Application of the hottest air-cooled heat pump he

2022-07-24
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Application of air-cooled heat pump heating in northern China

1. The heating problems faced by northern China environmental protection and energy conservation are challenging the heating source in China. Various traditional heating methods have different defects:

1. The coal-fired boiler heating pollution is serious and must be changed

2. The central heating charging system is being reformed, but even if the household metering problem is solved, there is still a problem of how to avoid the imbalance between water and heat in the system network. Unless automation is completely solved, it is difficult for users to adjust and use independently and pay the corresponding fees

3. The use of gas-fired boilers for heating, first, the user's expenditure is high, and second, there are still provincial (District, city) pollution problems that are randomly confirmed by the supervision and spot check every year. According to the test conducted by the Beijing Municipal Energy Conservation Office on residential quarters heated by this heat source, it is proved that the nitrogen oxide obviously exceeds the standard, and even there are potential safety hazards

4. Direct electric heating (e.g. electric heating, electric heating film, electric boiler, etc.) is not allowed under normal circumstances because the utilization rate of fuel is too low and the operation cost is very high. Table 1: comparison of heating costs of several common energy sources in winter

mode fuel price thermal conversion efficiency fuel calorific value costs required for 1kwh heat generation in Beijing operating cost characteristics coal-fired central heating 280 yuan/ton 55%5000wh/kg0.102 yuan/kwh13.4 yuan/m2 serious pollution, low cost gas 1.7 yuan 1, adopting high-precision, full digital speed regulation system and precision reducer/m375%10500wh/m30.216 yuan/kwh28.5 yuan/m2 slight pollution High cost fuel 3000 yuan/ton 85%10500wh/kg0.336 yuan/kwh 44.3 yuan/m2 slightly polluted, high cost electric heating, electric heating film 0.4 yuan/kWh 100%1000wh/kwh 0.4 yuan/kwh 52.8 yuan/m2 pollution-free, the highest cost heat pump 0.4 yuan/kWh 300%1000wh/kwh 0.133 yuan/kwh 17.6 yuan/m2 pollution-free, low cost note: according to the meteorological data, the heating load in Beijing in winter is calculated as 132kwh/m2. On the other hand, with the improvement of people's quality of life, The popularity of air conditioning and refrigeration has been greatly improved. If we can create artificial environmental facilities that combine cooling and heating, it will have the dual significance of environmental protection and energy conservation. Air cooled heat pump is a kind of electrically driven cooling and heating facility that only exchanges heat with air without water source. Air is available everywhere, and it is not used up. Therefore, the use of air-cooled heat pumps for cooling and heating in a wider area can achieve many purposes, such as environmental protection, energy conservation, convenient management, safe use and even beautiful, which is expected by all. However, can the air-cooled heat pump be used for heating in cold areas (within the range of heating design temperature -5 ~ -15 ℃)? In the academic circles, people have always had doubts. Therefore, we must clearly answer the following questions: 1. What kind of heat pump can operate in the above climate

2. How much does the heat supply of the heat pump decrease under the above low temperature weather? What is the maximum temperature of air or water outlet? What is the efficacy ratio

3. How is the defrosting condition? How much impact will it have on the heat supply

4. What kind of heating terminal can be combined to achieve the purpose of heating

5. How economical is it to be used in heating areas in China? And compared with other heating methods

the above problems are described below

II. Low temperature performance of air-cooled heat pumps in order to reveal the low temperature performance of air-cooled heat pumps, Beijing Tsinghua Solan Institute of environmental energy technology established a low temperature simulation laboratory, and conducted artificial climate tests on the following three representative heat pump units in August, 2001, Three types of units are:

a. heat pump test unit of Solan medium and low temperature compressor (hereinafter referred to as type A)

b. heat pump unit of a famous company (hereinafter referred to as type b)

c. the test results of Solan existing unit (hereinafter referred to as type C) are summarized in Table 2. Unit type ABC rated power (kw) 886 simulated external temperature -6 ~ -8 ℃ outlet air or outlet water temperature (℃) 33 ~ 3831.5 ~ 39.25,42 ~ 45 heating capacity (W) 3756 heating capacity decrease%02840 power consumption (W)220v 1388C. O. P2.563.5 2.58 external temperature -9 ~ -10 ℃ outlet air or outlet water temperature (℃) ~ 3332 ~ 40 heating capacity (W) 3489 percentage decrease of heating capacity%573642 power consumption (W) 1219c O. P1.233.45 2.86 external temperature -11 ~ -16 ℃ outlet air or outlet water temperature (℃) 33 ~ 3741 ~ 46 46 ~ 48 heating capacity (W) 3663 percentage decrease of heating capacity%1545.4 55 power consumption (W) 3480c O. P2.191.33 1.05 test result description:

1. Under the cold weather with outdoor temperature of -5 ~ -15 ℃, the outlet air or outlet water temperature of the three air-cooled heat pumps tested can meet the heating requirements of general houses, especially low-temperature floor radiant heating, provided that the unit output and load match. That is, when selecting heat pump unit, the rated output shall be larger than the design load. Otherwise, when the output is insufficient, power shall be added to supplement heat. The expansion percentage of the selected unit shall be determined according to the regional winter climate

2. Different compressors show different performance under the same evaporation and condensation temperature and pressure (temperature and pressure are monitored in the experiment), that is, different heat supply and power consumption. A is the best, C is the second, and B is poor. It indicates that a is more suitable for heating in the north and needs to be finalized for production as soon as possible

3. About the impact of frost flushing on heat supply: firstly, the northern region has a dry climate in winter, which determines that the frost flushing problem is not serious; Secondly, the defrosting process of many products has been greatly improved, and the time to complete the action is very short. According to the observation in the experiment, for a heating water system with large inertia, the water temperature has little change. Third, the lower the external temperature is, the smaller the absolute moisture content in the air is, and the time interval for frost flushing becomes very long. 3、 Terminal device of air-cooled heat pump heating 1. Combined with low-temperature radiant floor, radiant heating is a heating method with high sanitary and comfortable conditions. Floor radiant heating is more reasonable than ceiling heating. Since the human body can conduct heat exchange from contact, radiation and convection in the floor radiant heating room, many authoritative data point out that the indoor air temperature can be lower than the design temperature and the heating load can be reduced by about 15% under the condition of reaching the same comfortable conditions of the human body, the planned "four vertical and four horizontal" Railway Express passenger passage and three Intercity Express passenger transport systems, Therefore, it is also a reasonable and correct use of fixture, which is beneficial to the smooth experiment of energy-saving heating device. In addition, its outstanding advantage is that it can and must use low-grade heat medium and has great heat storage

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