Applied research on water loop heat pump system based on a novel mechanism of energy conversion

摘要

Water loop heat pump (WLHP) has been widely used as a heat recovery system to realize building energy efficiency, but it still was a difficult problem to how to determine the effect of extracting and rejecting heat on water loop, because the unit converted its operation to reverse mode with load changing but the process would have a reverse effect on system operation. In this paper, a novel mechanism of energy conversion is introduced into the WLHP system to solve the problem and its view is presented as follows. First, the operation of WLHP system produces a "Reverse Energy" and it originates from an energy difference caused by the converted unit to water loop and can be used as a quantitative index to illustrate the energy-saving principle of system operation. Second, system operation is a combined effect caused by load change and reverse energy and yields to a non-linear law due to the dynamic effect of reverse energy, so, it is characteristic of generality and individuality. Third, we can replace building load with circulating water to determine the energy-saving range of system operation and its law, and the idea that the energy carrier is used to solve the problem caused by operation will be of an important significance for a complex system. At last, the impact factors of system operation can be converted into a single function on circulating water by extracting and rejecting heat and the reverse energy is also determined by power equation of circulating water. To validate the previous conclusions and optimize heat pump systems, an office building group with different air-conditioning projects was tested in Tianjin and the results show that the change of system load determines the overall trend of operation, but the effect of reverse energy can reduce the fluctuation caused by load change and energy consumption of auxiliary power to improve operational efficiency, so, the WLHP system can achieve a higher efficiency compared to an air source heat pump (ASHP), in addition, the total energy consumption can further be reduced by building an energy balance between auxiliary heat source and units. These contributions contribute to the development of WLHP system and building energy efficiency.