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The cold and heat cycle impact test chamber is customized according to customer needs which is divided into two parts or three parts: high temperature zone and low temperature zone. The test sample is placed in a mobile hanging basket. It adopts unique heat storage and cold storage structure, at the same time, the cylinder drives the hanging basket in hot and cold, moves up and down in the tank to complete the hot and cold temperature impact test. The applicable objects include metal, plastic, rubber, electronics, and so on, which can be used as a basis or reference for product improvement. Frost is the result of rapid cooling and crystallization of water in the air when it is cold. Frost is a small ice crystal, which can easily be changed into ice when it is thick. The frost in the thermal shock test chamber is mainly on the energy storage components in the pre-cooling zone.
But do you know why defrosting is required for this type of environment test equipment; what is the frequency of defrosting? Firstly, we must understand where the frost comes from? Why do we need to defrost? Which method is used to calculate the frequency? This article will answer these questions one by one.
The source of frost and the principle of defrosting:
We know that the cold and heat cycle impact test chamber exchanges heat through the airflow conversion within the three boxes to achieve the impact effect. These three boxes are isolated from the air outside the box, that is to say, relative to the outside world, these three boxes are airtight. Since it is a closed space, their moisture content is quantitative, and resistance cannot be born out of thin air. When the extra moisture comes, that is to say, theoretically, there should be no frost in the pre-cooling zone. But tracing back to the source, where did the moisture come from? There is only the test area of these three boxes for customers to open and place products. If moisture is to be introduced, it can only be possible after the test area is opened. So one of the sources of moisture is the door-opening operation from customers. However, we do not allow to open the door in the middle of a complete impact test, otherwise, the test will fail. Another source of moisture must start from the test area.
Some test chamber manufacturers can do 1,000 cycles with defrosting once, which means that their equipment can avoid the introduction of moisture as much as possible. What is the reason why some manufacturers need to defrost once when doing 20 cycles? Is it that good-end equipment must be non-airtight? Or is there a deeper reason? The answer is yes. When some manufacturers in the industry design cold and heat shocks in order to minimize manufacturing costs and save compressor horsepower, they adopted a secret method of discharging heat energy, by opening the valve outside the test area to reduce the heat energy contained in the test area. In this way, no matter it is a high temperature impact or a low temperature impact, the low-temperature or high-temperature capabilities in the high and low temperature test chamber will be discharged outdoors. So it can achieve the goal of reducing the cost of energy storage components. In this way, a large amount of water will inevitably be introduced, and it will inevitably cause frost in the pre-cooling zone. This technique is called: "energy storage emission". It is also one of the key practices in the industry.
Defrost frequency method:
There are two methods. One is to set the time, and the other is to set cycle times. Generally, most manufacturers and customers seldom use the set time to defrost, because it has a disadvantage that the equipment may be still running after the set defrost time is up. During the test, the cycle time is to defrost after the thermal shock test is completed, so it is recommended to the cycle time.
All cold and heat cycle impact test chambers have been set defrost frequency before leaving the factory, such as once every 20 cycles or once every 20 hours. The defrost will be automatically performed after the number of cycles is reached. The user does not need to modify it according to the recommended value. If the customer has his own defrost frequency requirement, he can modify the cycle number or time in the defrost setting of the equipment control system. Regarding the range of settable values: it can be set within 1 to 9999 hours according to time, and within 1 to 9999 times according to cycle times.
The above is this article to explain to you why the cold and heat cycle impact test chamber is to be defrosted and all the contents of the frequency method.