We specialise in the design and installation of cold rooms, our company is the leading cold room and refrigeration unit designer, manufacturer and exporter dedicated in supplying finest quality cold room solutions to worldwide customers. we exported a large selection of fruits and vegetables cold rooms and refrigeration units to Philippines and Singapore. Our fruits and vegetables storage cold rooms are made of high quality materials and low energy consumption.
100mm cold room panels with 0.5mm thickness double face steel.
Bitzer air cooled condensing units
Bitzer CSH screw compressors
As your cold room experts, we had been specializing in delivering turn key cold room solutions to worldwide customers for 18 years. We had provided many types of effective and states of the art cold rooms and freezer rooms to over 40 countries. We have been exporetd cold rooms to Swiss, Sweden, Australia, USA, Canada, New Zealand, Pakistan, Spain, India, Malaysia, Singapore, Malaysia, Philippines, South Africa, Argentina, Indonesia, Kenya, Algeria, Ghana, Guyana, Mongolia, Chile, Peru, Dubai, Poland, Mexico, Brazil, Lebanon, Thailand, Kazakhstan, Turkmenistan, Bangladesh, Colombia, Bahrain, Papua New Guinea and so on
1, Poor heat insulation and sealing of cold room causes losing large cooling;
Poor insulation performance is due to insufficient thickness and lower quality of insulation on refrigeration pipes, cold room insulation walls, etc., It is mainly caused by improper selection of insulation panels thickness during design or poor quality of insulation material during construction. In addition, during the construction, the moisture resistance of heat insulation materials may be damaged, causing the insulation panels to be damped, deformed, or even eroded. Its heat insulation capacity is reduced, and the loss cooling of cold storage room is increased accordingly, then cause the cold room temperature slows down.
Another important reason for the large cooling loss is the poor sealing performance of the cold room, and more hot air penetrates into the cold room from the leak. Generally, if condensation occurs on the sealing strip of the cold room doors or the seal of the cold storage room insulation wall, it indicates that the seal is not tight. In addition, frequent opening and closing of the cold room doors or a large number of people entering the cold room together will also increase the cooling loss. Try to avoid opening the cold room doors to prevent a lot of hot air entering the cold room. Of course, when the cold room frequently receives goods or the quantity is too large, the thermal load increases sharply, and it usually takes a long time to cool down to the required temperature.
2, The thick frost and more dust on the surface of the refrigeration evaporator will cause the heat ex-changer reducing;
Another important reason for the cold room temperature dropping slowly is the low heat ex-changer of the evaporator, which is mainly caused by the thick frost or much dust on the evaporator surface. Since the surface temperature of the evaporator in the cold room is mostly lower than 0 ° C, and the humidity of the warehouse is relatively high, the moisture in the air is likely to frost and even freeze on the surface of the evaporator, which affects the evaporator heat ex-changer. In order to prevent the thick frost on the surface of the evaporator, it needs to be defrosted regularly.
3, More air or refrigeration oil in the evaporator will cause the heat ex-changer reducing.
Once more refrigerant oil is attached to the inner surface of the evaporator heat ex-changer tubes, its heat ex-changer coefficient will decrease. Similarly, if there is more air in the heat ex-changer tubes, the heat ex-changer area of the evaporator will decrease and its heat ex-changer will be reduced. So the temperature in cold room will dropping slowly. Therefore, in the daily operation and maintenance, should pay more attention to timely removing the oil on the inner surface of the heat ex-changer tubes and exhausting the air in the evaporator to improve the heat transfer efficiency of the evaporator.
4, Improperly adjusted or blocked of the throttle valve will cause the refrigerant flow too large or too small.
Improper adjustment or blockage of the throttle valve will directly affect the refrigerant flow into the evaporator. When the opening degree of the throttle valve is too large, the flow rate of the refrigerant is too large, and the evaporation pressure and the evaporation temperature are also increased, and the temperature of the cold room will drop slowly. At the same time, when the opening degree of the throttle valve is too small or blocked, the refrigerant flow rate is also reduced, the cooling capacity of the system is also reduced, and cold room temperature will also drop slowly. Generally, you can judge whether the refrigerant flow rate of the throttle valve is appropriate by observing the evaporation pressure, evaporation temperature, and frosting of the suction pipe. Throttle valve clogging is an important factor that affects the flow of refrigerant.
5, Low efficiency of the refrigeration compressor will cause lower cooling capacity;
Due to the long-term operation of the refrigeration compressor, severe wear of the cylinder liner and piston ring and other components, the clearance will increase, the sealing performance will decrease accordingly, the air transmission coefficient of the refrigeration compressor will also decrease, and the cooling capacity will decrease. When the cooling capacity is less than the heat load of the cold room, the temperature of the cold room will drop slowly. The refrigeration capacity of the compressor can be roughly judged by observing the suction and discharge pressure of the compressor.
