A Method for measuring Dry-bulb Temperatures during the Operation of a Fog System for Greenhouse Cooling

During operation of a fog system for greenhouse cooling, fog wafts in the air inside the greenhouse. If the fog adheres to a sensing part of a thermometer, such as a junction of a thermocouple, measurement of dry-bulb temperature decreases and sometimes reaches a wet-bulb temperature while the fog evaporates. In this study, the use of a non-aspirated thermocouple in a column-shaped shelter with a flat roof was examined to determine the dry-bulb temperature in a greenhouse equipped with the fog system. The results indicated that a combination use of the shelter and an empirical correction for eliminating radiation effects provided the most accurate determination of the dry-bulb temperature during the operation of the fog system. Owing to the fog adherence to a junction of a thermocouple in an aspirated psychrometer or a bare thermocouple without the shelter, its measurement was significantly lower than the actual dry-bulb temperature during the operation of the fog system.