Air conditioning load characteristics Certain air conditioning system modes are related to the characteristics of certain air conditioning objects. Residential buildings are different from other buildings served by air conditioning technology in the past, and their load distribution has its own obvious characteristics. China has a large population and increasingly tense land resources. In the future, residential buildings will continue to be dominated by high-density housing. This paper discusses the design of air conditioning systems based on high-density residential forms. The characteristics of residential air-conditioning systems on the scale of households are mainly characterized by strong randomness characteristics of use time and usage. These randomness are affected by factors such as family composition, professional nature, economic level, and living habits. For example, some households generally do not use air-conditioning equipment. They are only activated when the weather is very hot and very cold. They are only activated after work and after sleep at night. Try to reduce the number of activations. Some households have strong dependence on air-conditioning equipment/systems. Air-conditioning equipment is activated at a slightly higher or lower temperature. The opening time is long and the number is large. For each household, they form a certain usage rule according to their own situation. The random characteristics of the number of air-conditioning equipment used in the residential area are obeyed by the Benuri distribution, and the simultaneous use coefficient of the air-conditioning equipment of the residential community under the design conditions can be calculated. However, it is not enough to focus on the design conditions. The system analysis should be used throughout the day. According to the author's investigation, the air-conditioning equipment/system usage time can usually be considered in four time periods. (1) 07 time period, it is nighttime sleep time, the running time is long and fluid, the number of use is large, the general residents will have 2 rooms at the same time, and the use factor accounts for the second place in the whole day; (2) 712 time, morning The temperature is relatively cool, and ventilation is required at the same time. Even if there are people at home, air-conditioning equipment is generally not activated during this period, and the usage rate is the lowest in the whole day. (3) During the 1218 period, the outdoor temperature is the highest in the afternoon. At this time, most family members work outside. . However, some people in the home usually turn on the air-conditioning equipment, and the use factor is the third place in the whole day; (4) 1824 period, during which time, the air temperature in the room often reaches the highest, and the personnel are the most, so the number of power-on is the most, The number of rooms can reach about 3, and the use factor is the highest throughout the day. The size of the simultaneous use factor is also affected by the outdoor temperature. That is to say, when the relative coefficient of the coefficient is kept constant while maintaining different time periods, the values ​​of the different outdoor air temperatures are different, and the values ​​of the use coefficients are different. The outdoor daily average temperature t is used as a representative value of the outdoor temperature. In summer, t is divided into three categories, which correspond to three states: suitable, hot, and hot. That is, when t<25e, generally only the middle and afternoon temperatures are high, up to 30e, while the morning and night are cooler, the air-conditioning equipment opening rate is very low, only slightly higher in the afternoon. The most striking feature of residential air conditioning is the great dispersion of load distribution. The low-load operation occupies the main period, so the air-conditioning system mode adopted must have excellent load following, and the house is still in a low-load state, and the system still maintains high energy utilization efficiency. The water source heat pump and the district centralized air conditioner are classified into the same system because the water source heat pump has a concentrated cooling water delivery system, which is equivalent to the chilled water delivery system of the centralized air conditioning in the system. It can be considered that the structural form of the system is only cold quantity production, and there is no cold quantity transmission; the ò and ó type systems all have two links of production and transportation of cold quantity, but the scale of the two is different, resulting in performance difference. Disparity. The comparative analysis of operating energy consumption still uses the cooling coefficient as a comparison parameter for operating energy consumption. In view of the distribution characteristics of residential air conditioning load, the energy consumption analysis is not only to compare the full load conditions, but more importantly to compare the partial load conditions. Different from the traditional meaning and the partial load of the ARI550 standard, the partial load condition refers to the change of the air conditioning load when the outdoor climate parameter is unchanged (such as the number of room opening changes), and the refrigeration system adapts to it through energy regulation. The situation at the time. Rather than changes in outdoor climate parameters, changes in operating conditions in the refrigeration system result in changes in the refrigeration coefficient. Since the energy consumption of the cooling water and chilled water system accounts for 20% and 24% of the compressor's energy consumption, when it cannot be reduced with the load, it will constitute the dominant influence of the whole system under low load conditions. Therefore, in the actual project, the single-machine long-term load operation of less than 50% should be avoided. -K variation curve Therefore, when selecting the chiller, attention should be paid to the size of the load between the units. The load should not be evenly distributed. It must be combined with the air conditioning load characteristics of the house. At least one small load unit should be set up to meet the requirements of daytime low load operation under suitable and hot weather conditions. The load should be no more than 10% of the design load. Since the number of mainframes is not too large, sometimes small-load units may still have a load of less than 50% for a long period of time. At this point, it is necessary to run the variable flow of the cooling water and the chilled water system. Another effective way to improve operational economics is to use a cold storage system. A buffer and reservoir are created between the production of cold and the demand for cooling so that the production of cold is not directly affected by the drastic changes in air conditioning load. The chiller can operate at full capacity during the low price period at night. There is no doubt that the overall efficiency of the unit and the reduction in operating electricity prices during the cold production process will significantly increase the economics of operation. The cold conveying system can be flexibly configured, and the number of pumps can be increased appropriately, without being limited by the number of chillers, to adapt to different load requirements and avoid excessive flow. The cold storage system can also reduce the strong load impact on the urban power grid during the summer heat of the air conditioning system. Social benefits are also very significant. The way to improve efficiency of water source heat pump systems is to improve the design of centralized cooling water systems. The choice of cooling tower and the configuration of the cooling water pump are the same as the method and principle of chiller selection. Conclusions (1) For high-density residential quarters, the lowest energy consumption in the several air-conditioning modes discussed is the centralized cooling system, followed by household air conditioners and variable refrigerant flow heat pump air-conditioning systems, while household central air conditioners are the highest. (2) The most important factor affecting operating costs is the cooling efficiency of the chiller. The energy consumption of the conveyor system is only a significant impact on the overall efficiency at low loads (less than 50%) for a single unit. (3) In order to ensure the high efficiency advantage of the centralized cooling system drowning unit, the low-load operation of a single unit should be avoided in the system design. A single unit should not be operated to 50% load. According to the characteristics of residential load, a small load unit should be configured to meet the demand of daytime low load operation time during the daytime average temperature of <30e, which accounts for 74% of the total operating days. The load is configured no more than 10% of the design load. The number of units can be selected as 34 according to the total load. The cooling capacity of the unit should constitute 15% 25% of the cooling supply. (4) The centralized system facilitates the utilization of natural energy and waste heat waste, and also facilitates the recycling of air conditioning condensing heat. The other two types of systems do not have this condition and can only absorb air heat during the winter. In the case of natural energy and waste heat utilization, the advantages of centralized systems are more prominent.
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