Multi Span Tunnel Film Greenhouse Design Pricinple

Multi Span Film

Multi Span Film

Greenhouse Proposal&Solution

1. Proposal Introduction

1.1. Design Principle

① Selecting appropriate supporting equipment based on the principle of combining science, advantage and practicality and greenhouse actual use function to make sure good performance in cost and quality..

② Choose the design standards reasonably according to the local conditions, and make the production process, main equipment and main project advanced, applicable and reliable.

③ Adhere to the principle of local conditions, focus on local climate conditions and cultivation requirements design.

1.2. Greenhouse Design Standard

① Relevant greenhouse standards.

② The current design and construction and equipment requirements for building structures in China.

③ Actual use function of greenhouse.

④ Basic meteorological data of the project building site.

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2. Main parameters and configuration

2.1 Greenhouse Overview

According to the basic conditions of the greenhouse project and the requirements of the constructor, this project is multi-span film greenhouse, with beautiful and modern appearance, the discharge and unloading air smoothly, with stable and stronger the structure, this greenhouse is more suitable for the area with heavy wind and strong light. With Good shading system, economic etc. features, is more suitable for planting crops, the roof and around the greenhouse covered with 15 microns white film.

The basic configuration of multi span film greenhouse including : high-quality hot-dip galvanized skeleton, external shading system, cooling system, electronic control system.

2.2 Greenhouse Specification

This multi-span film greenhouse: span 9 meters, 5spans, total length 45 meters; Column space 4 meters,  8 columns, total length40 meters; gutter height 2 meters, arch height 3.8 meters; around the brick wall 0.5 meters.Column size: 50*100*2.0mm, auxiliary column 50*50*2.0mm, supporting pipe diameter32*2.0mm, gutter thickness 2.0mm, beam 30*50*2.0mm, end face arch pulling pipe:50*50*2.0mm, inner arch pulling pipe:30*50*2.0mm, lengthways pulling pipes: 25*2.0mm

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2.3 Features of Greenhouse

1.Control temperature easily, to provide good environment for crop growth and comfortable working place for staff.

Greenhouse ventilation system and cooling system to ensure that when the temperature is high in summer to cool down quickly; when the temperature is low in winter can keep warm, to ensure the appropriate temperature in whole year in the greenhouse.

2. Reasonable structure, high strength, beautiful appearance.

Reasonable design for greenhouse to ensure that the greenhouse has enough wind and rain load resistance, to ensure the appearance of the greenhouse neat, beautiful, but also to ensure the greenhouse cooling, heat insulation performance.

3. Good Performance, Low Maintenance Cost

The basic configuration of multi-span film greenhouse including: high quality hot-dip galvanized skeleton, external shading system, roof ventilation system, exhaust fan, water curtain cooling system, electric control system. This greenhouse use for crop planting according to the conditions of local site and the use requirements of the constructor.

Reasonable design, as far as possible to use natural conditions or low energy consumption equipment, improve the environment inside the greenhouse, reduce the overall cost of greenhouse; to reduce the daily operating costs of greenhouse. The high quality products as key parts of greenhouse will not obviously increase the overall cost, while improved the performance and reliability of greenhouse, greatly reduce the accidents during the use of greenhouse, and reduce the cost of daily maintenance.

3.G

3.Greenhouse foundation and main skeleton

3.1. Greenhouse base foundation

Considering the factors of heat preservation, economy and beauty of greenhouse, according to the requirements of soil endurance, groundwater level and design load, to avoid uneven settlement of greenhouse, to prevent column distortion and shear deformation ,240 mm of reinforced concrete beam is used around the greenhouse. Outside the wall to do 0.8 m wide water ditch, other end face add drainage ditch, foundation embed depth of 1.0 m( tentative, according to the actual value is greater than the thickness of frozen soil layer). The indoor column of greenhouse adopts 220*220 mm reinforced concrete independent foundation, the embed depth of foundation is 1.0 m( tentative, the value is larger than the thickness of frozen soil layer according to the actual situation), and the elevation of top surface is detailed in the foundation plan. embedded steel plate or anchor bolt at the top of the foundation, welded or bolted to the upper steel column. The elevation of the embedded parts on the foundation and independent foundation is 5‰; in the north-south two-way looking for slope, as detailed in the elevation schematic in the foundation plan.

