A. Please write a comprehensive description (200 words each) of the following mechanical equipment for buildings:
1. cooling tower
Through the cooling water stream system, A cooling tower, which is a heat rejection device, can reject wasted heat into the atmosphere and transfer it to a lower temperature. In this mechanical equipment, cooling tower uses water evaporation to remove heat in the process and cool down the mechanical work fluid to approach the wet-bulb air temperature as much as possible. In another situation of closed circuit dry cooling tower, this device will also only use air to cool down the mechanical work fluid to approach the wet-bulb air temperature as much as possible.
There are two types of cooling towers based on the type of air induction into the tower. The first one is natural draft cooling tower and the other is induced draft cooling tower.
Sizes of cooling towers also vary from one to another. It can be a small roof-top unit. It can also be a very large structure such as hyperboloid structures which is going to be up to 660 ft. tall and 330 ft in diameter, or 130 ft. wide and 260 ft. long. The larger cooling towers usually accompany with large industry factory or nuclear power plants.
When the mechanical equipment is mainly in the basement, the cooling tower should still be on the roof or on an out-of-the-way location with good outdoor air circulation.
2. chilled beams
The chilled beam is one type of the convection HVAC system which is designed to heat or cool large buildings. In the system, water in the pipes run through a heat exchanger which is known as a beam. It is integrated into standard suspended ceiling system or suspended a very short distance from the ceiling. The air will become much denser so that it will sink down to the floor and warm air will rise when the heat exchanger cools the air around. In this situation, the air flow or circulation is constant, so the room will cool down.
Chilled beams have two different types as well, which is passive and active. One passive type purely relying on convection and the other is radiant convection passive type which cools through the hybrid of 40% radiant exchange and 60% convection.
The active type use air ventilation momentum at a high velocity to create the air circulation in the whole unit.
Comparing passive with active type, passive type has higher thermal comfort level.
B. What function do they play in building mechanical heating, cooling and ventilation strategies?
The cooling tower is used to reject or dispose of heat which is unwanted from the chiller. It helps the building to satisfy itself in aspects of cooling without even considering the use of chiller in cold climates. Therefore, the cooling tower is essential to help in the strategy of building mechanical cooling, ventilation and heating through saving energy. In the building of this mechanical system, the cooling tower usually provides multiple heat pumps which have various water sources. This allows the cooling tower to facilitate water circulation within the condenser removing the unnecessary heat. There is also a mounted cooling system which is used in the water loop to remove heat externally and ensure that it is disposed to the atmosphere. The cooling tower is usually shut down when the heater loop is supplying heat to the building. Therefore a cooling tower is essential in laying down strategies for building mechanical heating, ventilation and cooling by providing a mode of saving energy in a building (Stanford, 40).
In the building of strategies which are related to mechanical cooling, ventilation and heating, the chilled beams usually offer thermal comfort, saves energy, minimize space and reduce noise. The chilled beams usually do not need large ductworks and mechanical rooms, hence, reducing the space to be used in the building and the floor heights are reduced at a significant level. The chilled beams usually reduce the maintenance cost and the noise in operation since they are quite, hence, increasing the damage risks associated with the same. One of the key strategists states that the chilled beam usually minimizes the fun use which is energy saving strategy. This is due to the high efficiency in moving water rather than blowing energy. This also increases the thermal comfort strategy through the provision of patterns of air distribution (Dieckmann, 85).
C. Compare their impact on building energy use and thermal comfort.
The cooling tower usually offers an opportunity for energy saving in the building. First, it is usually consumed in the fan driving which facilitates proper air movement. It was constructed to reduce the water which is used in the condenser that usually improves the saving of water as well as energy. On the other hand, chilled beams usually lead to reduced energy use which is attributed to the saving of the fan use due to the reduced primary inflow. There is usually a minimal opportunity for energy saving but those which are there are efficient energy savers. Due to the ability of the chilled beams to receive the war water, the chiller is efficient which minimizes the energy used in the building. Finally, the chiller beam usually avoids reheat due to the cooling coils which are essential to saving energy. Therefore, both have a significant impact in energy saving despite them using differing mode to facilitate the same.
In the indoor environment, the chilled beams in most efficient in regulating the thermal comfort levels (Dieckmann, 85). This can be attributed to the use of the right capacity of water in the heat transfer. This can be attributed to the reduced space and noise and ability to control the temperature at a minimal cost (Stanford, 40). The increased space also attributes the use of maximum high-temperature cooling and low heating which are essential for facilitating thermal control. The chilled is also able to control the humidity levels and ensures that there is a uniform temperature which is essential for the thermal control. On the other hand, the cooling tower does not play an essential role in the thermal control.
Work cited
Dieckmann, John, and Robert Zogg. "Chilled beam cooling." Ashrae journal 49.9 (2007): 84.
Stanford III, Herbert W. HVAC water chillers and cooling towers: fundamentals, application, and operation. CRC Press, 2016.
