1 Introduction
With the wide application of air conditioning, the total energy consumption of building air conditioning is increasing gradually. At the same time, air conditioning system will bring great threat to residents' health. Due to the increasing density of buildings, indoor pollutants will gradually increase. Therefore, it is of great significance to pay attention to the energy-saving problems of HVAC and reduce the energy consumption caused by HVAC.
2 HVAC energy-saving technology in building engineering significance
With the rapid economic and social progress, the urbanization process in China is getting faster and faster. HVAC system has been widely used, and its proportion in building energy consumption is gradually increasing. In the context of the increasing contradiction between supply and demand of resources, it is urgent to find effective ways to save energy. Consuming a lot of non-renewable resources will cause the shortage of earth resources and bring very bad influence to the earth environment. For example, after changing the atmospheric composition, acid rain and floating dust are produced. With less and less energy, environmental problems are increasing, which has a very negative impact on the sustainable development of the environment in China. It is hot in summer, and people have high requirements for HVAC. If good energy-saving design can be adopted to alleviate the pressure of insufficient energy supply to a certain extent, the energy consumption of users will be further reduced. The general energy saving rate can reach 20%~50%, which plays a certain role in promoting the sustainable development of the ecological environment. Therefore, for building engineering, HVAC energy-saving technology is of great significance.
3 problems in the application of HVAC technology in building engineering
3. 1 condensate water problem
Based on the in-depth study and analysis of the present situation, condensation and dripping of air conditioning often occur in HVAC systems of construction projects. The specific reasons for this problem are: first, the poor thermal insulation performance of chilled water pipes and valves leads to the condensation of air on the outer wall of pipes into water droplets; Secondly, the slope of the condensate pipe is relatively small or not set, and if the water collecting tray of the fan coil is not installed smoothly, it is very easy to cause the problem of drainage pipe blockage in the tray; Thirdly, secondary condensate dripping often occurs at the bottom of the sump. Most of the above problems are caused by improper operation of personnel during installation. Therefore, the construction personnel should pay close attention to the pipeline installation and strictly follow the operation specifications to ensure that the pipeline and equipment are more and more closely connected.
3.2 Energy-saving design issues
HVAC energy-saving designers and developers have no good energy-saving awareness, and research and development have not kept up with the development trend of the times. Most HVAC energy-saving developers have not fully integrated the energy-saving concept into HVAC design, and developers cannot achieve the successful application purpose of HVAC energy-saving design; In the process of use, the user's operation ability is poor. In the process of using HVAC, most users have never received the instruction of using HVAC at all, which leads to the waste of electric energy.
3.3 Water circulation of air conditioning system
It is not difficult to see from the operation principle of the whole air conditioning system that the water circulation of the air conditioning system is the key link in the central air conditioning construction of the whole water system, and the construction quality and efficiency directly affect the operation efficiency of the whole air conditioning system. However, from the actual operation of the air-conditioning water system, there are many faults in the water circulation problem of the air-conditioning water system. The causes of this problem can be summarized as the following two aspects: First, after the installation of the air-conditioning water system, it is not cleaned regularly in strict accordance with the standards, which leads to the blockage of some parts of the air-conditioning water system and threatens the normal operation of the water circulation. Secondly, in the process of building engineering construction, the construction contradictions among various professions can not be effectively handled, which has an impact on the construction quality and leads to the disorderly behavior of pipeline construction in various professions. This situation will definitely lead to a lot of airbags in the pipe network, which will adversely affect the circulation of the pipe network.
4 application strategy of HVAC technology in building engineering
4. The reasonable design of1system enhances the thermal insulation performance of the envelope.
The energy-saving of HVAC system has strong comprehensive performance, and the process is complicated, so it is of great significance to strengthen its reasonable design. In the energy-saving design of HVAC system, the maximum load principle should be followed, and the energy consumption of HVAC system should be reduced as much as possible while meeting this principle. The energy saving of air conditioning is largely determined by the building envelope. A well-designed building envelope will greatly reduce the load of air conditioning system. The state has also put forward clear regulations on energy saving of HVAC systems, especially on the maintenance of structural insulation, so we should pay strict attention to energy-saving design.
