High and low temperature test chambers are essential for evaluating the performance of products under extreme environmental conditions. These systems typically consist of a compressor, evaporator, condenser, and a network of piping. One of the common issues that can occur in the refrigeration system is clogging, which can be classified into two main types: dirt blockage and ice blockage. Oil blockage is less frequent but still possible in certain situations.
Dirt blockage occurs when impurities such as scale, copper shavings, or metal debris enter the refrigeration system. As the refrigerant circulates, these particles tend to accumulate in narrow sections like the capillary tube or filter, leading to restricted flow. This type of blockage is often the result of poor maintenance practices, improper installation, or contamination during servicing. To resolve dirt blockage, it's necessary to remove and replace components such as the capillary tube, filter, condenser, and evaporator. The molecular sieve inside the filter should be replaced, and all parts should be cleaned thoroughly. Afterward, the system must be dried, evacuated, and reassembled before charging with new refrigerant.
Ice blockage, on the other hand, happens when moisture enters the refrigeration system. This can occur due to improper evacuation during maintenance or fluorination, allowing water and air to get trapped inside. When the refrigerant passes through the capillary tube under high pressure, any moisture present can freeze, especially if the water content exceeds 20 mg per kilogram of refrigerant. Once the temperature at the capillary outlet drops below 0°C, the moisture separates from the refrigerant and forms ice, causing a blockage.
Both types of blockage can be complete or partial, and they lead to similar symptoms. For example, the evaporator may not frost properly, the condenser’s rear section might become excessively hot, and the filter or capillary inlet could feel close to ambient temperature. In some cases, the temperature might even drop below room level. Additionally, there may be a noticeable release of gas from the process tube.
When an ice blockage forms, it increases the resistance in the compressor’s discharge, causing it to overheat. This triggers the thermal protector, shutting down the system. After about 25 minutes, the ice partially melts, allowing the compressor to restart. This cycle results in periodic frosting and defrosting of the evaporator, making the cooling process irregular and inefficient. Identifying and resolving these issues promptly is crucial to maintaining the performance and longevity of the high and low temperature test chamber.
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