6, Lack of refrigerant in the refrigeration system;
There are two main reasons for the lack of refrigerant. First, the refrigerant charge less. Another reason is that there is a lot of refrigerant leakage in the system. In this case, you should first find the leak point, focus on the inspection of the pipeline and valve connections, repair the leaked part, and then fill the refrigerant with sufficient amount.
Before running one cold room especially low temperature cold room, the system debugging of the low-temperature cold room is a very important thing. Only the cooling adjustment can reach the temperature it needs, and avoiding the damage of the civil structure of the cold room due to the sudden temperature drop. Let’s learn how to do during the first time cooling of cold room?
First of all, we should do the corresponding preparation work, and do the vacuuming work for the refrigeration system. The cold room temperature will gradually decrease by a slow method.
Next, we can evaluate an effect of cooling. Why we should do slow cooling? It makes the moisture contained in the construction project to be slowly discharged to the outside. And also avoids the damage of civil structure works because of sudden temperature and due to freezing of water. It can also prevent a phenomenon of cold shrinkage caused by excessive temperature drop, which will cause damage of the external wall structure of civil engineering. This is actually an important part in the installation process of low temperature cold room.
Before starting the cold room cooling, for example, before the filling of the refrigerant, must be done vacuuming, so that it can check whether the system has strictness, and can also promote the air and moisture discharge in the cold room. And it should also be done with nitrogen filling and check leaking. This is also a better treatment method. Each cold room building materials is different, so the cooling temperature speed is also different.
The first time cooling step: 1, charge nitrogen using the pressure difference 2, supply liquid to the evaporator properly . 3, Do slowly cooling to the cold room temperature. 4, Do extremely rapid cooling. At this time, verify how is the cooling effect
The location of the cold storage room must be noted. First of all, it is necessary to make decisions based on its own operation. Take the rental cold storage room as an example, the location of the cold storage room needs to consider the surrounding market prospects and convenient transportation.
The volume of the cold storage room
Different goods needs different cold storage room volumes. Generally, our vegetables are calculated according to 5~7 cubic meters per ton. The frozen meat is calculated according to 4 cubic meters per ton, which is also related according to the shelf layout in the cold storage room.
Refrigeration unit selection
The cooling capacity and quantity of the cold storage room refrigeration units are calculated according to the goods maximum heat load, the quality of the refrigeration units is important, good quality and reasonable selection will have a great impact on the energy consumption.
4. Cold storage room insulation
There are two types of cold storage room insulation, one is polyurethane spraying, the other is cold room panels. The installation time of the cold storage panels is short, the appearance is neat, the spraying is not suitable for the steel structure workshop, and the spraying is manual operation, and the density is uneven usually.
5. Cold storage room temperature
The same cold storage room dimension, the lower the cold storage room temperature, the higher the cold storage room price.
◇ High temperature cold room design temperature (-2~8°C)
◇ Medium temperature cold room design temperature (-10~-23°C)
◇ Low temperature cold room design temperature (-23~-30°C)
◇ Ultra-low temperature cold room design temperature (-30~-80°C)
6. The numbers of rooms in one cold storage room
For the same dimension cold storage room, the more rooms, will use more refrigeration units, cold room panels and refrigeration accessories, the cold storage room price will be higher.
A common cause of premature reciprocating compressor failure is overheating. A reciprocating that is running too hot will surely fail before its time. A service tech should always look for this potential problem while servicing any refrigeration system.
The hottest location in a refrigeration system is at the discharge port of the valve plate inside the compressor head. It is difficult for a technician to measure the exact temperature at this location. It’s important to know the causes of overheating to repair the system.
Let’s learn the main causes of discharge port overheating: high return air temperature, large motor heating capacity, high compression ratio, high condensing pressure, and improper refrigerant selection.
(1) high return air temperature
The return air temperature is relative to the evaporation temperature. In order to prevent liquid back flow, the return air line generally requires a return air super heat of 20 °C. If the return line is not well insulated, the degree of super heat will far exceed 20 °C.
The higher the return air temperature, the higher the cylinder suction and exhaust temperatures. For every 1 °C increase in the return air temperature, the exhaust gas temperature will increase by 1 to 1.3 °C.
(2) Motor heating
For a return air cooled compressor, the refrigerant vapor is heated by the motor as it flows through the motor cavity, and the cylinder suction temperature is again increased. The heat generated by the motor is affected by power and efficiency, and the power consumption is closely related to exhaust, volumetric efficiency, working conditions, and frictional resistance etc.
About the return air-cooled semi hermetic compressor, the temperature rise of the refrigerant in the motor cavity is approximately between 15 and 45 °C. In the air-cooled (air-cooled) type compressor, the refrigerant does not pass through the winding, so there is no motor heating problem.
(3) The compression ratio is too high
The exhaust gas temperature is greatly affected by the compression ratio, and the larger the compression ratio, the higher the exhaust gas temperature. Reducing the compression ratio can significantly reduce the exhaust temperature, including increasing the suction pressure and reducing the discharge pressure.
The suction pressure is determined by the evaporation pressure and the suction line resistance. Increasing the evaporation temperature can effectively increase the suction pressure and rapidly reduce the compression ratio, thereby reducing the discharge gas temperature.
