Therefore, 30 ft x 0.5 gallons/ft = 15 gallons/min to accommodate the system. To accommodate the system, 0.50 gallons/min are required per linear foot per minute.
The pump capacity must take into account the volume of water flow required by the system (pipes and pads) as well as water loss through evaporation from the pads. In reality, a 30ft x 6ft pad wall would be constructed (pads come in heights of 1ft increments).ĭetermining pump and sump tank specifications and capacities Therefore, the pad should be 30 ft wide and (157 ft 2/30ft) 5.2 ft tall. The pad wall should extend the entire length of the way. Therefore, 39,200 cfm/250 = 157 ft 2 of pad wall is required.
One square foot of this type of pad will accommodate 250 cfm. In this example, 4-inch cellulose pads are included. These fans provide a total of 39,200 cfm which meets the required air flow.ĭetermining pad wall specifications and dimensionsĪspen pads, 4-inch or 6-inch cellulose pads could be included to create a fan-and-pad cooling system. From a list of fan specifications (taken from the table below but available from supply catalogs or manufacturer specifications), two 48-inch, 1 horsepower fans are selected. The structure will therefore require two fans with a capacity of (38,857cfm/2) 19,429 cfm each. Therefore, this structure requires two fans spaced along the 30 ft wall. In this example, 1 exchange per minute is used so that 38,857ft 3/min (cfm) is required.ĭetermining fan numbers, sizes and specificationsįans should be spaced not greater than 25 ft apart (center to center as a general rule) and should never be greater than 200 ft from the pad wall.
The value of 1.5 would be used if the greenhouse were to be used during summer months where very high solar loads and temperatures will be experienced. The volume of the quonset structure is determined (assuming it is half of a cylinder) as: 0.5(πr2L)Īn air exchange of 1 to 1.5 times per minute is required. Some basic geometric equations allow the determination of the volume of the greenhouse. In this example, cooling specifications are outlined below for a single-span quonset greenhouse that is 30 ft wide and 110 ft in length. This is one method to serve as an example. There are several ways of calculating required air flow capacities. To determine specifications for cooling system, the greenhouse volume must be determined, and based upon several assumptions, a flow rate per minute (air exchanges) requirement is determined.ĭetermining greenhouse volume and airflow requirement Section 4: Calculating Greenhouse Cooling Requirements for a Standard Fan-and-Pad System
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