Welcome to an exploration of filter driers in refrigeration systems, where we’ll delve into their functionality, components, and significance. Filter driers are crucial for maintaining the efficiency and longevity of HVACR systems by filtering and drying refrigerants. Let’s dive into how they work and why they’re essential.
Filter driers are integral to refrigeration systems, tasked with filtering and drying the refrigerant. They protect the system by capturing water particles and harmful solids, preventing these contaminants from circulating and damaging components like compressors, valves, and sensors. This ensures the system operates under optimal conditions.
When a refrigeration system is installed or serviced, air and dust can enter. Air contains water particles, and at 30 degrees Celsius, a cubic meter of air can hold up to 30 grams of water. This moisture can combine with refrigerant and lubricating oil to form acids, which corrode internal components. To prevent this, filter driers remove moisture and dirt, keeping the refrigerant dry.
Introducing a filter drier causes a slight restriction in refrigerant flow, resulting in minor pressure and temperature drops. As the filter drier accumulates dirt, these drops increase, potentially causing system issues. Regular checks and replacements are necessary to maintain system efficiency.
A sight glass, typically located between the filter drier and the expansion valve, helps monitor moisture levels in the system. Filter driers should be replaced periodically, usually every two years, or whenever the system is opened. This practice ensures the system remains free of contaminants.
Filter driers are installed in the liquid line, usually between the condenser and the expansion valve, and are often accompanied by a sight glass. They come in various sizes to accommodate different systems and should be protected from outdoor conditions to prevent casing corrosion.
The main casing, typically made of steel, is cylindrical to evenly distribute internal pressure. It must withstand both internal and atmospheric pressures. Connections at each end, either pure copper or copper-plated, allow for secure brazing.
Inside, a spring maintains the position of the solid core, which is composed of a molecular sieve and activated alumina. The molecular sieve captures large dirt particles, while activated alumina absorbs acids. Not all filter driers contain activated alumina; it depends on the application.
The refrigerant flows through the solid core, where dirt, moisture, and acids are trapped in the filter material’s pores. A screen captures smaller particles, and a perforated plate ensures all components remain in place while allowing refrigerant flow.
Filter driers play a vital role in maintaining the health and efficiency of refrigeration systems by filtering and drying refrigerants. Regular maintenance and monitoring are essential to prevent system issues and ensure optimal performance. For more insights into refrigeration engineering, explore additional resources and continue your learning journey.
Examine a detailed interactive diagram of a filter drier. Identify and label each component, including the casing, connections, solid core, and internal screens. Reflect on how each part contributes to the overall function of the filter drier.
Engage in a group discussion based on a case study where a refrigeration system failed due to improper filter drier maintenance. Analyze the consequences and propose a maintenance plan to prevent similar issues in the future.
Conduct a lab experiment to observe the pressure and temperature changes caused by a filter drier in a controlled refrigeration system. Record your findings and discuss how these changes impact system efficiency.
Create a comprehensive maintenance schedule for a hypothetical HVACR system, including filter drier checks and replacements. Justify your schedule based on system specifications and environmental conditions.
Research different types of filter driers and their applications. Compare their components, such as the use of molecular sieves versus activated alumina, and present your findings in a report.
Sure! Here’s a sanitized version of the transcript:
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[Applause] Hey there, everyone! Paul here from The Engineering Mindset. In this video, we’re going to explore the filter dryer to understand how it works, its main parts, and why we use them. This video is sponsored by Danfoss.
Filter dryers look something like this. They are found in refrigeration systems, and as you might guess from their name, their job is to filter and dry the refrigerant. They protect the refrigeration system and its components by capturing and absorbing water particles as well as harmful solid substances, preventing these from circulating around the system and entering the compressor, valves, sensors, etc. This keeps the system running at optimal conditions.
When a refrigeration system is first installed or anytime the unit is opened and serviced, there is a potential for air and dust to enter. As you might already know, air contains particles of water. For example, a cubic meter of air at 30 degrees Celsius contains up to 30 grams of water. So why does this matter? When refrigerant, lubricating oil, and moisture combine, it can create an acid that is then circulated around the system, corroding internal surfaces and parts. We definitely want to avoid that, so we use a filter dryer to filter out moisture and dirt and dry the refrigerant.
By adding a filter dryer to the system, we introduce a slight restriction to the flow of refrigerant, resulting in a very small pressure drop, which causes a small temperature drop. This pressure and temperature drop increases as the filter dryer becomes dirtier, making it harder for the refrigerant to pass through. Eventually, this can become excessive and cause problems in the system.
We can also check the sight glass, which should indicate whether moisture is present in the system. The sight glass is typically fitted between the filter dryer and the expansion valve. The filter dryer will need to be replaced periodically, typically every two years or so, depending on the system and the manufacturer’s recommendations. Every time the system is opened, it’s good practice to replace the filter dryer.
