Although they are still relatively unknown, misting systems have been in use for over 50 years. Some of the more common mist system applications include outdoor cooling, humidification, and dust control. Each application has it own set of design requirements for the misting system. In some cases, the misting systems design incorporates completely surrounding the area and in other cases, the mist system is simply a single line run down the center of the area. In order to properly design the most effective misting system, a complete understanding of the area and the misting systems requirements are needed.
MISTING SYSTEMS DEFINITION
A misting system can be defined as a series of misting nozzles that are placed in a tubing and pressurized to provide a fine spray, usually with droplets between 15 microns and 50 microns in size. To accomplish this, the mist system requires pressure of at least 500 psi. The industry standard for most misting systems is 1000 psi. If the mist system is operating at pressures below 500 psi, it will produce larger droplets and result in inefficient cooling.
MISTING SYSTEMS DESIGN REQUIREMEMNTS
The first application for the modern day misting system for cooling applications was for animals. In the 1950’s mist systems were introduced as an economical method of providing cooling for cattle and poultry. Mist systems were also introduced into the swine industry. In all of these cases, the cooling effect of the mist system was able to provide an improved product. In the case of cattle, the misting system cooled the summer air enough to provide increases in milk production as well as increases in the beef produced by the cattle. In the case of the poultry industry, the mist system reduced the mortality rate and provided larger eggs and more meat. In the case of the swine industry, larger pigs were produced in the same period of time. In all of these cases, the high pressure misting system was installed over the animals and operated during the peak summer months.
Misting systems were relegated to these few industrial applications for decades. It wasn’t until the 1980’s that the misting systems used in restaurants and homes started to be installed. Because these mist system applications are being used by and for people, complete evaporation is a requirement. To accomplish this, the area to be cooled needs to be carefully considered.
Generally, for patio cooling, the misting systems design will include placing the high pressure mist line on all open sides of the patio. The misting system will work most efficiently if there are no open sides of the patio where hot air can enter the patio. The mist system lines should be placed on the outer most perimeter of the patio at a height of at least 9 feet with the nozzles spaced every 24 to thirty six inches. By doing this, all of the water from the misting system can evaporate which provides the best possible cooling. In some cases, the misting system may include the use of fans to help circulate the cooled air.
If the misting systems application is in an open area, the cooling capability may be diminished due to a lack of shade and the inability to mount the mist system so that complete evaporation is achieved. In these cases, adding fans to the misting systems design will improve its cooling capacity. If there is no structure to mount to, the mist system can be laid on the ground with the misting system nozzles pointing directly upward. Although this is no the ideal design for a mist system, it can provide relatively good results.
The properties of a properly designed and installed mist system also allow for extremely effective humidification. Mist systems use in greenhouses was introduced in the early 1960’s and continues to this day. In these applications, the mist system design is based on several key factors including air exchange within the greenhouse, the ambient temperature and relative humidity outside the greenhouse, and the type of crop that is being grown. In all cases, a misting system can be designed to improve the results of the greenhouse propagation.
Other humidification applications for misting systems include textile plants, wineries, wood working facilities and concrete curing. In most of these applications, the misting systems job is to maintain an established level of humidity. The ideal humidity level for each different application may be different so the misting system will usually include the use of a humidistat and low voltage controls. These added controls will allow the mist system to react to changes in the environment and still maintain a preset humidity level.
Humidification projects in these various commercial facilities require a careful examination of the area to be sure the system is properly designed to achieve the needed results. It is critical that there is no moisture fallout that will adversely affect the product being produced. Using air circulation, smaller orifice nozzles, and specific placement of the mist system lines and the misting nozzles will determine the effectiveness of the misting system.
As with animal cooling, all humidification applications provide for a better product when used. Wineries will loose less wine through evaporation, wood working plants have less scrap and straighter lengths, textiles are stronger and textile equipment requires less maintenance. All of these benefits improve the commercial operation and improve the business’ profitability.