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Keywords: Ground source heat pump Low temperature radiant floor heating Energy saving Environmental protection Economy
1 Introduction
For a complete heating and air conditioning system, the basic composition must have three parts, namely, hot (cold) source, piping system and the end (indoor heating and cooling equipment), how to choose a reasonable system of heat Cold) Source and end devices have always been the tireless efforts of building equipment and environmental engineers and scientists. In many of the previous data and research literature, most of them are the technical, economic and other analyzes of cold or hot sources or ends alone. However, it is equally important for heating and air-conditioning systems to select matching sources and ends in the form of many cold (heat) sources and end systems.
1.1 ground source heat pump profile
Ground source heat pump was first proposed in a patent document of Switzerland in 1912. It is a high efficiency and energy saving heat pump system that utilizes the low temperature geothermal resources in the ground (soil or ground water at room temperature) to achieve cooling and heating. Winter as a heat pump heating, at the same time the earth to store cold, ready for summer cooling use; on the contrary as a cool source in summer, while storing heat for winter use, ground source heat pump has the following characteristics:
(1) Ground source heat pump is a renewable energy source. Because it can store both heat and cold alternately in winter and summer, the surface of the earth absorbs and stores 47% of the solar energy, which is the sum of energy used annually by human beings Times as much as this near-infinite energy stored in the shallow superficial layer is an inexhaustible supply of renewable energy that is in line with the trend of sustainable energy development.
(2) The discharge of ground-source heat pump pollutants, equivalent to only 60% of air-source heat pump, is 30% of ordinary boiler heating system. Although it also uses refrigerant, it is a true eco-friendly system with 25% less fill than conventional air conditioners.
(3) Ground source heat pump is a cost-effective cold (heat) source, its use of ground energy or surface temperature can be relatively stable throughout the year, winter than the ambient air temperature is higher than in summer, ambient air temperature is low, is Good heat pump heat source and air conditioning cooling source, this stable temperature makes the ground source heat pump COP value is relatively high in summer about 4.1 (traditional cold source 2.9), winter 3.1 (traditional heat pump 2.8), energy saving and saving running costs up to 40 %, Otherwise the temperature can be stable, which makes the heat pump operation more reliable and stable, to ensure the stability of the system, efficiency and economy.
(4) ground source heat pump can be a multi-purpose machine. It can be used for heating, air conditioning, domestic hot water, which is suitable for hotels, shopping malls, office buildings, schools, residential, more suitable for villas, is a great potential for the development of cold (heat) source.
1.2 low temperature radiant floor heating profile
Low-temperature radiant floor heating is a system that uses the interior floor of a building for heating. The system uses the whole or part of the floor as the cooling surface. The cooling area of ​​the floor radiates heat mainly to radiant heat (about 61.25% of the total heat) . Low temperature radiant floor heating as a form of heating in winter, as early as the 1930s in foreign countries have been applied in the 1950s in the Great Hall of the People, Overseas Chinese restaurants and other projects have also been applied, but at that time due to the Material industry and technical conditions, floor heating technology has been restricted.
With the development of China's plastics and chemical industry, plastic pipes such as PEX, PERT, PPR, PB and XPAP which are resistant to high temperature, high pressure, anti-aging and bending have been provided. They provide a reliable material guarantee for low temperature radiant floor heating technology, Compared with the plastic pipe, the pipe has the advantages of corrosion resistance, anti-aging, low cost, no interface under the ground, easy scaling, and low resistance. Generally, the service life of the plastic pipe can reach more than 50 years.
Low-temperature radiant floor heating system with high efficiency and energy saving (compared with the average radiator heating system up to 50% energy saving), low operating costs, comfortable and sanitary, long life, easy to heat measurement and charging, the available heat source, saving construction effective Use area and so on.
2 Ground source heat pump and radiant floor heating coupling analysis
As the ground source heat pump system can be used to create low-temperature hot water, the water temperature is generally about 50 ℃, are low-temperature hot water, and floor radiant heating water temperature is generally more suitable for about 50 ℃ water, and ground source Heat pump water temperature is lower, the better the performance of their work, the higher the unit COP, from this perspective, ground source heat pump technology and low temperature hot water radiant floor heating coordination is appropriate.
