Watertight polyurethane rigid foam has low water absorption, good permeability to water vapor, and state of foam pores. It is not connected with each other, and the obturator rate is more than 95%. It is a dense microporous foam material, which is more dense than the surface of the air and is not easy to permeate. It is an hydrophobic material.
The quick freezing storehouse of vegetables and fruits is not suitable to use exhaust cooling, but use fan to supply air for refrigeration, because the gas in the quick freezing storehouse needs to be circulated and dispersed regularly to avoid carbon oxide poisoning caused by high concentration of carbon oxide in local areas. Therefore, in the quick freezing warehouse, the refrigeration equipment needs to be used together with the air conditioning equipment. The selection of refrigeration equipment is different from that of low-temperature freezer and ordinary quick freezing warehouse.
Mercedes.If necessary, install a filter on the compressor return pipeline to prevent dirt in the system from entering the compressor and remove water in the system.
Step of cold storage design: selection and laying of cold storage thermal insulation materials. The use of cold storage thermal insulation materials must be adjusted to the time, which not only has excellent fire resistance, but also has high cost performance. There are several types of cold storage insulation materials. One is the plate produced and processed into a fixed shape and specification, with fixed length, total width and thickness. The cold storage plate with relative specification and model can be selected according to the installation of the warehouse body. The high and medium temperature cold storage generally adopts 10cm thick cold storage plate, 12cm or 15cm thick cold storage board is generally used for ultra-low temperature cold storage and freeze-cleaning cold storage; Another kind of cold storage can be sprayed with polyurethane spray paint and polyurethane foam, and the raw materials can be sprayed into the brick or concrete warehouse of the cold storage to be built immediately. After shaping, it is both waterproof and thermal insulation. Thermal insulation materials include polyurethane, polystyrene grease, etc. Polyurethane is non hygroscopic and has good fire resistance, but the cost is high; Polystyrene resin has strong water absorption capacity and weak fire resistance, the soil temperature shall be low, there shall be interlayer under the cold storage, and good natural ventilation shall be maintained. Maintaining dryness is very important for the cold storage. In addition, the phase electricity of the relative volume shall be built according to the output power of the refrigeration unit. If the cold storage is water-cooled and radiating, the tap water pipeline shall be paved and the FRP cooling tower shall be built.
The polyurethane insulation board used in the construction of cold storage shall be integral and continuous and there shall be no joint in the middle. The junction of polyurethane insulation board, top plate and ground shall be made into fillet arc for transition, which can well meet the health needs.
The drainage at the outlet of the cooling fan, the drainage of the volatile cooler and the road drainage of the refrigerated warehouse storing food or drinks shall not be immediately connected with the sewage and wastewater pipeline system software, but indirect drainage shall be adopted. For the flushing (thawing) water drainage of each layer in the double-layer cold storage, and the external unit shall be connected with the unit in the cold storage.
The evaporator surface is too thick or too much dust, and the heat transfer effect decreases: another important reason is that the heat transfer efficiency of evaporator is low, which is mainly caused by excessive frost or excessive dust on the evaporator surface.
Finance Department.The quick freezing storehouse of vegetables and fruits is not suitable to use exhaust cooling, but use fan to supply air for refrigeration because the gas in the quick freezing storehouse needs to be circulated and dispersed regularly to avoid carbon oxide poisoning caused by high concentration of carbon oxide in local areas. Therefore, in the quick freezing warehouse the refrigeration equipment needs to be used together with the air conditioning equipment. The selection of refrigeration equipment is different from that of low-temperature freezer and ordinary quick freezing warehouse.
The installation of top warehouse plate should be carried out alternately with the installation of wall plate, and the wall plate should leave a gap for withdrawing construction equipment; During the installation of the top warehouse plate, the end steel sheet at the overlap with the wall plate shall be disconnected for 50mm to prevent the cold bridge from running cold; Two layers of foaming materials shall be evenly and continuously punched on the joint surface between each top warehouse plate. Rivets shall be pulled and fixed at the internal and external lap joints of the steel plate and the rivet spacing shall be 300mm; According to the design drawings, if there are supporting beams, columns and supporting steel frames in the warehouse, the setting out and positioning shall be carried out and accurate and clear marks shall be made according to the requirements of the design drawings; Weld or install the support beam, support steel frame, etc., and the welded junction shall be moisture-proof and treated according to the drawing requirements.
