Cold storage defrost is mainly due to the frost of the surface of the evaporator in the cold storage, reducing the humidity in the cold storage, hindering the heat transmission of pipelines, and affecting the refrigeration effect.
一. Cold storage defrost measures
1. Hot gas defrost
The hot gaseous condenser is directly transmitted and the evaporator is flowing through the evaporator. When the temperature of the cold storage library increases to 1 ° C, the compressor is turned off. The temperature of the evaporator rises, which prompts the surface frost layer to dissolve or peel off;
The hot air fusion economy is reliable, convenient to maintain management, and its investment and construction are not difficult. However, there are many schemes in thermal frost. The usually method is to send the high -pressure and high -temperature gas discharged from the compressor into a evaporator to heat up the frost, so that the condensed liquid will enter another evaporator. Back to the compressor’s inhalation, complete a cycle.
2, water spray cream
Water spray defrost is regularly sprayed with water to cool the evaporator to prevent the frost layer from forming; although the water spray defrost is very good, it is more suitable for the air -cooler. It is difficult to operate for the evaporative disk.
There is also a solution with high freezing temperature, such as 5%— 8%thick salt water spray evaporator to prevent frost from forming.
Advantages: This scheme is high efficiency, the operation procedures are simple, and the library temperature fluctuates small. From an energy perspective, the cold volume per square meter of evaporation can reach 250-400KJ. Water cream is also likely to make the library fog, resulting in the water dripping water, reduced service life, and so on.
3. Electrical defrost
Heat thermal heating defrost. Although simple and easy to do, according to the actual structure of the cold storage and the bottom use at the time, the construction of electric heating wires is not small, and the failure rate in the future is relatively high, the maintenance management is more difficult, and the economy is poor.
4. Mechanical defrost
There are still many ways to defrost the cold storage. In addition to electrical defrosting, water spray defrosting and hot air defrosting, there are also mechanical defrosting. Mechanical defrosting mainly uses tools to artificial frost. When removing, because there is no automatic defrost device for designing cold storage, it can only be artificially deformed, but there are many inconveniences.
二. Selection of frost schemes
When the actual scheme is determined, sometimes a defrost scheme is adopted, sometimes different schemes are used.
For example, the cold storage shelves, walls, and top smooth tubes can be used to combine the heat gas method, usually artificial frost, regular thermal cream, in order to thoroughly clear the cream that is not easy to remove and discharge the accumulated oil in the pipeline. Essence Cold fans punch water and heat.
For frost more frequently, heat can be used to combine water to remove frost. When the refrigeration system of the cold storage is working, the surface temperature of the evaporator is usually below zero. Therefore, the evaporator should produce frost, and the thermal resistance of the frost layer is large, so the necessary frosting treatment is required when the frost is thicker.
The evaporator of the cold storage is divided into wall tube type and wing tablet according to its structure. The wall tube type is naturally replaced with heat convection, and the wing tablet is forced to replace heat. Frost, wing tablets use electric heating cream.
The manual cream is more troublesome. It is necessary to frost, clean the frost water, and move the items in the library. Usually, the user should be frosting for a long time or even a few months. The thermal resistance of the layer has made the evaporator far from reaching the refrigeration effect.
The electric heating cream has taken one step than the manual cream, but it is limited to the wing -type evaporator, and the wall tube evaporator cannot be used. The electric heating type should be inserted into the electric heating pipe in the winged evaporator. In the water disk, the electric heating tube must be placed. In order to remove the frost as soon as possible, the power of the electric heating pipe cannot be selected too small. Usually, it is usually all. To thousands of watts.
The control method of electric heating pipes generally uses timing heating control. During heating, the electric heating pipe passes to the evaporator. Some of the frost on the evaporate tray and the cream on the wing tablets dissolved, and some of them are not fully dissolved. This is a waste of electricity, and the refrigeration effect is very poor at the same time. Because the evaporator is full of frost, the heat exchange coefficient is extremely low.
三, other cold storage defrosting methods
1. It is suitable for thermal defrosting for small systems. The system and control methods are simple. The frost is fast, uniform and safe. It should further expand the scope of application.
2. Pneumatic defrost is particularly suitable for refrigeration systems that require frequent defrosting. Although it is necessary to increase special gas sources and air treatment equipment, as long as the utilization rate is high, the economy will be very good.
3. Ultrasonic defrosting is a obvious defrosting method. It should further study the layout of the ultrasonic generator to improve the thorough degree of defrosting so that engineering applications can be used.
4. Line refrigerant removal: The refrigeration process and the defrost process are carried out at the same time. There is no additional energy consumption during the frosting period. The frost and cooling amount is used for the liquid refrigerant in front of the cold expansion valve to improve the refrigeration efficiency so that the library temperature can be basically maintained. The temperature of the liquid refrigerant is within the normal temperature range. The temperature of the evaporator is small during frost, which has little effect on the deterioration of the heat transfer of the evaporator. The disadvantage is that the complex control of the system is cumbersome.
四, frosting time
During the frosting time, it is generally regardless of temperature. The frosting time is over, and then the dripping time is started. Don’t set your frosting time too long, and the electric cream must not exceed 25 minutes. Try to achieve a reasonable frost. (The frost cycle is generally two types of power delivery time or the time for the compressor.)
Some electronic temperature control also supports frost end temperature. It is the end of the two modes: the frost:
1. It’s time
2. It is Kwen
This generally uses 2 temperature probes.
五. Analysis of excessive frost
During the daily use process, the cold storage needs to be removed regularly on the cream on the cold storage. Too much cream on it is not conducive to the normal use of the cold storage. What are the common techniques?
1. Check the refrigerant and check if there is an air bubble in the visual liquid lens? If there is no bubble explanation, add the refrigerant from the low pressure tube.
2. Check whether there is a gap in the cold storage plate near the frost tube, which causes the cold volume to leak. If there is a gap, seal with glass glue or foam directly.
3. Check whether there is leakage at the copper tube welding, spray the spray detection liquid or soapy water to see if it is bubble.
4. The reasons for the compressor itself, for example, the high and low pressure are exhausting, and the valve sheet needs to be replaced, and it is sent to the compressor maintenance office for repair.
5. It depends on whether it is close to the air. If so, the leakage is leaked and the refrigerant is added.
In this case, the tube is generally not placed horizontally. It is recommended to flatten the horizontal ruler. Then there is not enough refrigerant to charge, it may be that the refrigerant is added, or there are ice blocking in the pipeline.
Post time: Apr-03-2023