Air flow rate is one of the crucial factors of ventilation units to maintain the climate inside the greenhouse. To offer better climate for plant growth, a ventilation system has to maintain sufficient and uniform ventilation rate both inside and outside greenhouse environment. Additionally, better ventilation rate allows to decrease the greenhouse air temperature and humidity to enhance the evapotranspiration process for crops.
By using window screens as insect proof nets in the ventilation of greenhouse is commonly used and it is become popular in many areas due to its capacity to prevent the crop damage by insect pests and viruses. Additionally, insect screens have many benefits among them decreasing the count of insects invading the greenhouse, reducing the need for pesticides and offering simple structural design hence reducing the construction cost.
Although nets supplied by window screen factory are effective in protecting from insect pests, installation of the screen on ventilation openings practically is checked to maintain sufficient air supply so a larger area is provided to allow the adequate air flow. For example to maintain sufficient ventilation, the ratio of total ventilator opening to the greenhouse floor in Germany conditions areas should be larger than 15 to 25%.
Many authors have reported reduced air flow due to insect screen implementation on the greenhouse. The reduced air flow rate can result into increase in air temperature and humidity. The concerns of reduced air flow in the greenhouse due to net implementation can be resolved by using high quality screens with sufficient pore size. Estimation of ventilation rate has been evaluated by authors by using a common technique of tracer gas with various media for example methane, nitrous oxide and carbon dioxide. For the humid tropics, naturally ventilated greenhouses often have large ventilation openings, so it is essential to follow a suitable method that offers fast, simple and accurate means for evaluating the ventilation rate. The China Window Screens offer good ventilation in addition of preventing insects and pests.
Water vapor mass balance and energy balance methods were used to determine the ventilation rates. The ventilation rates were measured in greenhouses covered with insect screens of different mesh sizes from measured crops transpiration rate and absolute humidity difference between in and outside the greenhouse. The calculated values were compared with energy balance method depending on the external microclimate.
An energy balance method provides a simple, quick and accurate way to determine the ventilation rates in the greenhouse, it is crucial to verify the method with the ones received from a tracer gas method as a standard method to evaluate ventilation rates. A significant effect of different mesh sizes on the ventilation rate was noticed despite the large ventilation opening. A greenhouse with the finest mesh size described the lowest ventilation rate unlike to greenhouses with 40 and 52 mesh. So an mesh screen with larger hole size will be helpful to maintain good ventilation rate.
Contact Reliable Window Screen Suppliers for good quality screens and nets for your greenhouse.