Greenhouse gutter design
Greenhouse gutter design
As a part of the greenhouse skeleton, the greenhouse gutter not only takes on the function of eliminating rain and snow, but also is an important stress component of the greenhouse structure. In the design of greenhouse gutter, the following points should be considered comprehensively: 1. In areas with large temperature difference between indoor and outdoor, such as northern areas, condensate is easily produced on the surface of the straight interior, because of the shape of the heavens, the design of loading coin except cold water; 2. The cross section of the gutter should meet the needs of eliminating rainwater;3.The mechanical properties of the gutter should meet the needs.
The shape of gutter
Fig. 1a is a flat-bottomed trench. It is easy to process and handle connection joints. The disadvantage is that if condensate water is produced.
Condensate water drops on both sides of flat bottom, so it is difficult to collect condensate water. Generally, it does not produce cold when used in southern rooms.
Condensate occasion: Fig. 1b, 1c and 1d are pointed-bottom trenches. Condensate collects heat at the bottom of the trench.
Pipe fittings for collecting condensate water are arranged at the bottom of the tip of the trench, which is suitable for all regions. Receive condensate as shown in 1d chart.
Design of drainage system for trench
Classification of drainage systems
Greenhouse drainage system can be divided into two kinds: internal drainage system and external drainage system.
Outside drainage system is generally used to extend the Tiangou out of the gable and drain rainwater outdoors directly through risers. In cold areas, in order to prevent the riser from freezing, drainage outlets and risers can also be installed on the inside of the gable. Composition of external drainage system: Tiangou, rainwater bucket (drainage outlet), drainage riser. Internal drainage system is a system that drains rainwater outdoors by utilizing water pipes in greenhouse. It is generally used in the case that the drainage system is too long to meet the requirements. Composition of internal drainage system: Tiangou, rainwater bucket (drainage outlet), drainage riser, drainage pipe or ditch.
Designed rainwater discharge is as follows
Qy—-Design rainwater flow(L/s);
Qj—-Design storm intensity(L/s·hm²)
The catchment area Fw should be calculated according to the horizontal projection area of the roof.
Gutter 1 catchment area:Fw=B1L
Gutter 2 catchment area:Fw=B2L
Capacity calculation of gutter drainage system
Maximum Drainage of gutter Calculated by the Formula below
Q=1000 X A X V,should Q≥Qy
V=R2/3 X I1/2/n
Q—–Maximum flow of gutter (L/S)
A—–Design cross-section area of trench,Generally, 80% of the maximum water depth of the gutter is taken.
V—-Flow Velocity in gutter (m/s)
I—–Slope of gutter, generally ≥ 0.003
n—-The roughness of trench is 0.012 for steel trench
S—–The sum of the side lengths of the cross-section in contact with the gutter
It can be seen from the above formula that when the shape of the trench is fixed, the requirement of drainage can be met by increasing the slope of the trench or reducing the catchment area.
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