Water source heat pump - an economical, energy saving and reliable air conditioning energy source

Abstract: In recent years, the main driving force for the development of water source heat pumps is that it can generate a large amount of low-level heat energy such as well water, groundwater, rivers, lakes, power plants cooling circulating water, mine water and industrial waste heat Energy, but also has a heat recovery function, you can use the condensing heat of the cooling and air conditioning room to heat the heating and air conditioning room, thereby increasing the building's internal energy efficiency.
Keywords: water source heat pump energy saving

Water source heat pump is a central air conditioning and decentralized air-conditioning between the optimization of air-conditioning energy, it has a central air conditioning and rational use of energy, equipment, high efficiency coefficient, low operating costs and safe, reliable and so on. It also has the advantages of decentralized air conditioning flexible, convenient, easy to manage and charge. Therefore, the public buildings (office buildings, commercial buildings, shopping malls, etc.) in the cities of Shanghai and Nanjing in the transition area from Shenzhen and Guangzhou in the south of our country have been widely used until the buildings in Beijing, Dalian and other cities in the north are heating.

In recent years, the main driving force behind the development of water source heat pumps is that it can generate energy from a wide range of low-level heat energy such as well water, groundwater, rivers, lakes, power plants cooling circulating water, mine water and industrial waste heat, But also has a heat recovery function, you can use the condensing heat of the cooling and air conditioning room to heat the heating and air conditioning room, thereby increasing the building's energy utilization coefficient.

First, the energy-saving heat pump system

Taking the heating operation as an example, the current heating methods include centralized boiler room heating mode, thermal power plant heating mode and household gas heating mode, and the water source heat pump mode utilizes well water, river, river, lake water and industrial waste heat; Winter water to help heating the way. Their energy consumption is shown in Table 1.

Table 1 calculation basis:

â‘  The residential building is a multi-storey house in Beijing. The existing building's heat consumption index q H is 31.82W / m 2 , the design heat load index q is 43.82W / m 2 , and the energy saving building q H is 20.6W / m 2 , Q is 28.37 W / m 2 . Heating needs heat throughout the year: the existing building is 95.46kwh / m 2 years, energy-saving building is 61.80kwh / m 2 years.

(2) Centralized boiler room: The heat transfer efficiency η 1 of the existing heating system is 0.85, the boiler efficiency η 2 is 0.55, the energy saving heating system η 1 is 0.9, η 2 is 0.68,

â‘¢ The standard coal consumption of thermal power plant is 0.408Kg / kwh, and the standard coal consumption for heating is 40.7Kg / GJ.

â‘£ water source heat pump heating COP = 4.25.

It can be seen from Table 1 that the annual energy consumption of water source heat pump heating mode is lower than that of centralized boiler room and thermal power plant, and the energy saving benefit is obvious.

The energy saving of water source heat pump using well water, river, river water or industrial waste heat as heat source is very obvious. When the energy efficiency coefficient of water source heat pump is 4.0, the energy saving rate of heating is about 40% compared with the cogeneration heating mode. When using auxiliary heating heat source, the water source heat pump energy saving is conditional, the main factors are: water source heat pump energy efficiency coefficient; auxiliary heat source heating capacity.

â‘  water source heat pump energy efficiency coefficient (see Table 2)

* The auxiliary heating capacity is 75% of the total heat supply.

As can be seen from Table 2, when the COP is increased from 4 to 4.5, the energy-saving rate is about 5.6%, which is equivalent to the reduction of the heating capacity of 0.3296KW, which is equivalent to about 10% of the reduction of the heat load.

â‘¡ auxiliary heater heating capacity (see Table 3)

* COP = 4

As can be seen from Table 3, when the auxiliary heating capacity is reduced from 0.75 to 0.5, the energy saving rate is about 16.6%.

â‘¢ energy-saving conditions

Heating capacity of 4KW cogeneration energy consumption is:

(4 × 860) / (7000 × 0.83 × 0.85) = 0.697 kg / 4kwh

From this we can see:

When the COP = 4.0, the auxiliary heating capacity of 0.5 for the total heat, compared with the cogeneration method, its energy saving rate of about 2%.

When the COP = 4.5, the auxiliary heating capacity of 0.5 for the total heat, compared with cogeneration heating mode, the water source heat pump energy saving rate of about 8%.

However, when the COP = 4.0, the auxiliary heating capacity of 0.75 total heat, the cogeneration will save energy than water source heat pump, saving about 15% energy efficiency. When COP = 4.5, its energy saving rate is about 10%.

The main factors of energy saving are as follows:

â‘  water source heat pump unit placed directly indoors, heat transmission and distribution losses can be neglected.

â‘¡ water source heat pump heating efficiency coefficient COP greater than 4, part load, the COP value is still very stable.

â‘¢ water, river, river, lake and industrial heat of low temperature heat as a heat pump water source heat pump system, heating consumption of heat is only one-fourth of the annual calories required.

(4) The water source heat pump system with auxiliary heat source in the winter with tap water as its source of heat requires about 1/2 to 1/3 of the thermal load due to the heat generated by the compressor, the coefficient of simultaneous use of the house, and the temperature at night. Heating is about 1/2 ~ 1/3 of the annual heat required.

Second, the water source heat pump system economy

Economy refers to the initial investment of various air-conditioning heating, operating costs and heat prices.

At home and abroad have adopted the program for heating and air conditioning are:

â‘  thermoelectric cooling triple for: Summer, thermal power plant steam absorption absorption refrigeration +

In winter, heat and power plant extraction + steam heat exchanger heating

 '¡triple thermoelectric cooling: summer, thermal power plants hot water + absorption refrigeration

In winter, thermal power plant + soda heat exchanger heating

â‘¢ direct-fired hot and cold water unit: summer, winter, direct-fired hot and cold water unit cooling, heating

â‘£ gas - steam joint no

⑤ electric refrigeration + gas (oil) boiler heating

â‘¥ electric water pump. The performance of such units is stable, the coefficient of performance COP value is high, the theoretical calculation of up to 7, the actual operation of about 5, and due to make full use of rivers, lakes, sea water and other natural energy sources, winter heating energy consumption is less, is a Energy-saving cold source equipment.

⑦ air source heat pump. Both hot and cold sources, good overall, easy installation, open-air installation, the use of air-cooled, eliminating the cooling tower and cooling water system, the disadvantage is that when the outdoor temperature is low, the need to increase the auxiliary heat source. The investment and costs of various programs (excluding indoor systems) are shown in Table 4.

* Data provided in "Study of the Triplex System in a Residential District" at a cost of annual operating costs.

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