Figure 1 ground source heat pump heating and radiant floor heating radiant heat load curve
The heating capacity of the ground source heat pump is stable during continuous normal operation, as indicated by line (1) in Figure 1. The heating load required for building floor radiant heating is 24 hours a day, 365 days a year as shown in line (2) in Figure 1. How to make the heat supply of ground source heat pump to adapt to the change of floor heating is an important part of ground source heat pump used in low temperature and low panel radiation heating. In the literature (application research of variable frequency control technology in ground source heat pump air conditioning system) Ground-source heat pump inverter operation made a pilot study, and achieved good coupling effect.
Economic Analysis of Ground Source Heat Pump and Radiant Floor Heating
The advantages of ground-source heat pumps and radiant floor heating are described earlier in this article, but how their initial investment and operating costs and the practical benefits of energy savings are an important part of rolling out the technology.
3.1 Ground source heat pump economic analysis
For the groundwater source heat pump investment and operating costs of the author based on the literature and the actual project analysis and calculation as shown in Table 1 shows the contrast.
3.2 low temperature radiant floor heating economic analysis
Low-temperature low-plate radiant heating system, its heat in the heat transfer process upwards, heat evenly and efficiently, no "cold feet Fever" feeling, nor the bad breath of the adverse reactions to take the floor radiant heat and the traditional heat Compared with heating, the operating costs and initial investment after calculation and analysis, the results shown in Table 2.
Table 1
Note: Table 1 operating costs per day by 10h, summer operation by 90 days calculation, electricity prices by 0.53 yuan / degree calculation.
As can be seen from Table 1, ground source heat pump operating costs savings of about 30% of the cost of operating air conditioning, while the initial investment increased by about 28%. Taking a building of 3,000 square meters as an example, the cost will be recovered in about 5 years (the service life of a typical air conditioner is about 15 years).
Table 2
Note: The construction cost in Table 2 is 4,000 yuan / square meter, and the average radiator is about 0.02 square meters per square meter. The operating cost is calculated according to 10h per day. The calculation is based on 100 days in winter and the electricity price is 0.53 yuan / kWh.
It can be seen that its operating costs can save energy by about 25% compared with ordinary heating. Although the direct investment is slightly higher than that of normal heating, the integrated decoration and the discount of the area of ​​the room reduce the floor radiant heating.
Table 1 and Table 2 can be drawn for the ordinary water-cooled central air-conditioning unit plus the fan coil used for its initial investment of 288.7 yuan / square meter, ground source heat pump and floor heating initial investment of about 323.3 yuan / square meter, Investment increased only 10.7%, while the reduction of energy conservation and operating costs up to 42.33%, it is clear that increased small investment is well worth it. In addition ground source heat pump and low temperature hot water radiant floor heating system building fresh air is relatively easy to solve, good indoor air quality, easy maintenance, quiet and noiseless.
Low temperature radiant floor cooling As the ground at low temperatures easily dew or even without condensation will make indoor air humidity, indoor environment deterioration, reduce indoor humidity is the key to using floor cooling in summer, but also the source Heat pump and radiant floor heating (cooling) the key to joint operation. The problem of reducing indoor air humidity and preventing condensation has been solved.
4 still need to solve the problem
4.1 For the economy of ground source heat pump, the longer the running time, the more efficient it will be. If the year runs, that is, the winter heating, the summer is used for the air conditioning and the spring and autumn joint production of sanitary hot water, Its energy-saving effect will be more prominent, and for the multi-joint operation, the required heat pump capacity matching and coupling with the capacity of each terminal remains to be studied.
Due to the ground energy of shallow ground used by ground source heat pump, and the heat transfer of buried heat exchanger is directly affected by the soil, the soil quality of each area has a greater impact on the performance of ground source heat pump. Heat exchange characteristics, how to choose the design of the buried heat exchanger is also an important factor restricting the promotion of ground-source heat pump, to be further studied in this regard.
Feasibility Analysis of Joint Operation of Ground Source Heat Pump and Surface Heating
Abstract: The characteristics of ground source heat pump and low temperature radiant floor heating system are introduced. By comparing the initial investment and operating cost of ground source heat pump, low temperature radiant floor heating system and traditional chiller unit and radiator system, The combined operation of floor radiant heating system has great advantages in terms of energy conservation, environmental protection and operation costs, and points out the problems to be solved in promoting this form of air conditioning heating.