1. The built environment
(1) Before building the cold storage, the user is required to lower the floor of the cold storage area by 200-250mm, and prepare the floor;
(2) Drainage floor drains and condensate discharge pipes are required to be left under each cold storage. There is no drainage floor drain in the freezer and the condensate discharge pipes must be located outside the cold storage;
(3) The low-temperature storage requires the laying of floor heating wires, and one is ready for another use. After the heating wires are laid on the ground, the floor insulation layer can be laid with about 2 mm of early protection. If the floor where the cold storage is located is the lowest floor, heating wires may not be used on the floor of the low-temperature storage.
2. Heat insulation board
The insulation board must comply with the national standard and have a test report from the Bureau of Technical Supervision.
2.1 Insulation material
The thermal insulation material should use polyurethane foam composite thermal insulation board with plastic-sprayed steel plate or stainless steel plate on both sides, with a thickness of at least 100mm. The insulation material is flame retardant and free of CFCs. It is allowed to add a certain proportion of reinforcing materials to improve performance, but it cannot reduce the thermal insulation performance.
2.2 Insulated panel siding
(1) The inner and outer panels are colored steel plates.
(2) The coating layer of colored steel plates must be non-toxic, odor-free, corrosion-resistant, and comply with international food hygiene standards.
2.3 Overall performance requirements of the heat shield
(1) No exposed heat insulation material is allowed on the installation joint surface of the heat insulation board, and there must be no defects with convexity greater than 1.5mm on the joint surface.
(2) The surface of the heat insulation board should be kept flat and smooth, and there should be no warping, scratches, bumps, or uneven defects.
(3) Reinforcing measures are allowed to be taken inside the heat insulation board to improve the mechanical strength, but it is not allowed to reduce the heat insulation effect.
(4) The surrounding material of the heat insulation board must be the same high-density hard material as the heat insulation material, and other materials with high thermal conductivity are not allowed.
(5) There should be measures to prevent cold bridges at the joints between the heat insulation wall panels and the ground.
(6) The joints between heat insulation boards must be sealed with glass glue or other non-toxic, no peculiar smell, no volatilization of harmful substances, meeting food hygiene requirements and good sealing performance.
(7) The connection structure between heat insulation panels should ensure the pressure between the joints and the firm connection of the joints.
2.4 Requirements for installation of heat shield
The seam between the warehouse board and the warehouse board must be well sealed, the joint between the two warehouse boards must be less than 1.5mm, and the structure must be firm and reliable. After splicing the storage body, all the joints of the storage boards should be coated with continuous and uniform sealant. The cross-sectional structures of various joints are described below.
2.5 Schematic diagram of library board splicing
When the span of the roof exceeds 4m or the roof of the cold storage is loaded, the roof of the cold storage must be hoisted. The position of the bolt should be selected at the midpoint of the library plate. In order to make the force on the library plate as uniform as possible, the aluminum alloy angle steel or mushroom cap must be used as shown in the figure.
2.6 Sealing requirements for the joints of heat insulation boards in storage
(1) It should be ensured that the heat insulation material of the wallboard at the joint between the wallboard and the ground is closely connected with the heat insulation material in the floor, with reliable sealing and moisture-proof treatment.
(2) If the joints of heat insulation boards are sealed and bonded by on-site pouring and foaming, first of all, ensure that the heat insulation materials of the two heat insulation boards can be closely attached to each other, and then use sealing tape to evenly paste the joint surface to eliminate gaps and ensure The insulation is firmly bonded.
(3) The sealing material at the joint of the heat insulation board itself should be anti-aging, corrosion-resistant, non-toxic, no peculiar smell, no volatilization of harmful substances, meet food hygiene requirements and have good sealing performance. The sealing material at the seam must not be shifted or out of position to ensure that the seal at the seam is tight and even.
(4) If sealing tape is used to seal the joints of heat insulation panels, the joint size shall not be greater than 3mm.
(5) The heat insulation panels that make up the storage body must be integral along its height direction, without horizontal middle joints.
