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With the rapid development of our country's national economy, air-conditioning technology has been widely used. According to statistics, the current energy consumption of HVAC accounts for 25% to 45% of the total energy consumption of buildings, and it is increasing at a large rate every year. It can be seen that the energy consumption of air-conditioning accounts for a relatively large share of the current social energy consumption, and the energy consumption of air-conditioning is wasted due to various reasons. Therefore, the research on energy-saving of air-conditioning systems is urgent and important.
In the energy saving of air-conditioning system, it is mainly manifested in the following aspects: ① energy saving in building and air conditioning system design; ② energy saving by improving the quality of air conditioning projects; ③ energy saving in air conditioning system operation and management.
1. Energy saving measures in architectural design
Building energy conservation is mainly manifested in: building orientation and surrounding environment, building materials, thermal insulation of envelope structures, building lighting and ventilation design, etc.
First, the orientation of the building and the surrounding environment. In order to achieve the goal of reducing the energy use of buildings as much as possible, the building is oriented as far south as possible, maximizing the absorption of solar energy in winter and minimizing the absorption of solar energy in summer.
Second, the outer structure of the building. Materials should be replaced by environmentally friendly materials with larger heat transfer resistance, such as porous bricks or hollow bricks, etc.; measures to prevent solar radiation heat such as the use of multi-layer architectural glass and transparent polyester film pasted with glass are promoted.
Third, promote external thermal HVAC insulation buildings. This kind of building thermal insulation system has been adopted in a number of projects, whether it is from the external decoration effect of the building or the comfort of living, this measure is a new energy-saving technology worthy of popularization and application.
Fourth, the architectural lighting and ventilation diffuser design. ① Since the heat consumption of external windows accounts for 35% to 45% of the total heat consumption of the building, it is very important to reasonably determine the window-to-wall ratio under the premise of ensuring indoor lighting. ② Improve the air tightness of doors and windows. Doors and windows with good air tightness are used in the design, and airtight strips are added to improve the air tightness of doors and windows, so as to reduce the energy consumption of buildings.
2. Energy saving measures in air conditioning system design
First, since the power transmission and distribution of the air-conditioning water system accounts for a large proportion of the energy consumption of the air-conditioning water system, the following points should be paid attention to in the design of the water system for energy saving: (1) The hydraulic balance calculation should be carried out for each water loop, and the loops with different pressure differences should be calculated. Take effective measures, such as the use of the same process system, the use of balance valves and other measures to control; ② to avoid the phenomenon of large flow and small temperature difference, the temperature difference between supply and return water in the design is generally 5 °C, but the actual measurement shows that the temperature difference between the return water of chilled water in summer The better one is 3.5°C, and the worse one is only 1.5～2°C, which causes the actual water flow to be more than 1.5 times larger than the designed water volume, which greatly increases the power consumption of the pump. Therefore, the design process should carefully check and calculate the correlation coefficient of the air-conditioning water system, and implement it effectively. The required value of the energy-saving design standard.
Second, according to the calculated load size, select the unit with the same capacity as the design, and do not select the host with too large capacity. The host with too large capacity cannot run at full load, which not only increases the investment of equipment, but also wastes operating energy consumption. When selecting a water pump, the model of the water pump should be selected according to the characteristic curve of the water pump according to the design value, rather than the data on the nameplate.
Third, in optimizing the selection and design of air-conditioning units and terminal equipment, pay attention to selecting units with light weight, less noise, and a large amount of cooling (heating) per unit fan power. The air-conditioning unit should choose the unit with reasonable matching of fan air volume and air pressure, less air leakage and large air transport coefficient.
Fourth, try to choose a unit with a high energy efficiency ratio according to the size of the capacity. Such as screw type, centrifugal chiller, etc., the energy efficiency ratio of such refrigeration units is generally between 4.5 and 5.8.
