As a new branch of heat pump technology application, ground source heat pump has been widely used in recent years due to its energy saving and superior environmental performance. The ground source heat pump is an engineering application of thermodynamic reverse circulation using the good heat storage and cold storage characteristics of the soil;
1. When heating in winter, the heat pump system absorbs the heat stored in the underground through the pipeline buried in the ground through the heat transfer medium, as a low-temperature heat source in the reverse cycle, the heat pump completes the reverse cycle and provides heat to the heat user;
2. When cooling in summer, the lowering of the underground environment temperature makes the condensation temperature in the refrigeration system lower, thereby increasing the refrigeration coefficient of the system, compared with the ordinary air conditioner refrigeration in which the condenser directly exchanges heat with the air environment. Have a certain energy saving effect.
Since the ground source heat pump system does not require other heat sources or powers in addition to the power to drive the heat pump during operation, the power to drive the heat pump is mainly electrical energy. Therefore, if the source of electric energy is not considered, the ground source heat pump system is a clean energy source for urban heating and cooling. It does not need to establish a boiler room for general urban heating, nor does it exist due to fuel combustion (burning coal). And the city's environmental pollution caused by fuel, can achieve cold and heat supply.
In addition, in actual use, for some places that are subject to objective conditions and cannot adopt other heating and cooling methods, such as highway toll stations, scientific research stations with relatively few personnel equipment, border guard posts, ground source heat pumps are even more It reflects its unique superiority; based on the above characteristics, this paper systematically analyzes the design and actual operation effect of the ground source heat pump system of the toll station of Jingang Expressway:
First, ground source heat pump system load calculation
1. Heat pump system load calculation
The Tianjin section of the Jinjin Expressway runs from Tianjin to Dagang, with a total length of 35 kilometers and three toll stations. The Tianjin-Hong Kong toll station includes a comprehensive building, an annex building for the complex and seven toll booths. The construction area of ​​the comprehensive building is 744m2; the attached restaurant of the comprehensive building is 80m2; the total construction area of ​​the seven toll booths is 47m2; the total construction area of ​​the Jingang toll station is 871m2.
According to the climatic conditions of Tianjin and the civil building envelope structure of the toll station building, the design uses the CLF cold load factor method recommended by ASHRAE to calculate the building load of the toll station; when the ground source heat pump system is in the cooling condition, the evaporator temperature is 7~ At 12 ° C, the condenser temperature was 30 to 35 ° C, and the indoor temperature was 25 ° C. The cooling load of the toll station complex and the auxiliary building is 120W/m2, and the toll booth cooling load is 220W/m2. Accordingly, the maximum maximum cooling load of the Tianjin-Hong Kong toll station is 113 KW, and the maximum heat release of the buried heat exchanger of the Tianjin-Hong Kong toll station is 146 KW.
For thermal load calculation, this design uses the method recommended by ASHRAE to calculate the building heat load of the toll station. When the ground source heat pump system is in heating condition, the condenser temperature is 45~50°C, and the evaporator temperature is 2～6°C. The temperature is 18 °C. The heating load of the toll station complex and the auxiliary building is 100w/m2, and the toll booth is loaded with 120 W/m2. From this, it can be calculated that the maximum heating load of the Tianjin Port toll station is 92KW.
2. Indoor end system design
The location of the rooms where heating and cooling are required for the toll stations in Tianjin Port is relatively concentrated and the functions are relatively simple. According to the actual situation of the toll station in Jingang, the ground source heat pump system is a centralized air conditioning system, and the heat pump room is designed separately for the auxiliary room. The indoor end system is designed with a fan coil system to achieve the required air conditioning temperature in each room.
3. Outdoor buried pipe system design
According to the actual situation of the building, the ground source heat pump system should be designed to meet the requirements of summer cooling and winter heating. The outdoor buried pipe system of the ground source heat pump system of the toll station of Jingang Expressway adopts the vertical U-shaped buried pipe method. According to the calculation of the maximum heat release of the buried heat exchanger, the vertical U-shaped buried pipe method requires 45 wells and a depth of 100 meters. The outdoor vertical buried pipe requires a minimum of 300 square meters, and the actual floor space of the toll station can fully meet the construction requirements. In addition, parking facilities, decoration or tree planting facilities can be built on the buried pipe site; there is no impact on the actual effective use of the ground. When heating in winter and cooling in summer, the ground source heat pump system can realize the conversion of different working conditions in winter and summer by controlling the four-way valve.
2. Operating costs of ground source heat pump air conditioning system at Jinang Toll Station
In summer, the air conditioner runs for 100 days and runs 24 hours a day. The air conditioner operates for 120 days in winter and runs 24 hours a day. The indoor air conditioning circulating water pump power is 3 KW, the outdoor air conditioning circulating water pump is 3KW, the heat pump unit is two, the single unit electric power is 13.3KW, and the running coefficient is 0.49. According to the actual operating conditions and indoor and outdoor parameters, the system is in winter. The power consumption and operating costs of the summer and summer seasons were analyzed and calculated. The results are shown in Table 1.
The electricity price is calculated by peak, valley and level, among which:
Peak electricity price: 0.8933 (yuan / kw · h), time: 8:00 ~ 11:00 18:00 ~ 23:00
Valley electricity price: 0.2873 (yuan / kw · h), time: 23:00 ~ 7:00
Flat price: 0.5793 (yuan / kw · h), time: 11:00 ~ 18:00 7:00 ~ 8:00
According to the field test data, the ground source heat pump system works Cop=4.50 when it is working in summer cooling conditions, and Cop=4.1 when it works in winter heating conditions.
Under the same heating and cooling load conditions, such as ordinary air conditioners for winter heating and summer cooling, in the heating condition, the performance coefficient of the ordinary air conditioner is 2.2, while in the cooling condition The refrigeration coefficient is 2.9. Under this condition, the operating cost is: winter heating: 71057 yuan, summer cooling 55175 yuan; the total amount is 126232 yuan. Compared with this, the ground source heat pump http:// can save about 63%.
Third, the conclusion
Based on the analysis of the ground source heat pump system of Jinjin Toll Station in Jinjinjin Expressway, the paper draws the following conclusions:
1. Due to the use of underground heat exchangers, the COP value of the ground source heat pump system during heating in winter is increased. The measured value in this paper is up to 4.5. This is because the underground temperature is higher than the ambient temperature when working in winter conditions. Increasing the evaporation temperature of the ground source heat pump system results in an increase in the COP value of the system.
2. When the ground source heat pump system is cooled in summer, because the underground temperature is lower than the ambient temperature, the condensation temperature of the heat pump system is lowered, resulting in an increase in the refrigeration coefficient of the system, which is higher than that of the ordinary air conditioner.
3. Compared with ordinary air conditioners that use air as a heat source, the ground source heat pump system can save about 65% of operating costs under the same conditions of cold and heat load.
4. Because the ground source heat pump system does not need to consume fuel, it is easy to use; it can effectively improve the local environment and has a positive effect on environmental protection.
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