We have also cut open a real filter dryer to look inside. If you’d like to see that, you can find links in the video description below. Filter dryers are installed in the liquid line of the refrigeration system, typically between the condenser and the expansion valve, and are usually accompanied by a sight glass.
Filter dryers can only hold a certain amount of moisture and come in different sizes for different systems. They should not be exposed to outdoor atmospheric conditions, as this can lead to corrosion of the casing and ultimately cause the unit to fail. While filter dryers do come with a corrosion-resistant coating, it will not last forever.
You can also find filters in the suction line, usually installed after a compressor burnout to absorb acid and moisture contamination, but we won’t go into much detail on that in this video. On the side of the filter dryer, you’ll find an arrow indicating the direction of refrigerant flow. Some models for heat pumps might have bi-directional filter dryers, but in this case, we have a single-direction filter dryer pointing towards the expansion valve.
When we look at a filter dryer, we see the main casing, which is made from steel and has a cylindrical design to distribute internal pressure evenly. The filter dryer must withstand both internal and atmospheric pressures, so a strong casing is necessary. At each end, we find a connection—one is an inlet and the other is an outlet. We can check the arrow on the casing to determine this. These connections will either be pure copper or copper-plated, depending on the model, allowing for brazing to form a strong airtight seal.
Inside the casing at the refrigerant inlet end, we find a large spring that pushes against the casing and the solid core, keeping the core in a fixed position. Next, we have the core or molecular sieve. This particular model has a solid core, with 80% being a molecular sieve and 20% being activated alumina. The solid core’s molecular structure acts as a filter to capture large dirt particles, and the aluminum oxide is added to capture and retain acids. Not all filter dryers will have activated alumina; it depends on the application.
Notice the groove inside; the refrigerant passes through the solid core and collects in this groove to continue its flow. At the end of the solid core, we have a screen that retains smaller dirt particles that might have passed through the solid core. This material can capture dirt particles down to around 25 microns with minimal pressure drop. After the screen, we have a perforated plate that keeps all the internal parts in position while allowing refrigerant to flow to the outlet.
The refrigerant enters through the inlet, passes across the spring, and surrounds the outside of the core. As it passes through the solid core, dirt, moisture, and acids are absorbed and trapped within the small pores of the filter material. The compressor continues to push more refrigerant, providing back pressure so that once the dirt and moisture enter the pores, they cannot escape. The refrigerant then continues to pass through the solid core, accumulating in the central chamber, before passing through the screen to capture any remaining particles of dirt. It then passes through the perforated plate and exits the unit, having been filtered and dried, continuing to the expansion valve.
That’s it for this video! To continue learning about refrigeration engineering, check out one of the videos on screen now, and I’ll catch you there for the next lesson. Don’t forget to follow us on Facebook, Twitter, Instagram, LinkedIn, and of course, TheEngineeringMindset.com.
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Filter – A device or process that removes impurities or unwanted elements from a fluid or gas. – In HVAC systems, a filter is essential to ensure that the air circulated is free from dust and other particulates.
Drier – A component used to remove moisture from a system, particularly in refrigeration and air conditioning. – The drier in the refrigeration cycle prevents moisture from freezing and causing blockages in the system.
Refrigerant – A substance used in a heat cycle to transfer heat from one area and remove it to another, commonly used in air conditioning and refrigeration systems. – Selecting the appropriate refrigerant is crucial for the efficiency and environmental impact of a cooling system.
Moisture – The presence of a liquid, especially water, often in trace amounts, within a substance or environment. – Excess moisture in electrical components can lead to short circuits and equipment failure.
Pressure – The force exerted per unit area within fluids or gases, often measured in pascals or psi. – Monitoring the pressure in a hydraulic system is vital to ensure safe and efficient operation.
Temperature – A measure of the thermal energy within a system, indicating how hot or cold the system is. – Maintaining the correct temperature in a chemical reactor is critical to ensure the desired reaction rate and product quality.
Maintenance – The process of preserving equipment and systems through regular inspection, servicing, and repair to ensure proper functioning. – Routine maintenance of machinery can prevent unexpected breakdowns and extend the lifespan of the equipment.
Components – Individual parts or elements that make up a larger system or machine. – Understanding the function of each component in a circuit is essential for troubleshooting and repair.
Efficiency – The ratio of useful output to total input in any system, often expressed as a percentage. – Improving the efficiency of an engine can lead to significant fuel savings and reduced emissions.
Corrosion – The gradual destruction or deterioration of materials, usually metals, due to chemical reactions with their environment. – Engineers must consider corrosion resistance when selecting materials for structures exposed to harsh environments.