Fifth, the application of frequency conversion technology. With the development of automatic control technology, various types of chillers and water pumps have relatively complete automatic control and adjustment devices, which can automatically adjust their operating conditions with load changes and maintain high-efficiency operation. In view of the characteristics of air-conditioning control system, coupled with the development of power electronic technology and microcomputer control technology, the application of frequency converter is becoming more and more extensive, so it is inevitable to use frequency conversion technology in air-conditioning control system. This gives us a way to achieve both control and energy savings.
Sixth, adopt a new energy-saving, comfortable and healthy air-conditioning method. For example, using a total hot fresh air ventilator can realize the heat exchange between the outdoor purified air and the indoor air, and keep the indoor temperature and humidity basically unchanged.
Seventh, promote the use of renewable energy or low-grade energy for air-conditioning systems. With the wide application of air-conditioning systems, the consumption of non-renewable energy by air-conditioning will increase significantly. How to utilize renewable energy and low-grade energy has become an important research topic in this field. The ground source heat pump air-conditioning system was developed under this situation. It uses the soil heat of the underground constant temperature layer to significantly increase the COP value of the air-conditioning system, which greatly reduces the energy consumption of the system under the same heating (or cooling) capacity. In addition, the use of solar heating or cooling technology is also being developed.
3. Energy-saving measures in the construction of air-conditioning system
First, strengthen the tightness and integrity of insulation. The temperature difference between the inside and outside of the conveying medium system of the air-conditioning system is large. If the insulation effect is poor, it will cause serious temperature loss. The size of the heat transfer system of the thermal insulation material and whether the thermal insulation layer is damaged will have a greater impact on the energy loss of the system. The thermal insulation quality of air-conditioning equipment and pipes is also very important for saving energy consumption and reducing operating costs. If the insulation effect is not good or the insulation layer is not repaired well after maintenance, it will not only consume too much cooling capacity, but also cause the air-conditioning system to fail to guarantee the air conditioning due to the excessive temperature rise of the supplied cold water. The relative humidity of the air-conditioned room exceeds the standard due to the dew point of the machine.
Second, reduce the resistance loss of the system and prevent the blockage of the pipe network. During the construction process, attention should be paid to the comprehensive layout of the pipeline network to reduce the local resistance and the resistance along the pipeline network. When installing the pipe network, pay attention to prevent debris from entering the pipe network to prevent blockage, and meet the requirements of construction acceptance specifications when the system is flushed.
4. Energy-saving measures in the operation and management of the air-conditioning system
An efficient operation and management system will play a key role in building energy conservation. If it is not managed properly, it will cause a great waste of energy. Energy-saving measures for air-conditioning operation management include:
First, implement a system for air-conditioning operators to hold certificates. At present, there is a phenomenon that the air-conditioning operation and management personnel in the society are not strong in air-conditioning expertise, which has a lot of influence on the implementation of various adjustment and energy-saving measures. Therefore, the training of air-conditioning operators should be strengthened, the quality of management personnel should be improved, and air-conditioning operators should be certified.
Second, the air-conditioning ventilation system that does not work continuously should shorten the pre-cooling time as much as possible, and use circulating air during pre-cooling instead of introducing fresh air. For systems with large changes in the number of personnel, the fresh air volume of the hottest month and the coldest month should be based on the indoor CO2 concentration detector, and the fresh air population valve should be automatically controlled to adjust the fresh air volume.
Third, when there is a cooling load indoors in the transitional season, the natural cooling capacity of outdoor fresh air should be used as much as possible to save the cooling capacity of artificial cooling sources. According to the change of seasons, the temperature of the controlled room is reasonably set to avoid the phenomenon that the indoor is too cold in summer and overheated in winter.
Fourth, strengthen the daily and regular maintenance of equipment and systems. The operation manager should always check the automatic control equipment and instruments, and record the operation data of the instrument, find out the problems existing in the operation of the system according to the data of the instrument, and ensure the normal operation of the system.
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