AbstractHigh environment temperature in humid tropical lowland can cause vary physiological problems for plants. Zone cooling system for substrate hydroponics was built to maintain root zone temperature of the plants. The objective of this research was to predict temperature distribution in substrate hydroponicssystem root zone with root zone cooling which is important parameter in evaluating root zone cooling system. The distribution of root zone temperature was simulated using computational fluid dynamics (CFD) approach. The simulation result showed uniformed temperature distribution in the planting medium for hydroponic substrate with minimum, maximum, and average temperature of 12.60oC, 39.90oC, and32.00oC, respectivelly. The comparison...