shamaal
Explorer Addict
- Joined
- April 25, 2005
- Messages
- 1,248
- Reaction score
- 5
- City, State
- Friensdwood, Texas
- Year, Model & Trim Level
- 91 Mazda Navajo
There was an earlier post to an air conditioning basics site. I have attached a diagram of the orifice type of A/C system used in my 91 Mazda Navajo. This may be the type used in all the Explorers but I can only speak for mine. I'll address the other type of A/C system (Expansion Valve) in another thread for completeness.
There are a lot of A/C experts in this forum willing to address specific questions. My practical experience is limited to a few systems, with some school. There are a number of websites that explain this sytem well.
The key point to remember in A/C is that when liquid changes to vapour, it absorbs heat. Think of when water is turned into steam you must add heat. Conversely when going from a vapor to a liquid, it sheds heat. Think of when steam condenses on a cold surface. The MAGIC occurs when another method of converting from a liquid to a vapor is used. If you force a liquid through a small enough hole (orifice) - it vaporizes. Think of water spraying from a hose nozzle. The key point to remember -it stilll absorbs heat! Now this is a simplistic explanation, there are a bunch of conditions such as temperature, volume and pressure and scientific terms like evaporation, latency, endothermic, exothermic, etc; but for this explanation the engineers have solved all that and provided us with a working system.
Looking at the diagram, let's start in the lower right with our liquid R134a refrigerant; being closed loop I'll explain at the end how it got liquid.
1. The liquid is forced through the orifice, where it is vaporized and expands in the evaporator. Rember the rule that when changing from a liquid to a vapor it absorbs heat. If we blow warm air through the evaporator, the vaporized refrigerant removes the heat and cool air exits the evaporator. In my Mazda the evaporator is on the passenger side firewall and this is where the cool air that is in the vents come from.
2. The low pressure vapor exits the evaporator and goes into the accumulator. The accumulator contains materials that remove any moisture form the system (Moisture is very bad) and is constructed in such a way to trap any refrigerant that is still liquid and only allow vapor (gas) to exit. The accumulator is the black appartus on the passenger side next to the evaporator. Also on the accumulator is the low pressure service port.
3. The vapor goes to the input or suction side of the compressor. Another rule is that gas can be compressed but liquids cannot. That is why the accumulator is constructed to only allow vapor into the compressor. The compressor .... compresses the gas; it goes from a warm low pressure gas to a hot high pressure gas. The high pressure gas exits the compressor (discharge) and goes to the condensor. On my Mazda there is also a component called a muffler that dampens the system and reduces noise. I don't know if it's in all the Explorers. The compressor is on the driver's side and is belt driven.
4. The high pressure gas (very hot) goes into the condensor. By blowing air over the hot gas we remove the heat and voila!; it is changed from a gas to a liquid, ready to re-enter the orifice in step 1. The condensor is on the front of the car, in front of the radiator. On the line that runs between the compressor and the condensor is the high pressure service port.
Of course this is a simplistic explanation, there a large number of variables and conditions that occur with various components added for efficiencies. If understood, this thread allows a greater range of discussion why the system behaves the way it does during low charge (not enough liquid to turn into gas in evaporator) to a bad compressor (not enough pressure differential to concentrate heat). If I ever figure out how to insert photgraphs instead of attachments, I will expand this into a tutorial.
There are a lot of A/C experts in this forum willing to address specific questions. My practical experience is limited to a few systems, with some school. There are a number of websites that explain this sytem well.
The key point to remember in A/C is that when liquid changes to vapour, it absorbs heat. Think of when water is turned into steam you must add heat. Conversely when going from a vapor to a liquid, it sheds heat. Think of when steam condenses on a cold surface. The MAGIC occurs when another method of converting from a liquid to a vapor is used. If you force a liquid through a small enough hole (orifice) - it vaporizes. Think of water spraying from a hose nozzle. The key point to remember -it stilll absorbs heat! Now this is a simplistic explanation, there are a bunch of conditions such as temperature, volume and pressure and scientific terms like evaporation, latency, endothermic, exothermic, etc; but for this explanation the engineers have solved all that and provided us with a working system.
Looking at the diagram, let's start in the lower right with our liquid R134a refrigerant; being closed loop I'll explain at the end how it got liquid.
1. The liquid is forced through the orifice, where it is vaporized and expands in the evaporator. Rember the rule that when changing from a liquid to a vapor it absorbs heat. If we blow warm air through the evaporator, the vaporized refrigerant removes the heat and cool air exits the evaporator. In my Mazda the evaporator is on the passenger side firewall and this is where the cool air that is in the vents come from.
2. The low pressure vapor exits the evaporator and goes into the accumulator. The accumulator contains materials that remove any moisture form the system (Moisture is very bad) and is constructed in such a way to trap any refrigerant that is still liquid and only allow vapor (gas) to exit. The accumulator is the black appartus on the passenger side next to the evaporator. Also on the accumulator is the low pressure service port.
3. The vapor goes to the input or suction side of the compressor. Another rule is that gas can be compressed but liquids cannot. That is why the accumulator is constructed to only allow vapor into the compressor. The compressor .... compresses the gas; it goes from a warm low pressure gas to a hot high pressure gas. The high pressure gas exits the compressor (discharge) and goes to the condensor. On my Mazda there is also a component called a muffler that dampens the system and reduces noise. I don't know if it's in all the Explorers. The compressor is on the driver's side and is belt driven.
4. The high pressure gas (very hot) goes into the condensor. By blowing air over the hot gas we remove the heat and voila!; it is changed from a gas to a liquid, ready to re-enter the orifice in step 1. The condensor is on the front of the car, in front of the radiator. On the line that runs between the compressor and the condensor is the high pressure service port.
Of course this is a simplistic explanation, there a large number of variables and conditions that occur with various components added for efficiencies. If understood, this thread allows a greater range of discussion why the system behaves the way it does during low charge (not enough liquid to turn into gas in evaporator) to a bad compressor (not enough pressure differential to concentrate heat). If I ever figure out how to insert photgraphs instead of attachments, I will expand this into a tutorial.
