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The Role of the Expansion Device

    • 990 posts
    May 20, 2022 11:25 PM EDT

    In the instance of a bicycle pump experiment, you will notice the air is heated as it escapes from the piston past your thumb, which is partially blocking the outlet.Get more news about Condenser Expansion Machine,you can vist our website!

    If you lift your thumb, the air is compressed much less, and the temperature drops. You can then operate the Pump with little difficulty, as the air being pumped out is at low pressure.

    The converse is also true. The more you block the outlet with your thumb the more you will notice the rise in temperature, and that it becomes more and more difficult to operate the pump.

    In effect, the more you obstruct the outlet orifice, the more the pressure increases and the temperature rises.
    bicycle pump experiment
    We can say that the outlet temperature rises when pressure of the gas rises!
    It’s exactly the same for a fridge compressor: the higher the pressure becomes the greater will be the temperature of the gas it pumps out.

    We saw that the condensation of R22 vapour was only possible if the temperature of the vapour was greater than that the environment. So with an ambient temperature of 20°C we must raise the temperature of the R22 to something greater than 20°C.The pressure temperature relation ship forR22 shows us that at 20°C. the condensation (or the evaporation step, since this is the reverse phenomenon of evaporation) occurs at a pressure of about 8 bar.

    We can conclude that in order to condense R22 vapour emerging from the evaporator at -42°C with the surrounding air at 20°C. we must not only increase the temperature of the vapour to above 20°C but also increase its pressure to something over 8 bar!

    It is precisely what the compressor does. By compressing the vapour it simultaneously raises its pressure and its temperature!The greater that the outlet pressure of the compressor is, the higher the temperature of the R22 vapour will be, and the easier it will be to cool and to condense

    Remember that in the bicycle pump the more the outlet is blocked the higher the resulting pressure and temperature is.Using the example of the bicycle pump, we may partially obstructs condenser outlet with our ‘thumb’!
    In this way, the refrigerant that is drawn in from LP, then compressed by the compressor will be pumped out at HP and maintained at high pressure in the condenser because of the ‘thumb’ that partially obstructs the its outlet.
    Since the refrigerant is at HP in the condenser (well above 8 bar), its temperature will be in excess of 20°C. The air at 20°C in the kitchen will therefore easily be able to cool the hot R22 vapour, and allow it to condense.

    As the R22 vapour is being condensed, liquid R22 will emerge from the condenser. But you may recall that liquid R22 vaporises at -42°C at atmospheric pressure. It’s fairly obvious that something other than a ‘thumb’ must be used to make a partial obstruction at the outlet of the condenser, or we’ll risk burning ourselves quite badly!