Structure Selection of 1. Cooling Tower
At present, the commonly used general cooling towers are countercurrent round tower or cross-flow square tower, and closed cooling towers are rare and have special uses, which are skipped here.
Cross-flow tower has many advantages, such as its water loss rate is small, the ventilation area is large, the cooling effect is good. The advantage is that the water distributor is fixed, unlike the rotating water distributor of the round tower, which requires water flow to push. It is very suitable for the cooling water pump to adopt frequency conversion and energy-saving systems. After many cooling pumps adopt frequency conversion to save energy, after the cooling water flow rate of the water distributor of the round tower cooling tower is reduced, the rotating water distributor cannot maintain the normal rotation speed or even stops due to insufficient water flow. The water flow cannot be evenly distributed but converges into water flow, the flow rate is accelerated, the contact surface and contact time with the air are greatly reduced, and the cooling effect is seriously weakened. The temperature of the cooling water will be higher and higher, and the refrigeration efficiency of the refrigeration equipment such as the refrigerator will be lower and lower (within the normal working range), but it will not have the due energy saving effect. However, because the water distributor is fixed, the water flow distribution of the cross-flow cooling tower is basically uniform when the water flow rate is reduced, and the water flow rate will be relatively slower, which will help to achieve better cooling and cooling effect, I .e. the temperature of the cooling water can be reduced lower after being better cooled, and the refrigeration equipment can obtain better cooling efficiency and reduce operating energy consumption. In addition, some large-capacity cross-flow towers are divided into several modules, each module has an independent fan, water distributor, packing layer, etc., which can work independently, so its work can be flexible and diverse. If the fan can be stopped separately for maintenance, it can better meet the quarterly changes, the fan for energy-saving control, only simple control start and stop without complex frequency control.
Capacity Selection of 2. Cooling Towers
In general design, although the capacity selection of the cooling tower is considered to have a certain margin, it is found that it is far from enough in actual operation. Cooling tower as auxiliary equipment, is generally designed and selected according to the cooling capacity required by refrigeration equipment. Since there is a margin in the selection of refrigeration equipment, when the cooling tower is matched, it is basically just right, and a margin coefficient is rarely considered for the cooling tower. In actual operation, when the weather is muggy, the air conditioning load is large, and the refrigeration equipment basically reaches the design value. At this time, because the working environment conditions of the cooling tower are far worse than the design conditions, the heat load in the cooling water cannot be effectively evaporated due to the high relative humidity of the ambient air, resulting in a serious reduction in the efficiency of the cooling tower and the design cooling capacity cannot be reached. The cooling water circulation of refrigeration equipment accumulates, and the cooling water temperature is getting higher and higher. The direct impact is the increase in the operating energy consumption of the refrigeration equipment and the increase in the water loss rate of the cooling tower, which may even cause the protection of the refrigeration equipment to jump, or the cooling water needs a large amount of direct low-temperature tap water to keep the cooling water meet the temperature requirements. Therefore, when selecting the cooling tower, it is necessary to fully consider the factors that the cooling efficiency of the cooling tower is seriously discounted when the weather is sultry and the environmental conditions are not up to the design temperature and humidity conditions. It is also necessary to consider the factors that the working efficiency of the filling layer, fan and water distributor of the cooling tower is reduced after several years of operation. Then the capacity of the cooling tower must be fully reserved when selecting the allowance. According to my personal experience, it is not too much to choose a cooling tower with twice the cooling capacity. If the standard cooling water flow rate is half of the standard flow rate of the selected cooling tower, the water flow will be dispersed, and better cooling effect can be obtained under normal conditions or abnormal conditions with severe sultry weather, and the water temperature after cooling will be lower. Although the sultry weather affects the cooling efficiency of the cooling tower, due to the large capacity of the cooling tower, the actual cooling capacity can basically meet the requirements of the cooling equipment, and the cooling water temperature can be guaranteed not to be too high. The investment proportion of cooling tower in the overall system is generally small, even if the choice of double the cooling tower will not be much investment, but in operation, the cooling water temperature can be controlled in a lower state, the refrigeration efficiency of refrigeration equipment is high, the energy consumption and water loss saved in one year of operation are basically enough to buy a matching cooling tower. Both theory and practice show that within a reasonable range, the cooling water temperature is reduced by one degree, the cooling efficiency is increased by 3% on average, the cooling tower is reasonably set, and the cooling water temperature can be basically reduced by about 2~4 degrees, so it is absolutely cost-effective and not wasteful to increase the selection of cooling towers. When the selected capacity of the cooling tower is twice as large as the actual demand, one problem should be paid attention to, that is, when selecting the round tower, it is necessary to consider that its rotating water distributor is driven by water flow. When the water flow is less than its design value, the overall efficiency of the cooling tower cannot be guaranteed. Therefore, when it is a round tower, at least two cooling towers with the same flow rate should be selected. Normally, only one cooling tower should be opened. When the weather is sultry, the two cooling towers can be put into operation after the cooling pump is added. The cross-flow square tower is fixed by the water distributor, so there is no such concern. In addition, because the air conditioning load has obvious characteristics of seasonal changes, the cooling capacity is also significantly changed. After the total amount of cooling is determined, the configuration scheme of a large number of small capacity cooling towers is superior to the configuration scheme of a large capacity and a small number of cooling towers in terms of energy saving operation and flexibility of downtime maintenance.