More and more skyscrapers are built for commercial and residential uses in modern cities. Air conditioning system for those building is quite common. However, as the total height of the super high-rise building exceed 100m, the water and static electricity pressure subjected to pipelines of the air conditioning system is also below the conventional construction. In particular, the lower part of the building’s water electrostatic pressure will be greater than the maximum pressure capacity of copper tube bundles in the air treatment equipment and tube bundles in the hot and cold water host.
HVAC
1) establish two independent high and low air conditioning water systems: set up areas of frozen – thermal room in the bottom (or basement), set high area frozen – Heat room in the middle layer (or roof). In this case, the high and low air conditioning systems and the pipe bundles of the air conditioning unit are up to only about half of the static water pressure of the building height;
2) set up frozen – heat room only in the bottom (or basement), the cold (hot) water (primary water) is supplied to the district air conditioning system at the same time to the plate heat exchanger in the middle layer. The plate heat exchanger where another air conditioner (secondary water) system is separated completely from the primary water system and connected with high layer air conditioners. In this case, the high and low air conditioning water system is actually divided into two relatively independent units. The two systems are linked through the plate heat exchanger. Its most advantage is that high and low two areas share a centralized heating room and equipment. Thus, although adding a plate heat exchanger makes the occupancy area much smaller, it can save another warm room and use an empty room in the low layer. This solution is economical, easy for maintenance and convenient for management.
Now there are two usual solutions:
In the air conditioning project (especially large central air conditioning project), the use of a closed cooling water system has great benefits. The open cooling water system is simple and practical, low cost. Still, there are some problems such as poor water quality, cooling water being seriously polluted, microbial reproduction and other issues. These further result in corrosion and scaling within the system, affect use efficiency and shorten the unit and pipeline life cycle.
The use of a closed cooling water system can overcome the above shortcomings and do an ‘economic cycle’ in the excessive season or winter. It can use natural energy effectively, making the cooling water directly to the air conditioning water pipeline system. But this system is also still at high cost in a closed cooling tower. Because of the weighty tube, it needs a strong foundation or stent, especially in the roof, which will bring some difficulties in the structural design, the cost of the equipment base increases. In the winter, tube bundles will be frozen. At present, some manufacturers produce sealed evaporative cooling towers, which have a compact structure, small size, low noise, flexible adjustment and other characteristics, but still, the price is relatively high.
Another more economical approach is to use an open cooling tower connected to a plate heat exchanger. A closed cooling water system is between the plate heat exchanger and the freezer’s condenser. As a result of using a plate heat exchanger, you can get a minimal heat transfer temperature difference. If you use low-quality cooling water such as river water or seawater, it is quite appropriate to use a plate heat exchanger. Most of the plates are made of alloy steel or soft metal, which has only increased the cost compared with stainless steel. This type of cooling water system has been widely used abroad.