Abstract
The author measured the air change and the thermal balance of a phytotron (1) on fine day in April.
1. The humidity variation in the growth room was quantitative to the generation of steam from a evaporative pan. The diurnal variation of humidity was found in the glass room where the plants transpired following to solar radiation.
2. The air change was measured by the tracer gas method (2) . The natural air change was 0.9 times per hour. The air change in normal operation closing the fresh air damper was 3 times per hour. The going and coming air leak were found due to the fan operation at the glass roof in growth room and at the door between room and corridor.
3. The needed steam quantity to humidify the circulating air was large as several tenfold than the steam quantity which is enough to humidify the room air. This shows that the air tight improve-ment is important at the humidity control of this phytotron.
4. The thermal balance was calculated from the data measuring 9.00-14.30 on 23th. April of the primary brine temperature (inlet and outlet), the secondary brine temperature (inlet and outlet), solar radiation, the temperature and humidity of room air and fresh air, the consumption of electric power and liquid fuel, etc.
Thermal loss at fan was comperatively large as 36 per cent.
The reduction of the thermal loss at pump (8 per cent) and at duct (5 per cent) would be practicable.