4.2 Application of Energy Storage Air Conditioning Technology
In the HVAC design process of building engineering in China, energy storage air conditioning technology greatly reduces the energy consumption of users and becomes an important energy-saving technology of HVAC. Cold storage air conditioning technology mainly uses solidified medium or reduces the temperature of medium to store cold energy in the form of latent heat and sensible heat. Such as pump valves and automatic control systems. Energy storage air conditioning technology uses water medium to achieve the effect of heat storage, which is safe, energy-saving and environmentally friendly, and reduces operating costs.
4.3 Application of Heat Recovery Device
Because in the process of use, HVAC system will produce a lot of waste heat, which actually has great application value. Therefore, in order to make full use of these residual heat, it is necessary to design and use the heat recovery device of air conditioning system, and use the heat exchanger to realize the transfer of total heat and damp heat, which will greatly reduce the energy consumption of this cold and heat source, fully meet the needs of the system in improving indoor damp heat change and indoor environment, and finally achieve the purpose of energy saving of air conditioning system. According to the research, the fresh air load accounts for 40% of the air conditioning in ordinary buildings, so in order to ensure the cleanliness of the indoor environment, a certain amount of air will be discharged during the operation of the air conditioning system, which is inevitable and will lead to the loss of energy consumption. Therefore, it is necessary to apply the heat recovery device in the fresh air system and re-invest energy to improve the recovery of the exhaust air volume of the HVAC system. Then use this energy to reduce the load of the unit, so as to achieve the ideal effect of greatly improving the economy and energy saving of the unit.
4.4 Choose a reasonable frequency conversion system
Nowadays, frequency conversion technology is more and more widely used in air conditioning, which can not only greatly improve the performance of air conditioning, but also reduce energy consumption and use cost. Designers should reserve a certain margin when choosing the equipment model to ensure that the equipment is always in normal working state, not overloaded working state. The load parameters of the actual use environment will change with the change of the external environment temperature. Once the air conditioner uses rated power output, the actual load is less than the rated load, which will lead to energy waste. Using frequency conversion technology will make HVAC intelligently adjust the output power of equipment and realize energy saving. With the change of air conditioning load, automatic adjustment of water flow and air flow will greatly reduce energy consumption. VAV system mainly maintains a relatively constant air supply temperature according to the change of indoor load and the correction of user-set parameter values, and automatically adjusts the air supply volume to ensure that the indoor temperature can meet the set parameter values. The actual power change of air conditioner is mainly due to partial load, so the reduction of air volume will greatly reduce the energy consumption of fans. The principle of VAV system is similar to that of VAV system, but it is different in the way of reducing energy consumption. Under the condition of keeping the circulating water constant, the variable flow system can realize automatic adjustment by changing the temperature difference between supply and return water, thus achieving the purpose of energy saving.
4.5 Heat pump technology
According to the different types of heat sources, heat pumps can be divided into the following types: First, air-source heat pumps, and the main products using this kind of heat pumps are heat pump cold and hot water units and air conditioners with heat pumps. There is a problem with this type of application. In winter heating operation, due to the low outdoor temperature, the frost condensed on the fin surface of outdoor heat exchanger should be removed by defrosting. Second, the underground water source heat pump, the principle is to pump water underground, absorb the heat of groundwater from the heat pump, and then let the groundwater flow back. This technology is widely used, but it is not suitable for any area because of its very high requirements for underground hydrogeological conditions. In order to better expand the application scope of this technology, it is particularly critical to develop effective recharge and water intake methods.
Third, the ground source heat pump, this kind of heat source pump uses the pipeline buried in the underground soil, and then uses the circulating working medium as the heat exchanger to ensure the cold and heat exchange between the circulating working medium and the soil. In winter, this heat pump is used to take heat underground, and geothermal energy is used as the heat source of the heat pump. In summer, heat pump is used to take cold from underground, and underground cold is used as the cold source of heat pump. There is also a problem with this technology, that is, the investment is high. In order to reduce investment, the purpose can be achieved by improving the cold and heat exchange capacity of heat exchange tubes. Compared with underground water source heat pump, this technology is not limited by hydrogeological conditions, and has great advantages and broad application prospects. Fourth, sewage source heat pump, comprehensive utilization of sewage, this technology is to directly extract heat from urban sewage. According to estimates, all urban sewage acts as a heat source, which can probably solve the heating problem of 20% in the city.
5 conclusion
Although there are some problems in HVAC in building engineering, energy-saving technology of HVAC is developing faster and faster. Only by comprehensively applying various HVAC energy-saving technologies can we ensure the sustainable development of energy in construction projects and realize the healthy and benign progress of human society.
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