Geological data: this design foundation bearing capacity standard value fka≥100 kPa, after the construction slotted must be by Party A, the constructor and the local geological department in accordance with the relevant constructor inspection slot, if not in accordance with the design must notify the relevant designers to negotiate to resolve

3.2 Major structure

The main steel structure of greenhouse adopts double-sides hot-dip galvanized pipe and tubes, the service life is 20 years. The main structure adopts multi-span arch type. Galvanizing method adopts the international general "modified Senji Mir method" continuous hot dip galvanizing. The raw material is cold rolled strip, which is better than hot rolled steel in terms of mechanical performance and anti corrosion performance. The excellent mechanical performance ensure the overall loading capacity of greenhouse, and good anti corrosion capacity is the guarantee of the service life of greenhouse. The main steel structure is be manufactured by our company with standard requirements, (including small connectors, accessories),  to improve the key parts of greenhouse standardization degree, avoid greenhouse components from different suppliers, which avoid to directly decline the greenhouse structure stability. Connection with bolts and self-tapping screw which to be treatment by the latest anti-corrosion technology (Dacromet coating), without welding joints. The greenhouse skeleton adopts domestic hot-dip galvanized steel pipe and plate.

All steel components are produced by our factory; the processing for welding components,  first step is welding and then the whole galvanized anti corrosion for the parts, installation the the site. The main structure column is installed on the foundation pre-embeded bolt, except some matching fittings, the connection of other superstructure parts are all bolt, self-tapping screw or rivet. The connection between the column and the beam adopts 8.8 grade steel structure special bolt, as the following picture.

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4.Covering Material

Greenhouse roof and around sides covered with 150 micron white film, anti-drop, quality assurance for 5 years. 

4.1. Film Features The film coating with high resistance and water-proof coating liquid, with good barrier, to prevent putrefy and metamorphic, good sticky ability, with good adhesion. with good performance of blocking water vapor

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4.2. Antiflaming & Heat insulation:

High-tech special organic flame retardants are used inside the film, and the high-resistance water-insulating coating solution is used. ensure the growth temperature of crops and shorten the maturity period.

5.Ventilation System

The top ventilation system belongs to the natural ventilation system, and the air flow inside the greenhouse is controlled by electric opening and closing vent without using fan and water curtain, which plays the role of cooling and ventilation.

The ventilation system use electric control, through the electric coil film device, roll the coil rod to open the vent, the opening area with anti- insect net, can effectively prevent insects come in the greenhouse.

6.External Shading System

6.1.Function & Feature

For the maximum cooling effect in summer, the greenhouse is equipped with an external shading system, the shading screen width is 4.3 m, the shading rate is 75%, and the energy saving rate is 25%.

The external shading system can improve the ecological environment of greenhouse by adjusting the opening and closing of sunshade net by electric control, and in summer, shading screen can block the sunlight according to the different shading rate, to protect the crops from strong light burns, while reducing the greenhouse temperature.

6.2. Principle

6.2.1 Overall composition: The external shading system is composed of sunshade curtain, transmission mechanism and power device, system support and other fixing parts. gear rack pull screen, working principle as below picture.

