Design problem
A large temperature range and aggressive ramp requirement create competing thermal demands. The chamber must remove heat rapidly at low temperature, add heat rapidly at high temperature, maintain acceptable temperature uniformity, and protect the product under test. The enclosure, insulation, air circulation, heat exchangers, refrigeration system, heaters and controls therefore have to be considered as one system.
1000 LNominal chamber volume
-40°C to +150°CTarget operating range
10°C/minTarget ramp-rate class
Thermal cyclingPrimary application
Engineering workflow
- Define chamber volume, payload, allowable ramp time, stability and uniformity requirements.
- Calculate enclosure conduction, infiltration and internal payload heat loads over the full operating envelope.
- Separate refrigeration and heating duties for pull-down, pull-up and steady-state operation.
- Select heat-exchanger and airflow architecture based on required air-side heat transfer and pressure drop.
- Check compressor, expansion device, condenser and evaporator operating envelopes at the actual design temperatures.
- Develop controls around chamber temperature, product temperature, pressure protection and operating limits.
- Validate ramp rate, overshoot, uniformity, recovery and steady-state stability with representative payloads.
Engineering note: A quoted chamber temperature range alone is not enough to size the system. Payload mass, product heat generation, pull-down/pull-up time, ambient conditions, insulation, airflow and duty cycle can materially change the refrigeration and heater capacities.
What the analysis should produce
- Thermal load table across operating points
- Refrigeration and heater capacity requirements
- Heat-exchanger and airflow basis
- Control and sensor architecture
- Component operating-envelope checks
- Prototype and validation test plan