(6) The thickness of the insulation layer of the cold storage floor should be ≥ 100mm.
(7) Measures must be taken to reduce the “cold bridge” effect for the lifting point structure of the roof of the storage body, and the holes in the lifting point should be sealed.
(8) The thermal conductivity of the material of the lifting point connected to the warehouse board should be small, and the inner surface of the warehouse should also be covered with a cap of the same material.
3. Prefabricated cold storage door requirements
1) The prefabricated cold storage is equipped with three types of doors: hinged door, automatic one-sided sliding door, and one-sided sliding door.
2) The thickness, surface layer and thermal insulation performance requirements of the cold storage door are the same as those of the storage panel, and the structure of the door frame and door should not have cold bridges.
3) All low-temperature cold storage door frames should be embedded with electric heating or medium heating devices to prevent the door seal from freezing. When electric heating is used, electric heating protection devices and safety measures must be provided.
4) The doors of small refrigerators and freezers are manual side-hung doors. The surface of the door is required to be the same as that of the heat insulation panel. There should be no “cold bridge” on the door handle and the door structure, and the door opening should be >90 degrees.
5) The cold storage door is equipped with a door lock, and the door lock has a safe release function.
6) All warehouse doors must be flexible and light to open and close. The sealing contact plane of the door frame and the door itself must be smooth and flat, and there must be no warping, burrs, or screw ends that are skewed or exposed to cause scratching and rubbing. It can be attached to the perimeter of the door frame.
4. Library accessories
1) Low-temperature cold storage (storage temperature <-5°C = electric heating antifreeze device and automatic temperature control device must be equipped under the ground to effectively prevent freezing and deformation of the bottom surface of the storage board.
2) The warehouse is equipped with moisture-proof and explosion-proof fluorescent lighting, which can work normally at -25°C. The lampshade should be moisture-proof, anti-corrosion, anti-acid, and anti-alkali. The lighting intensity in the warehouse should meet the requirements for the entry, exit and storage of goods, and the ground illumination should be greater than 200lux.
3) All devices and equipment in the cold storage should be treated with anti-corrosion and anti-rust treatment, but it must be ensured that the coating is non-toxic, does not pollute food, has no peculiar smell, is easy to clean, is not easy to breed bacteria, and meets food hygiene requirements.
4) The pipeline holes must be sealed, moisture-proof and heat-insulated, and the surface should be smooth.
5) The low-temperature cold storage should have a pressure balance device to prevent and eliminate the excessive pressure difference of the storage body and the deformation of the storage body caused by sudden temperature changes.
6) Anti-collision devices should be installed along the aisle outside the cold storage. A low temperature resistant transparent plastic curtain should be installed inside the warehouse door.
7) The temperature indicator is required to be installed near the warehouse door.
8) The cold storage must be equipped with a drainage floor drain so that the sewage can be discharged when cleaning the cold storage.
5. Standards for selection of main materials and accessories
All materials must comply with national standards, and hold a certificate of conformity and a test report from the Technical Supervision Bureau.
Installation standards for air coolers and pipes
1. Cooler installation
1) The installation position of the air cooler is required to be far away from the warehouse door, in the middle of the wall, and the air cooler after installation should be kept horizontal;
2) The air cooler is hoisted on the roof, and its fixing must be fixed with special nylon bolts (material nylon 66) to prevent the formation of cold bridges;
3) When bolts are used to fix the air cooler, it is required to install square wood blocks with a length greater than 100mm and a thickness greater than 5mm on the top of the roof to increase the load-bearing area of the warehouse board, prevent the warehouse board from being deformed, and prevent the formation of cold bridges;
4) The distance between the air cooler and the back wall is 300-500mm, or according to the size provided by the air cooler manufacturer;
5) The wind direction of the air cooler cannot be reversed to ensure that the air cooler blows outward;
6) When the cold storage is defrosting, the fan motor must be disconnected to prevent hot air from being blown into the storage during defrosting;
7) The loading height of the cold storage should be at least 30cm lower than the bottom of the air cooler.
