Overview
ISO 11520-1:1997 specifies general methods for evaluating the drying performance of agricultural grain driers. It covers both continuous-flow and batch driers, defining how to measure the evaporation rate under steady-state (continuous) or full-cycle (batch) conditions and how to correct observed performance to specified input and standard ambient conditions. The part includes instrumentation requirements, sensor placement, sampling and test preparation, calculation of results and recommended test report content. Annexes provide correction methods, uncertainty estimation, a checklist, airflow measurement guidance and an example report.
Key topics and technical requirements
- Test principle: Monitor continuous-flow driers at steady state (stable output moisture and exhaust temperature) and batch driers over a full drying/cooling cycle to determine evaporation and performance metrics.
- Instrumentation & accuracy:
- Air temperature sensors: max error ±1 °C or ±1.5 % of measured value; radiation shielding required when exposed to hot surfaces.
- Relative humidity: max error ±5 percentage points (or calculated to equivalent accuracy).
- Static pressure: max measurement error 5 %; barometric pressure instruments must be calibrated.
- Energy measurement: overall energy accuracy ±2 %.
- Sensor placement:
- Drying air entry: minimum six sensors (2×3 grid) to detect spatial gradients.
- Exhaust air: minimum six sensors (2×3 grid) near exit; one sensor at end of drying section.
- Cooling air: at least one sensor.
- Grain measurements:
- Moisture content: determined per referenced methods (ISO routine reference).
- Grain mass measurement: max error 1 %.
- Sample size formulas (e.g., required dry grain quantity for continuous-flow tests) and procedures for sampling and preparation are provided.
- Performance metrics:
- Evaporation (mass of water evaporated), evaporation rate, specific total/thermal energy consumption (J/kg water), residence time, and drier holding capacity.
- Documentation: test report structure, example formats and a checklist (Annexes).
Applications and users
- Who uses it: manufacturers, independent testing laboratories, agricultural engineers, equipment specifiers, purchasers, certification bodies and researchers involved in grain drying technology.
- Practical uses:
- Compare drying performance between machines.
- Verify manufacturer claims (evaporation rate, energy consumption).
- Support drier development, optimization and procurement specifications.
- Provide standardized test data for certification and purchasing decisions.
Related standards
Keywords: ISO 11520-1, grain driers, drying performance, evaporation rate, continuous-flow drier, batch drier, specific energy consumption, drier testing, instrumentation, grain moisture.