Research On Forms And Operating Condition Of Heat Pump System With Freezing Latent Heat Collection

With the serious issues about energy and environment increasingly, various heat pump technologies have been developed and applied in many fields.Surface water, such as river or lake, and urban sewage are cooling and heating resources of heat pump systems, which are considerable and spectacular in amount. But in contacts, we often meet some difficulties that the surface water winter temperature is excessively low or sewage flux is too insufficiency in the trunk sewers nearby the buildings. This paper brings out a new heat pump system named heat pump system with freezing latent heat collection (HPSFLHC), which is from actual demand of heat pump technology and low renewable energy. In this new system, freezing latent heat of non-clean water sources can be used as low temperature heat source,so it is valuable on practice and theory.Freezing latent heat exchanger (FLHE) is one of the key equipments of HPSFLHC. This paper develops two kinds of screwing and scraping FLHEs, which are the spiral screw FLHE and the spiral steel brush FLHE, elaborates its deicing principle, and points out the system parameter condition to remove the ice safely. Through fundamental research on freezing and heat transfer to the low temperature turbulent surface water and laminar urban sewage, it obtains the corresponding fitting formula. Experimental table and double-pipe spiral steel brush FLHE test sample has been independently designed and set up to conduct the freezing latent heat transfer experimental study through the laboratory system to turbulent surface water and the laminar sewage. The experimental result has confirmed the validity of de-icing and removing of the device and the accuracy of theoretical calculation method.The surface water temperature and its change relate correct design and the reasonable operation of the heat pump system. The summer surface water temperature model is established and simplified through the meteorological parameter sensitivity analysis, and staged surface water temperature model in the heating period is proposed by the method of theoretical analysis and the data analysis. Intake and outlet position can be simulated and determined with the hourly water temperature forecast method at cooling design day when using the lake water as cooling, and an example is carried on.The correct and reasonable structural style of HPSFLHC is the premise to achieve safe heating and display system's operating efficiency. For the different water source types and characteristics, it will be very different on structural style of HPSFLHC. This article analyzes and proposes three styles of HPSFLHC for each kind of different water source condition including clean or non-clean surface water source HPSFLHC, as well as the urban sewage source HPSFLHC. Then it analyzes various systems' rationality and elaborates the system whole year operating patterns.The form of heat pump system is the premise on heating safely and operating effectively. This article has established various systems' design optimization method, then forecasts the system's whole year operating characteristic, surveys system's economy, energy conservation, environmental protection performance comprehensively. With examples, we can obtain that performance of energy conservation and the environment-protection is prominent, and it shows that the clean surface water source HPSFLHC has favorable economic characteristic, and the initial investment is reasonable; the non-clean surface water source HPSFLHC has certain superiority, but the initial investment is high; the urban sewage source HPSFLHC has the obvious superiority, and the initial investment is slightly high.In brief, when gathering latent heat of environmental water by these new systems, the heat pump unit's COPh is low, but it runs at the partial load mainly in the heating period. In the cold areas, the surface water winter temperature is low, but its water flux usual sufficient, and the urban sewage water flux are low, but its water temperature is high. So through the operating condition analysis when heating by the example, the heat pump unit mean COPh in the heating period still can be 3.5 to 4.0. At economic efficiency aspect, comparing with the heating network and chiller plant system, initially invests of this new system is about 115~150% of the latter, operating cost of this new system is about 60~80% of the latter. Considering the huge social efficiency at energy-saving and environmental protection and different fiscal subsidy, this new system is worth promoting.