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7. Cooling System

7.1 Wet curtain

7.1.1.Design Principle: The cooling system by water evaporation to achieve the purpose of cooling. The system selects the domestic (Monte) high quality wet curtain paper and the domestic water pump system, the domestic low pressure large flow fan. The system has the advantages of simple structure, low cost, low energy consumption, large cooling capacity and reliable operation. The cost of the equipment is only one seventh of the air condition, and the operating cost is only one tenth of the air condition. The core of the cooling system is a wet curtain that allows water to evaporate. Wet curtain is a paper product, in the long-term unworking state, very dry and brittle, only when it is working with water to become elastic and hardness. In addition, the wet curtain has good air permeability inside and outside, no heat preservation effect, special polymer materials and wood pulp fiber molecules double space correlation, and made of high water resistance, weather resistance materials cemented, high cooling efficiency, long service life, small resistance loss. it not only ensures sufficient wet stiffness, high water resistance, but also has a large evaporation surface area and low over-current resistance loss. The special water conveyance wet curtain can ensure that the whole wet curtain wall is evenly wet with water. When the air penetrates through the wet curtain medium, the water-air exchange with the wet curtain surface converts the air sensible heat into the latent heat of vaporization realizes the humidification and cooling of the air.

This system is set up in the closed greenhouse, when the fan is pumped, the indoor negative pressure is produced, forcing the outdoor unsaturated air to flow through the surface of the porous wet curtain, and a large amount of sensible heat in the air is converted into latent heat, thus forcing the dry ball temperature into the indoor air to be reduced by 8~12℃, and continuously

This system is set up in the closed greenhouse, when the fan is pumped, the indoor negative pressure is produced, forcing the outdoor unsaturated air to flow through the surface of the porous wet curtain, and a large amount of sensible heat in the air is converted into latent heat, thus forcing the dry ball temperature into the indoor air to be reduced by 8~12℃, and continuously enter into the indoor to prevent heat and reduce temperature

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7.1.2.Technical requirements 

(1). The wet curtain device shall be manufactured in accordance with the drawings and technical documents approved by the prescribed procedure;

(2). Wet curtain size, the  plates and fittings and other materials in accordance with relevant standard

(3). The design of evaporative cooling heat transfer efficiency and overcurrent resistance loss under wind speed should be in accordance with the provisions of table 8; table 8 design evaporative cooling heat transfer efficiency under wind speed and overcurrent resistance technical parameters evaporate cooling heat transfer efficiency E(%)70 overcurrent resistance (Pa1.4. wet curtain installation wet curtain inside wall of greenhouse. The greenhouse for planting is generally required to be installed on the north side of the greenhouse, the fans are installed on the south side, and the fans are relatively low in the shade of the wet curtain, which is beneficial to the crops. In areas with strong summer how winds/air, wet curtains may also be considered for installation on windward walls. In addition, according to the instructions of Party A Install with requirements. The main factors that determine the installation position of wet curtain are the shading of crop angle, the blocking of human visual angle, and the beauty of wall layout.

7.1.3.Wet curtain fixed frame water supply and drainage: domestic greenhouse wet curtain special frame, wet curtain water collection should be smooth. The upper water pipe and drain pipe are connected with the wet curtain frame with special connector.

7.1.4. Basic configuration:

1) Wet curtain :15 cm thick 1.5 m high, aluminum alloy frame finished water curtain one set.

2) Water pump:  1 unit, pump motor power 1.1 kw/ unit.

3) water supply device :1 set of UPVC pipe ,ф32mm upper pipe.

4) backwater unit 1 set U PVC pipe ,ф75mm backwater pipe.

5) circulating pool 1 set, length 2 m× width 2 m× depth 1.5 m, placed in greenhouse.

7.1.5. Cooling fan installation: the fan placed on the wall opposite the wet curtain, in order not to affect the lighting, the fan on the south wall, wet curtain on the north wall. According to the plant root ventilation needs, fans generally sit on 600 mm brick wall. Due to the strong wind from exhaust fan outside, the air flow may blow to the passing crowd at the outdoor, so the placement height can be raised a few. In practical experience, the convection distance of the wet curtain and the fan is less than 60m.  The total number of fans in this greenhouse is 10 units, size 1380×1380×400, exhaust volume 44000 m3/h, power 1.1 kw.