Evaluation of a prototype thermal anemometer for use in low airspeed drying measure calculations

Abstract

An indicator of the drying rate of an airflow is the product of airspeed and humidity ratio (or vapour pressure) deficit. Significant sensor errors are present in both the high relative humidity and low airspeed ranges. Also, the margin for error is small relative to the desired drying measure for mushroom growth. The objective of this study was to evaluate the suitability of a low-cost prototype anemometer for use in a mushroom growth environment. A calibrated thermal anemometer was used as a performance reference for the prototype airspeed sensor. Case studies were carried out on two prototype airspeed sensors to determine suitability for use in this drying measure application. The study required the construction of a custom wind tunnel to produce a unidirectional airflow. The sensors (housed in the wind tunnel) were evaluated in an environmental chamber over the range of relevant temperatures. Results show promise for the future application of the prototype sensors subject to the sensors being thermally compensated. Reduction in the cost of a low velocity anemometer by an order of magnitude, would facilitate their purchase and subsequent use for airspeed control by the grower, thus broadening the range of control variables available to the grower.