Size the cooling for a sealed electrical cabinet: enter the enclosure dimensions, the internal heat load, and your temperature limits, and get the net cooling capacity a heat exchanger, air conditioner, or thermoelectric assembly must provide.
The diagram is labeled with the same symbols as the input fields below.
The cabinet starts heat-soaked at ambient with the equipment running. A cooler with EXACTLY the capacity the calculator computed pulls it down and duty-cycles on the thermostat - watch the relay work.
This preview solves a handful of lumped nodes. The NovaThermal engine behind ThermalResults.com (coming soon) runs the same physics on tens of thousands of nodes - full transients with phase change, radiation, fluid loops, and Monte-Carlo design envelopes, GPU-accelerated at 400× real-solver speed - and hands you review-ready margin reports.
A sealed enclosure protects electronics from dust, washdown, and corrosive air, but every watt dissipated inside must leave through the walls or through a cooler. This calculator does the fundamental bookkeeping: the wall exchange term U·A·ΔT either helps you (ambient colder than the interior) or hurts you (hot ambient leaking heat in on top of your internal load).
The classic mistake is sizing a cooler at the nameplate rating without checking the rating conditions. A cabinet air conditioner rated 800 W at 35°C ambient may deliver barely 500 W at 50°C. Always size at the HOTTEST realistic ambient with the enclosure's own maximum allowed internal temperature, and remember that lowering the internal setpoint below ambient makes the surface term work against you.
When is a closed-form estimate not enough? Duty-cycled loads, solar exposure, stratification in tall cabinets, and cold-start condensation are all transient, spatial effects that a single U·A·ΔT balance cannot resolve. For those, a lumped-network transient simulation of the cabinet (walls, air zones, equipment masses, cooler control) is the correct next step and typically changes the answer by 20-40% versus the steady estimate.
Painted steel sealed enclosures in still air are typically 5.5 W/m2K, stainless steel about 3.7, and aluminum about 12. These are industry-standard planning values; forced air over the outside or radiant sun exposure changes them significantly.
Only when the ambient is COLDER than your allowed internal temperature. If the ambient is hotter, the surface term adds heat and your cooler must remove both the internal load and the leakage.
A negative result means the walls alone reject more heat than the electronics produce at your temperature limits - the enclosure can run passively. Verify against the hottest ambient case and consider dust, sun, and future load growth before deleting the cooler.