Initial operation unit of cold storage equipment: regularly observe the oil level and oil return of the compressor and the cleanliness of the oil. If the oil is dirty or the oil level drops, it shall be solved in time to avoid adverse effects.
Polyurethane foam foam dimensional stability: cold storage polyurethane foam in severe temperature changes or at a relatively low temperature will appear dimensional changes (as contraction), the size changes often reflect bubble cracking or falling off, and these will inevitably affect the normal use of cold storage. In addition to regular simulation of performance testing, more emphasis is placed on the selection of high quality materials: special energy polyether compound use, so that the foam body mesh structure, 4110 polyether commonly used in spraying materials contains a large number of functional components, and a large number of linear structures formed after reaction are difficult to be stable at low temperature; The use of the energy crosslinking agent also greatly improved the dimensional stability of the foam. The selected polyether adopts catalysis in the production stage, and the reaction is complete, so that the polyether maintains a high reaction rate (that is, it can react completely with black material); Some manufacturers in order to achieve foam appearance does not produce deformation phenomenon and add a hole component to foam material, reduce the bubble closed hole rate, achieve the effect of stable size, but it has sacrificed the thermal insulation performance of polyurethane cold storage insulation material foam.
Latest consultation.Energy saving and power saving: the design cost of quick freezing warehouse mentioned above is very low, but it has a great impact on the cost of quick freezing warehouse and later use cost. The electricity bill is often an important expenditure item in the later stage. The design scheme of the show can greatly reduce the power consumption of the quick freezing warehouse. The selection of the back sunny side of the quick freezing warehouse, the selection of the thickness of the thermal insulation board should be appropriate, the tightness of the quick freezing warehouse door, and the temperature difference between the adjacent cold storage rooms should not be too large are all issues that we need to consider. There are also some tips, such as the use of air curtain machine on the quick freezing warehouse door. We remind users to use parallel units in quick freezing warehouse as far as possible and start them reasonably.
OK, it has little impact on the storage temperature, but it has high labor intensity, incomplete defrosting and limitations.
The bubble density is 38 kg to 40 kg / m3 per cubic meter, and the steel plate thickness generally needs to be more than 0.4 mm to meet the standard. On the market, the main raw materials of special cold storage board for cold storage project are polyphenylene, polyethylene and polyphenylene grease. The density of thermal insulation material foamed by polyphenylene is thin, and the thermal insulation coefficient is not very high; After a certain ratio of polyethylene, it can foam cold storage insulation materials with appropriate density and good thermal insulation effect, and has high load-bearing capacity; Polyphenylene resin has strong water absorption, but poor heat insulation. Therefore, the polyurethane sandwich board with very good performance belongs to the polyurethane sandwich board. Although it is slightly higher, the polyurethane board has very good thermal insulation performance and does not absorb moisture.
Mercedes.The refrigeration equipment in the fresh-keeping environment of the quick-frozen warehouse mostly adopts the single-stage compression refrigeration system, with freon as the refrigerant. The evaporation mode in the warehouse is the cooling fan, which can be ceiling type. If the number of warehouses is small and the volume does not exceed 500 cubic meters, the refrigeration mode of the warehouse machine can be considered. If there are a large number of warehouses, the mode of multiple heads in parallel can be considered.
Cold storage has good water tightness. Polyurethane rigid foam has low water absorption, good permeability to water vapor, foam holes, disconnected and closed porosity of more than 95%. It is a dense microporous foam material, which is more dense than air surface, and is not easy to permeate. It belongs to hydrophobic materials.
At ordinary times, users should check the sealing degree of the gap of the cold storage, and notify the cold storage for maintenance in time if damaged parts are found.