###### Abstract  
In a plant factory, maintaining proper and uniform air/moisture movement above the crop canopy is crucial for aiding plant growth. This research has utilized a three-dimensional computation model to investigate airflow and heat transfer in a plant factory, where airflow, heat, and humidity distributions above plant crops were calculated concerning five categories of crop planting density (\(P_{d}\)) and air change rate (\(ACH\)) in the crop area. Spatial uniformities of airflow velocity, temperature, and relative humidity immediately above the crops are evaluated using the objective uniformity parameter (\(OU\)), relative standard deviation of temperature (\(RSD_{T}\)) and relative standard deviation of relative humidity (\(RSD_{RH}\)), respectively. Furthermore, a factor of effectiveness (\(\theta\)) is defined, depending on the uniformity of velocity, temperature, and relative humidity distribution, to comprehensively evaluate the impact of various \(ACH\) with \(P_{d}\) on overall effectiveness. Full numerical results show that air velocity, temperature, and relative humidity above the crops are notably influenced by \(P_{d}\) and \(ACH\). As \(ACH\) increases, the \(OU\) of the air above the indoor crop also expands. Moreover, higher \(OU\) values are observed for smaller crop \(P_{d}\). However, excessively small crop area planting densities and excessively large \(ACH\) do not result in a higher \(OU\) for the air above the crop. As \(ACH\) increases, both \(RSD_{T}\) and \(RSD_{RH}\) decay for the whole range of crop \(P_{d}\). Moreover, smaller \(P_{d}\) values could achieve the uniformity of thermal fields, while having minimal effects on the relative humidity distributions. Generally, increasing \(ACH\) and decreasing \(P_{d}\) could enhance overall value of \(\theta\). However, excessively increasing \(ACH\) and decreasing \(P_{d}\) does not have a significant effect on \(\theta\), which is jointly influenced by \(OU\), \(RSD_{T}\), and \(RSD_{RH}\). Therefore, a more suitable combination of \(ACH\) and \(P_{d}\) is urgently required to improve the design of agricultural system to enhance crop microclimate uniformity for optimal plant growth and productivity. crop airflow; planting density; air change rate; indoor agricultural systems; computational fluid dynamics (CFD) 20251 is crucial for people's daily lives and social activities. To meet the escalating demand for food, it becomes imperative to explore methods to enhance food production. While expanding arable land or increasing yields on existing land seems like viable options, the availability of arable land is diminishing [6]. Therefore, there is a need to prioritize the development of new technologies [7,8] that can achieve higher yields and ensure food security. In this context, plant factories have emerged as a promising alternative [9] to address the challenges of shrinking arable land and increasing food production. Plant factory is a new facility which could be used for agricultural production with simple control of the indoor environment and has gained widespread attention for its high and stable rate of utilization of resources per unit. In the plant factory closed or semi-closed condition, the indoor environment in the plant factory could adjust the system to achieve accurate control of light, temperature, humidity, nutrient solution, and other parameters in the process of plant growth, so that the plant grows almost unaffected by the external environment to achieve high yield. Indoor ventilation plays a vital role in maintaining a healthy environment in plant factories. Poorly designed ventilation systems can negatively affect air quality in the crop canopy of cultivation trays, ultimately affecting crop growth and yield [10]. Stagnant airflow within the crop canopy is particularly detrimental to plant growth [11]. Therefore, it is important to ensure proper airflow and ventilation within the plant factory to create favorable conditions for crop growth and optimize productivity.