The thermal patterns predicted by Energy2D roughly match those from a thermal camera. The pictures to the right show a comparison of the results of Energy2D simulations with images from infrared That involve convection and radiation, Energy2D results should be considered as qualitative. The conduction part of Energy2D is highly accurate, but the convection and radiation parts are not 100% accurate. This is why special refrigerants with low boiling points are chosen.An IR image of a heated model house with a ceiling An IR image of a heated model house without a ceilingĪn Energy2D simulation of a heated house with a ceiling An Energy2D simulation of a heated house without a ceiling Even at low pressure there is no real beneficial cooling effect that could be achieved when it evaporates. Water is not useable for one in an air conditioning system as a refrigerant since its boiling point is too high. Refrigerants which are used in automobile air conditioning systems behave in a similar way to water with the exception that they boil at much lower temperatures than water (R134a boils at -27✬) and they have got varying values for the specific heat capacity and also the latent heat vaporization depending on which refrigerant you are using. It is this point that we are particularly interested in with respect to an air conditioning system. Then and only then will the temperature of the water begin to increase again. Irrespective of how much more heat energy is applied at this point the temperature of the water will not increase until a complete state change has taken place from liquid to gas. At this point the water begins to boil (changing state from liquid to gas). Using water as an example again, it takes 420 kJ of heat energy to raise the temp of 1 kg from 1✬ to 100✬. This is the same for many other liquids when evaporating from liquid to gas including the refrigerants in an air conditioning system. In the case of water it has a very large latent heat vaporization. Therefore, it follows that the latent heat of vaporization is the heat taken in or given out when a substance is changing from liquid to gas without changing temperature. The latent heat of a substance is the heat taken in or given out when changing state without changing temperature (the hidden heat). In the case of water it takes 4.2 kJ to raise the temperature of 1 kg by 1✬ so conversely in order to reduce the temperature of 1 kg of water by 1✬ it will have to release 4.2 kJ of heat energy. Heat since it is a form of energy is measured in kilojoules. Now since the air is cooler than the liquid refrigerant, heat is transferred from the liquid refrigerant to the air via the condenser causing the air to heat up and the refrigerant to loose heat and cool down. The heat transfer externally in the condenser occurs between hotter liquid refrigerant and cooler ambient air (relative to the temp of the refrigerant liquid). The cool refrigerant is taking heat away from the warmer passenger compartment, which in turn causes the passenger compartment to become cooler and the refrigerant to become hotter. The heat transfer that occurs in the interior of a vehicle occurs between the refrigerant in gaseous form and the interior air. On a sunny day an automobile in effect acts as a miniature greenhouse that stores up the heat due to radiation. You cannot see the waves, which transfer heat since they are in the invisible region of the electromagnetic spectrum. Radiation is the only one of the three modes of heat transfer, which does not require a medium to transfer the heat along. When this type of air circulation forms, known as convection, it repeats itself it eventually distributes the warmer heated air evenly around the interior of the vehicle.ģ) Radiation is the heat transfer means by which waves located in the infrared portion of the spectrum (electromagnetic) transfer heat with or without the use of a medium. If air which is hotter than the passenger compartment air is blown into the passenger compartment, it will move in the upwards direction forcing the cooler, more dense air downwards. 2) Convection is the heat transfer means by which the molecules or atoms of a liquid or gas move in a circular motion and carry the heat.
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