How do you estimate UV lamp heat load on a part?

Multiply lamp electrical input by the IR fraction reaching the part and by the lamp-on duty fraction, then convert to BTU/hr with the 3,412 factor. With 8 kW, an IR fraction of 0.55, and 0.6 duty, the heat to the part is 2.64 kW, which is the basis of the reported load.

Why does a UV lamp heat the substrate so much?

Medium-pressure mercury arc lamps convert only a fraction of input into usable UV; a large share leaves as infrared and visible light. That IR is absorbed by the part and reflector housing, which is why heat-sensitive films need IR management.

What is a cold mirror and does it lower this number?

A cold mirror (dichroic reflector) reflects UV toward the part while transmitting IR out the back, sharply lowering the IR fraction reaching the substrate. Dropping that fraction in the calculator directly cuts the heat load.

How does duty cycle affect heat load?

Heat load scales linearly with the lamp-on fraction. At 0.6 duty the lamp is on 60% of the hour, so the part sees 60% of the continuous-run heat; running at full duty would raise the load proportionally.

What is a typical IR fraction reaching the part?

For a bare medium-pressure mercury lamp, roughly half the input can arrive as IR at the part, hence the 0.55 default. UV LEDs run far cooler and a cold-mirror system can push the effective fraction well below 0.2.

How do I reduce heat load without slowing the line?

Options include cold mirrors, IR-reflective filters, quartz plates with forced air or water cooling, shorter lamp-to-part distance with focused optics, or switching to UV LED curing which emits almost no broadband IR.

UV Curing calculator

UV Heat Load Calculator

UV Heat Load on Substrate estimates how much infrared heat, in BTU per hour, a UV curing lamp dumps into the part it is curing. This matters because most UV arc and medium-pressure mercury lamps emit substantial IR alongside the useful UV, and that heat can warp thin plastics, distort films, or scorch heat-sensitive substrates. Process engineers and tooling designers use it to decide whether a heat-sensitive part needs cold mirrors, IR filters, quartz cooling, or simply a faster line. It converts electrical input, the fraction of IR that actually reaches the part, and the lamp-on duty cycle into a real thermal load you can design cooling around.

What this calculator does

Estimate the IR / convective heat load a mercury UV lamp dumps on a heat-sensitive substrate during cure - the number that drives chiller plates, cool blocks, and substrate distortion risk.
Use it during process design when the substrate is heat-sensitive (thin film, electronics, low-Tg polymer) and the cure cell needs cooling fixtures sized correctly.
It estimates the infrared heat load transferred to the substrate in BTU/hr from lamp electrical input, the IR fraction reaching the part, and the fraction of the hour the lamp is on.

Formula used

Estimated heat to part (kW) = lamp electrical input × IR fraction × exposure time fraction
Hourly load (BTU/hr) = estimated heat × 3,412

Inputs explained

Lamp electrical input power:
IR fraction reaching the part:
Lamp-on duty fraction per hour:

How to use the result

Use it when curing heat-sensitive substrates, spec'ing cold mirrors or IR filters, or troubleshooting warp and distortion under a UV lamp.
It is a first-order estimate; actual heating depends on substrate absorptivity, distance, dwell time, airflow, and reflector condition, none of which are modeled individually.

Common questions

How do you estimate UV lamp heat load on a part? Multiply lamp electrical input by the IR fraction reaching the part and by the lamp-on duty fraction, then convert to BTU/hr with the 3,412 factor. With 8 kW, an IR fraction of 0.55, and 0.6 duty, the heat to the part is 2.64 kW, which is the basis of the reported load.
Why does a UV lamp heat the substrate so much? Medium-pressure mercury arc lamps convert only a fraction of input into usable UV; a large share leaves as infrared and visible light. That IR is absorbed by the part and reflector housing, which is why heat-sensitive films need IR management.
What is a cold mirror and does it lower this number? A cold mirror (dichroic reflector) reflects UV toward the part while transmitting IR out the back, sharply lowering the IR fraction reaching the substrate. Dropping that fraction in the calculator directly cuts the heat load.
How does duty cycle affect heat load? Heat load scales linearly with the lamp-on fraction. At 0.6 duty the lamp is on 60% of the hour, so the part sees 60% of the continuous-run heat; running at full duty would raise the load proportionally.
What is a typical IR fraction reaching the part? For a bare medium-pressure mercury lamp, roughly half the input can arrive as IR at the part, hence the 0.55 default. UV LEDs run far cooler and a cold-mirror system can push the effective fraction well below 0.2.

Last reviewed 2026-05-12.