School centralized hot water supply system with air source heat pump
Abstract: Taking a dormitory building of a middle school in Xiamen as an example, the design of centralized hot water supply system using air source heat pump as heat source is studied. The advantages of using air source heat pump to produce hot water are analyzed. The technical economy of air source heat pump, hot water boiler, gas hot water boiler, hot water boiler and solar water heater are compared. The technical and economical advantages of using air source heat pump to prepare hot water are the best.
Keywords: air source heat pump; centralized hot water supply system; school
Centralized Hot Water Supply System Using Air Source Heat
Pump in Schools
YANG Xiu-mei
(Xiamen Eastern District Construction Supervision Co., Ltd., Xiamen 361009, China)
Abstract: Taking the student dormitory buildings of a middle school in Xiamen for example, the design of centralized hot water supply system using air source heat pump as heat source is studied, and the advantages of using air source heat pump to prepare hot water are analyzed . The technical economy of air source heat pump, oil-fired hot water boiler, gas-fired hot water boiler, electric hot water boiler and solar water heater is compared, and the technical economy of using air source heat pump to prepare hot water is optimal .
Key words: air source heat pump; centralized hot water supply system; school
A high school middle school in Xiamen 4 4 to 6-storey dormitory building, a total of about 450 dormitories, can accommodate 2700 students, the use of centralized hot water supply system, taking into account all of the school boarding students and water time is more concentrated , Using regular water supply, regular water supply 1h. Xiamen minimum temperature in winter is 2 ℃, and the lowest temperature appeared in the school during the winter vacation. This article focuses on hot water supply system design.
A centralized hot water supply system design â‘ design standards based on the norms of the design based on the norms and standards for the design: GB "Building Water Supply and Drainage Design Code" GBJ 16-87 "Building Code for Fire Protection Design", GB "Design Specification for Industrial Metal Pipe", GB 50050-95 "Code for Design of Industrial Recycling Cooling Water Treatment", GB 3096-82 "Urban Area Environmental Noise Standard".
â‘¡ determine the heat source At present, the air source heat pump for the heat source of centralized hot water supply system has been widely used, has the following advantages: a. Safe and reliable. The use of air source heat pump to prepare hot water, to avoid the electric water heater, gas water heater used in the existence of easy to touch, flammable, explosive, poisoning and other safety issues, is more safe and reliable heating equipment. b. Efficient power-saving. Air-source heat pump coefficient of heating performance up to 4.0 [1], the electricity consumption is only a quarter of the traditional electric water heater, can save a lot of electricity. c. long lasting. Air source heat pump life of up to 10a or more, and low maintenance costs. d. Can be used around the clock. Air source heat pump can be used all day, to make up for the general solar water heater affected by the weather, can not guarantee the availability of hot water defects. Therefore, the project uses air source heat pump to prepare hot water.
③ air-source heat pump and heat storage tank selection Each dormitory separate set centralized hot water supply system. Air-source heat pump and heat storage tank installed in the dormitory roof, hot water pipe connected to the installed water inlet port. Air source heat pump indirect heat storage tank cold water to 55 ℃, according to set the water temperature to automatically control the operating state, when the storage tank temperature dropped 5 ℃ air source heat pump automatically starts to ensure that the water tank temperature is set state .
On a dormitory building air-source heat pump equipment selection, air-source heat pump design heat load calculation is [2]:
Where Φ - air source heat pump design heat load, kW
qv - single shower design volume flow, m3 / h, take 0.21m3 / h
Th - hot water temperature, K, take 328K
Tc - tap water temperature, K, take 288K
Ï - water density, kg / m3
cp - water than the constant pressure heat capacity, kJ / (kg · K)
n - the number of the same type of shower, according to 112 units b - Shower at the same time, take 1
t - air source heat pump heating time, h
Air-source heat pump working time is generally set in the daytime energy efficiency is relatively large period of time, set the working time of 10h. Calculated by equation (1), the design of air source heat pump thermal load Φ = 109.42kW. Each dormitory building design hot water volume flow of 23.52m3 / h, daily water supply 1h, determine the capacity of the storage tank 23.52m3.
Considering the size and price of air source heat pump, each dormitory selects 2 air source heat pumps with a heating capacity of 70kW and a rated volume of hot water volume of 1.5m3 / h and 2 heat storage water tanks with a capacity of 12m3.
â‘£ centralized hot water supply system layout centralized hot water supply system layout shown in Figure 1.
Fig. 1 Centralized hot water supply system
⑤ system debugging equipment and pipe installation is complete and after the pressure test, rinse, you can enter the commissioning phase. First, adjust the water distribution of the hot water supply system proportionally, and record the relative opening of the balance valve. After adjusting the water volume, lock all balance valves and mark them with paint on the adjustment handle. Then, according to the design conditions of the trial run, measure and adjust the hot water temperature in the hot water tank to meet the design requirements. Maintain a centralized hot water supply system for continuous operation of not less than 16h, and conduct a comprehensive inspection, adjust and assess the indicators to meet all the design requirements for the qualified.
2 Technical and Economic Analysis In the same conditions, respectively, the use of air-source heat pump, hot water boiler, gas water heater and electric water boiler, the water temperature of 1m3 0 ℃ heated to 35 ℃ consumption of electricity or fuel and see Table 1. The electricity price is 0.55 yuan / (kW · h), the diesel price is 3.90 yuan / kg and the liquefied petroleum gas price is 10 yuan / m3. The low heat value of diesel is 42.7MJ / kg, the low heat value of liquefied petroleum gas is 100.5MJ / m3.
Table 1 different heat source of hot water consumption of electricity or fuel and costs
Tab. 1 Power or fuel consumed by different heat sources for preparing hot water and cost
Heat Source Air Source Heat Pump Fuel Hot Water Boiler Gas Hot Water Boiler Electric Hot Water Boiler Thermal Efficiency 3.50 O.80 0.80 0.95
Consumed electricity or fuel 11.63kW · h 4.29kg 1.82m3 42.84kW · h
Expenses / $ 6.40 16.73 18.20 23.56
The use of air-source heat pump to prepare hot water is the lowest cost, and there is no leakage of oil, gas leakage and then the risk of fire and explosion. Compared with the solar water heater, although the two centralized hot water supply system cost is not much difference, but the water temperature of the solar water heater is greatly affected by the weather, some time each year to use auxiliary heat source heating. Therefore, the use of air-source heat pump hot water technology is the most economical and economical.
3 Conclusion The hot water supply system has been fully operational, operating in good condition, the practice proved that the use of air-source heat pump hot water for the school has brought good economic and social benefits.
references:
[1] Zhang enjoy the country. Air source heat pump in the construction of hot water supply application [J]. Water Supply and Drainage, 2006, (1): 82-84.
[2] GB, building water supply and drainage design specifications [S].
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