Atmospheric Thermodynamics
Introduction:
In industry, a heat exchanger is used to cool down streams for temperature sensitive processes. The now hot cooling water is useless to the plant unless something is done to cool it down. In industry, cooling water towers are used to bring the water back down to a sufficient level . In a cooling tower, outside atmospheric air is flowed through a “column” while the hot water sprayed into the system. Since air is never at full saturation of water (unless it is raining), some of the hot water will evaporate to satisfy equilibrium. When this water evaporates, heat is taken from the surrounding liquid water which cools it down. In cooling tower design, a very important variable is the wet bulb temperature of the air. The wet bulb corresponds to the current humidity of the air. The greater the difference between the air temperature and wet bulb temperature, the greater the humidity.
In many equilibrium based operations such as a cooling tower, it is common to define and use two terms, the number of theoretical plates and the height of those plates. The product of these two values will always equal the tower height. The greater the number of theoretical plates, the better the tower is at achieving equilibrium multiple times which results in greater efficiency. The same goes for decreasing plate height. In design, there are tables and assumptions which ease the process of finding the tower height and area. In this particular lab, we have a tower and are testing multiple cooling loads and air flow rates for a constant water flow rate. By measuring the difference between the inlet and outlet wet and dry bulb temperatures, we can approximate Noy using the following equation:
Also, once we know the actual tower height we can find Hoy from the following relation:
Since the cooling water tower is a combination of both heat and mass transfer, we can also relate Hoy to the heat transfer coefficient (h) using the following equation:
where Gy is the mass
In industry, a heat exchanger is used to cool down streams for temperature sensitive processes. The now hot cooling water is useless to the plant unless something is done to cool it down. In industry, cooling water towers are used to bring the water back down to a sufficient level . In a cooling tower, outside atmospheric air is flowed through a “column” while the hot water sprayed into the system. Since air is never at full saturation of water (unless it is raining), some of the hot water will evaporate to satisfy equilibrium. When this water evaporates, heat is taken from the surrounding liquid water which cools it down. In cooling tower design, a very important variable is the wet bulb temperature of the air. The wet bulb corresponds to the current humidity of the air. The greater the difference between the air temperature and wet bulb temperature, the greater the humidity.
In many equilibrium based operations such as a cooling tower, it is common to define and use two terms, the number of theoretical plates and the height of those plates. The product of these two values will always equal the tower height. The greater the number of theoretical plates, the better the tower is at achieving equilibrium multiple times which results in greater efficiency. The same goes for decreasing plate height. In design, there are tables and assumptions which ease the process of finding the tower height and area. In this particular lab, we have a tower and are testing multiple cooling loads and air flow rates for a constant water flow rate. By measuring the difference between the inlet and outlet wet and dry bulb temperatures, we can approximate Noy using the following equation:
Also, once we know the actual tower height we can find Hoy from the following relation:
Since the cooling water tower is a combination of both heat and mass transfer, we can also relate Hoy to the heat transfer coefficient (h) using the following equation:
where Gy is the mass