2. Refrigeration pipeline installation
1) When installing the expansion valve, the temperature-sensing package must be fastened on the upper part of the horizontal air return pipe, and ensure good contact with the return air pipe. The outside of the return air pipe should be insulated to prevent the temperature-sensing package from being affected by the storage temperature;
2) Before the air return pipe of the air cooler climbs out of the warehouse, an oil return bend must be installed at the bottom of the riser pipe;
3) When the refrigerated processing room and the refrigerated storage or medium-temperature cabinet share one unit, an evaporating pressure regulating valve must be installed before the return air pipeline of the refrigerated processing room is connected to the pipelines of other refrigerated storage or medium-temperature cabinets;
4) Each cold storage must install independent ball valves on the air return pipe and liquid supply pipe to facilitate commissioning and maintenance.
The selection, welding, laying, fixing, and heat preservation of other pipelines must be carried out in accordance with the standards specified in the “Refrigeration Pipeline Engineering Materials, Construction, and Inspection Standards”.
3. Drain pipe installation
1) The drainage pipeline running inside the warehouse should be as short as possible; the drainage pipe running outside the warehouse should be run in an inconspicuous place on the back or side of the cold storage to prevent collision and affect the appearance;
2) The drain pipe of the cooling fan should have a certain slope leading to the outside of the cold storage, so that the defrosting water can be discharged out of the cold storage smoothly;
3) For cold storage with working temperature less than 5°C, the drainage pipe in the storage must be equipped with insulation pipe (wall thickness greater than 25mm);
4) Heating wire must be installed in the drain pipe of the freezer;
5) The connecting pipe outside the warehouse must be equipped with a drainage trap, and a certain liquid seal must be ensured in the pipe to prevent a large amount of hot air outside the warehouse from entering the cold storage;
6) In order to prevent the drain pipe from becoming dirty and blocked, each cold storage must be equipped with a separate floor drain for defrosting water (refrigerated storage can be installed inside the storage, and the freezer must be installed outdoors).
4. Other engineering standards
The construction of the location of the machine room, ventilation, unit fixing, etc. shall be carried out in strict accordance with the “Construction and Inspection Standards for Basic Engineering”.
The electrical engineering construction of the cold storage should be carried out in accordance with the “Electrical Engineering Construction and Inspection Standards”.
5. Cold storage load calculation
The accurate cold storage load should be calculated according to the calculation software. Commonly used software includes Wittboxnp 4.12, Crs.exe, etc. If factors such as food storage, food storage temperature, storage period, number of door openings, and number of operators cannot be determined, the following methods can be used to estimate:
5.1 The cooling load of refrigerators and freezers is calculated according to W0=75W/m3 per cubic meter, and multiplied by the following correction factors.
1) If V (volume of cold storage) < 30 m3, for cold storage with more frequent door openings, the multiplication factor A=1.2
2) If 30 m3≤V<100 m3, the cold storage with frequent door opening times, the multiplication factor A=1.1
3) If V≥100 m3, the cold storage with frequent door opening times, the multiplication factor A=1.0
4) If it is a single cold storage, the multiplication factor B=1.1, other B=1
Final cooling load W=A*B*W0*volume
5.2 Load matching between processing
For open processing rooms, calculate by W0=100W/m3 per cubic meter, and multiply by the following correction coefficients.
For the closed processing room, calculate according to W0=80W/m3 per cubic meter, and multiply by the following correction coefficient.
1) If V (volume of processing room) < 50 m3, multiply by factor A = 1.1
2) If V≥50 m3, the multiplication factor A=1.0
The final cooling load W=A*W0*volume
5.3 Under normal circumstances, the fin spacing of the cooling fan in the processing room and cold storage is 3-5mm, and the fin spacing of the cooling fan in the freezer is 6-8mm
5.4 The refrigerating capacity of the selected refrigeration unit must be ≥ cold storage load/0.85, and the corresponding evaporation temperature must be 2-3°C lower than the evaporation temperature of the air cooler (resistance loss must be considered).
Post time: Jan-30-2023