Some users believe that the lower the evaporation temperature, the faster the cooling rate. This idea has many problems. Although lowering the evaporation temperature can increase the freezing temperature difference, the refrigeration capacity of the compressor is reduced, so the freezing speed is not necessarily fast. Moreover, the lower the evaporation temperature, the lower the refrigeration coefficient, the higher the load, the longer the running time, and the higher the power consumption.
(4) Refrigerant type
Different refrigerants have different thermos physical properties, and discharge gas temperature rises differently after undergoing the same compression process. Therefore, different refrigerants should be used for different cooling temperatures.
If the compressor is operating normally, there should be no overheating such as high motor temperature and high discharge temperature. Overheating of the compressor is an important failure signal indicating a serious problem with the refrigeration system or improper usage and maintenance of the compressor.
During using cold room, there will be some common faults for the refrigeration system, let us check and solve them.
Fault Analysis: After the refrigerant leaking in the system, the cooling capacity is insufficient, the suction and exhaust pressures are low, and the expansion valve can hear the intermittent airflow sound much larger than usual. The evaporator does not hang frost or hang a small amount of floating frost. If adjusting the expansion valve hole, the suction pressure does not change much. After shutdown, the equilibrium pressure in the system is generally lower than the saturation pressure corresponding to the same ambient temperature.
Solution: After the refrigerant leaking, don’t rush to fill the system with refrigerant. Instead, should find the leak point immediately, and fill the refrigerant after repair.
Filling too much refrigerant after maintenance:
Fault Analysis: The amount of refrigerant charged in the refrigeration system after maintenance exceeds the normal volume of the system. The refrigerant will take up a certain volume of the condenser, reduce the heat dissipation area, reduce the cooling efficiency, and generally have high suction and discharge pressures. The evaporators don’t frost and the temperature cooling is slow.
Solution: According to the operating procedure, it is necessary to stop the machine for a few minutes and then release excess refrigerant at the high pressure shut-off valve. At this time, the residual air in the system can also be released together.
Air in the refrigeration system:
Fault Analysis: If there is air in the refrigeration system will reduce the cooling efficiency. The prominent phenomenon is that the suction and exhaust pressures increase (but the exhaust pressure has not exceeded the rated value), and the temperature at the compressor outlet to the condenser inlet is significantly increased. Due to the air in the system, the exhaust pressure and exhaust temperature increase.
Solution: It is possible to release air from the high pressure shut-off valve several times after a few minutes after the shutdown, and it is also possible to properly fill some refrigerant according to the actual situation.
4. The efficiency of compressor is low:
Fault Analysis: The low efficiency of the refrigeration compressor means that the actual exhaust gas volume decreases and the cooling capacity responds less when the operating conditions are constant. This phenomenon occurs mostly on compressors that have been used for a long time, and the wear is large, the clearance of each component is large, and the sealing performance of the gas valve is lowered to cause the actual exhaust gas to decrease.
(1) Check if the cylinder head paper pad is broken down and cause leakage. If it is, replace it.
(2) Check if the high and low pressure exhaust valves are not closed tightly, If it is, replace it.
(3) Check the clearance between the piston and the cylinder. If it is too large, replace it.
The frost on the surface of the evaporator is too thick:
Fault analysis: Long-term use of the cold room evaporator should be timed defrosting, such as no defrosting, the frost layer on the evaporator line is thicker and thicker, when the whole pipeline is wrapped into a transparent ice layer, it will seriously affect heat transfer. Causes the cold room inside temperature can’t reach to required value.
Stop the defrosting, open the cold room door to let the air circulate, and use the fan to accelerate the air circulation and reduce the defrosting time.
Refrigerantoil in the evaporator line:
Fault Analysis: During the cooling cycle, some of the refrigerant oil remains in the evaporator line. After a long period of use, when there is more residual oil in the evaporator, the heat transfer effect will be seriously affected, and the cooling efficiency will decrease.
Solution: Remove the refrigerant oil from the evaporator. Remove the evaporator, cleaned and then dried. If it is not easy to remove, it can be pumped from the evaporator inlet and then blown with a blowtorch.
The refrigerant leakage in the temperature sensor of the expansion valve:
Fault analysis: After the refrigerant leaking in the temperature sensor of the expansion valve, the two forces below the diaphragm push the diaphragm up, the valve hole is closed, the refrigerant in the system can not pass, and the expansion valve doesn’t frost, the low pressure is vacuum, and no sound is heard in the evaporator.
Solution: Shut down the shut-off valve and remove the expansion valve to check if the filter is clogged and replaced when damaged.
The compressor suddenly stopped during operation
For air-cooled condenser:
1 The fan is not turned on.
2 The fan motor is damaged.
3 The fan is reversed.
4 The ambient temperature is high (up to 40 °C).
5 The condenser fins are blocked by oil dust and the air does not circulate.
For water-cooled condenser:
1 The cooling water valve is not open or opened too small, the inlet pressure is too low