The way to solve this problem is to introduce low-temperature heat source from the outside of the building to replace the residual heat in the building. Solar energy, water (surface water, well water, river water, etc.), soil and air can be used as external energy of water loop heat pump air conditioning system. For example, Dalian electric power building (high-rise unit building) uses the cooling water of thermal power plant as the external heat source of the water loop heat pump air conditioning system, which achieves good energy-saving effect. In addition, Harbin University of technology proposes a two-stage heat pump heating system with air / water heat pump and water / air heat pump coupling. In the cold area, the system uses the air source heat pump cold and hot water unit to prepare low temperature water of 10 ℃ ~ 20 ℃, which is sent to each indoor water / air heat pump unit through the water loop. The water / air heat pump draws heat from the water and directly heats the indoor air to achieve the heating purpose. All in all, it can solve the problem of insufficient residual heat in the building through the cheap auxiliary heat source, and expand the application range of water loop heat pump air conditioning system.
3.2 small water / air heat pump unit
First of all, the cop of small water / air heat pump unit is far less than that of large water chiller unit, and the price of other types of main engine is also high under the same refrigeration capacity. Another important problem is that the small water / air heat pump unit is installed indoors, and the compressor and fan inside the heat pump unit will become a big noise source, which can not meet the noise standard requirements of indoor environment.
In order to solve the problem of how to improve the economy of water loop heat pump air conditioning system in cooling, we can use the form of hybrid system in the design of air conditioning system. Hybrid system is a new air conditioning system which is composed of water / air heat pump unit and other air conditioning equipment (such as water chiller, unit cabinet air conditioner, etc.). Similarly, in order to improve the economy of the system operation, the unit air conditioning unit (water-cooling) is set in the inner area of the building to supply cooling to the inner area, while the water / air heat pump unit is set in the surrounding area to supply cooling or heating to the surrounding area, which is also a noteworthy hybrid system form.