Heat Exchanger Institute Pdf Download
a common use of the azeotrope is in refrigeration, where f1is a saturated liquid and f2is an unsaturated gas. as the refrigerant flows through the heat exchanger, it absorbs heat from f2as it condenses and becomes saturated, and then releases its heat to f1as it vaporizes and becomes unsaturated. as the refrigerant continues to absorb heat from the fluid, it also continues to condense and become saturated, which then allows it to become a saturated liquid again.
in countercurrent heat exchangers, one fluid flows through the device while the other flows across it. this is commonly used in refrigeration applications to remove heat from one fluid and transfer it to the other while it is cooling.
if the heat is generated at a single point, it is called an induced heat. it may be hot air from an electric heater, heat in a gas furnace or stove, or steam or hot water running through a pipe. it is always an increase in temperature. in a heat exchanger, the heat is transferred to a second fluid, which then becomes the heat source for the second fluid. the second fluid will become hotter than the first fluid, since all heat is transferred to the second fluid.
the first type of heat exchanger is the condenser. condensers can be used to remove heat from a fluid, lowering the temperature. the refrigerant is an example. this type of heat exchanger is used most often in air conditioning systems. the second type of heat exchanger is the evaporator. evaporators can be used to remove heat from a fluid, raising the temperature. this type of heat exchanger is used most often in refrigeration systems. there are other types of heat exchangers, which are similar in function to the above types. there are once again, single-phase and two-phase heat exchangers. in a single-phase heat exchanger, two fluids pass through the heat exchanger with a single phase of a fluid in the same stream. in a two-phase heat exchanger, two fluids pass through the heat exchanger with two separate phases of each fluid in the same stream. they are both used in refrigeration systems. there is also a heat pump.
the most common types of heat exchangers are open-ended heat exchangers, closed-ended heat exchangers, and plate-and-frame heat exchangers. open-ended heat exchangers are typically used where there is a large volume of heat transfer. they can be used in long, narrow tubes or pipes, with the hot fluid flowing through the tubes and the cold fluid flowing around the outside of the tubes, or in u-shaped tubes in which the cold fluid flows into the ends of the tube and the hot fluid flows out the middle of the tube. closed-ended heat exchangers are typically used where there is a small volume of heat transfer. they can be used in a number of different ways. first, the cold fluid can flow through the tubes and the hot fluid can flow around the outside of the tubes. second, the hot fluid can flow through the tubes and the cold fluid can flow around the inside of the tubes. third, the hot fluid can flow through the tubes and the cold fluid can flow through a chamber or shell.
heat exchangers are used for a wide variety of purposes. some are produced specifically for a particular application and are used to transfer heat between two other fluids, while others are manufactured to be reused in many different applications. the most common types of heat exchangers are:
the conversion of thermal energy from one state to another is a function of both the temperature difference between the source and the sink, and the rate of transfer of thermal energy. in general, thermal energy can be transferred in two ways, either by conduction or by convection. conduction of heat is typically associated with the transfer of thermal energy from a region of higher temperature to one of lower temperature. the speed of conduction is equal to the square root of the product of the material’s thermal conductivity and the thermal gradient. conduction is most effective for materials with low thermal conductivities and low thermal gradients, as is the case for gas phase heat transfer.