat Exchange Calculator uses the standard equation for heat transfer:
[
Q = U \times A \times \Delta T_{lm}
]
Where:
- Q = Heat transfer rate (BTU/hr)
- U = Overall heat transfer coefficient (BTU/hr·ft²·°F)
- A = Heat transfer area (ft²)
- ΔTlm = Log Mean Temperature Difference (°F)
It assumes a counter-flow configuration, where the hot and cold fluids move in opposite directions — the most thermally efficient arrangement.
How the Calculator Works
The calculator follows a simple process:
- Select or enter the heat transfer coefficient (U)
You can choose from preset system types (e.g., Water-to-Water ~400, Oil-to-Water ~25) or input a custom U-value. - Enter the heat transfer area (A)
Typically measured in square feet, this depends on exchanger size or plate count. - Input temperature data for both fluids:
- Hot fluid inlet and outlet temperatures
- Cold fluid inlet and outlet temperatures
- Click “Calculate Heat Transfer Rate”
The calculator determines:- ΔTlm (Log Mean Temperature Difference)
- Total Heat Transfer Rate (Q)
- View your results instantly
It displays both LMTD and Q in clean, color-highlighted outputs for easy interpretation.
Example Calculation
Let’s take an example:
Parameter | Symbol | Value |
---|---|---|
Overall heat transfer coefficient | U | 100 BTU/hr·ft²·°F |
Heat transfer area | A | 50 ft² |
Hot inlet | Th,in | 180°F |
Hot outlet | Th,out | 140°F |
Cold inlet | Tc,in | 60°F |
Cold outlet | Tc,out | 100°F |
Step 1:
ΔT₁ = Th,in – Tc,out = 180 – 100 = 80°F
ΔT₂ = Th,out – Tc,in = 140 – 60 = 80°F
Since ΔT₁ ≈ ΔT₂,
ΔTlm ≈ (ΔT₁ + ΔT₂)/2 = 80°F
Step 2:
Q = U × A × ΔTlm
Q = 100 × 50 × 80 = 400,000 BTU/hr
Your system transfers about 400,000 BTU per hour — that’s the total rate of heat energy exchanged between the fluids.
Why This Calculator Is Useful
The Heat Exchange Calculator saves time and prevents manual math errors. It’s ideal for:
- Mechanical and process engineers designing exchangers.
- HVAC technicians checking coil or condenser performance.
- Students learning thermodynamics and heat transfer.
- Energy auditors verifying efficiency and system losses.
It supports both quick design checks and detailed thermal balance studies.
The Formula Behind the Tool
The log mean temperature difference (LMTD) is crucial for accurate results:
[
\Delta T_{lm} = \frac{(\Delta T_1 - \Delta T_2)}{\ln(\Delta T_1 / \Delta T_2)}
]
It accounts for temperature variation along the exchanger’s length — ensuring precision when one fluid cools while the other warms up.
If ΔT₁ ≈ ΔT₂, the arithmetic mean is used to prevent mathematical errors in the logarithmic expression.
Common Mistakes to Avoid
When using the calculator, double-check the following:
- Hot fluid must cool → Th,in > Th,out
- Cold fluid must heat → Tc,out > Tc,in
- All temperature differences must be positive
- Area and U-value must be valid (non-zero and numerical)
Any violation of these conditions will trigger an error message for easy correction.
Quick Reference – Typical U Values
Type of Heat Exchanger | Approx. U (BTU/hr·ft²·°F) |
---|---|
Shell & Tube (General) | 100 |
Water-to-Water (Clean) | 400 |
Oil-to-Water | 25 |
Steam Condenser (Clean) | 15 |
Air-to-Air | 75 |
Practical Applications
This calculator is widely applicable in fields like:
- Chemical & Petrochemical Plants – for process optimization.
- Food & Beverage Industry – for pasteurization or cooling.
- HVAC Systems – for coil and radiator efficiency checks.
- Power Generation – for condensers and economizers.
Wherever heat exchange occurs, this tool simplifies the math.
Key Benefits
- Instant and accurate heat transfer results
- Supports counter-flow heat exchanger modeling
- Accepts both predefined and custom U-values
- Real-time validation with error handling
- Sleek dark UI with responsive layout
Formula Summary
[
\begin{aligned}
Q &= U \times A \times \Delta T_{lm} \
\Delta T_{lm} &= \frac{(\Delta T_1 - \Delta T_2)}{\ln(\Delta T_1 / \Delta T_2)}
\end{aligned}
]
Where:
- ΔT₁ = Th,in – Tc,out
- ΔT₂ = Th,out – Tc,in